Hopes high as HIV trial kicks off

If the vaccine works, it could cut infections in some countries by 50% in its first 10 years

The largest and most advanced HIV vaccine trial to be undertaken in South Africa has begun. At its centre is a tiny jab likely to be the strongest experimental vaccine against the virus the world has ever seen. If it works, it could at the very least halve people’s chances of contracting HIV.

If the vaccine can be shown to be 70% effective, it could cut HIV infections by nearly 50% in low- and middle-income countries in its first decade, according to mathematical models published earlier this year in the PLoS ONE journal.

“The fact remains that the HIV epidemic is still really, in many respects, out of control and South Africa has more infections than essentially any other country,” says Anthony Fauci, who heads the United States government’s National Institutes of Allergy and Infectious Diseases. “A safe and effective vaccine could be the final nail in the coffin for HIV.”

Launched publicly this week, the HVTN 702 trial began enrolling the first of the participants in October. Over 20 months, about half of them in 15 sites around the country will receive the active vaccine. The other half will get a placebo.

The injection is a variation of the only HIV vaccine ever to show modest results. In 2009, Thai researchers found that, although an HIV vaccine tested in the country had been about 60% effective initially, its protection quickly fell to about 31% about two years later. This meant the vaccine was too weak to be marketed. But South African researchers are hoping to have learnt from the Thai trial and have formulated HVTN 702 not only to fight off HIV strains found in South Africa but also to pack a better punch.

Principal investigator Linda-Gail Bekker, from the University of Cape Town’s Desmond Tutu HIV Centre, says the South African vaccine contains a new adjuvant or ingredient used to stimulate immune system responses that will give it added “voema”. Pharmaceutical company GlaxoSmithKline has also provided a new booster shot that will be given to participants at the one-year mark to increase the vaccine’s potency.

The vaccine contains artificial proteins created to “look” like HIV although they are not actually infectious. Scientists are hoping that these HIV imposters will trick volunteers’ bodies into producing antibodies, or proteins used by the immune system to fight off bacteria or viruses such as HIV.

The common polio vaccine works in much the same way. Both vaccines aim to trick the body into fighting off an infection that isn’t there in the hope that, if a person encounters the virus later, the body will already be primed to fight it off. At the end of 20 months, researchers will compare HIV-infection rates between the two groups to see whether the experimental vaccine worked. Volunteers will then be followed up for about another 18 months to see whether any protection against HIV offered by the vaccine holds out.

If by 2021, the vaccine has been shown to cut HIV infection rates by at least 50%, it could become available in Southern Africa, with other regions not far behind.

Glenda Gray, also a principal investigator and president of South Africa’s Medical Research Council, says, if the vaccine is effective in adults, smaller and quicker studies will enable scientists to determine whether it will work for other groups, such as adolescents.

“The best place [to administer] an HIV vaccine would be with HPV [human papillomavirus] vaccine in a school-based programme. Our schoolbased programme is well established and already giving the HPV vaccine. The idea would be to piggyback on the HPV vaccine,” Gray says.

But she cautions that the makers of the vaccine, pharmaceutical companies GlaxoSmithKline and Sanofi, would first have to be able to produce millions of doses. “We first need a vaccine that works,” she says.

Researchers are already planning ahead. South Africa’s drug regulator, the Medicines Control Council, will receive updates throughout the trial. Fauci says: “We’re working with the companies to get them enough data to get it past regulatory authorities in South Africa and perhaps even in other places in the world.”

See “HIV: Will pill reduce infections?” and “Six ways ARVs can help to end Aids by 2030”, Pages 18 & 19