This document provides an overview of viruses and their structure and life cycle. It discusses:
1. The history of virus discovery and early research showing that viruses are smaller than bacteria and can pass through filters.
2. The basic structure of viruses, which typically includes a protein capsid enclosing nucleic acids, and some viruses having an outer envelope.
3. The virus life cycle, which generally involves adsorption to a host cell, penetration, replication of viral components, assembly of new virus particles, and release through budding or cell lysis.
Viruses are the smallest infectious agents that can only replicate inside living cells. They contain either DNA or RNA surrounded by a protein coat called a capsid. Some viruses have an outer envelope. Viruses infect cells by binding to receptors on the cell surface and releasing their genetic material inside. The genetic material is then used to hijack the cell's machinery to produce new viral components and assemble new virus particles, which are then released to infect other cells. Viruses are classified based on their structure, genome, proteins, and pathogenicity. Their rapid replication within host cells allows viruses to spread efficiently between individuals.
General virology 4 - Laboratory diagnosis, by Dr. Himanshu KhatriDrHimanshuKhatri
Laboratory diagnosis of viral infections can be performed through several methods: (1) demonstrating characteristic cytopathic effects of viruses in cell cultures, (2) directly detecting viruses in clinical samples through electron or fluorescence microscopy, (3) isolating and culturing viruses in animals, eggs, or various cell culture systems, and (4) detecting viral antibodies through serological tests like ELISA, Western blot, or hemagglutination inhibition tests. Tissue culture using various cell lines is now the most widely used method for virus isolation. Laboratory diagnosis helps confirm viral infections, screen blood donations, and conduct epidemiological and research studies.
Viruses are composed of nucleic acids enclosed in a protein coat and are smaller than bacteria. They cannot replicate without a host cell and are considered non-living. A virus infects a host cell by attaching to receptors on its surface, and then either injects its nucleic acid inside or fuses with the host cell's membrane. Once inside, the virus takes over the cell's machinery to replicate itself through one of two cycles - lytic kills the host cell, while lysogenic integrates viral DNA into the host genome without immediately killing the cell. Retroviruses like HIV are unique as they use reverse transcriptase to transcribe their RNA into DNA before integrating into the host cell's chromosome.
Picornaviruses are a family of small RNA viruses that includes enteroviruses like poliovirus and rhinoviruses that cause the common cold. They are spherical and non-enveloped, around 30nm in diameter, and contain a single strand of positive-sense RNA genome around 7-8kb in size. Picornaviruses infect the cytoplasm and their replication results in cell lysis and spread to other cells. Important human pathogens include the polioviruses, coxsackieviruses, echoviruses and rhinoviruses. Both live attenuated and inactivated vaccines have been developed to prevent diseases like polio.
Viruses infect host cells and use the host's cellular machinery to replicate themselves. This involves the virus attaching and entering the host cell, releasing its genome, producing new viral components, assembling new virus particles, and causing the host cell to burst and release the new virus particles to infect other cells. Viruses can spread systemically throughout the host's body or remain localized to sites of infection. The replication cycle allows viruses to efficiently propagate and spread infection.
Viruses are obligate intracellular infectious agents that contain either DNA or RNA as their genome but no organelles. They range in size from 20-400 nm and have a variety of shapes. Viruses consist of a nucleic acid core surrounded by a protein capsid and some have an outer envelope. Their genomes can be single or double stranded and either DNA or RNA. Viruses infect all forms of life including animals, plants, bacteria and archaea.
General Characters and Classification of Viruses. Includes ICTV classification and Baltimore classification of viruses. A brief explanation of the Viral structure and Lifecycle.
Viruses are obligate intracellular parasites that lack cell organelles and exist in two phases - an extracellular phase where they possess few enzymes, and an intracellular phase where they induce host cells to synthesize viral components. They have a nucleocapsid containing either DNA or RNA surrounded by a protein capsid. Viruses replicate through either lytic or lysogenic cycles, with the lytic cycle involving adsorption to and penetration of host cells, synthesis of viral components, assembly of new virus particles, and cell lysis. Viruses can be grown in tissue culture or through plaque assays using bacterial hosts.
Viruses are the smallest infectious agents that can only replicate inside living cells. They contain either DNA or RNA surrounded by a protein coat called a capsid. Some viruses have an outer envelope. Viruses infect cells by binding to receptors on the cell surface and releasing their genetic material inside. The genetic material is then used to hijack the cell's machinery to produce new viral components and assemble new virus particles, which are then released to infect other cells. Viruses are classified based on their structure, genome, proteins, and pathogenicity. Their rapid replication within host cells allows viruses to spread efficiently between individuals.
General virology 4 - Laboratory diagnosis, by Dr. Himanshu KhatriDrHimanshuKhatri
Laboratory diagnosis of viral infections can be performed through several methods: (1) demonstrating characteristic cytopathic effects of viruses in cell cultures, (2) directly detecting viruses in clinical samples through electron or fluorescence microscopy, (3) isolating and culturing viruses in animals, eggs, or various cell culture systems, and (4) detecting viral antibodies through serological tests like ELISA, Western blot, or hemagglutination inhibition tests. Tissue culture using various cell lines is now the most widely used method for virus isolation. Laboratory diagnosis helps confirm viral infections, screen blood donations, and conduct epidemiological and research studies.
Viruses are composed of nucleic acids enclosed in a protein coat and are smaller than bacteria. They cannot replicate without a host cell and are considered non-living. A virus infects a host cell by attaching to receptors on its surface, and then either injects its nucleic acid inside or fuses with the host cell's membrane. Once inside, the virus takes over the cell's machinery to replicate itself through one of two cycles - lytic kills the host cell, while lysogenic integrates viral DNA into the host genome without immediately killing the cell. Retroviruses like HIV are unique as they use reverse transcriptase to transcribe their RNA into DNA before integrating into the host cell's chromosome.
Picornaviruses are a family of small RNA viruses that includes enteroviruses like poliovirus and rhinoviruses that cause the common cold. They are spherical and non-enveloped, around 30nm in diameter, and contain a single strand of positive-sense RNA genome around 7-8kb in size. Picornaviruses infect the cytoplasm and their replication results in cell lysis and spread to other cells. Important human pathogens include the polioviruses, coxsackieviruses, echoviruses and rhinoviruses. Both live attenuated and inactivated vaccines have been developed to prevent diseases like polio.
Viruses infect host cells and use the host's cellular machinery to replicate themselves. This involves the virus attaching and entering the host cell, releasing its genome, producing new viral components, assembling new virus particles, and causing the host cell to burst and release the new virus particles to infect other cells. Viruses can spread systemically throughout the host's body or remain localized to sites of infection. The replication cycle allows viruses to efficiently propagate and spread infection.
Viruses are obligate intracellular infectious agents that contain either DNA or RNA as their genome but no organelles. They range in size from 20-400 nm and have a variety of shapes. Viruses consist of a nucleic acid core surrounded by a protein capsid and some have an outer envelope. Their genomes can be single or double stranded and either DNA or RNA. Viruses infect all forms of life including animals, plants, bacteria and archaea.
General Characters and Classification of Viruses. Includes ICTV classification and Baltimore classification of viruses. A brief explanation of the Viral structure and Lifecycle.
Viruses are obligate intracellular parasites that lack cell organelles and exist in two phases - an extracellular phase where they possess few enzymes, and an intracellular phase where they induce host cells to synthesize viral components. They have a nucleocapsid containing either DNA or RNA surrounded by a protein capsid. Viruses replicate through either lytic or lysogenic cycles, with the lytic cycle involving adsorption to and penetration of host cells, synthesis of viral components, assembly of new virus particles, and cell lysis. Viruses can be grown in tissue culture or through plaque assays using bacterial hosts.
Viruses are non-living particles that can only replicate inside host cells. They contain genetic material surrounded by a protective coat. Viruses infect both eukaryotes and prokaryotes. Vaccines work by introducing a weakened form of a virus to stimulate an immune response and generate memory cells to fight future infections. Edward Jenner developed the first vaccine for smallpox in 1796 by inoculating people with cowpox to protect against smallpox. Modern vaccines are either live attenuated viruses or inactivated viruses and work by priming the immune system without causing disease. Common childhood vaccines protect against measles, mumps, rubella, polio and other diseases.
Virology is the study of viruses – submicroscopic, parasitic particles of genetic material contained in a protein coat and virus-like agents. It focuses on the following aspects of viruses: their structure, classification and evolution, their ways to infect and exploit host cells for reproduction, their interaction with host organism physiology and immunity, the diseases they cause, the techniques to isolate and culture them, and their use in research and therapy. Virology is considered to be a subfield of microbiology or of medicine.
Viruses have capsids made of protein subunits that enclose and protect their nucleic acid. Viruses come in two main shapes - helical or icosahedral - determined by the arrangement of capsomers in the capsid. Some viruses have an envelope in addition to the capsid.
Viral replication involves the virus binding to and entering a host cell, then using the cell's machinery to produce new viral components which are assembled and released to infect new cells. DNA and RNA viruses replicate via different mechanisms using virus-specific enzymes. Animal virus replication is more complex than bacterial viruses due to host cell complexity.
Growing viruses requires appropriate cell cultures or animal hosts that provide an environment where the virus can replicate
Viruses can be cultivated through several methods, including inoculation in animals, embryonated eggs, and tissue/cell culture. Inoculation in animals allows study of viral replication and immune responses but is expensive. Embryonated eggs are widely used as they are inexpensive and viruses can replicate, though not all human viruses grow well. Tissue/cell culture is now preferred, using primary cultures, continuous cell lines, or explant cultures. Growth is detected through cytopathic effects, staining, or metabolic changes in infected cells.
Viruses are the smallest infectious agents that can only replicate inside host cells. They are classified based on characteristics like genome type and virus structure. The International Committee on Taxonomy of Viruses (ICTV) establishes standardized virus classification and nomenclature. Viruses vary greatly in size and shape but generally contain nucleic acid surrounded by a protein coat. They may have an outer envelope and infect a wide range of organisms.
The document provides information about viruses, including their structure, classification, and life cycles. It describes that viruses are non-living particles composed of genetic material and protein that can infect host cells. Viruses come in different shapes and sizes, and some have envelopes while others do not. They are classified based on their genetic material and hosts. The document also explains the lytic and lysogenic life cycles of bacteriophages and how they reproduce and infect bacterial cells.
- Retroviridae are a family of enveloped RNA viruses that include HIV and have been associated with cancers and AIDS. HIV is classified as a lentivirus within this family.
- There are two main theories for the origin of HIV in humans - natural transfer from chimpanzees through hunting or a contaminated oral polio vaccine.
- HIV infects CD4+ T cells using its envelope proteins to bind host receptors, then integrates into the host genome and uses host cell machinery to replicate. This evades immune detection and allows the virus to persist.
This document provides an overview of virology and viral replication. It begins with an outline of topics to be covered, including the structure and classification of viruses, basic virology, and clinical virology. It then discusses viral structure, noting there are five basic types. Viral replication is summarized in seven steps: adsorption, entry, uncoating, transcription, synthesis of viral components, assembly, and release. Control methods involve knowledge of reservoirs, transmission, inactivation methods, vaccines, antiviral drugs, and drug resistance. Emerging viral diseases and some examples are also mentioned.
Poxviruses are brick or oval-shaped viruses with large double-stranded DNA genomes. Poxviruses exist throughout the world and cause disease in humans and many other types of animals. Poxvirus infections typically result in the formation of lesions, skin nodules, or disseminated rash.
This document discusses bacteriophages, which are viruses that infect bacteria. It describes the two main cycles of bacteriophage multiplication: the lytic cycle and lysogenic cycle. The lytic cycle involves the T-even bacteriophage infecting E. coli, reproducing through five stages, and ultimately causing the host cell to lyse. The lysogenic cycle is exemplified by the lambda bacteriophage infecting E. coli, which can either undergo the lytic cycle or integrate its DNA into the host and remain dormant. Bacteriophages can be grown and quantified using plaque assays. They have various applications including phage therapy and transduction.
Picornaviruses are a diverse family of viruses that includes poliovirus, rhinovirus, enterovirus, and others. They have a positive-sense RNA genome surrounded by an icosahedral capsid. The genome encodes a single polyprotein that is cleaved into structural and non-structural proteins. Replication is rapid, shutting down host cell protein synthesis. Transmission is usually fecal-oral or respiratory. Infections can cause a variety of illnesses depending on the virus, including poliomyelitis, hand foot and mouth disease, myocarditis, and the common cold. Diagnosis involves cell culture or PCR detection of the virus. Treatment is supportive and prevention includes vaccines for polio
This document provides information about viruses, including their history, structure, composition and examples. Some key points:
- Viruses were first observed in 1892 by Iwanowski who discovered the Tobacco Mosaic Virus. Louis Pasteur coined the term "virus" in 1884.
- Viruses have either DNA or RNA as their genetic material but not both. They come in a variety of shapes and sizes from 10-400nm.
- A virus particle consists of nucleic acid surrounded by a protein coat called a capsid. Some have an additional outer envelope. They require a host cell to replicate.
- Examples of important viruses discussed include HIV, influenza, measles, polio and tobacco mosaic
Viruses are obligate intracellular parasites that contain either DNA or RNA. They replicate through a series of steps within a host cell. There are two main viral life cycles: lytic and lysogenic. The lytic cycle involves virus replication, assembly, and lysis of the host cell. The lysogenic cycle involves integration of the viral genome into the host cell genome without immediate cell lysis. Viruses are also classified based on their genome type and replication strategy, such as retroviruses which contain RNA and replicate through a DNA intermediate.
The document provides an overview of virus classification systems. It discusses how viruses were initially named randomly but are now classified systematically. The main classification criteria include the type of nucleic acid (DNA or RNA), number of strands, presence of an envelope, capsid structure, host type, and mode of transmission. Two major classification systems are described - the International Committee on Taxonomy of Viruses (ICTV) system which is based on genomic properties, and the Baltimore classification which is based on mRNA synthesis strategies. The document also discusses classification based on replication properties and site.
The document discusses the different types of nucleic acids that viruses can use to store their genetic information, including double-stranded DNA, single-stranded DNA, double-stranded RNA, negative-sense RNA, positive-sense RNA, and positive-sense RNA retroviruses. It provides details on how each type replicates and produces viral mRNA.
This document provides information on the classification and characteristics of viruses. It discusses their size, composition, nucleic acid content, structure, sites of replication, and examples from different virus families. Key details include that viruses possess either DNA or RNA, have specific structures like helical or icosahedral capsids, may have envelopes, and replicate in the nucleus or cytoplasm of infected cells. Common virus families and their disease associations are also outlined.
The document discusses several arthropod-borne diseases transmitted by mosquitoes, ticks, and fleas including malaria, yellow fever, dengue fever, encephalitis, epidemic typhus, and bubonic plague. It then focuses on arboviruses, which are viruses transmitted between animals and humans by arthropod vectors like mosquitoes and ticks. Major arboviruses include those in the Togavirus, Bunyavirus, and Flavivirus families that cause diseases such as dengue, yellow fever, Japanese encephalitis, and eastern and western equine encephalitis.
Viruses, viroids, and prions are infectious agents. Viruses contain genetic material surrounded by a protein coat and infect all domains of life. Viroids are small, circular RNA molecules that infect plants and require a host RNA polymerase for replication. Prions are composed primarily of misfolded protein and cause neurodegenerative diseases in humans and animals by inducing normal protein molecules to take on their abnormal shape.
Viral classification and Types of Replication in virus Rakshith K, DVM
Precise presentation on Viral classification and Types of replication in Virus.
Entry of virus
Spread of virus
General steps in a virus replication cycle
Attachment, Penetration, Uncoating, Multiplication
Multiplication of Single-Stranded RNA (ss RNA) Viruses
Multiplication of Double-Stranded RNA (ds RNA) Viruses
Multiplication of Single-Stranded DNA (ss DNA) Viruses
Multiplication of Double-Stranded DNA (ds DNA) Viruses
Release of new virions
Common viral diseases of Bovines
Viruses are small infectious agents that can cause diseases in humans. They replicate inside host cells by using the cell's resources. There are three main stages of viral replication: early, central, and final. In the early stage, viruses attach and enter cells. In the central stage, they produce mRNA, proteins, and genomic material. In the final stage, new virus particles assemble and are released. Viruses can mutate, allowing them to evolve and evade host immune responses. They also interact genetically with each other and their hosts. Viruses cause a wide range of human diseases and conditions, from common colds to cancers.
morphologyyyy of VIRUSSSSSSSSSSSSSS.pptxDiptiPriya6
Viruses can be cultivated using three main methods:
1. Using laboratory animals by inoculation via various routes.
2. Inoculating embryonated eggs, usually in the allantois.
3. Cell culture techniques using cell suspensions in containers. Primary cell cultures, diploid cell strains and continuous cell lines can be used.
Viruses vary greatly in size and structure. They contain a protein capsid that protects the viral nucleic acid genome, which can be DNA or RNA. Capsids have different symmetries like icosahedral, filamentous or head-tail shapes. Viruses replicate inside host cells by attaching, entering, releasing their genome, replicating it, assembling new viral particles, and exiting via lysis or budding. Their ability to highjack host cell machinery allows replication but also determines their pathogenicity and transmission between hosts.
Viruses are non-living particles that can only replicate inside host cells. They contain genetic material surrounded by a protective coat. Viruses infect both eukaryotes and prokaryotes. Vaccines work by introducing a weakened form of a virus to stimulate an immune response and generate memory cells to fight future infections. Edward Jenner developed the first vaccine for smallpox in 1796 by inoculating people with cowpox to protect against smallpox. Modern vaccines are either live attenuated viruses or inactivated viruses and work by priming the immune system without causing disease. Common childhood vaccines protect against measles, mumps, rubella, polio and other diseases.
Virology is the study of viruses – submicroscopic, parasitic particles of genetic material contained in a protein coat and virus-like agents. It focuses on the following aspects of viruses: their structure, classification and evolution, their ways to infect and exploit host cells for reproduction, their interaction with host organism physiology and immunity, the diseases they cause, the techniques to isolate and culture them, and their use in research and therapy. Virology is considered to be a subfield of microbiology or of medicine.
Viruses have capsids made of protein subunits that enclose and protect their nucleic acid. Viruses come in two main shapes - helical or icosahedral - determined by the arrangement of capsomers in the capsid. Some viruses have an envelope in addition to the capsid.
Viral replication involves the virus binding to and entering a host cell, then using the cell's machinery to produce new viral components which are assembled and released to infect new cells. DNA and RNA viruses replicate via different mechanisms using virus-specific enzymes. Animal virus replication is more complex than bacterial viruses due to host cell complexity.
Growing viruses requires appropriate cell cultures or animal hosts that provide an environment where the virus can replicate
Viruses can be cultivated through several methods, including inoculation in animals, embryonated eggs, and tissue/cell culture. Inoculation in animals allows study of viral replication and immune responses but is expensive. Embryonated eggs are widely used as they are inexpensive and viruses can replicate, though not all human viruses grow well. Tissue/cell culture is now preferred, using primary cultures, continuous cell lines, or explant cultures. Growth is detected through cytopathic effects, staining, or metabolic changes in infected cells.
Viruses are the smallest infectious agents that can only replicate inside host cells. They are classified based on characteristics like genome type and virus structure. The International Committee on Taxonomy of Viruses (ICTV) establishes standardized virus classification and nomenclature. Viruses vary greatly in size and shape but generally contain nucleic acid surrounded by a protein coat. They may have an outer envelope and infect a wide range of organisms.
The document provides information about viruses, including their structure, classification, and life cycles. It describes that viruses are non-living particles composed of genetic material and protein that can infect host cells. Viruses come in different shapes and sizes, and some have envelopes while others do not. They are classified based on their genetic material and hosts. The document also explains the lytic and lysogenic life cycles of bacteriophages and how they reproduce and infect bacterial cells.
- Retroviridae are a family of enveloped RNA viruses that include HIV and have been associated with cancers and AIDS. HIV is classified as a lentivirus within this family.
- There are two main theories for the origin of HIV in humans - natural transfer from chimpanzees through hunting or a contaminated oral polio vaccine.
- HIV infects CD4+ T cells using its envelope proteins to bind host receptors, then integrates into the host genome and uses host cell machinery to replicate. This evades immune detection and allows the virus to persist.
This document provides an overview of virology and viral replication. It begins with an outline of topics to be covered, including the structure and classification of viruses, basic virology, and clinical virology. It then discusses viral structure, noting there are five basic types. Viral replication is summarized in seven steps: adsorption, entry, uncoating, transcription, synthesis of viral components, assembly, and release. Control methods involve knowledge of reservoirs, transmission, inactivation methods, vaccines, antiviral drugs, and drug resistance. Emerging viral diseases and some examples are also mentioned.
Poxviruses are brick or oval-shaped viruses with large double-stranded DNA genomes. Poxviruses exist throughout the world and cause disease in humans and many other types of animals. Poxvirus infections typically result in the formation of lesions, skin nodules, or disseminated rash.
This document discusses bacteriophages, which are viruses that infect bacteria. It describes the two main cycles of bacteriophage multiplication: the lytic cycle and lysogenic cycle. The lytic cycle involves the T-even bacteriophage infecting E. coli, reproducing through five stages, and ultimately causing the host cell to lyse. The lysogenic cycle is exemplified by the lambda bacteriophage infecting E. coli, which can either undergo the lytic cycle or integrate its DNA into the host and remain dormant. Bacteriophages can be grown and quantified using plaque assays. They have various applications including phage therapy and transduction.
Picornaviruses are a diverse family of viruses that includes poliovirus, rhinovirus, enterovirus, and others. They have a positive-sense RNA genome surrounded by an icosahedral capsid. The genome encodes a single polyprotein that is cleaved into structural and non-structural proteins. Replication is rapid, shutting down host cell protein synthesis. Transmission is usually fecal-oral or respiratory. Infections can cause a variety of illnesses depending on the virus, including poliomyelitis, hand foot and mouth disease, myocarditis, and the common cold. Diagnosis involves cell culture or PCR detection of the virus. Treatment is supportive and prevention includes vaccines for polio
This document provides information about viruses, including their history, structure, composition and examples. Some key points:
- Viruses were first observed in 1892 by Iwanowski who discovered the Tobacco Mosaic Virus. Louis Pasteur coined the term "virus" in 1884.
- Viruses have either DNA or RNA as their genetic material but not both. They come in a variety of shapes and sizes from 10-400nm.
- A virus particle consists of nucleic acid surrounded by a protein coat called a capsid. Some have an additional outer envelope. They require a host cell to replicate.
- Examples of important viruses discussed include HIV, influenza, measles, polio and tobacco mosaic
Viruses are obligate intracellular parasites that contain either DNA or RNA. They replicate through a series of steps within a host cell. There are two main viral life cycles: lytic and lysogenic. The lytic cycle involves virus replication, assembly, and lysis of the host cell. The lysogenic cycle involves integration of the viral genome into the host cell genome without immediate cell lysis. Viruses are also classified based on their genome type and replication strategy, such as retroviruses which contain RNA and replicate through a DNA intermediate.
The document provides an overview of virus classification systems. It discusses how viruses were initially named randomly but are now classified systematically. The main classification criteria include the type of nucleic acid (DNA or RNA), number of strands, presence of an envelope, capsid structure, host type, and mode of transmission. Two major classification systems are described - the International Committee on Taxonomy of Viruses (ICTV) system which is based on genomic properties, and the Baltimore classification which is based on mRNA synthesis strategies. The document also discusses classification based on replication properties and site.
The document discusses the different types of nucleic acids that viruses can use to store their genetic information, including double-stranded DNA, single-stranded DNA, double-stranded RNA, negative-sense RNA, positive-sense RNA, and positive-sense RNA retroviruses. It provides details on how each type replicates and produces viral mRNA.
This document provides information on the classification and characteristics of viruses. It discusses their size, composition, nucleic acid content, structure, sites of replication, and examples from different virus families. Key details include that viruses possess either DNA or RNA, have specific structures like helical or icosahedral capsids, may have envelopes, and replicate in the nucleus or cytoplasm of infected cells. Common virus families and their disease associations are also outlined.
The document discusses several arthropod-borne diseases transmitted by mosquitoes, ticks, and fleas including malaria, yellow fever, dengue fever, encephalitis, epidemic typhus, and bubonic plague. It then focuses on arboviruses, which are viruses transmitted between animals and humans by arthropod vectors like mosquitoes and ticks. Major arboviruses include those in the Togavirus, Bunyavirus, and Flavivirus families that cause diseases such as dengue, yellow fever, Japanese encephalitis, and eastern and western equine encephalitis.
Viruses, viroids, and prions are infectious agents. Viruses contain genetic material surrounded by a protein coat and infect all domains of life. Viroids are small, circular RNA molecules that infect plants and require a host RNA polymerase for replication. Prions are composed primarily of misfolded protein and cause neurodegenerative diseases in humans and animals by inducing normal protein molecules to take on their abnormal shape.
Viral classification and Types of Replication in virus Rakshith K, DVM
Precise presentation on Viral classification and Types of replication in Virus.
Entry of virus
Spread of virus
General steps in a virus replication cycle
Attachment, Penetration, Uncoating, Multiplication
Multiplication of Single-Stranded RNA (ss RNA) Viruses
Multiplication of Double-Stranded RNA (ds RNA) Viruses
Multiplication of Single-Stranded DNA (ss DNA) Viruses
Multiplication of Double-Stranded DNA (ds DNA) Viruses
Release of new virions
Common viral diseases of Bovines
Viruses are small infectious agents that can cause diseases in humans. They replicate inside host cells by using the cell's resources. There are three main stages of viral replication: early, central, and final. In the early stage, viruses attach and enter cells. In the central stage, they produce mRNA, proteins, and genomic material. In the final stage, new virus particles assemble and are released. Viruses can mutate, allowing them to evolve and evade host immune responses. They also interact genetically with each other and their hosts. Viruses cause a wide range of human diseases and conditions, from common colds to cancers.
morphologyyyy of VIRUSSSSSSSSSSSSSS.pptxDiptiPriya6
Viruses can be cultivated using three main methods:
1. Using laboratory animals by inoculation via various routes.
2. Inoculating embryonated eggs, usually in the allantois.
3. Cell culture techniques using cell suspensions in containers. Primary cell cultures, diploid cell strains and continuous cell lines can be used.
Viruses vary greatly in size and structure. They contain a protein capsid that protects the viral nucleic acid genome, which can be DNA or RNA. Capsids have different symmetries like icosahedral, filamentous or head-tail shapes. Viruses replicate inside host cells by attaching, entering, releasing their genome, replicating it, assembling new viral particles, and exiting via lysis or budding. Their ability to highjack host cell machinery allows replication but also determines their pathogenicity and transmission between hosts.
Viruses were first discovered in the late 19th century through experiments showing that certain plant diseases could be transmitted through filters that blocked bacteria. Viruses have a simple structure consisting of genetic material encased in a protein shell or capsid that may be surrounded by a membrane. They range widely in size but are typically 50 times smaller than bacteria. Viruses are classified based on structure, host specificity, nucleic acid type, and cause a variety of diseases in plants, animals, and humans.
Viruses are obligate intracellular parasites that infect all living organisms. They possess either DNA or RNA and lack organelles like cell membranes and ribosomes. Viruses come in a variety of shapes and sizes, with the smallest being 20nm and largest 400nm. They enter host cells and hijack the cell's machinery to replicate their genome and proteins. Viruses can undergo lytic or lysogenic replication cycles. Laboratory diagnosis of viral infections involves direct visualization of viruses, detection of antigens and antibodies, and molecular methods like PCR to detect viral genes.
General virology,Introduction, structure,classification - Copy.pptxShishirer Vor
Viruses are acellular infectious agents that are too small to be seen with a light microscope. They are composed of nucleic acids surrounded by a protein coat called a capsid. Some viruses have an outer envelope. Viruses must replicate within host cells as they cannot generate their own energy or synthesize proteins. Viruses come in various shapes and sizes determined by the arrangement of subunits in their capsids. Their nucleic acids can be single or double stranded DNA or RNA. Classification is based on nucleic acid type and structure, capsid size/symmetry, and presence of an envelope. Enveloped viruses are more sensitive to inactivation than non-enveloped viruses.
Viruses have both living and non-living properties. They contain nucleic acids surrounded by a protein coat called a capsid, and some have an additional lipid envelope. Viruses come in various shapes and sizes, and infect bacteria, plants, and animals. They are able to replicate by entering host cells and using the host's cellular machinery to produce new virus particles, which then exit and infect new host cells.
Viruses are microscopic organisms that exist almost everywhere on earth. They can infect animals, plants, fungi, and even bacteria.Viruses vary in complexity. They consist of genetic material, RNA or DNA, surrounded by a coat of protein, lipid (fat), or glycoprotein. Viruses cannot replicate without a host, so they are classified as parasitic.They are considered the most abundant biological entity on the planet.
Here we discuss the general properties of viruses in detail.
Viruses replicate by taking over the host cell's machinery. They produce mRNA using their genome as a template. This mRNA directs the production of viral proteins, including structural proteins that make up the capsid and non-structural proteins that help with replication. The virus growth cycle involves adsorption to receptors, entry, uncoating, synthesis of new viral components, assembly, and release. DNA viruses replicate in the nucleus while RNA viruses replicate in the cytoplasm, except retroviruses and influenza which enter the nucleus. New viruses are assembled and released to infect other cells.
This document provides an overview of viruses, including:
- The history of virus discovery from Iwanowski's experiments in 1892 showing that the cause of tobacco mosaic disease was able to pass through filters that removed bacteria.
- Characteristics of viruses that distinguish them from living cells, including being acellular and only able to reproduce within host cells.
- The components of viruses, which include nucleic acids and protein capsids, with some viruses also having envelopes.
- The replication cycles of bacteriophages and how they can either undergo lytic or lysogenic cycles, and the replication processes of enveloped DNA, RNA, and retroviruses within host cells.
- Emerging viruses
Viruses are the smallest infectious agents that can only replicate inside host cells. They contain nucleic acid (DNA or RNA) as their genome and do not have cells or metabolic machinery. Viruses come in a wide range of sizes and shapes. They enter host cells and use the host's cellular machinery to produce new viral components and assemble new virus particles. The replication cycle involves adsorption, penetration, uncoating, biosynthesis of viral components, assembly, and release of new virus particles. Viruses can be cultivated using animal inoculation, embryonated eggs, or tissue culture methods.
Viruses are the smallest infectious agents that can only replicate inside living host cells. They contain nucleic acid (DNA or RNA) as their genome and do not have their own metabolism. Viruses come in a variety of shapes and sizes, with capsids that enclose and protect their genomes. They enter host cells and hijack the cell's machinery to produce new viral particles, which are then released to infect new host cells. Common methods for cultivating and studying viruses include infecting animals or embryos, and growing viruses in various types of tissue cultures.
This document discusses the role of viruses in periodontal diseases. It begins with an introduction to viruses and their evolution. It then covers the Baltimore classification system for viruses and viral components. The document discusses viral replication and the host immune response. It examines specific virus families like HIV, herpesviruses, and papillomaviruses in relation to periodontal diseases. It concludes with a section on herpetic gingivostomatitis.
This document provides information about virus structure and classification. It begins with the history of virology and defines viruses. It describes the differences between bacteria and viruses, and between DNA and RNA viruses. It outlines the characteristics, structure, replication process, and reaction to physical and chemical agents of viruses. It discusses viral morphology, classification based on shape and presence of an envelope. It also covers bacteriophage structure and important human viruses classified by genome type and associated disease.
Viruses have a basic structure consisting of nucleic acid surrounded by a protein coat called a capsid. Some viruses have an additional phospholipid envelope. Viruses come in a few different symmetries for their capsids including icosahedral, helical, binal, and complex. Icosahedral capsids can be enveloped or non-enveloped while helical capsids are long and spiral-shaped. Binal symmetry combines icosahedral and helical features with a head and tail. Complex symmetry refers to asymmetrical virus structures.
Viruses come in a variety of shapes and sizes, with the main morphological types being helical, icosahedral, prolate, enveloped, and complex. They are composed of a nucleic acid core surrounded by a protein capsid, and some have an additional outer envelope. Viruses infect all types of living organisms by introducing their genetic material inside host cells and hijacking the cells' machinery to replicate themselves.
Viruses contain either DNA or RNA surrounded by a protein coat called a capsid. Some viruses have an outer envelope as well. Viruses infect host cells and use the cell's machinery to replicate their nucleic acid and proteins, eventually causing the cell to burst and release new virus particles. Viruses are classified based on their nucleic acid, replication strategy, and morphology. Common virus families include Herpesviridae, Retroviridae, and Adenoviridae. Viruses can cause disease through lytic infection cycles or establish latent or persistent infections. Some viruses are also associated with cancer development in hosts.
The earliest indications of the biological nature of viruses came from studies in 1892 by the Russian scientist Dmitry I. Ivanovsky and in 1898 by the Dutch scientist Martinus W. Beijerinck.
Beijerinck first surmised that the virus under study was a new kind of infectious agent, which he designated contagium vivum
fluidum, meaning that it was a live, reproducing organism that differed from other organisms.
Both of these investigators found that a disease of tobacco plants could be transmitted by an agent, later called tobacco mosaic virus, passing through a minute filter that would not allow the passage of bacteria.
10- Introduction to Viruses Classification, morphology and structure, Replica...AbdallahAlasal1
Viruses are the smallest infectious agents that can only replicate inside host cells. They contain genetic material (DNA or RNA) surrounded by a protein coat called a capsid, and some have an outer lipid envelope. Viruses infect cells by attaching to and entering the cell, then using the cell's machinery to replicate their genome and proteins. New viral particles assemble and exit the cell, either by bursting the cell or budding through its membrane. Viral infections may be localized to the initial site or spread systemically. The immune response can help control infection but also sometimes contributes to disease symptoms. Some viruses can establish persistent infections by integrating into the host genome, evading immunity, or rapidly mutating antigens.
Pelajar zaman sekarang cenderung kurang rajin mencatat pelajaran guru di kelas dan lebih memilih mengambil gambar tulisan guru di papan tulis menggunakan gadget. Hal ini berdampak negatif pada pemahaman pelajaran dan prestasi belajar siswa. Guru mengingatkan pentingnya mencatat secara manual untuk memaksimalkan proses pembelajaran dan pengingatan di otak.
Hubungan pola konsumsi makanan dengan status gizi pada siswa sma negeri 2 rin...Vivi Yunisa
Skripsi ini membahas hubungan pola konsumsi makanan dengan status gizi pada siswa SMA Negeri 2 RSBI Banda Aceh. Penelitian ini bertujuan untuk mengetahui hubungan pola konsumsi makanan dan aktivitas yang berpengaruh terhadap status gizi siswa. Metode penelitian menggunakan survei dengan sampel 80 siswa. Hasilnya menunjukkan bahwa sebagian besar siswa memiliki status gizi baik berdasarkan indeks BB/U
The document discusses the human movement and framework systems. It describes how motion systems in the body allow for movement through muscles and bones. It then explains the different types of bones in the human body based on their shapes, including pipe bones, flat bones, and small bones. Finally, it discusses joints and how bones connect to each other, including immovable and movable joint types.
Fire ants, (solenopsis invicta), dry and store pieces of insect for later use...Vivi Yunisa
The document discusses how fire ant colonies store food. It found that fire ants collect insect prey and transform it into small dried pieces (jerky) in their nest. The ants transport solid food pieces in their mandibles but take liquid foods into their crop and distribute it through trophallaxis. This separation of solid and liquid food streams in their collection and storage may be evolutionarily advantageous.
2. History (1)
• For many years, the cause of viral infections such as
smallpox and polio was unknown, even though it was
clear that the diseases were transmitted from person to
person.
• The French bacteriologist Louis Pasteur was certainly on the right
track when he postulated that rabies was caused by a “living
thing” smaller than bacteria,
• in 1884 he was able to develop the first vaccine for rabies.
• Pasteur also proposed the term virus to denote this special
group of infectious agents.
Program PGMIPABI-FKIP Unsyiah
3. History (2)
• The first substantial revelations about the unique
characteristics of viruses occurred in the 1890s.
• First, D. Ivanovski and M. Beijerinck showed that a disease in
tobacco was caused by a virus (tobacco mosaic virus).
• Friedrich Loeffler and Paul Frosch discovered a virus that causes
foot-and-mouth disease in cattle.
• These early researchers found that when infectious
fluids from host organisms were passed through
porcelain filters designed to trap bacteria, the filtrate
remained infectious.
Program PGMIPABI-FKIP Unsyiah
4. History (3)
• Over the succeeding decades, a remarkable picture of
the physical, chemical, and biological nature of viruses
began to take form.
• Years of experimentation were required to show that
viruses were noncellular particles with a definite size,
shape, and chemical composition.
• Using special techniques, they could be cultured in the
laboratory.
• By the 1950s, virology had grown into a multifaceted discipline
that promised to provide much information on disease, genetics,
and even life itself
Program PGMIPABI-FKIP Unsyiah
5. The Position of Viruses in the Biological
Spectrum
• Viruses are a unique group of biological entities known
to infect every type of cell, including bacteria, algae,
fungi, protozoa, plants, and animals.
• it is best to describe viruses as infectious particles
(rather than organisms) and as either active or inactive
(rather than alive or dead).
• Viruses are different from their host cells in size,
structure, behavior, and physiology.
• They are a type of obligate intracellular parasite that cannot
multiply unless it invades a specific host cell and instructs its
genetic and metabolic machinery to make and release quantities
of new viruses.
Program PGMIPABI-FKIP Unsyiah
7. General Structure of Viruses
• As a group, viruses represent the smallest
infectious agents.
• Their size places them in the realm of the
ultramicroscopic .
• This term means that most of them are so minute (<0.2 μm)
that an electron microscope is necessary to detect them or
to examine their fine structures.
Program PGMIPABI-FKIP Unsyiah
8. The Size of Viruses
Size comparison of viruses with a eukaryotic cell (yeast) and bacteria. Viruses range from largest (1) to smallest
(9). A molecule of a large protein (10) is included to indicate proportion of macromolecules.
Program PGMIPABI-FKIP Unsyiah
9. Viral Components: Capsids, Nucleic Acids,
and Envelopes (1)
• The general plan of virus organization is the
utmost in simplicity and compactness.
• Viruses contain only those parts needed to
invade and control a host cell:
• an external coating and a core containing one or more
nucleic acid strands of either DNA or RNA.
Program PGMIPABI-FKIP Unsyiah
11. Capsids (1)
• All viruses have capsids - protein coats that
enclose and protect their nucleic acid.
• Each capsid is constructed from identical
subunits called capsomers made of protein.
• The capsid together with the nucleic acid are
nucleoscapsid.
• Some viruses have an external covering called
envelope; those lacking an envelope are
naked.
Program PGMIPABI-FKIP Unsyiah
12. Capsids (2)
Generalized structure of viruses. (a) The simplest virus is a naked virus (nucleocapsid) consisting of a geometric
capsid assembled around a nucleic acid strand or strands. (b) An enveloped virus is composed of a nucleocapsid
surrounded by a flexible membrane called an envelope. The envelope usually has special receptor spikes inserted into
it.
Program PGMIPABI-FKIP Unsyiah
13. Capsids (3)
• Two structural types:
• helical - continuous helix of capsomers forming a
cylindrical nucleocapsid
• The nucleocapsids of naked helical viruses are very rigid and tightly
wound into a cylinder-shaped package. Ex: TMV
• Enveloped helical nucleocapsids are more flexible and tend to be
arranged as a looser helix within the envelope. Ex: influenza,
measles, and rabies viruses
• icosahedral - 20-sided with 12 corners
• vary in the number of capsomers
• a poliovirus has 32, and an adenovirus has 242 capsomers
• Each capsomer may be made of 1 or several proteins.
Program PGMIPABI-FKIP Unsyiah
14. Helical capsids
Typical variations of viruses with helical nucleocapsids. Naked helical virus (tobacco mosaic virus):
(a) a schematic view and (b) a greatly magnified micrograph. Note the overall cylindrical morphology.
Enveloped helical virus (influenza virus): (c) a schematic view and (d) a colorized micrograph featuring a
positive stain of the avian influenza virus. This virus has a well-developed envelope with prominent spikes
termed H5N1 type.
Program PGMIPABI-FKIP Unsyiah
16. Icosahedral viruses (2)
Two types of icosahedral viruses, highly magnified. (a) Upper view: A negative stain of rotaviruses
with unusual capsomers that look like spokes on a wheel; lower view is a three
dimensional model of this virus. (b) Herpes simplex virus, a type of enveloped icosahedral virus.
Program PGMIPABI-FKIP Unsyiah
17. Viral envelope
• When enveloped viruses (mostly animal) are released from the
host cell, they take with them a bit of its membrane system in the
form of an envelope.
• Some viruses bud off the cell membrane; others leave via the
nuclear envelope or the endoplasmic reticulum.
• Some proteins form a binding layer between the envelope and
capsid of the virus, and glycoproteins (proteins bound to a
carbohydrate) remain exposed on the outside of the envelope.
• These protruding molecules, called spikes or peplomers, are
essential for the attachment of viruses to the next host cell.
Program PGMIPABI-FKIP Unsyiah
18. Functions of Capsid/Envelope
• The outermost covering of a virus is
indispensable to viral function
• it protects the nucleic acid from the effects of various
enzymes and chemicals when the virus is outside the
host cell.
• Capsids and envelopes are also responsible for helping
to introduce the viral DNA or RNA into a suitable host
cell,
• by binding to the cell surface
• by assisting in penetration of the viral nucleic acid
Program PGMIPABI-FKIP Unsyiah
19. Complex viruses: atypical viruses (1)
• Two special groups of viruses, termed complex viruses
are more intricate in structure than the helical,
icosahedral, naked, or enveloped viruses just described.
• Poxviruses lack a typical capsid and are covered by a
dense layer of lipoproteins.
• Some bacteriophages have a polyhedral nucleocapsid
along with a helical tail and attachment fibers.
Program PGMIPABI-FKIP Unsyiah
20. Complex viruses: atypical viruses (2)
Detailed structure of complex viruses. (a) Section through the vaccinia virus, a poxvirus, shows its
internal components. (b) Photomicrograph and (c) diagram of a T4 bacteriophage.
Program PGMIPABI-FKIP Unsyiah
21. Basic types of viral morphology
A. Complex viruses: (1) poxvirus, a large DNA virus (2) flexible-tailed bacteriophage
B. Enveloped viruses:
• With a helical nucleocapsid: (3) mumps virus(4) rhabdovirus
• With an icosahedral nucleocapsid: (5) Herpesvirus (6) HIV (AIDS)
C. Naked viruses:
• Helical capsid: (7) plum poxvirus
• Icosahedral capsid: (8) Poliovirus ; (9) papillomavirus
Program PGMIPABI-FKIP Unsyiah
22. Nucleic acids (1)
• Viral genome – either DNA or RNA but never
both
• Carries genes necessary to invade host cell and
redirect cell’s activity to make new viruses
• Number of genes varies for each type of virus –
few to hundreds
Program PGMIPABI-FKIP Unsyiah
23. Nucleic acids (2)
• DNA viruses
• usually double stranded (ds) but may be single stranded
(ss)
• circular or linear
• RNA viruses
• usually single stranded, may be double stranded, may be
segmented into separate RNA pieces
• ssRNA genomes ready for immediate translation are
positive-sense RNA.
• ssRNA genomes that must be converted into proper form
are negative-sense RNA.
Program PGMIPABI-FKIP Unsyiah
24. Other Substances in the Virus
Particle
• In addition to the protein of the capsid, the proteins and lipids of
envelopes, and the nucleic acid of the core, viruses can contain
enzymes for specific operations within their host cell.
• They may come with preformed enzymes that are required for viral
replication.
• polymerases that synthesize DNA and RNA and replicases that copy
RNA.
• The AIDS virus comes equipped with reverse transcriptase for
synthesizing DNA from RNA.
• However, viruses completely lack the genes for synthesis of
metabolic enzymes.
• this deficiency has little consequence, because viruses have adapted to
assume total control over the cell’s metabolic resources.
Program PGMIPABI-FKIP Unsyiah
25. How Viruses Are Classified and
Named (1)
• Classified based on structures, size, nucleic acids,
host species, target cells.
• 3 orders, 63 families, and 263 genera of viruses
• Family name ends in -viridae
• Genus name ends in -virus, Simplexvirus,
Hantavirus, Enterovirus
• Name of genus or family begins with description of
virus
• appearance: togavirus, coronavirus
• place collected: adenovirus, hantavirus
• effect on host: lentivirus
• acronymns: picornavirus; hepadnavirus
Program PGMIPABI-FKIP Unsyiah
26. How Viruses Are Classified and
Named (2)
Program PGMIPABI-FKIP Unsyiah
29. Modes of Viral Multiplication (1)
• General phases in animal virus multiplication cycle:
1. Adsorption - binding of virus to specific molecule
on host cell
2. Penetration - genome enters host cell
3. Uncoating – the viral nucleic acid is released from
the capsid
4. Synthesis – viral components are produced
5. Assembly – new viral particles are constructed
6. Release – assembled viruses are released by
budding (exocytosis) or cell lysis
Program PGMIPABI-FKIP Unsyiah
30. Modes of Viral Multiplication (2)
General features in the multiplication cycle
of an enveloped animal virus. Using an RNA
virus (rubella virus), the major events are
outlined, although other viruses will vary in
exact details of the cycle.
Program PGMIPABI-FKIP Unsyiah
31. Adsorption and Host Range (1)
• Virus coincidentally collides with a susceptible
host cell and adsorbs specifically to receptor
sites on the cell membrane
• Spectrum of cells a virus can infect – host
range
• hepatitis B – human liver cells
• poliovirus – primate intestinal and nerve cells
• rabies – various cells of many mammals
Program PGMIPABI-FKIP Unsyiah
32. Adsorption and Host Range (2)
The mode by which animal viruses adsorb to the host cell membrane. (a) An enveloped
coronavirus with prominent spikes. The configuration of the spike has a complementary fit for cell
receptors. The process in which the virus lands on the cell and plugs into receptors is termed docking.
(b) An adenovirus has a naked capsid that adheres to its host cell by nestling surface molecules on its
capsid into the receptors on the host cell’s membrane.
Program PGMIPABI-FKIP Unsyiah
33. Penetration/Uncoating (1)
• Flexible cell membrane is penetrated by the
whole virus or its nucleic acid by:
• endocytosis – entire virus is engulfed and
enclosed in a vacuole or vesicle
• fusion – envelope merges directly with membrane
resulting in nucleocapsid’s entry into cytoplasm
Program PGMIPABI-FKIP Unsyiah
34. Penetration/Uncoating (2)
Two principal means by which animal viruses penetrate. (a) Endocytosis (engulfment) and
uncoating of a herpesvirus. (b) Fusion of the cell membrane with the viral envelope (mumps virus).
Program PGMIPABI-FKIP Unsyiah
36. Replication and Protein Production
• Varies depending on whether the virus is a DNA or RNA
virus
• DNA viruses generally are replicated and assembled in
the nucleus.
• RNA viruses generally are replicated and assembled in
the cytoplasm.
• Positive-sense RNA contain the message for translation.
• Negative-sense RNA must be converted into positive-sense
message.
Program PGMIPABI-FKIP Unsyiah
37. Assembly: Filling the capsid
• Capsid proteins made in cytoplasm
• DNA or RNA gets fills empty capsids
• final modifications to capsid
• to plug any holes from DNA/RNA entry
• to mature the outer proteins
Program PGMIPABI-FKIP Unsyiah
38. Release (1)
• Assembled viruses leave host cell in one of two ways:
• budding – exocytosis; nucleocapsid binds to membrane
which pinches off and sheds the viruses gradually; cell is
not immediately destroyed
• lysis – nonenveloped and complex viruses released when
cell dies and ruptures
• A fully formed, extracellular virus particle that is virulent
(able to establish infection in a host) is called a virion
• Number of viruses released is variable
• 3,000-4,000 released by poxvirus
• >100,000 released by poliovirus
Program PGMIPABI-FKIP Unsyiah
39. Release (2)
Maturation and release of enveloped viruses. As parainfluenza virus is budded off the membrane, it
simultaneously picks up an envelope and spikes.
Program PGMIPABI-FKIP Unsyiah
41. Damage to Host Cell
• Cytopathic effects - virus-induced damage to
cells
1. Changes in size & shape
2. Cytoplasmic inclusion bodies
3. Nuclear inclusion bodies
4. Cells fuse to form multinucleated cells.
5. Cell lysis
6. Alter DNA
7. Transform cells into cancerous cells
Program PGMIPABI-FKIP Unsyiah
42. Persistent Infections (1)
• Persistent infections - cell harbors the virus
and is not immediately lysed
• Can last weeks or host’s lifetime; several can
periodically reactivate – chronic latent state
• measles virus – may remain hidden in brain cells for
many years
• herpes simplex virus – cold sores and genital herpes
• herpes zoster virus – chickenpox and shingles
Program PGMIPABI-FKIP Unsyiah
43. Persistent Infections (2)
• Some animal viruses enter host cell and
permanently alter its genetic material resulting in
cancer – transformation of the cell.
• Transformed cells have increased rate of growth,
alterations in chromosomes, and capacity to divide
for indefinite time periods resulting in tumors.
• Mammalian viruses capable of initiating tumors are
called oncoviruses.
• Papillomavirus – cervical cancer
• Epstein-Barr virus – Burkitt’s lymphoma
Program PGMIPABI-FKIP Unsyiah
44. Multiplication Cycle in
Bacteriophages
• Bacteriophages – bacterial viruses (phages)
• Most widely studied are those that infect Escherichia coli
– complex structure, DNA
• Multiplication goes through similar stages as animal
viruses.
• Only the nucleic acid enters the cytoplasm - uncoating is
not necessary.
• Release is a result of cell lysis induced by viral enzymes
and accumulation of viruses - lytic cycle.
Program PGMIPABI-FKIP Unsyiah
45. 6 Steps in Phage Replication
1. Adsorption – binding of virus to specific molecule on
host cell
2. Penetration –genome enters host cell
3. Replication – viral components produced
4. Assembly - viral components assembled
5. Maturation – completion of viral formation
6. Release – viruses leave cell to infect other cells
Program PGMIPABI-FKIP Unsyiah
48. Penetration & Release of Phage
Penetration of a bacterial cell by a T-even bacteriophage and A weakened bacterial cell, crowded with viruses.
Program PGMIPABI-FKIP Unsyiah
49. Lysogeny: The Silent Virus Infection
• Not all phages complete the lytic cycle.
• Some DNA phages, called temperate phages, undergo
adsorption and penetration but don’t replicate.
• The viral genome inserts into bacterial genome and
becomes an inactive prophage - the cell is not lysed.
• Prophage is retained and copied during normal cell
division resulting in the transfer of temperate phage
genome to all host cell progeny – lysogeny.
• Induction can occur resulting in activation of lysogenic
prophage followed by viral replication and cell lysis.
Program PGMIPABI-FKIP Unsyiah
50. Techniques in Cultivating and
Identifying Animal Viruses (1)
• Obligate intracellular parasites that require
appropriate cells to replicate
• Methods used:
• cell (tissue) cultures – cultured cells grow in sheets
that support viral replication and permit observation for
cytopathic effect
• bird embryos – incubating egg is an ideal system;
virus is injected through the shell
• live animal inoculation – occasionally used when
necessary
Program PGMIPABI-FKIP Unsyiah
51. Techniques in Cultivating and
Identifying Animal Viruses (2)
Cell Culture
Program PGMIPABI-FKIP Unsyiah
52. Techniques in Cultivating and
Identifying Animal Viruses (3)
Cultivating animal viruses in a developing bird embryo
Program PGMIPABI-FKIP Unsyiah
53. Detection of Animal Viral Infections
• More difficult than other agents
• Consider overall clinical picture
• Take appropriate sample
• Infect cell culture – look for characteristic
cytopathic effects
• Screen for parts of the virus
• Screen for immune response to virus
(antibodies)
Program PGMIPABI-FKIP Unsyiah
55. Treatment of viral infections
• The nature of viruses has at times been a major impediment to effective therapy.
• Because viruses are not bacteria, antibiotics aimed at bacterial infections do not
work.
• While there are increasing numbers of antiviral drugs, most of them block
virus replication by targeting the function of host cells. This can cause severe side
effects.
• Antiviral drugs are designed to target one of the steps in the viral life cycle you
learned about earlier in this chapter.
• Azidothymide (AZT), a drug used to treat AIDS, targets the nucleic acid synthesis
stage.
• A newer class of HIV drugs, the protease inhibitors, disrupts the final assembly
phase of the viral life cycle.
• Another compound that shows some potential for treating and preventing viral
infections is a naturally occurring human cell product called interferon
• Vaccines that stimulate immunity are an extremely valuable tool but are
available for only a limited number of viral diseases
Program PGMIPABI-FKIP Unsyiah
56. Important viruses you should know…
• Smallpox (variola major, minor) – complex virus;
inclusions
• Herpesviridae – (herpes; chicken pox – varicella zoster);
chronic latent state reactivated; nuclear inclusions
• HPV – can transform cells; warts cervical cancer
• Hepatovirus (A, B, C)
• SARS – coronavirus (like the virus that causes
bronchitis); prominent spikes on envelope
• influenza – Flu; Type A is the one you’ve had;
• Rotavirus – viral food poisoning; vomiting and diarrhea –
sometimes concurrently!!
• HIV – retrovirus; latency;
Program PGMIPABI-FKIP Unsyiah