An international research group has reported promising data from an early clinical trial of a prophylactic vaccine against HIV-1 in healthy volunteers and a parallel study of the same vaccine in rhesus monkeys. The study results were published online in The Lancet on 6 July.
The trial, APPROACH, showed that the vaccine induced robust humoral and cellular immune responses in humans and was found to be safe and generally well tolerated. It also elicited largely comparable immune responses in the monkeys, providing substantial protection against repetitive challenges from the simian-human immunodeficiency virus, wrote Dan Barouch, professor of medicine at Beth Israel Deaconess Medical Center and Harvard Medical School and colleagues. The vaccine is currently being evaluated in a Phase 2b efficacy study in sub-Saharan Africa.
The mosaic Ad26/Ad26 plus gp140 HIV-1 vaccine candidate is based on optimised mosaic antigens delivered in an adenovirus serotype 26 vector. Mosiac antigens are synthetic antigens designed to give optimal coverage against global viruses. Between 24 February and 16 October 2015, the researchers randomly assigned 393 volunteers to receive at least one dose of the vaccine or a placebo. At week 50, the vaccine elicited T cell responses in 83% of participants and at week 52, env-specific binding antibody responses in 100%. The participants were recruited from 12 clinics in east Africa, South Africa, Thailand and the US.
To date, only four HIV-1 vaccine concepts have been evaluated for clinical efficacy and no prophylactic vaccine has ever been approved by a regulator for marketing. The APPROACH trial represents a new concept. “HIV is a hugely diverse virus, and one of the big challenges in the development of an HIV vaccine is the diversity of the virus worldwide,” Dr Barough said in an interview. “We believe that these sequences [the mosaic antigens] will likely raise immune responses that are the best we can do now to cover this global diversity of the virus.”
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