NEW ORLEANS, Sep 13 (Reuters Health) - The results of an animal study suggest the possibility that sexually acquired HIV infection could be eliminated by a single prior oral inoculation with a live attenuated virus.

The conclusion is based on experiments in macaques using chimeric simian-human immunodeficiency virus, SHIV. Dr. Glenn A. MacKay from the University of Kansas Medical Center, Kansas City presented the work at the 38th annual meeting of the Infectious Diseases Society of America last week.

"We provided a cohort of monkeys with a live attenuated vaccine," Dr. MacKay told Reuters Health. The orally administered vaccine virus consisted of SHIV devoid of the vpu gene, which "produced a very strong immune response." The vaccine virus disappeared from peripheral blood mononuclear cells, but viral DNA persisted in lymph nodes.

To simulate HIV transmission, the monkeys were then challenged intravaginally with a strongly pathogenic SHIV strain. "This was important," Dr. MacKay said, "because the infection of the challenge virus seemed to have developed a stronger immune response against the virus itself."

The SHIV challenge virus initially produced systemic and lymphatic infection, then replication dropped to minimal levels. Challenge virus DNA declined steadily and became undetectable in five of the six monkeys. "We would like to think that it is being cleared," Dr. MacKay said .

He told Reuters Health that they are approaching the FDA with a slightly weaker version of an attenuated vaccine that has been developed for human trials. The plan is to recruit patients already infected with HIV for clinical trials "because we don't know how it is going to react in patients who are not infected." One of the problems with the live vaccine, he said, is that people are afraid it will become pathogenic.

"We hope this is the first step [in] vaccine trials," he added. "In the animals, the results are very promising. The vaccine has not shown any severe side effects; our monkeys are very healthy."

(From Reuters Health)