"This finding has strong public health implications because it means that if you are already infected with HIV you can become infected with a second strain of the virus," said the study's senior author Bruce D. Walker, a Howard Hughes Medical Institute investigator at Harvard Medical School and Massachusetts General Hospital. "We now know that superinfection is possible, but we still need to determine how frequently people become infected by a second virus upon exposure."
Walker cautioned that the findings in no way undercut the importance of developing an effective HIV vaccine. But they do emphasize that vaccine developers are likely to be locked in a long-term duel with a continually mutating virus, he said.
Walker and colleagues from Los Alamos National Laboratory, Duke University Medical Center, University of Wisconsin and Oxford University published their article in the November 28, 2002, issue of the journal Nature.
The patient described in the article was enrolled in a clinical trial of an experimental antiviral drug therapy known as supervised treatment interruption, or STI. The regimen aims to boost anti-HIV immune response in patients with acute infection. During treatment, physicians periodically interrupt antiviral therapy to allow the patient's immune system to mobilize to help control the infection. Doctors carefully monitor the level of virus present in the patient's blood. Drug therapy is reinstated if levels of the virus rise significantly.
Walker and his colleagues found that even though the patient's immune system showed enhanced responses and prolonged immune control following treatment interruption, he abruptly developed an increased in the level of virus in his bloodstream.