of the immune system.
In 2008, Philip Goulder, a medical researcher at Oxford, led an international team of scientists
who found evidence for the ongoing evolution of HIV. They studied the immune systems of 2,800
people from all over the world, examining proteins known as human leukocyte antigens, which
infected cells use to transport fragments of viruses to their surface. The fragments can then be
recognized by immune cells, which destroys the infected cell. Different people carry different
variations in the genes for human leukocyte antigens. Goulder and his colleagues found that most of
the HIV in each country carried mutations to the most effective human leukocyte antigens in that
country’s population. Their findings tell us that HIV is rapidly adapting to the variations in human
immune systems around the world. That is sobering news to those who are trying to build HIV
vaccines. If a vaccine ever succeeds in boosting an effective immune response in people, HIV might
well evolve a way to escape.
It’s possible that vaccine developers could keep HIV from escaping by continually rolling out new
vaccines that would stay one step ahead of the virus. Another intriguing possibility is to look back
over its history. A team of American scientists compared a wide range of HIV-1 subtype B strains and
reconstructed one of the proteins made by their common ancestor. They then used that ancestral
protein to make a vaccine. The researchers found that monkeys injected with the vaccine were able to
produce an immune response to a much wider range of HIV strains than more conventional vaccines.
The future of fighting HIV, perhaps, may lie in its past.