Man Contracts Second Strain of HIV Two Years After Initial Infection; Could Have Ramifications for Vaccine Research
A 38-year-old man has contracted a second strain of HIV more than two years after initially becoming infected with the virus, a finding that could have ramifications for HIV vaccine research, according to a case study published in today's issue of the New England Journal of Medicine, the AP/Baltimore Sun reports. Researchers were able to thoroughly document the case because the man, who first contracted HIV in 1998, was enrolled in a study to test early treatment of the virus. After two years of successful antiretroviral treatment in the study, which was sponsored by the Swiss government and GlaxoSmithKline, the man ceased taking the drugs and was given an experimental vaccine designed to "boost" his body's immune response to the virus. In April 2001, a few months after being given the vaccine, the man's viral levels increased significantly. After performing several tests to determine the cause of the increase in viral load, researchers discovered that the man, who had recently engaged in unprotected sex with several anonymous partners while on a trip to Brazil, had become infected with a second strain of HIV. A similar case documented in Boston was presented at the XIV International AIDS Conference in July (AP/Baltimore Sun, 9/5).
Doctors had previously assumed that the body's immune response to one strain of HIV would keep HIV-positive individuals from contracting a second strain of the virus. However, the "rare" case of "superinfection" documented in the Swiss study demonstrates that co-infection is possible and could have major implications for vaccine research and public health, Reuters Health reports. Dr. Bernard Hirschel of the University of Geneva, one of the researchers who led the study, noted that the patient had already received an experimental vaccine designed to boost his HIV immunity. "Not only did this experimental vaccination not protect against a rebound of the original strain, it didn't protect against superinfection," he said. However, in an accompanying editorial, Drs. Bruce Walker and Philip Goulder of Massachusetts General Hospital state that the case "need not leave [researchers] in despair." They note that people are generally more likely to be exposed to the same strain of HIV over time, whereas the man in the study had become infected while traveling (Norton, Reuters Health, 9/4). They warn that, although rare, superinfection may "precipitate more rapid progression" to AIDS. Therefore, HIV-positive and HIV-negative people should "exercise the same degree of vigilance to prevent HIV exposure," meaning that HIV-positive people should follow safe-sex practices when engaging in sex with another HIV-positive or HIV-negative individual (Reuters/Toronto Globe and Mail, 9/5).