Scientists have found that some of the ‘friendly bacteria’ found in yoghurt can be genetically modified to release a drug that blocks HIV infection.

They say in the future women visiting health centres in Africa may be offered a bacterial gel to help fight the spread of AIDS.

Although the bacteria has to date only been tested in a lab dish, the scientists are optimistic that the technique could provide a cheaper and more effective way of delivering drugs to fight the spread of AIDS, by getting the bugs to live right where the drugs are needed most.

The researchers say the bacterium Lactococcus lactis which naturally produces lactic acid, and is used to produce cheese and yoghurt, is also found in some parts of the human anatomy, including the gut and the vagina.

There the acid it produces damps down the growth of other, harmful bacteria.

There are on the market at present some ‘probiotic’ yoghurts which are enhanced with such bacteria with the aim of keeping consumers’ guts healthy.

Bharat Ramratnam, an HIV specialist at Brown Medical School, Providence, Rhode Island, and his colleagues altered the genetic make-up of L. lactis so that it generated Cyanovirin, a drug that has prevented HIV infection in monkeys and human cells, and is well on track for human trials in 2007.

According to the researchers, Cyanovirin binds to sugar molecules attached to the HIV virus, blocking a receptor that HIV uses to infect cells, thus creating passive immunization.

They believe gels containing Cyanovirin could provide some protection for women against the transmission of HIV, but since the drug breaks down quickly these would have to be smeared in the vagina immediately before sex.

They say because lactic-acid bacteria live naturally in the vagina, one application of a bacterial gel should ensure the modified bugs thrive there for at least a week.

The next step might be to find other bacteria that can survive for even longer.

The team suggest that the bugs may have advantages over injected vaccines, which often have trouble reaching peripheral areas of the body, such as mucosal surfaces in the vagina.

The bacteria should also be much simpler and cheaper than producing a drug gel, and if the bugs could be taken orally, as in probiotic yoghurts, production would be even easier, and treatment more easily maintained.

As treating people in developing countries is seen as the biggest problem regarding HIV at present, the new approach could answer those needs.

One of the barriers perceived at present is the public’s fear of genetic modification.

But success in other areas with such treatments might alleviate concerns.

The team say the same technique could also be used to deliver a wide variety of drugs and presents a completely new version of pharmacology.

The research is published in the JAIDS - Journal of Acquired Immune Deficiency Syndrome.