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Virus and its classification
- 1. Dr. J. B. Kathiriya
- 12. THE BALTIMORE CLASSIFICATION OF VIRUSES Animal viruses are classified in the following 7 groups according to relationship between virion, nucleic acid & mRNA transcription : Group1. ds DNA viruses Group2. ss DNA viruses Group3. ds RNAviruses Group4. (+) sense ss RNAviruses Group5. (-) sense ss RNAviruses Group6. ss RNA reverse transcribing viruses Group7. ds DNA reverse transcribingviruses
- 15. Group1. ds DNA viruses:the mRNA is synthesized on a ds DNA genome template.following are eg. Of some viruses 1. adenoviruses 2.herpes virus 3. papovavirus 4. poxvirus
- 16. 1. Adenoviruses •virions are naked , non enveloped. 90-100 nm diameter & have icosahedral symmetry. •The penton fiberswith a globular head are involved in the process of attachment of the virus to the hostcell. •Hexons consists of protein II with a central core, invoved in the stabilization & assembly of particles.
- 17. Diseases caused by adenoviruses are : 1. respiratory disease 2.conjunctival pneumonia 3.acute hemorrhagic cyctitis 4.acute gastroenteritis
- 18. 2.Herpes virus •The nucleocapsid is spherical icosahedral &100 nm in diameter , enclosed in glycoprotein lipid envelop. •Glycoprotein are visible as “spikes” that are projected from thesurface. •The nucleic acid is linear ds DNA which is converted intoa circular DNA molecule upon slight digestion. •Disease caused by herpesvirus : herpes simplex I ( cold sores), herpes simplex II (genitalsores) & varicellovirus (chickenpox. Shingles) .
- 19. 3. Papovavirus •Capsid is of 45-55 nm diameter, naked , icosahedral, virion consists of DNA & protein. capsid is made up of 72 capsomers. •Virus enter the cell & migrates to thenucleus forreplication. •Disease: •Papilomavirus (cervical cancer,human warts) •Polyomavirus (cause tumor in mice)
- 20. 4. poxvirus •Poxvirus are brick shaped (240- 300nm),dsDNAgenome (130-260kb) & naturally associated withenzyme •Virions are enveloped . Viral multiplication is started by viral transcriptase, the viral components are synthesized & assemble in the cytoplasm of the hostcell. •Pathogenesis: •Human monkey pox •Smallpox (variolavirus)
- 21. Grpoup 2. ssDNA virus: parvovirus •Parvovirus are linear, average genome sizeof 5000 nucleotide, smallest virus with 18- 28 nm diameter. •Viral capsid s madeup of 2-4 protein form naked icosahedral structure. •Diseases: •Human parvovirusB19 •Erythema infectiosum •Joint diseasesyndrome
- 22. Group3. (+) ss RNA virus:1. corona virus •Corona virus are enveloped, helical & 60- 200 nm diameter.genomes size are 16-21kb. •it replicates inthe cytoplasm. •Diseases : •Respiratorysyndrome •Severe acute respiratory syndrome
- 23. 2.Picorna virus Virions naked ,icosahedral. Capsid is composed of 60 copies of 4 structiural protein . Viral genome are linear 7.1-8.9 kb size Diseases: poliovirus (polio) Rihinovirus( common cold) Hepatitis Avirus (hepatitis A)
- 24. 3.Togavirus •Envelop consists of 80 trimer spikes . The spikes consists of glycoprotein that help in attachment protein to receptor of host cell membrane. •Eg. Alphavirus •Eastern equine encephalitisvirus •Yellow fevervirus •Rubellavirus
- 25. Group 4. (-) ssRNA viruses 1.Rhabdovirus Envelop with spikes made upof gly coprotein linked matrix protein contain nucleocapsid Eg. Mumps virus , Rabies virus
- 27. Group 5. ds RNA virus :eg. reovirus Group6. ss RNA RT virus :eg.reterovirus Group 7. ds DNA RT virus: eg Hepadna virus.