Classification Of Virus[Summary]
Upcoming SlideShare
Loading in...5
×
 

Classification Of Virus[Summary]

on

  • 2,790 views

 

Statistics

Views

Total Views
2,790
Views on SlideShare
2,782
Embed Views
8

Actions

Likes
4
Downloads
209
Comments
0

5 Embeds 8

http://freelivedoctor.com 3
http://sweetppl.com 2
http://www.slideshare.net 1
http://blackboard.cpsb.org 1
http://eleap.ust.edu.ph 1

Accessibility

Categories

Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

Classification Of Virus[Summary] Classification Of Virus[Summary] Presentation Transcript

  • Basic virus structure Capsid protein Nucleocapsid Naked capsid virus = + Nucleocapsid Lipid membrane, glycoproteins Enveloped virus + www.freelivedoctor.com DNA RNA or
  • Properties of enveloped viruses
    • Envelope is sensitive to
      • Drying
      • Heat
      • Detergents
      • Acid
    • Consequences
      • Must stay wet during transmission
      • Transmission in large droplets and secretions
      • Cannot survive in the gastrointestinal tract
      • Do not need to kill cells in order to spread
      • May require both a humoral and a cellular immune response
    Adapted from Murray, P.R. Rosenthal K.S., Pfaller, M.A. (2005) Medical Microbiology, 5 th edition, Elsevier Mosby, Philadelphia, PA Box 6-5 www.freelivedoctor.com
  • Properties of naked capsid viruses
    • Capsid is resistant to
      • Drying
      • Heat
      • Detergents
      • Acids
      • Proteases
    • Consequences
      • Can survive in the gastrointestinal tract
      • Retain infectivity on drying
      • Survive well on environmental surfaces
      • Spread easily via fomites
      • Must kill host cells for release of mature virus particles
      • Humoral antibody response may be sufficient to neutralize infection
    Adapted from Murray, P.R. Rosenthal K.S., Pfaller, M.A. (2005) Medical Microbiology, 5 th edition, Elsevier Mosby, Philadelphia, PA , Box 6-4 www.freelivedoctor.com
  • Classification of Human Viruses www.freelivedoctor.com
  • Variations on the replication theme www.freelivedoctor.com
  • Summary: structure, classification & replication
    • Structure
      • Nucleic acid in a protein shell, +/- lipid envelope
      • Structure impacts on biological properties
    • Classification
      • Many virus families, organized by structure and biology
    • Replication
      • Generic scheme
      • Varying strategies depending on nucleic acid
    www.freelivedoctor.com
  • Summary: laboratory virology
    • 4 main clinical diagnostic techniques
      • Culture, serology, antigen detection, nucleic acid detection
    • Virus culture
      • Cultured cell types
      • Cytopathic effect
      • Not all viruses can be cultured
    • Virus quantitation
      • Biological
      • Physical
    • Basic serological techniques
    www.freelivedoctor.com
  • Cycle of infection Secondary sites Spread Entry Shedding Shedding Local Lymphatic Neuronal Blood (viremia) Primary site www.freelivedoctor.com
  • Time course of infection; host response infection without spread: infection with spread: host response: www.freelivedoctor.com 0 2 4 6 8 10 12 time (days)
  • Patterns of disease www.freelivedoctor.com
  • Summary: Pathogenesis & Genetics
    • Cycle of infection
    • Effects on cells
      • Abortive, lytic, persistent, latent, transforming infections
    • Effects on the organism
    • Genetics
      • Mutation, genotype, phenotype, reversion, recombination
    www.freelivedoctor.com
  • For each virus, know:
    • Structure (cheat sheet)
    • Pathogenesis
      • transmission/entry/shedding
      • replication
      • spread
      • immune response/counter response
      • damage/disease mechanism
    • Diagnosis
    • Treatment/prevention
      • drugs
      • vaccines
    www.freelivedoctor.com
  • Human papillomavirus
    • Structure
      • Small (8 kb) circular dsDNA genome, naked capsid
    • Pathogenesis
      • transmission by direct contact or sexual; skin, mucosa
      • replication in nucleus of basal cells of epithelium; very host dependent; coupled to epithelial differentiation
      • no spread
      • primarily cellular immune response
      • transforming infection; warts are tumors; cervical carcinoma
    • Diagnosis
      • cytology (PAP smear; koilocytosis)
      • immunohistochemistry
      • nucleic acid
    • Prevention/treatment
      • recombinant subunit (VLP) vaccine
      • PAP smear
      • surgery
    www.freelivedoctor.com
  • Parvovirus
    • Structure
      • Small (5 kb) linear ssDNA genome, naked capsid
    • Pathogenesis
      • respiratory transmission
      • replication in nucleus, very host dependent, needs S phase cells or helper virus
      • viremia
      • antibody important in immunity
      • targets erythroid lineage cells; fifth disease (symptoms immunological); transient aplastic crisis; hydrops fetalis
    • Diagnosis
      • serology, viral nucleic acid
    • Treatment/prevention
      • none
    www.freelivedoctor.com
  • Polyomavirus
    • Structure
      • Small (5 kb) circular dsDNA genome, naked capsid
    • Pathogenesis
      • respiratory transmission
      • replication in nucleus; very host dependent
      • viremia
      • persistence in kidneys; reactivation with immune compromise
      • inapparent infection; hemorrhagic cystitis; PML
    • Diagnosis
      • viral nucleic acid
    • Treatment/prevention
      • cidofovir ?
    www.freelivedoctor.com
  • Adenovirus
    • Structure
      • Medium sized (36 kb) dsDNA genome, naked capsid
    • Pathogenesis
      • respiratory or fecal oral transmission
      • replication in nucleus; moderately host dependent
      • local spread; viremia
      • cellular and humoral immunity important; virus encodes countermeasures against MHC I expression and apoptosis
      • direct cell damage from replication; respiratory illness, conjunctivitis, gastroenteritis, cystitis
    • Diagnosis
      • culture, viral antigen detection
    • Treatment/prevention
      • live military vaccine
    www.freelivedoctor.com
  • Influenza
    • Structure
      • Negative sense segmented ssRNA genome, helical nucleocapsid, enveloped
    • Pathogenesis
      • respiratory transmission
      • replication in nucleus; budding
      • no spread (usually)
      • innate and antibody response important; antigenic shift and drift
      • local symptoms from cell killing; systemic symptoms from immune response; exaggerated disease in young and elderly; viral and bacterial pneumonia complications
    • Diagnosis
      • culture, hemadsorbtion, viral antigen detection
    • Treatment/prevention
      • amantidine and rimantidine target matrix; zanamivir and oseltamivir target NA
      • killed and live vaccines need constant updating
    www.freelivedoctor.com
  • Paramyxoviruses
    • Structure
      • Negative sense ssRNA genome, helical nucleocapsid, envelope with attachment protein and F protein
    • Pathogenesis
      • Transmission in respiratory droplets and fusion of virus envelope via F protein with plasma membrane of cells in the respiratory tract
      • Replication in cytoplasm, budding
      • Viremia except for RSV and PIV
      • Innate and antibody response important; many symptoms from immune response: rash in measles and swelling in mumps; PIV bronchitis and croup; RSV bronchiolitis and pneumonia in infants
      • Sequelae in CNS for measles and mumps
    • Diagnosis
      • Serology or nucleic acid
      • Measles: Koplik spots; mumps: swelling of parotid gland
    • Treatment/prevention
      • MMR live attenuated viral vaccine for measles and mumps, none for RSV or PIV
    www.freelivedoctor.com
    • Structure
      • Negative sense ssRNA, helical nucleocapsid, envelope
    • Pathogenesis
      • Transmitted by bite of rabid animal
      • Replication in cytoplasm; budding
      • Spread by axonal transport to brain; long incubation period
      • Fever, nausea, hydrophobia, coma
      • Almost always fatal
    • Diagnosis
      • Viral antigen or nucleic acid, Negri bodies
    • Treatment/prevention
      • Inactivated viral vaccine for humans after exposure, live virus vaccine for animals
    Rabies www.freelivedoctor.com
  • Rotavirus
    • Structure
      • Naked double shell capsid
      • 11 segment double stranded RNA genome
    • Pathogenesis
      • Fecal oral transmission
      • Replication in cytoplasm
      • Fever, vomiting, diarrhea in infants and young children
      • Incubation period less than 48 hr, highly infectious
      • Infection of intestinal epithelium causes loss of electrolytes and prevents readsorption of water
      • Long term immunity; asymptomatic infection in adults
    • Diagnosis
      • viral antigen detection
    • Treatment/prevention
      • RotaTeq live, oral vaccine
    www.freelivedoctor.com
  • Summary www.freelivedoctor.com
  • Paramyxoviruses
    • Structure
      • Negative sense ssRNA genome, helical nucleocapsid, envelope with attachment protein and F protein
    • Pathogenesis
      • Transmission in respiratory droplets and fusion of virus envelope via F protein with plasma membrane of cells in the respiratory tract
      • Replication in cytoplasm, budding
      • Viremia except for RSV and PIV
      • innate and antibody response important; many symptoms from immune response: rash in measles and swelling in mumps; PIV bronchitis and croup; RSV bronchiolitis and pneumonia in infants
      • Sequelae in CNS for measles and mumps
    • Diagnosis – serology or nucleic acid
      • Measles Koplik spots; mumps swelling of parotid gland
    • Treatment/prevention
      • MMR live attenuated viral vaccine for measles and mumps, none for RSV or PIV
    www.freelivedoctor.com
  • Rabies
    • Structure
      • Negative sense ssRNA, helical nucleocapsid, envelope
    • Pathogenesis
      • Transmitted by bite of rabid animal
      • replication in cytoplasm; budding
      • Spread by axonal transport to brain; long incubation period
      • Fever, nausea, hydrophobia, coma
      • Almost always fatal
    • Diagnosis
      • Viral antigen or nucleic acid, Negri bodies
    • Treatment/prevention
      • Inactivated viral vaccine for humans after exposure, live virus vaccine for animals
    www.freelivedoctor.com
  • Time course of Rabies infections www.freelivedoctor.com
  • Rotavirus
    • Structure
      • Double stranded, 11 segment RNA genome, two protein coats
    • Pathogenesis
      • Fecal oral transmission
      • replication in cytoplasm
      • Epidemic diarrhea in infants and young children- fever, vomiting, diarrhea
      • Incubation period less than 48 hr, highly infectious
      • Infection of intestinal epithelium causes loss of electrolytes and prevents re-adsorption of water
    • Diagnosis
      • culture, viral antigen detection
    • Treatment/prevention
      • RotaTeq live, oral vaccine
    www.freelivedoctor.com
  • Enteroviruses
    • Structure
      • Positive sense ssRNA genome, protein coat
    • Pathogenesis
      • Fecal oral transmission
      • replication in cytoplasm
      • Viremia to diverse target tissues. Viruses very cytopathic, killing cells they infect
      • Infections often asymptomatic; polio causes paralytic poliomyelitis; rhinoviruses restricted to upper respiratory tract, common cold; caliciviruses diarrhea
    • Diagnosis
      • Serology and nucleic acid
    • Treatment/prevention
      • Only polio vaccines, Salk and Sabin
    www.freelivedoctor.com
  • www.freelivedoctor.com
  • Arboviruses
    • Structure
      • Positive sense ssRNA genome, icosahedral nucleocapsid, enveloped
    • Pathogenesis
      • Transmitted by bite of insect from host species; sylvan and urban cycles
      • replication in cytoplasm; budding
      • Viremia to target tissue
      • Influenza-like initial symptoms; different viruses cause encephalitis, hemorrhagic fever, hepatitis, rash, arthritis
    • Diagnosis
      • Serology and nucleic acid
    • Treatment/prevention
      • No human vaccines, except yellow fever virus live attenuated vaccine, control of insect population
    www.freelivedoctor.com
  • Arboviruses: Vectors, Hosts, and Diseases www.freelivedoctor.com
  • Rubella virus
    • Structure
      • Positive sense ssRNA genome, helical nucleocapsid, enveloped
    • Pathogenesis
      • respiratory transmission
      • replication in cytoplasm; budding
      • Viremia
      • Mild rash in adults; congenital rubella syndrome (CRS) after infection in first trimester when virus passes the placenta and infects fetus
      • CRS- deafness, blindness, mental retardation
    • Diagnosis
      • Nucleic acid, viral antigen detection
    • Treatment/prevention
      • MMR live attenuated virus vaccine
    www.freelivedoctor.com
  • RNA Hepatitis Viruses
    • Structure
    • Various different families for HAV, HCV, HEV, HGV all positive sense ssRNA
    • Pathogenesis
    • HAV and HEV fecal oral then viremia; others sexual and blood borne, viremia
    • Liver is target organ; most infections are subclinical, acute infections differ in onset and severity.
    • HAV and HEV cause hepatitis with no carrier state; others cause hepatitis with chronic infection and possible carcinoma
    • Liver damage due to cell mediated immune response
    • Diagnosis
    • viral antigen detection, nucleic acid
    • Treatment/prevention
    • HAV killed virus vaccine; HCV alpha-interferon effective for some serotypes
    www.freelivedoctor.com
  • HGV Flavi ///////////hepe www.freelivedoctor.com
  • Hepatitis B Virus
    • Structure
      • Small (3.2 kb) circular partially dsDNA genome, envel. capsid
    • Pathogenesis
      • Sexual, parenteral, and perinatal transmission
      • Replication via an RNA intermediate (reverse transcriptase)
      • Tropism for liver
      • Acute vs. chronic infections occur: highly age dependent
      • Chronic infections are a major cause of PHC
    • Diagnosis
      • Multiple serological components (viral proteins and anti-bodies)
    • Treatment/prevention
      • Subunit vaccine (based on HBsAg)
    www.freelivedoctor.com
  • Hepatitis B virus www.freelivedoctor.com
  • Immunological events of acute vs. chronic HBV infection From Murray et. al., Medical Microbiology 5 th edition, 2005, Chapter 66, published by Mosby Philadelphia,, A) Acute B) Chronic www.freelivedoctor.com
  • Clinical interpretation of the Hepatitis B antigen panel www.freelivedoctor.com
  • Hepatitis D Virus
    • Structure
      • Very Small (1.7 kb) circular ssRNA genome, envel. capsid
    • Pathogenesis
      • Sexual, parenteral, and perinatal transmission
      • Replication by RNA-directed RNA Pol (Host RNA Pol II)
      • Requires concurrent HBV infection (needs it for HBsAg)
      • HDV greatly exacerbates liver damage caused by HDV
      • Chronic infections are a major cause of PHC
    • Diagnosis
      • Serologically for HDV delta antigen
    • Treatment/prevention
      • Subunit vaccine for HBV prevents productive infection
    www.freelivedoctor.com
  • HIV
    • Structure
      • 9.0 kb diploid ssRNA genome, envel. capsid
    • Pathogenesis
      • Sexual, parenteral, and perinatal transmission
      • Replication by cDNA intermediate (reverse transcriptase)
      • Replication cycle requires the DNA intermediate to integrate
      • HIV establishes a persistent infection that ultimately reduces CD4 helper T cell population
      • During course of infection, tropism shift from M-tropic to T-tropic
    • Diagnosis
      • Serologically for antibodies against HIV antigens (gp120)
    • Treatment/prevention
      • Antivirals (HAART)
    www.freelivedoctor.com
  • HIV-1 Replication Cycle CCR5 CD4 CXCR4 Reverse Transcriptase Integrase Protease Beth D. Jamieson, Ph.D. www.freelivedoctor.com Reverse Transcription Integration Uncoating Assembly Budding Attachment Maturation
  • Natural Course of HIV-1 Infection www.freelivedoctor.com
  • Herpesviruses Herpes simplex I & II (cold sores, genital herpes) Varicella zoster (chicken pox, shingles) Cytomegalovirus (microcephaly, infectious mono) Epstein-Barr virus (mononucleosis, Burkitt’s lymphoma) Human herpesvirus 6 & 7 (Roseola) Human herpesvirus 8 (Kaposi’s sarcoma) www.freelivedoctor.com
  • Virus Subfamily Disease Site of Latency Herpes Simplex Virus I  Orofacial lesions Sensory Nerve Ganglia Herpes Simplex Virus II  Genital lesions Sensory Nerve Ganglia Varicella Zoster Virus  Chicken Pox Sensory Nerve Ganglia Recurs as Shingles Cytomegalovirus  Microcephaly/Mono Lymphocytes Human Herpesvirus 6  Roseola Infantum CD4 T cells Human Herpesvirus 7  Roseola Infantum CD4T cells Epstein-Barr Virus  Infectious Mono B lymphocytes, salivary Human Herpesvirus 8  Kaposi’s Sarcoma Kaposi’s Sarcoma Tissue Human Herpesviruses www.freelivedoctor.com
  • A study of HSV-2 recurrence in women www.freelivedoctor.com
  • www.freelivedoctor.com
  • Vaccines – live or killed ? www.freelivedoctor.com
  • FDA approved antiviral drugs www.freelivedoctor.com
  • Non-equilibrium human virus
          • 1. Virus has a stable relationship with an animal host.
          • 2. Virus can be strikingly lethal since it hasn’t evolved to coexist with humans.
          • 3. Virus will be in genetic flux until it reaches equilibrium or human infection chain is broken.
    • 4 . HIV, Ebola virus, Hantavirus and Influenza virus are examples
    www.freelivedoctor.com