Viral multiplication

• 1. Viruses are obligate intracellularparasites They can only replicate in living cells.

2. Viral Multiplication Cycle 1) Adsorption 2) Entry 3) Uncoating 4) Component production 5) Assembly 6) release 3. 1)ADSORPTION requires viral attachment protein cellular receptors specie specific. some neutralizing antibodies are specificfor the attachment proteins4 4. 2)Penetration (enveloped viruses) Either Fusion with plasma membrane or Entry via endosomes, fusion with acidic endosome membrane 5. 2)Penetrationherpes viruses, paramyxo viruses, HIV 6 6. 7 7. 2)Penetration (Enveloped Viruses)8 8. 2)Penetration (non enveloped) Only viaendosomes (endocytosis or viropexis) 9. 10 10. 3)Uncoating & eclipse release of viral genome Viral particle can no more bedetected. 11. 4)Synthesis of Viral Nucleic Acid and Protein Nucleic acid may be made in thenucleus or the cytoplasm Protein synthesis is always in the cytoplasm Latent viruses. 12 12. Transcription/Translation/Synthes is: DNA viruses: replicate their DNA in host cell nucleus. Exception - Poxviruses synthesize capsid and other proteins in cytoplasm 13. Transcription, translation and synthesis: RNA viruses: Most RNA viruses replicate in the cytoplasm Few exceptions e.g. Influenza virus, retroviruses. 14. 5)Assembly: Takes place in cell nucleus, cytoplasm or (with most enveloped viruses) at the plasma membrane 15. 6)Release Either Lysis Or Budding through plasma membrane16 16. Virus replication: general 17. 1,000 100,000 viruses/cell, 5 24 hours 18. Adsorption (attachment) EntryReplicationLatencyRelease