YOKAHAMA, JAPAN _ Fifty-seven healthy adult volunteers haveshown that an investigational, recombinant HIV vaccine is safe andimmunogenic. Whether it can actually protect high-risk humans frominfection remains to be proven.AIDS researcher Mary Clare Walker of the National Institute ofAllergy and Infectious Diseases was scheduled to present the Phase Istudy Saturday at a press briefing here on the periphery of the 10thInternational AIDS Conference, which began yesterday and endsFriday.Some 10,000 registrants and speakers (plus 1,000 from the media) areexpected to attend the event, which is sponsored by the InternationalAIDS Society, the World Health Organization and the JapaneseFoundation for AIDS Prevention.The 11th AIDS conference is set for Vancouver, B.C. in 1996, whenthe previously annual meeting becomes biennial.The press briefing was organized by the Journal of the AmericanMedical Association (JAMA), to introduce the results of the novelvaccine, which was supplied for the trial by Genentech Inc. of SouthSan Francisco. Formal publication of the data will appear in this week'sissue of JAMA, out Wednesday, August 10. Its title: "NeutralizingAntibodies to HIV-1 in Seronegative Volunteers Immunized WithRecombinant gp120 From the MN Strain of HIV-1."The paper's first author is vaccine virologist Robert Belshe, who directsthe vaccine development center at St. Louis University School ofMedicine. Belshe originally presented these Phase I clinical trialfindings orally at the Ninth AIDS Conference last year in Berlin. (SeeBioWorld Today, June 8, 1993, Page 1.)Phase II results of Genentech's gp120 vaccine, he told BioWorldToday, will be communicated to the Conference here this week by JulieMcElrath of the University of Washington, Seattle. She will also reporton another gp120 vaccine, developed by Biocine, a joint venture ofChiron and Ciba-Geigy.Only a single minor side effect occurred in the Genentech gp120 trial:One volunteer experienced itching after the third of four scheduledinjections of the vaccine, so did not receive the fourth.All 57 subjects tested free of HIV infection upon admission to the trial,and all affirmed a low-risk lifestyle, including no needle-delivereddrugs of abuse. Of the 57, all 21 to 57 years old, 39 were women, 18men. The study took place at the AIDS Vaccine Evaluation Units in St.Louis, the University of Rochester in New York and VanderbiltUniversity in Nashville, Tenn.A genetically engineered envelope surface protein, gp120 on HIV-1'sMN strain, is the chosen antigen of the experimental vaccine. Itinduced strong antibody responses in 46 volunteers after three doses.Such antigen-antibody interaction neutralizes the virus' ability to replicate, or invadeits target cell.Besides this humoral (B-cell, antibody-generating) response, over one-third of the subjects in the trial acquired antibody-dependent cell-mediated cytotoxic (ADCC) antibodies after a fourth vaccine injection.This is the first AIDS vaccine, Belshe said, shown to stimulate theseADCC antibodies, which kill HIV-1-infected cells rather than the virusitself.The MN rgp120 vaccine also produced T-cell memory, which primesan immune system once exposed to be twice shy, by recognizing HIV-1 in the future."Ultimately," the paper concluded, "efficacy trials in humans at highrisk of infection will be required." But setting up such costly clinicaltrials, Belshe said, "has been the subject of ongoing scientific debate. InJune," he added, "the AIDS Research Advisory Committee to the NIHrecommended not to proceed with such studies at this time; that theircost could more usefully be spent on additional basic research." n
-- David N. Leff Science Editor
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