Infection by closely related HIV strains possible.

2003 JAN 1 - (NewsRx.com & NewsRx.net) -- A report of an individual infected with a second strain of HIV despite effective drug treatment following the first infection has researchers concerned.

"For the first time, we've shown it is possible for an individual to become infected with two closely related strains of HIV," said Bruce D. Walker, MD, a grantee of the National Institute of Allergy and Infectious Diseases (NIAID) and a researcher at Massachusetts General Hospital and Harvard Medical School.

Published in Nature, these findings underscore the challenges vaccine developers face in creating a broadly effective vaccine against HIV. The first HIV vaccines may not prevent infection altogether, but rather may prevent HIV from causing disease by limiting the virus' ability to reproduce, explained Walker. This case shows that a hypothetical vaccine against one strain of HIV may not necessarily protect the vaccinee against other, closely related strains.

"The implications of superinfection for an individual with HIV/AIDS are not yet clear," said Anthony S. Fauci, MD, NIAID's director. "However, there is little doubt what these new data mean in terms of public health: It is imperative that safer sex be practiced during each encounter, even when both partners are HIV-infected."

The new case involves a person whose HIV infection was kept in check for many months during structured treatment interruption (STI). In STI, antiviral therapies are frequently given during the early, acute stage of infection, but halted after the immune system has had time to adapt to the virus. Often, as in this case, a patient's immune system rebounds enough to keep HIV suppressed. "This patient's immune response against HIV was really quite robust," said Dr. Walker. Thus, the researchers were perplexed when, after successfully suppressing HIV for close to 1 year, the patient's viral load suddenly shot upwards. Despite several more attempts to interrupt therapy, the patient was unable to hold the virus to previously attained low levels.

To understand why STI stopped working for this individual, ...