Science of the future?
An AIDS vaccine is being touted by many as the ‘only hope’ for developing countries. But there is a dearth of ideas in the world of science about how to outwit the virus.
The International AIDS Vaccine Initiative (IAVI) notes that almost all the 30-odd candidate vaccines currently in human trials are ‘narrowly focused on a single hypothesis that a vaccine can confer protection by eliciting a cell-mediated immune response.
‘If the hypothesis is proven incorrect, the pipeline of candidates now in trials will be rendered mostly irrelevant,’ says IAVI.
Last year, the candidate AIDSVax was found to be ineffective. The vaccine candidates currently on trial are only in phase I (small safety) and phase II (large safety) trials. The actual efficacy of the vaccine is only be tested in a phase III trial. The earliest the world can expect the results of these is in four years’ time.
South Africa’s first phase I vaccine trials started a year ago in Durban and Johannesburg. Two candidate vaccines are being tested.
The VEE subtype C is the first candidate for the subtype of HIV most common in southern Africa, and has a ‘proudly South African women’ stamped all over it, as scientist Dr Carolyn Williamson developed it in collaboration with the US’s Bob Johnson, while Dr Glenda Gray is the principal investigator.
The second, MVA subtype A, is for the kind of HIV most common in East Africa.
‘There have been no adverse reactions so far, and this phase trial will be completed in about six months’ time,’ says Michelle Galloway from the SA AIDS Vaccine Initiative. ‘If all goes well, we will move on to a phase II trial which will take about two years.’
The phase I trial of another candidate developed by Williamson and her sister Ana-lise, may begin next year.
However, IAVI says that it is not feasible to manufacture some of the candidate vaccines on a large scale, while there is little global co-operation to ensure that ‘resources could be focused as quickly as possible on testing the best candidates in large-scale trials’.
There is better news for those already living with the virus, however. At the moment, the most effective treatment for people with HIV with weakened immunity is a ‘cocktail’ of three antiretroviral (ARV) drugs.
Each of the three drugs is taken from a different class of ARVs and acts in a different way to interrupt the life cycle of the virus once it has entered a cell. These classes are called protease inhibitors (PIs), nucleoside reverse transcriptase inhibitors (NRTIs), and non-nucleoside reverse transcriptase inhibitors (NNRTIs).
But a new class of ARVs called entry inhibitors has been developed and one, Fuzeon or T-20, has already been approved by the FDA.
Entry inhibitors work by preventing HIV from entering healthy T-cells in the body and are expected to have fewer side effects as a result.
Fuzeon is currently only available as an injection and is very expensive. However, a trial of a pill version is underway.
Considerable effort is also being put into developing a microbicide ‘ a barrier gel that could be used vaginally or anally to block HIV from entering the body.
This is particularly important for women who are unable to get their male partners to wear condoms, but could also be used by gay men.
Carraguard, a seaweed based gel, is currently in being tested for safety in South Africa.
Clearly, it is unrealistic to expect science to come up with the answers to this epidemic. Yet the simple ABC ‘ abstain, be faithful to one partner and, if you can’t, condomise ‘ does offer protection to those not infected. In addition, if a person living with HIV takes antiretroviral drugs they lower the viral load in their body and make them less likely to transmit the disease.
Any behaviour that can transmit HIV ‘ from people having multiple sexual partners without using condoms to rape ‘ needs to be identified as anti-social behaviour that threatens South Africa’s future.
E-mail Kerry Cullinan
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