Picture: 123RF/PIXNOO
Picture: 123RF/PIXNOO

A senior scientist from the biggest external funder of SA HIV research says he remains optimistic about the prospects of an effective vaccine, despite the failure of the HVTN 702 trial.

The experimental HVTN 702/Uhambo trial, funded by the US National Institutes of Health (NIH) and the Bill & Melinda Gates Foundation, tested a modified version of the 2009 Thai RV144 vaccine, the only one to date to provide some protection against the virus. But the trial, which was conducted among 5,400 volunteers at 14 different sites in SA, was halted early because it did not work.

The scale of SA’s HIV epidemic, its strict regulatory environment and its strong track record in biomedical science made it an attractive place for conducting HIV research, Carl Dieffenbach, director of the division of Aids at the NIH, said in a recent interview with Business Day.

“HIV vaccine research is not for the faint of heart,” said Dieffenbach. “If you can make it in SA, you can make it anywhere,” he said, referring to the intensity of SA’s HIV/Aids epidemic.

SA is at the epicentre of the world’s HIV/Aids epidemic, with 7.7-million people living with the disease. More than three decades after the virus was first identified, there is still no cure or effective vaccine.

The NIH channels about $100m a year to HIV research in SA, according to Dieffenbach, dwarfing the contributions made by the Medical Research Council, which put R39.6m into the field in 2019-2020, and the department of science & innovation, which provides about R29m a year.

Dieffenbach said scientists had yet to figure out why the HVTN702 vaccine did not provide any protection against HIV, but one possibility was that the clade C strain of the virus circulating in SA was more powerfully adapted to its host than the strains circulating in Thailand. The Thai version of the vaccine, which showed very modest protection, was originally designed to combat clade B.

“Every human disease has a unique adaptation to persist as a human pathogen,” said Dieffenbach.

He expressed optimism about the international AMP trial, which includes SA women and is expected to announce its results in August. The AMP trial is taking a different tack to the HVTN702 trial. Instead of giving volunteers a vaccine to prompt their bodies to make protective antibodies, AMP trial participants are getting intravenous infusions every eight weeks of a broadly neutralising antibody called VRC01.

About half the people living with HIV make broadly neutralising antibodies, but only after they have been infected for a long time. Scientists hope that  VCR01, which has previously been shown to block up to 90% of HIV strains from infecting human cells, will protect people from infection.

Dieffenbach said it was too soon to tell how Covid-19, the novel coronavirus that emerged in China in December, would affect people with HIV.

“There is no data,” he said.