Case Study of ‘Dual’ HIV Infection Raises Doubts About Possible Effectiveness of an AIDS Vaccine
A "sobering and fascinating case study" of an HIV-positive man from Boston who was infected with a second strain of HIV, presented yesterday at the XIV International AIDS Conference in Barcelona, Spain, indicates that producing an AIDS vaccine may be "much more difficult than previously thought," the Wall Street Journal reports. Presented by Bruce Walker of the Harvard Medical School, the case involved a man whose immune system was suppressing HIV for several months without the assistance of medications. Tests of the man, known by his research code AC06, indicated he had high levels of "killer" T cells, which provided him with "broad immunity" to the virus. The Journal reports that the man's immune response was the "robust and powerful attack on HIV" that vaccine researchers had hoped to mimic. However, the man subsequently had unprotected sex and became infected with a second strain of HIV, which his immune system was unable to control.
HIV is classified into at least 10 subtypes, each including "countless strains," the Journal reports. Some researchers say the case study indicates that a vaccine that provides immunity to one strain may not protect against another, much as AC06's immune system could not handle the second strain. In addition, the case study has raised concerns about using killer T cells as the basis for a vaccine. Although most vaccines stimulate antibodies -- which attack viruses free floating in the bloodstream -- Wyeth and Merck & Co., the National Institutes of Health, the International AIDS Vaccine Initiative and Emory and Yale Universities are all developing HIV vaccines based on killer T cells. Ronald Desrosiers, an HIV vaccine researcher at Harvard University, called the findings a "huge blow to vaccine development." Walker, however, cautioned that "broad conclusions" could not be drawn from the case study. The Journal, for example, reports that AC06 may be a "fluke" that simply happened to occur under observation. "To leap from this one patient to saying that this is the end of the vaccine business is really crazy," Wayne Koff, the scientific leader of IAVI, said (Schoofs, Wall Street Journal, 7/11).
NPR's "Morning Edition" yesterday reported on the study. The full segment is available in RealPlayer Audio online (Knox, "Morning Edition," NPR, 7/10).