New cause suggested for high African HIV rates

Immune cells may contribute to higher HIV infection rates in Kenya

Flickr/DFID UK Department for International Development

[NAIROBI] Malaria, and other common African infections, may make women more susceptible to HIV/AIDS than they are in the developed world, according to a study that may help solve the mystery of the vastly different infection rates around the globe.

Researchers who compared immune cells in the genital tracts of women in Kenya and the United States, found that Kenyan women had more "activated" cells, which are more vulnerable to attack by HIV. Cells can become activated as a reaction to infection.

It is the first time that scientists have shown that immune cells in the genital tract are more activated in African women, though higher activation elsewhere in the body has already been demonstrated. The activation may be an "important additional contributor" to the high infection rates in African women, according to the scientists, led by Craig Cohen, of the University of California, San Francisco, in the United States.

"We believe that these findings should also start to dispel some of the preconceptions and stigma surrounding HIV acquisition among young women in Sub-Saharan Africa," said the authors, writing in the journal AIDS.

The scientists compared CD4 cell counts — an indicator of immune system strength — of women aged 18–24 years in San Francisco, with those from Kisumu, Kenya. They found that Kenyan women had more activated CD4 cells. The researchers controlled for other genital infections and sexual behaviour, which are therefore unlikely to be an explanation of the increased activity.

They say that it is possible that other "systemic" infections, such as malaria, that affect the whole body, might cause the increase. Another possible cause is schistosomiasis and similar infections that occur at other mucosal sites in the body. It is also possible that there is a genetic cause.

"Although it has been suggested that reasons for the discrepancy in HIV seroprevalence include higher prevalence of sexually transmitted infections ... as well as structural and sociocultural factors, for the first time our observations suggest that differences in the genital tract immune milieu may be an important additional contributor," said the team.

François Venter, head of the HIV management cluster at the Reproductive Health and HIV Research Unit, University of the Witwatersrand, South Africa, said: "[The study] is exciting, and hopefully will start to answer why the epidemic is so bad in our region — 70 per cent of the entire world's population of HIV-infected people live in Sub-Saharan Africa.

"We've had many theories around culture, behaviour and biology, but none has proven adequate alone to explain this disproportionate vulnerability to infection. This research may help provide some, if not all, of the answers."

Carolyn Deal, chief of the sexually transmitted diseases branch of the National Institute of Allergy and Infectious Diseases, United States, said the study's strength lay in its detailed immunological tests. It "fits into what is an ongoing discussion and a growing recognition that there are differences [in HIV infection rates] in different geographic regions".

But Caroline Kabiru, an associate research scientist with the African Population and Health Research Center, Kenya, said: "Beyond the biological factor, women are more vulnerable due to poverty. It means we need to provide programmes where women can have alternative methods of raising their livelihoods so that they are not turning to sex."

The research was published in the journal AIDS last month (24 August).

Link to abstract in AIDS