24/25: more virus Flashcards
What are the types of flu? Which cause epidemics?
four types: A,B,C,D
A and B: seasonal epidemics, most common
C and D: cause mild disease but no epidemic
What are the components of the influenza particle?
RDrp head, NP monomer, viral RNA, NP loop
no capside, each segment coated with NP
How does flu virus entry work?
1.HA binds to silica acid containing proteins on the cell surface
- HA binds silica acid containing Ca2+ channel to rigger intracellular Ca2+ oscillation
2. virus endocytosed
3. endoscope acidification, decrease pH, lead to conformtational change in HA proteins
4. membrane fusion
5. allows escape of viral RNA and proteins into cytoplasm
What is haemaglutanin(H)?
trimeric protein that binds to receptors in the respiratory tract, H1-3 have caused pandemics
What is neuraminidase(N)?
tetramer that is critical for the release of virions from injected cells
What is antigenic drift?
accumulations of point mutations or deletions in H and N genes
- results in viruses that are not well inhibited by antibodies by previous strains
- easier spread through partially immune population
seasonal epidemics: drift in H and N
What is antigenic shift?
recipe for pandemic
1. generation of a new flu virus to which the population has little immunity
-> caused by major mutational changed or reassortment of chromosomes
2. virus acquires ability to replicate in humans and cause disease
3. efficient and sustained transmission
What is a retrovirus?
Does reverse transcriptase to go from DNA->RNA
genome includes long terminal repeats, gag gene, RT and Integrate genes, env genes
What is the life cycle of HIV
HIV fuses to cell
cell contents integrated into host
viral DNA is formed by RT
viral DNA is transported and cross into host
viral RNA is used to make genomic RNA
mature virus is lysed and released by protease
what is the HIV virus transactivator?
Tat, activates transcription
What is the HIV binding sit for Tat?
TAR, binds nascent viral RNA, forms hair loop that blocks elongation
Why can’t we clear HIV?
viruses stay ahead of immune response and can form quasispecies
What is Spike protein?
trimeric protein with S1 receptor binding domain thats critical to Ab neutralization
RNA genes of a retrovirus
gag(matrix, capsid, nc)
pol gene (RT and integrase)
env(glycoprotein and transmembrane polyprotein)
Keep part of influence virus replication
cap snatching
