Flashcards in HIV Deck (76)
What type of cells are the target of HIV infection?
T cells with CD-4 and CCR5 receptors, macrophages/monocytes
How does HIV utilize a cells machinery to replicate?
After binding CD4 or CCR5 receptors on a cell surface, viral RNA is transcribed into DNA using the cell’s reverse transcriptase. The DNA is then integrated into the infected cell’s genome.
Pathophysiology of HIV
HIV primarily infects T lymphocytes that express the CD4 antigen, resulting in a progressive loss of these cells and impairment of cellular immunity as well as humoral immunity. When CD4 lymphocytes are sufficiently depleted there is the progression to AIDS, characterized by the development of opportunistic infections and malignancies.
How rapidly does HIV replicate?
Infected CD4 population doubles every 15 days.
While HIV1 is the most common strain of HIV seen in the US, where is HIV2 most commonly seen?
How does HIV2 differ from HIV1?
HIV2 is less virulent but more indolent, with decreased transmission rates
How quickly can HIV be detected after a primary infection?
How common are symptoms during the acute phase?
40-90% have symptoms within 2w of exposure
What are the primary symptoms with acute HIV?
Fever, LAD, pharyngitis, rash, and myalgias/arthralgias
Following the acute infection, what is the typical latency period before symptoms develop?
What is the typical rate of CD4 drop/year during the latency period?
Diagnosis of HIV
Screening ELISA is positive and is followed by a confirmatory positive Western blot.
When is rapid testing for HIV indicated?
Previously untested women presenting in labor, or those expected to be delivered for maternal or fetal indications before results of conventional testing can be obtained.
Sensitivity & specificity, PPV of rapid HIV testing
The sensitivity and specificity of each of the available rapid testing assays ranges from 95% to 100%, while the positive predictive value depends on the prevalence of disease in the population. In a population with low prevalence of disease, the positive predictive value is low while the false- positive rate is high. For example, with a prevalence of disease of *1% in the population, the positive predictive value of the test may be as low as 60%.
What should be done if a rapid HIV test is positive?
ARV prophylaxis should be offered without waiting for the results of the confirmatory conventional tests.
How does viral load affect transmission rates?
27% with VL >100,000, <20
Diagnosis of AIDS
Regardless of symptoms, a CD4 <200 cells/mm3 or the presence of an AIDS-defining illness in an HIV-positive person is an AIDS diagnosis.
What is the recommended approach to HIV screening in pregnancy? Opt-in or opt-out?
An opt-out approach has been shown to increase acceptance rates for HIV testing in pregnant women and is the recommended approach to universal prenatal screening.
After initial prenatal testing for HIV, who should have a repeat test? When?
28-32 wksHigh-risk behaviorHigh-prevalence areaPreviously declined testing
Risk factors for perinatal HIV transmission
Closely related to viral load at the time of delivery. Other risk factors: Low CD4+ T-lymphocyte countLack of ARV therapyBiologic phenotype of the virusSubstance abuseProlonged duration of membrane ruptureHCV coinfectionSexually transmitted infections (STIs)Preterm birthChorioamnionitis
Fetal complications of HIV
Possible increased risk of preterm delivery if on a protease inhibitor (PI) containing regimen, but no increased risk of FGR, stillbirth, or low Apgar scores.
Effect of pregnancy on HIV progression
Pregnancy has no clear effect on HIV progression. A transient but clinically insignificant decrease in the CD4+ T-lymphocyte count has been described.
Antepartum perinatal HIV transmission risk
Intrapartum perinatal HIV transmission risk
Postpartum breastfeeding transmission risk
Transmission rate of HIV without ART
Transmission rate of HIV on AZT monotherapy
Transmission rate of HIV with ART
If you had only intrapartum AZT and C/S available, what would be the transmission rates?
5-8% with ZDV, 2% with C/S + ZDV