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A Phase II trial Confirms That a Candidate HIV Vaccine Induces an Immune Response

 LYON, France, July 13, 1999 - Preliminary findings from the largest Phase II trial ever to be conducted with a candidate vaccine against the AIDS virus, HIV, shows that an HIV vaccine induces immune responses. The findings were presented today by Dr. Robert Belshe, of Saint-Louis University during the International Society for Sexually Transmitted Diseases Research Conference in Denver, CO. The trial is sponsored by the National Institute of Allergy and Infectious Diseases (NIAID), a component of the National Institutes of Health (NIH).

This trial assesses the safety and immunogenicity of a combination of two vaccine preparations:

A recombinant virus studied in numerous Phase I trials, an ALVAC vector (canarypox virus) into which have been inserted HIV genes (surface protein gp120 and internal gag and protease proteins). This vector has been developed by Pasteur Mérieux Connaught, (Rhône-Poulenc Group) with support from the French ANRS (Agence Nationale de Recherches sur le Sida), and tested for many years in Phase I trials. This is vector vCP205.

A preparation of recombinant HIV surface proteins (gp120) made by Chiron from the SF-2 strain of the HIV virus (SF-2 rgp12), which has already been tested in Phase I trials.
The recombinant virus, which holds no risk for humans, penetrates the cells of the vaccinated individual and activates the production of immune cells that can kill HIV-infected cells, CTLs (Cytotoxic T lymphocytes). In contrast, the recombinant proteins stimulate the production of HIV neutralizing antibodies.

The trial, known as AVEG 202/HIVNET 014, enrolled 435 healthy men and women not infected with HIV and with a majority of participants belonging to high-risk groups for exposure to the virus. The trial is being carried out at fourteen medical centers in the United States through two networks sponsored by the NIAD (National Institute of Allergy and Infectious Diseases), the AIDS Vaccine Evaluation Group (AVEG) and the HIV Prevention Trials Network (HIVNET). The volunteers were divided into three groups, each receiving four doses spread out over six months:

of both vaccines, vCP205 and SF-2 rgp120,

or of vCP205 and a placebo,

or of two placebos.
The first participants were included in May 1997 and the last vaccinations were given in July 1998. The vaccinated volunteers will be followed for four years.

The preparations induced immune responses in the majority of the vaccinated individuals. More than half of the volunteers who received vCP205 alone and more than 90% of those who received the vaccine combination have developed antibodies, which have been shown to inhibit HIV in laboratory assays. To date, a CTL response has been detected in about one-third of the individuals who received vCP205 alone or the vaccine combination. The vaccine preparations have been shown to be safe, with no serious adverse effects reported.

The induction of two types of immune response in the trial's volunteers, CTLs and neutralizing antibodies, confirms the results already obtained with a smaller number of subjects in Phase I trials. "This encourages us to contemplate the possibility of an efficacy trial, to be conducted on a larger scale in a population at a high risk of exposure to AIDS," states Michel Klein, who is in charge of the AIDS program at Pasteur Mérieux Connaught.

The research program to find a vaccine against HIV being conducted at Pasteur Mérieux Connaught (Rhône-Poulenc Group) is the most extensive in the pharmaceutical industry. Almost half of the Phase I clinical trials conducted throughout the world to date have involved its candidate vaccines. The first Phase I trial to be conducted in a developing country is the one started in February 1999 in Uganda with Pasteur Mérieux Connaught's recombinant vCP205 virus. In addition to canarypox vectors, the company is also studying several other approaches, including the use of lipopeptides and naked DNA. Pasteur Mérieux Connaught's main research partners in the field of AIDS vaccines are the ANRS in France and the NIAID in the United States.

Pasteur Mérieux Connaught (Rhône-Poulenc Group) is the world's largest vaccine company with the broadest range of products. The company produces more than one billion doses every year.

Rhône-Poulenc SA is a leading life sciences company, growing through innovations in human, plant and animal health and through its specialty chemicals subsidiary, Rhodia. With sales in 1998 of FF86,8 billion, the company employs 65,000 people in 160 countries worldwide.

Koren Wolman-Tardy
Aventis Pasteur Global Media Relations
Tel. : +33 (0)
Fax. : +33 (0) 4.

Posted: June 2004