Dossiers Sexologiques

21 January 2008

New research from Oxford scientists shows that sexual education programmes that only teach abstinence as a way of reducing risky sexual behaviours in teenagers don’t work.

After analysing 13 different programmes being taught to almost 16,000 teenagers across the US, scientists reported in the British Medical Journal that these abstinence-only programmes do not seem to reduce the risk of HIV infection. The programmes also fail to reduce number of sexual partners, incidence of unprotected sex, condom use or pregnancy. Regardless of these findings, the US government throws millions of tax payers’ dollars into these programmes.

The same group from Oxford writing in PloS Medicine showed that ‘abstinence-plus’ programmes that teach abstinence but also safe sex alternatives (such as condom use) do have an effect in lowering the risky sexual behaviours. Although some argue teaching abstinence alongside condom use might confuse teenagers, it seems that this is a much safer way to implement sexual education. Apparently it is difficult, but not impossible, to make young people stop having sex; policymakers might as well accept it and push for the programmes that teach how to have sex safely if they want to tackle the HIV epidemic.

We don’t like it when politicians in African countries ignore scientific advice on HIV, but what about the politicians closer to home who push these programmes that do nothing for HIV prevention? Most cases of AIDS are transmitted through sexual intercourse. Scientists are currently investigating the molecular details of infection which may help to reduce transmission of the virus even if unprotected sex does occur.

However, so far we lack detailed knowledge of how the infectivity of the HIV virus is affected by semen. A recent study published in Cell shows how proteins naturally found in semen may help the virus infect the cells. Researchers were looking for molecules in semen that might block the virus’s activity but instead came across an enhancer that may actually help the virus become up to 100,000 times more infective.

This means even low levels of virus can infect us with the help from our own treacherous proteins. The way this works is that fragments of prostatic acidic phosphatase (PAP), a protein found in semen, form fibres that capture and protect viral particles until they reach human cells, where the fibres may help the virus interact with the cells and allow for an easier entry.

So this “Trojan horse” strategy helps the HIV virus to overcome our initial defences and infect us more effectively. This finding has two important implications for potential future prevention of HIV transmission. Firstly, molecules that can block PAP’s activity may be used in microbicidal gels to inhibit the infection. Secondly, scientists can learn how to use these PAP fibres to deliver vaccines more effectively (100,000x more effectively!).

AIDS is not the only deadly disease that can be transmitted through unprotected sex, though. An intriguing possibility is that prions, proteins that cause mad cow disease in cattle and variable Creutzfeld-Jakob disease (vCJD) in humans, can also be transmitted through semen. Although no one has yet found infectious prions in semen, the number of bodily fluids known to harbour prions is ever increasing: blood, saliva, urine, even milk! The very possibility of having the deadly prions present in semen has brought about a ban in the US on use of sperm donated by Europeans who lived in a country with exposure to mad cow disease. This now means that there is a shortage of European sperm in the US sperm banks and this leads to development of “fertility tourism” in Europe where some Americans come for artificial inseminations.

Current expert opinion published in 2006 in the Reproductive Biomedicine Online is that the risk of vCJD transmission through donated sperm is 1:10,000,000. Future research will show if vCJD really can be considered to be an STD. What this example shows, though, is that one can never be too careful about protection when it comes to sex-related activities!