Researchers Document Rare Case of Second HIV Infection With Different Strain

Swiss researchers have documented a rare case of a patient contracting a second HIV infection two years later with a different strain of the virus. The researchers said the case could have implications for the development of an AIDS vaccine, and its occurrence strongly supports the practice of safe sex for those already infected with HIV.

Dr. Bernard Hirschel of the University of Geneva, one of the researchers, said they were able to document the case because the patients was enrolled in an AIDS drug study to test early treatment of the virus. Successfully treated for over two years, the patient was taken off the drugs when he received an experimental vaccine intended to boost his immune system. Months later in April 2001, and weeks after he had unprotected sex with men, his virus level increased sharply and he was found to be infected with a different strain of HIV. The research, with an accompanying editorial, is published in Thursday's New England Journal of Medicine (Vol. 347, No. 10, P. 731-736; with editorial at P. 756-758).

"It just shows how little we understand what's happening with HIV-related immunity," said Hirschel. Doctors have long assumed that a patient's natural immunity would keep them from getting HIV more than once. A similar Boston case was reported by Dr. Bruce D. Walker at the Barcelona AIDS conference; last month a report on two cases in injection-drug users in Thailand was published. According to an editorial by Walker and Dr. Philip J.R. Goulder of Massachusetts General Hospital, the Swiss report provides "convincing evidence that HIV-1 superinfection can occur long after an initial infection is established."

"With sexual activity seemingly increasing among persons with HIV-1 infection, this is a public health message that needs to be broadcast loud and clear," they wrote. Walker added that vaccines are already being developed for geographic areas and that researchers anticipate that one vaccine may not protect against all strains. He noted that variations in HIV are greater than those in the flu virus, which requires a new vaccine every year.

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