no African renaissance’
Despite its limited resources, South Africa stands to gain by developing its own HIV vaccine, instead of waiting for the West to provide, writes Lesley Cowling
More than 25 clinical trials of different types of vaccines against HIV – the virus that causes Aids – are under way all over the world. Africa will host at least one trial, scheduled to take place in Uganda. In the United States, a group of doctors has volunteered to become guinea pigs in a trial of a vaccine containing a weakened form of HIV. The announcement sparked a flood of offers from Americans willing to become volunteers.
With so much going on, you could be forgiven for sitting back with a sigh of relief and saying: “Well, that’s taken care of.”
But South African scientists have not responded that way: a local initiative to develop a vaccine was launched earlier this year and a workshop in September on the ethical issues of HIV vaccine trials brought together more than 100 players in the field.
Apart from the apparent bad timing – South African vaccine development is a decade behind the front-runners – the numbers also suggest the South African initiative is quixotic.
The 50-odd medical and scientific experts who have been discussing the initiative at meetings around the country estimate the basic research will cost about R100- million to R150-million. They are trying to raise the funds from the health department, research bodies and companies.
Compare this to the US, where the country’s National Institute of Health has budgeted $179,9-million for research for 1999 alone, according to a report by the International Aids Vaccine Initiative (IAVI), an advocacy body. The report also puts the cost of developing a new pharmaceutical product at between $150- million and $250-million.
But local experts say that South Africa cannot afford not to get involved in vaccine development.
“There is currently no effort specifically to develop appropriate vaccines for South Africa, where we have a different strain of HIV from what we find in the US and Europe,” says Dr Walter Prozesky, one of South Africa’s leading virologists and president of the Medical Research Council.
HIV mutates into different forms and, at last count, there were at least 10 sub- types of HIV-1, numbered from A to J.
Subtype B is prevalent in North America, Europe, Australia and much of South America. Subtype C, the so-called African form of the virus, is the dominant virus in Southern Africa and Asia and is causing the fastest-growing epidemic of them all.
If you imagine the virus as a round sac of viral matter contained in an “envelope”, then it is the outside “envelope” that mutates to make the different subtypes. The matter inside the sac also varies, but not as a much.
Most of the 25 trials under way are testing vaccines for subtype B. Only two trials are testing vaccines that might provide protection against subtype C. There are a few trials testing E (South- East Asian subtype), as well as A and D (Central and East African strains).
There are many different types of vaccines being tested, but all are designed to help the body recognise and eliminate invading HIV by stimulating the immune system before the person is exposed to the virus.
But if HIV can change its outer envelope (the face it shows the body’s cells), it will be difficult to design a vaccine that can help the body recognise all the different subtypes.
South African researchers, therefore, need to be involved in the international initiative to develop a vaccine so that they can contribute local knowledge of subtype C in order to design appropriate vaccines.
“We need to develop a vaccine that is specific and relevant to our people,” says Dr Malegapuru Makgoba, who will take over as president of the Medical Research Council next year. He says the initiative will build capacity in South Africa to design, manage and co-ordinate vaccine development. “If you don’t have the capacity, you are not able to enter the game,” he says.
“Being part of the global network ensures that nobody has got the monopoly over knowledge. We have a facility to produce vaccines, so the infrastructure is not a problem.”
The IAVI report says that South Africa is uniquely situated in Africa “in that it has a strong clinical infrastructure, talented researchers and access to high- risk populations”.
Access to high-risk populations is crucial to testing vaccines. After the first phase of testing, which is designed to make sure the vaccine does not cause health problems, the second and third phases need to test whether the vaccine works, something that cannot be done if the people in the trial are not exposed to the virus.
It has been suggested that trials of vaccines for subtype B could take place in high-risk populations here, to see what kind of immune responses it would generate in South Africans and to test the possibility that the vaccine could also protect against subtype C – a phenomenon called cross-reactivity.
But Makgoba argues that testing other subtypes is unlikely to benefit South Africa. “Speaking purely as a scientist, there is not enough evidence that B cross-reacts with subtype C. The immune response is quite specific.
“If you want to test subtype B, you test it on a population vulnerable to subtype B. This is simply common sense,” he says.
There are many difficult ethical issues around conducting vaccine trials, so trials for B, if ineffective, could also prejudice the process of testing vaccines for subtype C.
But ethical problems are in the future. “We are at least seven to 10 years away from having a local vaccine ready for human trials,” says Dr Lynn Morris, a scientist at the National Institute for Virology.
It’s going to be a long, difficult costly process. But, says Makgoba, “there is no economic recovery without tackling Aids. If we don’t stop Aids, there will be no `African renaissance’.”