Viruses Flashcards
Nucelocapsid
Genetic material and structural proteins
3 types of capsid symmetry
Helical/tubular
Icosahedral
Complex
Properties of naked vs enveloped virsuses
Naked: environmentally stable, spread easily, can survive gut/drying/detergents
Enveloped: environmentally labile, must stay wet, cannot survive GI tract
How do naked vs enveloped viruses leave a cell?
Naked: cell lysis
Enveloped: budding and cell lysis
7 general steps of viral replication
Adsorption (attachment) Entry Uncoating Transcription Synthesis of virus components Assembly Release
Tropism
The interaction between specific proteins on a viral surface and specific receptors on a target cell membrane
2 mechanisms of viral entry
Endocytosis
Fusion of virus envelope with cell membrane
Synthesis of new DNA viruses
Replication of DNA in host cell nucleus mediated by viral enzymes
Capsid and other proteins synthesized in cytoplasm using host cell enzymes
How are + sense RNA transcribed differently from - sense RNA
+: acts as mRNA, viral proteins are made immediately in cytoplasm by viral enzymes
-: first makes a + sense RNA copy via viral enzymes
Reverse transcriptase
HIV
Converts + sense viral RNA to cDNA, which is then integrated into host cell chromosome
Host cell enzymes make the mRNA from viral DNA
3 types of persistent viral infections and an example of each
- Chronic carrier (Hep B)
- Latent infection (herpesviridae)
- Slow virus infections (Measles virus-Rubeola, due to prolonged incubation period)
Horizontal transmission examples
Direct contact Respiratory Fomites Insect vector Zoonoses
Potential sites of action for antiviral agents
Attachment to the host cell Uncoating of the viral genome Genome replication Assembly of progeny virions Release of virus particles from the host cell
How does HIV enter the cell?
Binds to CD4
Rolls and binds to co-receptor (CCR5 or CXCR4)
Virus cell fusion occurs
2 general ways to prevent viral attachment
Agents that mimic the virus attachment protein and bind to cellular receptors
Agents that mimic the receptor and bind to the viral proteins