viral serology (HIV) Flashcards
1
Q
- detects: IgG & IgM to HIV
- window period: 4-12 weeks
- immunochromatographic assays
- can be performed on whole blood, serum, oral fluid
A
rapid tests
2
Q
stages
- 2-10 years after initial infection
- a syndrome of CD4 depletion resulting in opportunistic infections and cancers suggestive of cell-mediated immunity defects
A
final stage
3
Q
hiv genes
p16 (viral assembly and budding)
A
vpu
4
Q
most widely used screening test for HIV antibodies
A
ELISA (indirect)
5
Q
generations
- detects: IgG to HIV-1
- window period: 6-12 weeks
A
1st generation
6
Q
p24 ag & HIV ab
A
established infection
7
Q
HIV screening tests
A
- ELISA
- RAPID TEST (immunochromatographic)
8
Q
p24 without HIV ab
A
acute infection
9
Q
generation
- detects: IgG to HIV-1/2
- window period: 6-12 weeks
A
2nd generation
10
Q
hiv genes
- gp120 (binds to CD4 on T cells)
- gp41 (transmembrane protein associated with gp120)
A
env
11
Q
stages
patient is either asymptomatic or may show lymphadenopathy
A
primary stage
12
Q
hiv genes
- p66 (subunit of reverse transcriptase; degrades original HIV RNA)
- p51 (subunit of reverse transcriptase)
- p31 (integrase: mediates integration of HIV DNA into host genome)
- p10 (protease that cleaves gag precursor)
A
pol
13
Q
first Ab to be detected; persist throughout the infection
A
anti-gp41
14
Q
generation
- detects: IgG & IgM to HIV-1/2
- window period: 3-4 weeks
A
3rd generation
15
Q
marker
- detecable shortly after IgM
- gradual inccrease in titer over several months
- long lasting
A
IgG ab
16
Q
hiv
normal CD4:CD8 ratio (?), in AIDS patients (?)
A
- 2:1
- 0.5:1
17
Q
- detects Ab to HIV
- sensitivity & specificity comparable to western blot
- not frequently used
- expensive, subjective
A
IFA
18
Q
generation
- detects: IgG & IgM to HIV-1/2 & p24 ag
- window period: 2 weeks
- currently not approved for screening blood donors
A
4th generation
19
Q
marker
detecable within days of infection
A
viral RNA
20
Q
CD4 T-CELL COUNT
- HIV infects CD4 cells
- (?)/uL defines AIDS according to CDC
- also used to monitor (?)
- perform every (?) to (?) months
- (?) is the gold standard
A
- <200
- therapy
- 3, 6
- flow cytometry
21
Q
the nine genes of HIV
A
- gag
- env
- pol
- tat
- rev
- nef
- vpu
- vpr
- vif
22
Q
hiv genes
p19 (transports viral mRNA to the cytoplasm of the host cell)
A
rev
23
Q
when HIV replication occurs, the (?) cell is killed
A
CD4
24
Q
stages
- this state is known as the ARC (aids-related complex)
- quantitative T cell deficiencies with inverted CD4:CD8 ratio
A
intermediate stage
25
* detects Ab to HIV
* traditional confirmatory test but not as sensitive as 4th-gen EIA or NAAT
* interpretation is controversial but most labs report pos if at least 2 of the following 3 bands are present (p24, gp42, gp120/160)
* NAAT required following neg or indeterminate results
* time-consuming, difficult to interpret
western blot
26
HIV CONFIRMATORY TESTS
* WB
* IFA
* NAAT
27
# marker
* usually detectable in 2-8 weeks
* transient
* peaks in about 1-2 weeks, undetecable about 1-2 weeks later
IgM ab
28
# marker
* core coat for nucleic acids
* detectable in 2-3 weeks
* becomes undetectable as abs develop, then detectable again in late stages as immune system fails & virus replicates
p24 ag
29
# hiv
Composed of (?) genes encoding (?) structural and (?) regulatory proteins
* 9
* 3
* 6
30
# hiv genes
* p17 (inner surface of envelope)
* p24 (core coat for nucleic acids)
* p9 (core-binding protein)
* p6 (bonds to genomic RNA)
gag
31
three subtypes of HIV-1
* M: clades (A,C,D,H,G,K, F1,F2,J), clade B (homosexual), clade A, C, E (asia and africa)
* N (non-M, non-O)
* O (outlier)
32
# hiv genes
p27 (enhances HIV replication)
nef
33
# hiv genes
p14 (activates transcription of HIV provirus)
tat
34
TEST STAGE AND MONITOR HIV
* viral load
* CD4 T-CELL COUNT
35
# HIV-1 viral load assay
* quantitative (?) to determine plasma HIV RNA
* used to predict disease progression, determine when to start antiretroviral therapy, & monitor response to therapy
* test (?) to (?) weeks after start of therapy & then every (?) to (?) months
* NAAT
* 2, 8
* 3, 4
36
window period of seronegativity (no Ab production)
6-8 weeks
37
* detects: HIV RNA
* window period: 5 days
* not cost effective in screening in most settings
* used for screening blood donors & infants
nucleic acid amplification testing (NAAT)
38
# hive genes
p23 (infectivity factor)
vif
39
* detecs HIV RNA
* qualitative test used for confirmation
NAAT
40
# hiv genes
p15 (integration of HIV DNA into host genome)
vpr
41
subtypes of HIV-2
subtypes A-E
42
most widely used supplementary test for confirming reactive HIV ELISA Ab test
western blot assay
