Hope for HIV: Vaccine Regimen Elicits Immune Responses Against HIV

An investigational HIV vaccine regimen generated an immune response against HIV in healthy adults, new findings show.

The experimental vaccine regimens are based on mosaic vaccines designed to induce immunological responses against a variety of HIV subtypes.

Included in the APPROACH clinical trial were 400 volunteers from the United States, Rwanda, South Africa, Uganda, and Thailand. Pre-clinical development of the vaccines used in the trial were funded by the National Institute of Allergy and Infectious Diseases (NIAID).

“A safe and effective HIV vaccine would be a powerful tool to reduce new HIV infections worldwide and help bring about a durable end to the HIV/AIDS pandemic,” said Anthony S. Fauci, MD, NIAID director. “By exploring multiple promising avenues of vaccine development research, we expand our opportunities to achieve these goals.”

The participants were randomized to receive 1 of 7 investigational vaccine regimens or a placebo. Over a 48-week period, individuals received 4 vaccinations: 2 doses of a prime vaccine, followed by 2 doses of a booster vaccine. The experimental regimens all incorporated the same vaccine components in the prime vaccination called Ad26.Mos.HIV.

The vaccine uses adenovirus serotype 26 (AD26) as a vector to deliver 3 mosaic antigens produced from genes of different HIV variants, and was engineered to not cause illness. The booster vaccine included a different mosaic component called MVA-mosaic and/or 2 different doses of clade C HIV gp140 envelope protein, which contained an aluminum adjuvant to boost an immune response.

Findings from the study showed that different mosaic vaccine regimens were well-tolerated among the participants and able to generate anti-HIV immune responses in HIV-negative adults.

Most of the participants developed antibody and cellular immune responses against HIV following the third vaccination.

Interestingly, the vaccine that was most protective in pre-clinical studies of animals elicited one of the greatest immune responses among the study participants.

In the pre-clinical studies, the regimens that included the mosaic vaccines were found to protect monkeys against SHIV infection. The prime-boost regimen found to be most efficacious reduced the risk of infection per exposure to SHIV by 94%, resulting in a 66% complete protection after 6 exposures.

“The promising, early-stage results from the APPROACH study support further evaluation of these candidate vaccines to assess their ability to protect those at risk of acquiring HIV,” said principal investigator Dr Barouch.

The authors noted that the findings from the APPROACH trial and the animal studies further support the investigational vaccine regimen in a clinical trial to assess its safety and efficacy. This clinical trial is currently in development and will be conducted in southern Africa. The projected enrollment is 2600 healthy, HIV-negative women.

The ongoing TRAVERSE clinical trial is comparing Ad26-based regimens that contain trivalent with Ad26-based regiments contain tetravalent. The results are expected in late 2017.

The findings were presented at the 9th International AIDS Society conference on HIV Science in Paris.