One-two punch for AIDS prevention.

Attempts to develop an AIDS vaccine have so far run up against a road block: Infected people die even with high blood levels of antibodies against the AIDS virus, because the antibodies don't attack infected cells, which can produce new generations of viruses. For this reason, many researchers are trying to create vaccines that stimulate cytotoxic T-lymphocytes (CTLs), immune-system cells that kill virus-infected cells in the body. But because the AIDS virus continually mutates, such a vaccine would have to spur the body to make CTLs that work against a wide range of different AIDS viruses.

Now, U.S. and Japanese researchers have hit on a double-barreled vaccination strategy that recruits CTLs to fight a variety of AIDS virus strains. In the Jan. 17 SCIENCE, they report that two genetically engineered Vaccinia viruses - one bearing pieces of a common AIDS virus, the other containing slightly altered pieces of a less common strain - can prime lab-cultured CTLs to attack a range of AIDS viruses.

The team, led by Hidemi Takashi of Nippon Medical School in Tokyo and Jay A. Berzofsky of the National Cancer Institute in Bethesda, Md., writes that such cross-reactive CTLs "may suffice to protect [humans] against at least low-level exposure to a variety [of AIDS virus strains]." But they caution that they have not yet tested the strategy outside a test tube.