Slight differences in five HLA amino acids may explain why certain people resist the human immunodeficiency virus, US researchers said in a study that lends new clues about how to make an Aids vaccine.
"For a long time, we've known that some people progress extremely rapidly when they get infected, and others can stay well for three decades and never need treatment and still look entirely well," said Dr. Bruce Walker of Massachusetts General Hospital and Harvard University, whose study appeared online in Science.
"We thought we could apply new techniques from the human genome project to understand what the genetic basis was for that," he said.
About one in 300 people infected with HIV have an intrinsic ability to maintain low viral loads. To learn more about this ability, the researchers conducted genome-wide association analyses in a multiethnic cohort of such HIV-1 controllers, and in so-called progressors as well.
That helped them identify some 300 single nucleotide polymorphisms in the major histocompatibility complex, "and none elsewhere," according to their paper.
"We did a second study where we looked amino acid by amino acid in that region," Dr Walker said.
Specific amino acids in the human leukocyte antigen (HLA)-B peptide binding groove, and an independent HLA-C effect, explained the SNP associations and reconciled protective and risk HLA alleles, he and his team reported.
"We've got a clearer indication of why people can survive in the face of HIV, and we've gotten more focused in terms of the research we need to do to get where we've got to go," Dr. Walker said.
In September 2009, scientists reported their biggest success yet with an experimental vaccine that showed a modest effect and appeared to slow the rate of infection by about 30%. In July 2010, US researchers found antibodies that can protect against a wide range of Aids viruses and said they may be able to use them to design a vaccine.
(Reuters Health, Julie Steenhuysen, November 2010)