Therapeutic vaccine trial shows no benefit

At the 14th annual Conference on Retroviruses and Opportunistic Infections, Brigitte Autran of the Hospital Pitié-Salpétrière in Paris presented results showing that therapeutic vaccination with the recombinant canarypox vaccine candidate vCP1452, developed by Sanofi Pasteur, offered no benefit to individuals interrupting their current antiretroviral (ARV) treatment (CROI). Volunteers in this trial received either three or four injections (three primes and one boost) of the vaccine candidate or placebo and were given the option to suspend ARV therapy after receiving the first dose of vaccine. Researchers then monitored these individuals closely and placed them back on therapy if their CD4+ T cells declined below 250 cells per ml of blood-a sign that the immune system is starting to fail.

In previous studies the vaccine candidate showed significant immunogenicity in HIV-infected volunteers and provided modest benefit, according to Autran. But at CROI she reported that in this latest study all volunteers who received the vaccine candidate actually had to resume HAART sooner than those who received placebo. Half of the 20 volunteers who received three immunizations and 14 of 19 who received four injections of vCP1452 had to resume therapy. Meanwhile, only 3 of the 15 volunteers who received placebo had a decline in CD4+ T-cell count that warranted resuming ARV treatment.

Autran called these results "very disappointing" but said that she didn't think this trial should stop further study of this therapeutic vaccination approach. This Sanofi-Pasteur vaccine candidate, vCP1452, is also currently being tested in a preventive AIDS vaccine clinical trial alone or in combination with another vaccine, known as LIPO-5, at HIV Vaccine Trials Network (HVTN) sites in the US. For more information about this or other preventive AIDS vaccine trials, visit the IAVI Report clinical trials database.