Viral Replication & Pathogenesis Flashcards
Mention the stages of viral replication
- Recognition
- Attachment
- Penetration/Uncoating
- Early expression of viral genes
- Replication of viral nucleic acid
- Synthesis of new viral components
- Assembly and packaging of new virions
- Exit from cell
Which one of the steps of viral replication is an energy-dependent step❓
Penetration
Describe the process of uncoating
Separation of viral nucleic acid from outer structural components
After the process of uncoating, how are viruses released❓
As free n.a eg picornavirus
Nucleocapsid eg reovirus
Naked viruses accumulate in the cytoplasm and are released during lysis
True or false
True
Enveloped viruses are released gradually by budding or exocytosis
True or false
True
List the factors in viral pathogenesis
Virulence of virus Effects of viral infection Entry into host Course of infection Cell tropism Cell damage Host immune response Virus persistence
The course of a viral infection would go as follows…
•Primary replication
Where virus replicates after gaining initial entry into the host
•Systemic spread
Virus many spread via blood stream
•Secondary replication
Takes place at susceptible tissues following systemic spread
Viral virulence depend on what factors❓
Dose
Virus strain
Inoculation route
Host factors
Viral affinity for specific body tissues is determined by❓
Cell receptors for virus
Ability of cell to support viral replication
Physical barriers
Temperature, pH, oxygen tension
Digestive enzymes and bile
Retroviruses do not generally cause cell death. Why❓
They are released from the cell by budding rather than by cell lysis and cause persistent infections
Mention a few viruses that cause lysis and death of the cells in which they replicate
Picornavirus
Rhinovirus (fever, ⬆️mucus secretion)
Poliovirus (paralysis or death due to respiratory failure)
Immune response to a virus has the greatest impact on the outcome of infection
True or false
True
Cellular immunity plays the major role in clearing virus infection whereas humoral immunity protects against reinfection
True or false
True
Enhanced viral injury could be due to what mechanisms❓
⬆️secondary response to Tc cells eg HBV
Complement mediated cell lysis
Binding of unneutralized virus complexes to cell-surface Fc receptors, thus ⬆️no of affected cells eg Dengue haemorrhagic fever, HIV
Immune complex deposition in organs eg rash of rubella and measles
What are the two types of chronic persistent infections❓
- True latency-
•Complete latency after infection eg HSV, VSV
•Genome maybe integrated into cellular genome or exist as episome - Persistence-
•replication is continuous at a very low level eg HIV, HBV, CMV, EBV
What are the mechanisms of viral persistence❓
Antigenic variation
Immune tolerance due to genetics, pre-natal infection, molecular mimicry
Restricted gene expression
⬇️regulation of MCH1
🚫recognition of infected cells
Eg adenovirus
⬇️regulation of molecules involved in immune recognition eg LFA-3 and ICAM-1 by EBV
Infection of immunopriviliged sites within the body eg HSV in sensory ganglia in the CNS
Direct infection of cells of immune system itself eg Herpes virus and HIV
Which virus causes a down regulation of LFA-3 and ICAM-1❓
EBV
Which virus causes a direct infection of cells of immune system itself❓
Herpes virus
HIV
Adenovirus causes a ⬇️regulation of MHC_2
True or false
False, MHC_1
How would
- DNA genomes undergo replication❓
- +ssRNA genomes undergo replication❓
- -ssRNA genomes undergo replication❓
- Similar to cellular replication; transcription, translation
- Either translation/reverse transcribed to DNA first
- Used as template to make +ssRNA first, then continues like no.3
HSV causes an infection of immunopriviliged sites (CNS) in the body
True or false
True
