London, Mar 21 : HIV has long been considered dangerous because of its ability to dodge the immune system to stay undetected. But now, researchers have found that certain mutated strains of the deadly virus are easier to combat in subsequent infections, paving the way for designing an HIV vaccine.
According to Carolyn Williamson at the University of Cape Town in South Africa, there are patients who have genetic mutations in the machinery of their immune system that can track and respond to HIV infection. And in such patients, HIV ceases its ability to grow for staying unaffected by the immune attack.
"HIV strives to survive. It will even compromise its fitness to evade detection - and that might impair its ability to replicate," New Scientist quoted Williamson, as saying.
The researchers demonstrated that in its other form, HIV fails to stay on if it is transmitted to a new host, even though the person doesn't have the favourable mutations in their immune system.
These mutations are located on chromosome 6, which is a region that controls the production of virus-fighting white blood cells, called the Human Leukocyte Antigen (HLA) locus.
For the study, the researchers followed 21 South African women, who got the HIV infection recently and were known to lack the beneficial HLA mutations.
After analysing their HIV, it was confirmed that recently it had passed through a host who carried the advantageous forms of HLA. This implies that the virus had the tell-tale "escape mutations" for averting detection by an enhanced immune system.
It was discovered that after three months of infection, the women carried, on average, 4.7 copies of the virus per millilitre in their blood plasma.
Nine months later, the women were re-examined and a slight drop, an average of 4.6 copies per millilitre, in the viral load was detected. However, normally after nine months, there would be a huge spike in the number of viral particles.
On the other hand, people who did not have the HIV-busting form of HLA, it was found that the virus was no longer under pressure to avoid detection and eventually shed the valuable escape mutations that impede its ability to replicate.
However, Williamson thinks that the fact that it carried those mutations at the time of infection is key.
"There is a massive destruction of the immune system immediately following infection. One hypothesis is that, if people have less immune destruction during this time, they will have better long-term prospects," she said.
According to Michael Busch of the University of California, San Francisco, the result could have implications for delaying HIV infections in general.
"One possible direction from this research is to develop vaccines which stimulate an immune system that selects for the less fit variant. This would not only help the infected individuals, but could help the community at large," he said.