A certain gene in some monkeys can help boost vaccine protection against simian immunodeficiency virus, a trait that could help researchers develop better AIDS vaccines for humans, a study has suggested.

Researchers vaccinated a large group of rhesus monkeys and then exposed them to SIV repeatedly over the course of two weeks. Half became infected, but the other half did not.

Those that resisted infection were more likely to express a certain gene, identified as TRIM5.

The findings could help researchers in the elusive search to develop a vaccine against human immunodeficiency virus, which causes AIDS, said lead author Norman Letvin.

“It tells us – probably much to our surprise – that there will likely be in humans certain genes expressed by some people but not in others that may well be contributing to protection,” said Dr Letvin, a Harvard Medical School professor.

“So that we not only have to look at vaccine-induced antibody responses but we also have to look at the genetic make-up of the individuals who are being vaccinated because these data in monkeys suggest that both of these can be contributing.”

A 2009 AIDS vaccine trial on humans in Thailand showed a partial shield against HIV – 31.2 per cent reduction in the risk – but effectiveness dropped after three years, Dr Letvin said.

“We have demonstrated in the Thai vaccine trial that with existing technologies we see modest protection against HIV infections,” he said.