Researchers from Repligen Corp. and Merck & Co. Inc. haveshown that antibodies to the V3 loop (principal neutralizingdeterminant) of one AIDS virus strain can provide protectionfrom infection by other strains.

Several studies have been conducted with larger pieces of thevirus, including the gp120 and gp160 envelope proteins of HIV,which contain the V3 loop. Until now, however, no experimenthas been conducted exclusively with antibodies to the V3 loop.

The antibodies bound to a single six-amino acid peptide foundin the V3 loop of all variants that were neutralized. Thissequence was found in 65 percent of 245 HIV strains tested.

Repligen and Merck, which are collaborating to develop an AIDSvaccine, said they hope to devise a cocktail of V3 peptidesrepresenting this virus group and other major groups thatwould induce immunity to major HIV strains found in NorthAmerica and Europe.

Data on this cross-neutralization was presented by Walter C.Herlihey, senior vice president of research and development atCambridge, Mass.-based Repligen, at today's session of theSeventh International Conference on AIDS in Florence, Italy.

On Thursday, Emilio Emini of Merck reported that a chimpanzeepassively immunized with a monoclonal antibody directedagainst the V3 loop of an HIV-1 strain and then exposed to theAIDS virus has not developed signs of infection for up to 18weeks.

A control animal exposed to the virus developed signs ofinfection in six weeks.062191V3LOOP

-- Karen Bernstein BioWorld Staff

(c) 1997 American Health Consultants. All rights reserved.