lecture 3 Flashcards
Where are the VAP on naked and enveloped viruses
naked: on the capsid
enveloped: glycoproteins on the envelope
What is Tropism?
ability of a virus to productively infect a cell
How do naked viruses penetrate a host?
usually endocytosis, but maybe by poking a hole in the capsid to release the genome, could release lytic protein to disrupt host membrane
How do enveloped viruses penetrate a host?
membrane fusion, endocytosis or fusing with an endocytic vessicle
What is the maturation phase of virus replication?
when virus becomes infectious, can occur in host or after release, may be blocked by viral proteases
How are viruses propagated?
Because they are obligate intracellular parasites, they must be cultured with live cells (either animals, tissue culture, embryos)
What is the cytopathic effect?
a change or abnormality in microscopic appearance of cultured cells due to virus infection
What causes the cytopathic effect?
interactions between virus and cell, can be caused In any stage
What can the cytopathic effect cause?
multi nucleation, cell death, cell fusion, cancerous cell growth
When does a plaque form?
when virus kills cells
What is PFU?
plaque forming units, ability of a particle to form a plaque in cell culture, one virus particle= one plaque
Why might some viruses not form plaques?
mutations that prevent replication, VAP destroyed, partial genome
What does PCR test for?
can measure the number of particles by determining the viral nucleic acid count. It is sensitive and rapid but does not measure PFU, only virus number
What is an antigen test?
use antibodies specific to viral protein to probe for presence of viral protein
what is serology?
test serum for presence of antibodies to virus, does not differentiate between recent and old infections
