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In another setback to HIV immunization research, the ALVAC 1452 therapeutic vaccine led to higher viral loads and less time off antiretroviral (ARV) treatment in HIV-positive patients in a study published in the July 11 issue of AIDS and reported by AIDSmap.
Therapeutic vaccines have a long history in AIDS research. Experts have been using various types of vaccines to stimulate the immune systems of people living with HIV—notably those with undetectable viral loads while on ARV treatment—in hopes that the new, more robust immune responses will help control viral replication in the absence of therapy. This theory was supported with the positive results of an earlier vaccine candidate, ALVAC 1433.
With the newer vaccine, Brigitte Autran, MD, from the Institut National de la Santé et de la Recherche Médicale (INSERM) in Paris, and her colleagues enrolled 66 people taking ARV treatment with CD4 counts over 350. Twenty-two people were given four doses of ALVAC 1452 over a 20-week period, 22 people received three doses, and 22 were given placebo.
Four weeks after the last dose of the vaccine or placebo, 56 of the 66 patients chose to stop ARV treatment. They agreed to restart treatment if their CD4 count dropped either below 250 or more than 50 percent from when they started the study, or if their viral load climbed above 50,000.
Autran’s team found that patients who received the vaccine ended up with much higher viral loads than patients who received a placebo, and that those who got four doses of the vaccine had higher viral loads even than those who got just three doses. Moreover, people who got four doses of the vaccine were four times as likely as the placebo group to have to restart ARV treatment.
As with the failure of the Merck preventive vaccine, it appears that the vaccine-induced immune stimulation actually harmed people more than it helped them, and Autran’s team state that they are keen to discover the reasons why this occurred.
