AIDS: The Elusive Vaccine

After twenty-three years of intense research into the human immunodeficiency virus (HIV), together with the accumulated experience of more than twenty million deaths from the in-fection worldwide, there is still no prospect of a vaccine to prevent AIDS. Is the discovery of a vaccine simply a matter of time? Or has this virus presented scientists with a hitherto underestimated, perhaps even impossible, challenge?

The International AIDS Vaccine Initiative (IAVI), the world’s largest single organization devoted to finding an AIDS vac-cine, has argued that the obsta-cles to progress are clear and resolvable—lack of political commitment and inadequate scientific resources. With offices in New York, Amsterdam, Nairobi, and New Delhi, it has invested $100 million in the search for a vaccine. At the Bangkok AIDS conference held in July of this year, Seth Berkley, IAVI’s president, argued that “only a vaccine can end the epidemic,” that “a vaccine is achievable,” and that spending on vaccine research must double to $1.3 billion annually in order to find it. “The world is inching toward a vaccine, when we should be making strides,” he said. The present situation was little short of “a global disgrace.”

But contrary to the predictions and promises of most AIDS experts, the signs are that a vaccine to prevent HIV infection will not be found for, at the very least, several decades to come—if at all. Those responsible for carrying on the global fight against AIDS do not accept this grim outlook, at least publicly. Yet it is a conclusion, based on all the evidence gathered so far, which increasingly defies rebuttal. Until the gravity of this scientific failure is openly acknowledged, a serious debate about how to end HIV’s lethal grip on some of the poorest and most vulnerable human populations in the world cannot take place.

1.

The holy grail of AIDS prevention is a single-dose, safe, affordable, oral vaccine that gives lifelong protection against all subtypes of HIV. The first hurdle facing vaccine designers, therefore, is dealing with the extraordinary genetic complexity of the HIV epidemic.

HIV exists as two strains—HIV-1, which dominates the epidemic, and HIV-2, which is largely confined to West Africa. So far, at least ten different patterns of HIV-1 infection have been identified. These patterns reflect particular geographic and genetic profiles of viral spread. For example, HIV-1 subtype B (there are nine genetic subtypes) is the common form of the virus in North America and Western Europe. India, by contrast, is under threat from HIV-1 subtype C. In Africa, where some two thirds of those with HIV now live (about 25 million people) and where there were three million new infections in 2003 alone, the situation is more diverse. Southern and eastern regions of the continent face a predominantly HIV-1 subtype C epidemic. Central Africa sees a highly mixed picture—HIV-1 subtypes A, D, F, G, H, J, and K. The implications of these differences for vaccine development remain uncertain. The best guess is that the genetic complexity of HIV will influence the effectiveness…


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