In an international study, published on Wednesday in the scientific journal, Nature, researchers looked at HIV genetic sequences in over 2,800 people in six different countries in Europe, North America, the Caribbean, Asia and sub-Saharan Africa to determine how the virus had evolved to respond to a key set of molecules in the human immune system called human leukocyte antigens (HLAs).
The type of HLA genes an individual has can determine their ability to fight HIV infection, which partly explains why some people can live with the virus for more than 20 years without treatment while others progress to AIDS within a year.
Researchers have determined that certain HLA genes that are effective at controlling HIV are more prevalent in some populations than others. But the study also found that in these populations, mutations in the HI virus - enabling it to counteract the protective effect of these genes - were also more common.
The findings help explain why different strains of HIV have developed in different parts of the world. In countries with high rates of HIV infection, strains carrying what the researchers called 'escape mutations' have been able to replicate more rapidly than in countries with low infection rates.
"The effect we're describing is far more likely to be seen in the very places where we're trying to make vaccines," said lead researcher Prof Philip Goulder of Oxford University in the UK.
Scientists have long known that the HI virus can mutate rapidly in an individual, but the study provides evidence that mutations in the virus can also spread in a population, posing immense challenges to vaccine development.
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However, the findings are not a reason to give up hope. "It doesn't necessarily mean the virus is winning, just that the ground is shifting. It may be less virulent in the future - we just don't know," Goulder insisted.
"In spite of the fact that we haven't got a vaccine yet, and there have been major setbacks, there's also been major progress," he told IRIN/PlusNews.