HIV infection increases the risk of malaria in pregnant women. For the first time, a study in Malawi suggests why this happens. The results have implications for the development of anti-malaria vaccines and further justify increasing access to anti-retroviral treatment for HIV.

Malaria is an important cause of low birth weight and may kill up to 200,000 children each year. Malaria-endemic areas also have high rates of HIV infection. Antibodies have an important role in protection against malaria. But one of the earliest effects of HIV infection is disrupted antibody production. Does this hamper immunity to malaria?

Researchers, from Australia’s University of Melbourne, the University of North Carolina, USA, and the University of Malawi, analysed blood samples from 298 pregnant women at the Queen Elizabeth Central Hospital in Blantyre, Malawi. Of these women, 44 were infected with both HIV and malaria; 161 had only HIV infection; 43 had only malaria; and 50 were uninfected by either HIV or malaria. The researchers measured blood levels of antibodies that protect against malaria during pregnancy, and related this to the presence and severity of HIV infection.

They found that:

• HIV-infected pregnant women have lower concentrations of these antibodies than women without HIV.
• This difference between HIV-infected and uninfected women is greatest during first pregnancies.
• The effect of HIV on malaria antibodies was most dramatic in the most women with the lowest immunity levels: they had low counts of CD4 T cells (white blood cells which HIV targets) and high levels of HIV in their blood.
• Socioeconomic factors also affect antibody levels. Antibodies were higher in women in rural areas, in women living in poorer houses and in women with less education.

The researchers conclude that HIV infection lowers immunity to malaria. The effect is greatest in women with the lowest immunity levels and could explain the increased risk of malaria seen in pregnant women with HIV infection.

Similar HIV-related effects have been seen in antibody responses to influenza and tetanus vaccinations. Safety and efficacy trials of malaria vaccines should take account of this HIV-related immunosuppression. Anti-retroviral drug treatment for HIV restores some immunity to influenza vaccine, and this may also be true for protection against malaria in pregnancy.

Source(s):
‘Impairment of humoral immunity to Plasmodium falciparum malaria in pregnancy by HIV infection’, The Lancet 363: 1860-1867, by S. Rogerson, et al., 2004 Full document.

Funded by: Wellcome Trust; National Health and Medical Research Council of Australia; US National Institutes of Health

id21 Research Highlight: 21 January 2005

Further Information:
Stephen Rogerson
Department of Medicine
University of Melbourne
Post Office Royal Melbourne Hospital
Parkville
VIC 3050
Australia

Tel: +61 3 8344 3259
Fax: +61 3 9347 1863
Contact the contributor: sroger@unimelb.edu.au

University of Melbourne, Australia

University of North Carolina, USA

University of Malawi

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