virology Flashcards
1
Q
in diagnostic methods, what can we detect?
A
- infectious virus: virus isolation and EM
- protein components: antigens of the virus
- genetic components: DNA or RNA
- host response: antibody or cell responses
2
Q
what are the different methods of diagnosing?
A
- cell culture and electron microscopy
- PCR (detects specific sequences of DNA)
- antibody detection
- antigen detection
- quantification of an antibody/antigen
- serotyping
- quantification of genome (viral load)
- genome sequencing
3
Q
what are the limitations of laboratory tests?
A
- false negative results = sensitivity
- false positive results = specificity
4
Q
define sensitivty
A
tests ability to correctly identify positive sample
5
Q
define specificity
A
tests ability to correctly identify negative samples
6
Q
what are the different types of samples used? what method is used to asses it?
A
- throat swab, NPA, BAL, ET (PCR)
- stools (antigen detection, PCR)
- urine (PCR)
CSF (PCR) - clotted blood (serology - antibody detection)
- EDTA blood (PCR/ viral testing load)
- saliva (serology, PCR)
7
Q
which antibody is a marker of recent infection?
A
- IgM is marker of recent infection
- IgG is created later in host response and lasts longer
- both are created in acute phase of disease
8
Q
what is avidity and what does an antibody avidity test condirm?
A
- avidity: strength with which antibodies bind to a specific antigen
- confirms a positive IgM result
- early on in infection avidity is low but it gets better over a period of months as antibodies mature
9
Q
why is virus isolation in cell culture rarely used?
A
- slow
- time consuming
- still used for phenotypic antiretroviral susceptibiltiy testing
10
Q
what is immunofluorescence used for?
A
- direct detection of viral antigens
- typing and cell culture conformation
- rapid and inexpensive
11
Q
how does PCR work?
A
- carry out 30 cycles usually
- dsDNA is starting block
- denaturing strands by heating
- Taq polymerase elongates chain
- cycles induce exponential expansion
