Two steps forward in AIDS vaccine search.

Researchers seeking a vaccine to stem the spread of AIDS have taken two significant strides toward that goal. They have found a primate species besides humans and the endangered chimpanzee that they can use to test the safety and efficacy of possible AIDS vaccines. And they have developed an AIDS vaccine that provides protection in chimps against white blood cells-such as those in infected blood or semen-that carry the AIDS-causing virus HIV-1.

In the first discovery, a group led by Lawrence Corey of the University of Washington in Seattle has successfully infected with HIV-1 a common type of Indonesian monkey called the pigtail macaque. Because pigtail macaques are more plentiful than chimpanzeez -- the only other animals known to be susceptible to HIV-1 infection -- Corey and his colleagues say their finding should expand the number of candidate AIDS vaccines that researchers can evaluate at any given time. This, in turn, should speed the development of an effective vaccine, they say.

Corey's group tested whether HIV-1 could infect pigtail macaques after finding that the monkeys are especially vulnerable to HIV-2, a related but separate virus responsible for many AIDS cases in Africa. The researchers began by demonstrating that four different strains of HIV-1 could infect pigtail macaque white blood cells grown in laboratory cultures and cause the cells to produce new infectious viruses.

Next, they injected a group of eight pigtail macaques with infected white blood cells, purified HIV-1 or a mixture of both. In a paper scheduled for publication in the July 3 Science, the researchers report that all of the monkeys became infected with HIV-1 and produced telltale antiobodies to the virus. Moreover, the monkeys developed swollen lymph nodes, rashes and fever -- early symptoms of HIV infection that previously have been seen only in humans.

Corey says these results suggest that the pigtail macaques may later develop the wasting, loss of immune system function and neurological symptoms that afflict humans with AIDS. This would make the monkeys the first true animal model for AIDS, because chimpanzees do not get sick following HIV infection.

AIDS vaccine researcher Jonathan S. Allan of the Southwest Foundation for Biomedical Research in San Antonio, Texas, agrees that pigtail macaques offer "a nice alternative to chimps, or an addition to chimps" for AIDS vaccine testing. "They are more amenable to AIDS vaccine research," he says, "because there are enough around so that you could use statistically relevant numbers of unvaccinated controls" in vaccine studies.

Because of an international treaty barring the importation of chimpanzees -- whcih are endangered in their native Africa -- the National Institutes of Health funds a program to breed the animals in captivity (SN: 3/11/89, p.155). Even so, only some two dozen chimpanzees are available for AIDS vaccine studies each year. In contrast, between 200 and 300 pigtail macaques are born in U.S. breeding facilities annually, and there are no restrictions on their sale.

In the second AIDS vaccine development, a U.S.-French research team led by Patricia N. Fultz of the University of Alabama at Birmingham demonstrated that multiple immunizations with several HIV-1 protiens protected three chimpanzees from infection with HIV-1 carried by white blood cells. Although several AIDS vaccines have been shown to protect chimpanzees against infection with purified HIV (SN: 6/9/90, p.363), Fultz and her colleagues assert that this is the first time a vaccine has shield against cells carrying HIV. They report thier results in the June 19 Science.

Fultz says the finding suggests it will be possible to develop a long-acting human vaccine to protect against HIV particles carried by infected white blood cells. She says that one of the chimpanzees her group studied resisted infection from such cells even a year after its vaccination.