It is well known that HIV progresses faster in women than in men with similar levels of HIV in the blood. Now a US research team has found that a receptor molecule involved in the first-line recognition of HIV responds differently in women.
The findings in Nature Medicine might provide new ways to treat HIV and slow or stop the progression to Aids.
The Massachusetts General Hospital team explored whether known gender differences in the immune system might explain why HIV progresses faster in women.
They focused on immune cells called plasmacytoid dendritic cells or pDCs which are among the first cells to recognise and fight HIV.
Lab studies showed that a higher percentage of these cells from healthy, uninfected women became activated when presented with HIV-1 as compared with pDCs from healthy men.
Lead researcher Dr Marcus Altfeld said: "While stronger activation of the immune system might be beneficial in the early stages of infection, resulting in lower levels of HIV-1 replication, persistent viral replication and stronger chronic immune activation can lead to the faster progression of Aids that has been seen in women."
Ultimately, drugs that work to modify this pathway might help patients with HIV, he said. His team is beginning preliminary laboratory studies into this.
In Rwanda, research presented at an international HIV/Aids symposium in Kigali July last years showed that more men were dying while on anti-retroviral (ARV) treatment compared to women.
Among about 53.615 ARV recipients at that time, there were more women taking the drugs. The death rate among men stood at 3% compared to just 1.9 percent in women, according to the 2007 TRAC Plus report on HIV/AIDS Prevention, Care and Treatment in Rwanda.
"Part of the explanation could be that men are drinking alcohol and more often they are engaging in sex where they have multiple partners", said Dr. Jules Mugabo from TRAC Plus.
Jo Robinson from Terrence Higgins Trust in the UK said the new research by American scientists was “an interesting piece of research exploring whether HIV progresses faster in women than in men.
"Whilst there are some genetic differences based on sex, access to treatment remains the single most important factor in preventing HIV from progressing to Aids.
"Unfortunately women are most likely to be affected by the virus in places like sub-Saharan Africa, where they are also least likely to be able to access HIV treatment", he added.
With additional files and reporting from BBC