Research updates
HIV - a global challenge   page 5
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4. HIV and women  Link to the Medical Research Council web site
 
Heterosexual intercourse is now the most frequent means of transmission of HIV worldwide. As a consequence, HIV infection is occurring in growing numbers of women. By early 1993, an estimated 8 million women were infected with HIV. In the US, 79% of female AIDS patients are aged between 13 and 44 years, with AIDS being the most common cause of death for women aged 25-39 in New York City.
Developing virucides
In Sub-Saharan Africa, 50% of all cases of HIV infection occur in women, the majority of whom are young adults with the potential to transmit the virus to their partner(s) or children. Although the correct and consistent use of condoms by men is known to reduce the risk of HIV transmission significantly, women may be unable to negotiate such safe sexual practices. This is particularly the case where women have less power in sexual relationships than men. Consequently, there is a need to develop additional and complementary methods of protection which women can control.

MRC scientist Prof. Andrew Nunn and Dr Sheena McCormack at the MRC Clinical Trials Unit are currently coordinating a large research programme to develop potential vaginal virucides in close collaboration with teams at Imperial College. One promising candidate is dextrin sulphate (D2S). Related to heparin, dextrin sulphate is a sulphated poly-saccharide and, although described as a virucide, is actually virostatic. D2S has been shown, in the test tube, to prevent binding and entry of HIV to susceptible cells. In gel form D2S could be used to coat the outside of epithelial cells lining the vagina and so may prevent sexual transmission of HIV. Feasibility studies for clinical trials to test this hypothesis are currently under way in Africa.

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Question 4
a) Explain the meaning of the words virucide and virostatic (in bold and underlined) in the last paragraph.

b) Explain why a virostatic agent may be only partially successful in preventing heterosexual transmission of HIV.

c) What would you regard as the essential features of any vaginal virucide?

d) Given that such virucides are being designed primarily for use in developing countries, what extra features would you add?

e) What do you think is meant by ‘confounding factors’ in a trial?