The latest article in our Medical Progress review series is on Acute HIV-1 Infection.
There are now 33.2 million people living with human immunodeficiency type 1 (HIV-1) infection, and 2.6 million additional cases are diagnosed each year. The need for effective HIV-1 prevention has never been greater.
• How quickly after exposure can HIV infection be detected?
Immediately after exposure and transmission, as HIV-1 is replicating in the mucosa, submucosa, and draining lymphoreticular tissues, the virus cannot be detected in plasma; this so-called eclipse phase generally lasts 7 to 21 days. The stages that define acute and early HIV-1 infection are characterized by the sequential appearance of viral markers and antibodies in the blood. More sensitive, fourth-generation tests, which detect both antigens and antibodies, shrink the virus-positive-antibody-negative window by about 5 days. Testing for viral RNA in plasma closes this gap by an additional 7 days.
• When are patients infected with HIV most contagious?
The per-person probability of transmitting HIV-1 is most closely correlated with the viral burden in blood; each time the viral burden in an HIV-1-infected person increases by a factor of 10, the risk of transmission is expected to increase by a factor of 2.5. The risk of contagion from patients with acute, early infection appears to be much higher than that from patients with established infection, at least in part because of the high viral load and the homogeneity of viral variants clearly capable of causing infection.
Figure 2. Natural History and Immunopathogenesis of HIV-1 Infection.
Morning Report Questions
Q: What is the efficacy of preexposure prophylaxis for HIV?
A: Use of the antiretroviral drug tenofovir as a topical prophylactic agent before viral exposure in women at high risk led to a 39% reduction in incident cases of HIV infection that was directly correlated with concentrations of the drug in mucosal tissue. A multinational trial focused on men who have sex with men showed that a once-daily pill containing tenofovir plus emtricitabine provided an average of 44% protection over and above that conferred by the provision of comprehensive preventive services, including provision of condoms and counseling. The level of protection varied widely, depending on how consistently participants used preexposure prophylaxis.
Q: What antiretrovirals are likely to be most effective for the treatment of acute HIV?
A: If antiretroviral therapy is to be provided for patients with acute infection, the preferred treatment regimen, which has yet to be determined, might include antiviral agents that concentrate in the genital tract of men and women and an integrase inhibitor, the latter because of the rapidity with which this class of agents lowers the viral load.