AIDS I Flashcards
What retrovirus subtype is the human immunodeficiency virus?
Lentivirus.
Where is HIV-2 found almost exclusively?
Western Africa.
What co-receptors on the surface of the CD4+ T-lymphocytes are necessary for HIV-1 fusion?
CCR5 and CXCR4.
What viral enzyme is required for transcription of HIV-1 proviral RNA into proviral DNA?
Reverse transcriptase.
What HIV-1 enzyme is required for integration of proviral DNA into the host genome?
Integrase.
What HIV-1 enzyme is required for assembly of viral proteins into replication-competent viruses?
Protease.
True or false: There is a period of microbiologic latency between prior to the onset of AIDS.
False. Although there is a period of clinical latency which can last for years (marked by a progressive loss of CD4+ T-lymphocytes), there is never a period of true microbiologic latency.
Following an acute retroviral syndrome, the immune system incompletely clears HIV-1 from the body. Where do HIV-1-infected cells persist?
Within lymphoid tissue.
Where in the world are the greatest numbers of HIV-1 infection occurring today? What is the predominant mode of transmission?
Sub-Saharan Africa (by far). Predominant mode is heterosexual intercourse.
What is the most efficient sexual means of spreading HIV-1?
Receptive anal intercourse. Penile-vaginal intercourse is relatively inefficient when it comes to spreading HIV-1, especially from women to men.
Which is the most frequent period of mother-to-child HIV-1 transmission: prenatal, perinatal, or postnatal?
Perinatal, although prenatal (transplacental) and postnatal (breast-feeding) do occur as well.
What is the standard testing for making the diagnosis of HIV-1 infection?
A serum HIV antibody ELISA screening test and a confirmatory Western blot test.
What must be present for a Western blot to be read as positive for an HIV-1 infection?
An antibody against one protein from each of the three main retroviral genes: env, pol, or gag.
What has been shown to be the strongest predictor of outcome in HIV-1 patients over 1-year to 10-year periods of observation?
The level of HIV RNA in plasma. Declines in plasma HIV RNA concentrations during therapy are strongly associated with a decrease in risk of subsequent disease progression.
What are the six groups of current antiretrovirals?
- Nucleoside reverse transcriptase inhibitors (NRTIs)
One of the key elements to preventing antiretroviral resistance is strict patient compliance. What percentage compliance is believed to be necessary for maximum efficacy? Why is this especially tricky?
Greater than 95%. Unfortunately, these drugs frequently have difficult dosing schedules and significant side effects/toxicities.
What is lipodystrophy? Why is it particularly problematic with regards to treating HIV-infected individuals?
The development of either metabolic or morphologic (body habitus) changes in patients taking antiretroviral therapy. Such changes appear to put patients at risk for the development of myocardial infarction. The exact etiology is not clear, but several drug classes are implicated.
Approximately what percentage of patients taking their initial antiretroviral regimen will display virologic failure within the first year?
40 percent. This means that 40 percent either fail to drive viral levels down to undetectable or return to detectable levels after becoming undetectable.
What are the three causes most often attributed to virologic failure in patients taking antiretrovirals?
1) Poor medication compliance, 2) inadequate blood levels of the antiretroviral, and 3) the presence of antiretroviral resistance.
What special qualities of HIV contribute to its genetic variability? Why is this problematic?
Reverse transcriptase is a low fidelity enzyme that results in a high mutation rate. Additionally, the rate of replication in HIV in vivo is extremely high. Combined, this can often result in resistant strains with a selective advantage.
What are the two main types of testing employed to identify the presence of antiretroviral resistance?
The viral genotype test (uses PCR to identify genomic mutations typically conferring resistance) and the viral phenotype test (identifies ability of virus to grow in the presence of certain antiretrovirals).
