A larger-scale HIV vaccine trial will begin in South Africa later this year, scientists announced this week at the International AIDS conference in Durban, South Africa.
The modified vaccine is based on the results of a small trial, known as HVTN 100, which took place in South Africa in 2015 to test the safety and efficacy of the vaccine’s immunity. In this trial, approximately 250 participants received either the vaccine, ALVAC-HIV/gp120, or a placebo. The results of this modified vaccine were promising enough to expand the trial.
“The obvious question is: Can we now replicate those results and can we improve upon them with greater breadth, depth and potency?” said Anthony Fauci, director of the National Institutes of Allergy and Infectious Disease, in a CNN article.
In November, 5,400 adult volunteers across four sites in South Africa will receive five injections, either the modified vaccine or placebo, over the course of a year. This trial will be named HVTN 702, and its results are expected in 2020.
The virus’s complicated nature
When the HIV virus invades the body by destroying the immune system’s CD4 cells, which are necessary to generate antibodies against the virus, it mutates so frequently that it evades the body’s immune response. There are also nine HIV subtypes, called clades, in different global populations and for a vaccine to be successful it must be specific to a population’s clade.
In the case of the very first HIV vaccine to show protection against infection, a 2009 trial in Thailand tested a combination vaccine, RV144 in more than 16,000 volunteers. However, RV144 reduced HIV risk by a modest 31.2 percent at the end of the three-year study.
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The HVTN 100 trial built on the success of the 2009 Thai trial by using the same vaccine regimen from RV144, except making it specific to the Clade C subtype, found in South Africa, and adding an adjuvant. “The durability of the Thai HIV vaccine regimen was not maintained,” Glenda Gray, MBBCH, director of HIV Vaccine Trials Network (HVTN) Africa Programs, told Drug Discovery & Development in an exclusive interview. “So the idea was to add a more potent adjuvant to the protein part of the regimen, and boost again at 12 months to increase the potency and durability of the regimen.” The results of HVTN 100 exceeded the immune responses seen in RV144.
The hope for the new trial
Although RV144, the Thai vaccine, showed 60 percent protection against HIV after a year, that fell to a modest 31.2 percent by the end of the trial. With the larger-scale trial, HVTN 702, the anticipation is to get that immunity percentage back up to at least 60 percent — and to maintain that level throughout.
Despite more than 30 years of efforts, scientists have yet to license a reliably effective HIV vaccine regimen. Although it’s unlikely the upcoming trial, HVTN 702, will directly result in an effective vaccine, it will advance its research.
An estimated 35 million people live with HIV globally. Although deaths from HIV/AIDS have steadily declined from a peak in 2005, 2.5 million people worldwide became newly infected with HIV in 2015, according to a new analysis published in The Lancet HIV journal.
Filed Under: Drug Discovery