Just five amino acids could make the difference between a person who naturally controls HIV and someone who would progress to AIDS if not treated, a new human genome study has found.
The research analyzed the genetic makeup of almost 1,000 HIV controllers and 2,600 progressors, finding more than 300 points associated with immune control of HIV. All were in regions of chromosome six that code for HLA (human leukocyte antigen system) proteins. Scientists then pinpointed five amino acids in the HLA-B protein as key.
HLA-B is involved in the immune process that recognizes and destroys virus-infected cells. A protein called the binding pocket moves peptides from inside the virus onto the cell membrane, marking the cell for destruction by CD8 "killer" T cells of the immune system. The five distinguishing amino acids are in the binding pocket, according to scientists from Massachusetts General Hospital (MGH), Massachusetts Institute of Technology and Harvard University.
"We found that, of the 3 billion nucleotides in the human genome, just a handful make the difference between those who can stay healthy in spite of HIV infection and those who, without treatment, will develop AIDS," said study co-author Bruce Walker of MGH.
"We have a long way to go before translating this into a treatment for infected patients and a vaccine to prevent infection, but we are an important step closer," Walker said. "Knowing how an effective immune response against HIV is generated is an important step toward replicating that response with a vaccine."
The study, "The Major Genetic Determinants of HIV-1 Control Affect HLA Class 1 Peptide Presentation," was published online ahead of print by Science (2010;doi:10.1126/science.1195271).
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Source: BBC News (11.04.10):: Caroline Parkinson; Courtesy of the CDC National Center for HIV, STD, and TB Prevention