An experimental HIV vaccine was well-tolerated and generated immune responses against the deadly virus in healthy human adults, scientists say. The vaccine regimens evaluated in APPROACH – an early- stage clinical trial – are based on “mosaic” vaccines designed to induce immunological responses against a wide variety of HIV subtypes responsible for HIV infections globally, researchers said. They found that different mosaic vaccine regimens were well-tolerated and capable of generating anti-HIV immune responses in healthy, HIV-negative adults.
Researchers found that the vaccine called Ad26.Mos.HIV was most protective in pre-clinical studies in animals elicited among the greatest immune responses in the study participants. “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, Director at National Institute of Allergy and Infectious Diseases (NIAID) in the US. “By exploring multiple promising avenues of vaccine development research, we expand our opportunities to achieve these goals,” Fauci added.
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Researchers randomly assigned 400 volunteers in the US, Rwanda, Uganda, South Africa and Thailand to receive one of seven experimental vaccine regimens or a placebo. Participants received four vaccinations over 48 weeks: two doses of an initial, or “prime,” vaccine, followed by two doses of a booster vaccine. The experimental regimens all incorporated the same vaccine components in the prime vaccination, Ad26.Mos.HIV. The vaccine used a strain of common-cold virus engineered so that it does not cause illness, as a vector to deliver three mosaic antigens created from genes from many HIV variants.
The booster vaccination included various combinations of the Ad26.Mos.HIV components or a different mosaic component, and two different doses of a protein containing an aluminium adjuvant to boost immune responses. Researchers found that the most effective prime-boost regimen reduced the risk of infection per exposure to simian human immunodeficiency virus (SHIV) by 94 per cent and resulted in 66 per cent complete protection after six exposures. The team identified and characterised the vaccine-induced immune responses that correlated with this protection. “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 Dan H Barouch from NIAID.