New prophylactic HIV vaccine shows promise

A new prophylactic vaccine aimed at providing immunity against several types of HIV-1 infection has provided promising results in a Phase I/IIa clinical trial, recently published in The Lancet, of just under 400 patients.

Currently, there are no licensed prophylactic HIV-1 vaccines available, which the study authors reported as being potential related to the lack of direct compatibility between the preclinical studies and clinical trials.

Study participants in the APPROACH trial were taken from 12 clinics located in east Africa, South Africa, Thailand and the USA. Additionally, healthy participants were included in the trial, who were considered to be at low risk of HIV infection.

The patient population included in the trial were randomly assigned into eight groups and were either administered with a vaccine combination dose or placebo. Primary endpoints of the study included safety and tolerability of the vaccine regimens as well as immunogenicity.

A parallel study in rhesus monkeys was also performed so that immunogenicity and protective efficacy of the various vaccines could be assessed and the optimal vaccine regimen could be realised to transfer to further clinical studies.

It was found that the mosaic Ad26/Ad26 plus high-dose gp140 boost vaccine was the most immunogenic in humans and these results were comparable in the parallel monkey study where 67% of the 72 monkeys evaluated were protected against disease with this combination vaccine.

The vaccine itself is a mosaic vaccine — one which contains genetic sequences from various HIV strains — and was originated in the lab of the lead author Dan Barouch.

“These results represent an important milestone,” Barouch said when speaking with BBC News. However, he warned: “The challenges in the development of an HIV vaccine are unprecedented, and the ability to induce HIV-specific immune responses does not necessarily indicate that a vaccine will protect humans from HIV infection.”

As a result of these findings further trials are set to be performed in sub-Saharan Africa on 2,600 women who are considered to be at risk of getting HIV to evaluate the vaccine concept.