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HIV research provides cause for optimism

HIV research provides cause for optimism

Research into vaccines to prevent HIV infection are offering new hope for those vulnerable to the condition, an international conference was told.

Delegates attending the 21st International AIDS Conference (AIDS 2016) in Durban, South Africa, were told about advances in the development of novel vaccines in the field of antibody mediated prevention (AMP). They heard about encouraging results from the HVTN 100 study, conducted by the US-based HIV Vaccine Trails Network (HVTN) in partnership with South African research sites.

HVTN 100 tested the immune responses of South African volunteers to a modified version of the RV144 regimen, the only HIV vaccine regimen to show efficacy to date. The original RV144 vaccine reduced the HIV infection rate among study participants in Thailand by 31% over three and a half years.

HVTN 100 Protocol Chair Linda-Gail Bekker, who is also Deputy Director of the Desmond Tutu HIV Centre in Cape Town and International AIDS Society President-Elect, said: “HVTN 100 used the same vaccines that RV144 tested, but made them specific to the Clade C subtype of HIV, which is widespread in southern Africa.

“We also changed the adjuvant used with one of the vaccines, with the goal of eliciting a more powerful immune response, and added a booster injection to prolong the period of protection.

“Interim results from HVTN 100 provided the green light for a Phase III efficacy trial on the modified RV144 regimen. Criteria for the go-ahead centred on the percentage of HVTN 100 vaccine-recipients who displayed a range of immune responses and the strength of those responses.

“All the criteria were met unequivocally and, in many instances, the HVTN 100 outcomes exceeded both our own criteria and the immune responses seen in RV144.”

Larry Corey, HVTN Principal Investigator, said: “It is gratifying to see vaccines that were designed and manufactured specifically for South Africa meet and even exceed the criteria established to advance them into the large efficacy trial. HVTN 702 is a pivotal study that could lead to a licensed HIV vaccine in South Africa – the first preventive HIV vaccine worldwide.”

HVTN 702, a placebo-controlled study, will begin enrolling 5,400 HIV-negative men and women at 15 research sites across South Africa before the end of 2016. Participants will receive five injections over the course of a year and be followed-for two years to establish whether the vaccine elicits a sustained protective effect. The trial will also seek to confirm earlier findings from HVTN 100 that the modified RV144 regimen is safe.

The work fits in with other work in the field, the conference heard. A major difficulty in the field of HIV vaccine development is the extraordinary capacity of HIV to mutate and evade the antibodies that might block it.

A landmark event in this field of research was the start of the first large-scale human trials to evaluate whether a bNAb called VRC01, given by infusion, is effective in preventing HIV.

The first of the two studies, HVTN 704/HPTN 085, commenced in March in the United States. It will enrol 2,700 gay men and transgender individuals who have sex with men in the US, South America and Europe.

The second study, HVTN 703/HPTN 081, began in June in South Africa and will enrol 1,500 heterosexual women in seven sub-Saharan African countries. Researchers agree that the greatest value of the studies may be the scientific insights they yield for future vaccine development. Laboratory analysis of how bNAbs block HIV’s entry into healthy cells has already provided invaluable information for vaccine scientists and more lessons are expected.

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