Immuno - Anti-viral agents Flashcards
(26 cards)
Definition of viruses
Obligate infectious intracellular parasites
What is a tegument and give an example of a virus with such structure?
Proteins in coat encapsulated with an envelope which surround the capsid of the virus
Herpes virus
Why do RNA and retroviruses have a higher mutation rate?
Lack of proof-reading capacity
They use own polymerase to replicate (reverse transcriptase)
Why are RNA viruses smaller than DNA viruses?
Inherent instability of RNA limits size
How do smaller viruses utilize their genetic material more efficiently?
Overlapping reading frames
What do DNA viruses have that RNA viruses can’t have due to size?
Accessory genes
What are accessory genes?
Genes that modify the immune response of the host cell and are often lost in passage in cultures because are not utilized
What is a rapid form of evolution for viruses and what is required for them to do that?
Recombination when two different viruses infect the same cell
Need to have segmented genome like the human one
E.g. - influenza has 8 segments and rotavirus - 2
Describe the replication of HIV
HIV spike protein Gp120 binds to cell surface CD4 receptor => T helper cell specific
Virus further interacts with second co-receptor CCR5 or CXCR4 depending on whether it’s a macrophage or a T-cell
integrase splices the reverse transcribed viral DNA into host
Genome of influenza virus
8 segment or negative sense RNA
How does influenza replicate?
RNA dependent RNA polymerase in nucleus replicates them into mRNAs and new genomes
exponential viral culture
What is the cytopathic effect?
Virus lysing the cell due to shut down of host protein synthesis or due to accumulation of viral proteins
How can you detect a viral infection using monolayers?
Plaques are formed and you can use a plaque assay to determine how many virions are in a particular preparation
What is a syncitium
Viruses with surface proteins that can fuse at neutral pH often fuse cells together
What does electron microscopy or haemagglutination assay detect?
Presence of viral particles
When can you look at the serum (serology) for the presence of virus?
2-3 weeks later when the person has seroconverted (made an immune response to the virus)
What is serology useful for?
Counting how many people have been infected during an outbreak and how many people have some level of immunity
What does aetiology mean?
Cause or origin of the disease
What is a therapeutic index?
How much drug you have to use to control virus and how much drug makes a person feel ill from side effects because it affects the host function
What is key to improving the therapeutic index?
Selectivity and specificity => find things that the virus does that the host cell doesn’t
Why do we strive to an acceptable therapeutic index?
Difficult to distinguish between virus replicative mechanisms and host
What does understanding the structure of viral components and enzymes lead to?
Rational drug design
What is important to consider in nucleoside analogues?
They need a certain level of specificity to viral polymerase so they don’t interfere with human cell replication
When are DAAs used?
Usually possible to act on one virus because they target specific viral factors => need for accurate diagnosis
