AIDS: "Natural killer" clue to virus vulnerability

Individuals with key variants in an important immune cell and a molecule that controls it show a slower progression to AIDS after they are infected with the human immunodeficiency virus (HIV), a study released on Sunday says.

The paper focuses on "natural killer" cells, which are unleashed by the immune system to crush viral intruders.

Natural killers are switched on or off by receptors, or docking sites, on their surface. The receptors are activated by a molecule presented to the cell by the immune system's signallers.
Researchers led by Mary Carrington of the United States'National Cancer Institute, Maryland, looked at variants in two genes -- one that creates a receptor named KIR3DL1, and one that creates a signalling molecule called HLA-B.

In a study of 1,500 people with HIV, they found that individuals who had specific variants in both genes were helped "significantly and strongly," progressing to AIDS much later than counterparts without these variants and also having lower levels of virus in the blood.

The study is released online by Nature Genetics.

Meanwhile, work published in a sister journal, Nature Immunology, casts light on how HIV can foil the immune system by stifling a sentry cell called a dendritic cell.

By latching onto the DC-SIGN receptor on this cell, the virus blocked the signalling pathway, enabling itself to swarm around nearby immune T-cells and penetrate them.

Around 39.5 million people were living with HIV or AIDS at the end of last year, according to the World Health Organisation (WHO) and UNAIDS.