Posted by: davidjolson | 11/22/2010

The secret of HIV immunity among Kenyan sex workers

This guest blog was written by Jeanette Strydom, the relationship officer at Africa Health Placements, a member organization of GHC based in Johannesburg.

JOHANNESBURG, South Africa — In the last two decades, there have been numerous reports of a group of commercial sex workers in Nairobi’s Majengo red-light district who remain HIV-negative. These women are thought to have become immune to the HIV virus despite long-term exposure to HIV-positive men. There are around 140 women considered to have this immunity. Scientists are studying these women in the hope of discovering what has kept them HIV-negative in order to produce an HIV/AIDS vaccine.

A group of scientists – known as the “Majengo Researchers” — are investigating why some sex workers and remain uninfected despite repeatedly having unprotected sexual intercourse with HIV-infected partners/clients. The women in question have intense exposure to HIV through their occupation and, although condom use is frequent, their risk of acquiring HIV infection is monumental. Despite this, the small group remains HIV uninfected for prolonged periods – some for up to 13 years.

Normally, an HIV-infected human body creates antibodies, however, due to genetic differences and factors involving repeated exposure to the virus, the Majengo prostitutes react differently argues Joshua Kimani, director of Kenya’s AIDS Control Program. This is evident as they have developed a strong enough response of cytotoxic T-lymphocytes (CTLs) to block HIV infection.

By 1992, the team concluded that the women’s immune system could produce cells known as cytotoxic T-lymphocyte (CTL), also called killer T-cells, that could destroy cells infected with HIV before it was able to multiply in the body.

A setback was suffered in 2000 when 11 of the prostitutes being researched became HIV-positive after being negative for years. This was a massive blow to the project. Upon further investigation, it was found that the women, who are now positive, had stopped prostitution for about up to six months and only got infected after going back to the trade. It was then that they concluded the prostitutes were only able to produce the killer T-cells after continually being exposed to HIV.

Upon quitting or taking a break from prostitution, the immune systems of these women “assumed all was well and reduced the production of the killer T-cells.” This means that by the time they returned to the profession, their bodies could not mount another defence soon enough to counter HIV and they got infected. The Majengo researchers hypothised that the more these prostitutes are exposed to HIV, the higher number of CTLs their bodies produce – which also means that they constantly have to be exposed to HIV to produce enough CTLs.

According to reports, a possible vaccine developed by the researchers has passed a phase I and II safety trial and doctors are currently conducting studies to find out whether HIV-negative people on the vaccine produce the required CTLs instead of antibodies when exposed to HIV.

HIV/AIDS affects almost 40 million people worldwide and has orphaned more than 14 million children in the process. There are 7,000 new infections daily — 67% of these infections occur in Sub-Saharan Africa. The discovery of the secret of these women’s protection could lead to the improved design of vaccines and drugs to fight the deadly virus and save countless lives.


  1. The only secrets here are the lack of ethics of these researchers. I cannot believe that people can read this without being sickened by the ethics. The assumption that unsafe sex with HIV positive men stops when you stop selling sex is ridiculous. If that was so, rates of HIV among Kenyan women would look more like rates in Saudi Arabia. These researchers have systematically edited out much of the relevant information. They have bled these women – literally – and thrown them nothing but a pennies, few aspirins, a couple of condoms and instructions to be very very grateful.

    • It’s a matter of science and facts, not your opinion. From the articles, it is a certain number women who are immune because of repeated exposure so there is genetic link. In other words, not every woman repeatedly exposed will be immune.
      What ethics you talk about? Who’s ethics? who decides your ethics are superior to others’ ethics?

  2. I would be interested in finding out also about how this research is being done and the ethics of this project…

  3. It might be a bit late to ask now, but I was hoping there would be a paper published with the results of the research? Could you possibly point me in the right direction to finding that paper?

  4. There is a great deal of research on this. Nothing recent or conclusive, however.

  5. Thank you!

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