Structural basis of disease - viruses Flashcards
what happens when the herpes genetic material enters the nucleus and why
circulisation of the linear DNA occurs
it enters a dormant state when circular and then reactivated under stress
what is the function of tegument proteins
regulate production of mRNAs and proteins IE immediate early genes
what is the purpose of tegument proteins for viruses
viruses release tegument proteins to dampen the innate immune response
promotes production of early (E) proteins - replication and late (L) proteins for viral assembly
what are the genomic features of the herpes virus
dsDNA - 120-240kb
linear in acute phase
circular in dormant phase
how does herpes regulate the host immune response
down-regulation of pro-inflammatories
down-regulate MHC-II in infected cells
can infect B-cells and T-cells
what does IFNy response produce
autocrine - inhibition of viral replication/apoptosis
paracrine - up-regulation of MHC-I/NK cell activation
what is dexamethasome
a corticosteroid used in a wide range of conditions (anti-inflammatory/immunosuppressant)
so why does dexamethasome work
because in alot of cases its not the virus itself that kills, its the immune response - such as in herpes
what is the function of protease inhibitors
stops polyprotein chains from forming into a mature viral protein by inhibiting protease
where does protease inhibitors act in covid
at the polyprotein processing stage
basically viruses bring their own proteases with them so they can cleave and modify their polyprotein chains into a mature viral protein
protease inhibitors prevent this
how are monoclonal antibodies such as Sotrovimab used for viruses
recognises and binds to the spike protein that viruses use to attach to cells
prevents viruses from entering the cells
what are examples of cytoplasmic viral structures
coronaviridae - double membrane vesicle where the dsRNA is produced
poxvididae - forms a viruplasm for viral replication and assembly
what is an example of a nuclear viral structure
herpes - form nuclear replication compartments for viral replication and late gene transcription
what are some examples of RNA viruses
measles
mumps
paramyxovirus
features of mumps
infection of the ductal epithelium
leads to parotitis
mumps virus can cross BBB
able to infect ependymal cells
features of paramyxovirus
downregulates the innate immune response by interfering with interferon responses
in a viral genome what is the difference between a positive/negative ssRNA
positive - needs to synthesise its complementary strand for transcription of mRNA
negative - is already complementary to mRNA so can begin transcription without a complementary positive strand
how does influenza enter the cell
1 - attachment
2 - endocytosis
3 - acidification of the endosome
4 - change in pH causes conformational change of haemagluttinin
5 - causes the release of the virus from the endosome via the loss of the envelope
what are the features of haemagluttinin
trimeric membrane protein
binds glycosylated proteins on the surface membranes of the cell
how does the structure of haemagluttinin alter due to a change in pH
after binding of the glycosylated protein
causes a reorientation and exposure of the fusion peptide
this exposure leads to the fusion of the viral membrane and the cell membrane
function of neuraminidase
cell surface membrane on viruse
hydrolyses sialic acid glycosylation
needed to release the virus - otherwise it would just be fused and stuck to the cell membrane
what does haemagluttinin specifically bind to
sialic-acid
which viruses have positive/negative RNA strands
negative - paramyxovirus/orthomyxovirus
positive - coronavirus/HIV
what is unique about the HIV virus
possesses reverse transcriptase
RNA to DNA
