ALVAC-HIV and AIDSVAX resurected in promising South Africa Trial of the two HIV Vaccines
A new trial of the ALVAC-HIV + AIDSVAX HIV vaccine regimen, conducted in South Africa, has demonstrated its safety and a robust immune response amongst 100 healthy adults. This trial, named HVTN 097, comes in the wake of the high-profile disappointment for the vaccine combo in 2009 wherein an 18,000 strong trial conducted in Thailand demonstrated just 31% efficacy in reducing HIV transmission amongst participants, the RV144 trial or Thai Trial.
“The HVTN 097 study clearly shows that the investigational HIV vaccine regimen is safe in South Africans and induces comparable if not somewhat stronger immune responses than seen among Thais in the RV144 trial,” said NIAID Director Anthony S. Fauci, M.D. “The findings are encouraging as we move toward evaluating a modified and potentially improved version of the vaccine regimen in South Africa.”
The significance of the South Africa trial however is that the two vaccines in the regime were in fact tailored towards the two most common HIV sub-types found in Thailand (B & E). Sub-type C is the most common in Sub-Saharan Africa, but despite this vaccine combo demonstrated similar efficacy in South Africans. Not only this, but the CD4+ T responses elicited amongst those in the South African trial were ‘at least comparable to or better than those induced in the RV144 study.’
ALVAC-HIV, the primer in this regime, carries three engineered versions of HIV genes contained in a canarypox virus vector developed by Sanofi Pasteur. the role of Sanofi Pasteur’s vaccine is to contain viral load and slow, or stop, the progression to aids. AIDSVAX, developed by VaxGen before their closure, now owned by the non-profit Global Solutions for Infectious Diseases, was designed to produce an antibody response against the HIV surface protein gp120.
The findings of the Thai trial puzzled many in the industry because whilst viral load was not contained, but that the virus did appear to have been blocked in participants, indicating an antibody response. The confusion arose because shortly after the Thai trial began, the idea of eliciting an antibody response to anything but a tiny fraction of HIV was widely discredited. Dr. Robert Gallo even said that ‘this is not a vaccine approach that was based on science.’
But these new results offer a positive outlook for researchers looking to test the effectiveness of HIV vaccines in Sub-Saharan Africa. There are already trials slated to begin in early 2015 using a modified version of ALVAC-HIV containing the more relevant HIV sub-type C. Work is also being undertaken to increase immune responses over a longer periot of time. Data from the Thai trial showed that participants initialy had up 60% protection for the first year, but this had droped to 31% after 3 years.
The trial was funded by the National Institute of Allergy and Infectious Diseases (NIAID) and was conducted through the HIV Vaccine Trials Network.
Find the NIH bullitin here.