(BETA) Vaccine Research: HIV-2 Infection Partially Protects against HIV-1 Infection - Significant implications for HIV-1 vaccine development

(BETA) Vaccine Research: HIV-2 Infection Partially Protects against HIV-1 Infection - Significant implications for HIV-1 vaccine development

Bulletin of Experimental Treatments for AIDS, No. 26; September 1995
Harvey Bartnof, MD

A newly published epidemiological study indicates that infection with HIV-2, the less virulent strain of HIV, partially prevents infection with HIV-1, the much more common and more virulent strain. HIV-1 is the strain most commonly associated with AIDS throughout the world; HIV-2 is the variant first discovered in Western Africa. Many people infected with HIV-2 show no signs of progression to disease for years. The lead author of the report is K. Travers, MD, from the Harvard School of Public Health. The research paper appears in the June 16, 1995 issue of Science.

The observational study took place over a 9-year period in Dakar, Senegal. The study participants were 756 female commercial sex workers. Those women who were infected with HIV-2 at the onset of the study (or who seroconverted to HIV-2) were found to be 70% less likely to become infected with HIV-1 than those women who remained negative for HIV-2. Among the HIV-2 positive women, 3.7% seroconverted to HIV-1, whereas 9.9% of the HIV-2 negative women seroconverted to HIV-1. The background rate of HIV-1 is so high in this part of sub-Saharan Africa that all women were assumed to be exposed to HIV-1. Moreover, the HIV-2-infected women had higher rates of other sexually transmitted diseasese (STD) than did the HIV-2 negative women, indicating ongoing unprotected sexual contact.

The implications of the report are very significant from the perspective of HIV vaccine development. It is likely that there are some protective immune responses to HIV-2 that are able to help block future infection with HIV-1. Detailed immune studies of the HIV-2-infected women's blood cells and antibodies are likely to provide insights into developing a successful vaccine for HIV-1.

A similar observation in medical history allowed for the successful development of human smallpox vaccine. Smallpox is the only human viral illness known to be eradicated from the earth due to an intensive worldwide vaccine program. Cattle farmers had noted that people who milked cows rarely acquired human smallpox disease. The farmers noticed that the same people did, however, develop minor cowpox sores on their fingers, acquired from cowpox sores on the cows' udders. The physician Edward Jenner was among the first to apply cowpox fluid from cattle by scratching it onto the surface of his children's skin. Although the children did develop minor sores at the skin site, they healed and the children were thereafter protected from smallpox.

Cohen J. Can one type of HIV protect against another type? Science 268(5217): 1566. June 16, 1995.

Travers S and others. Natural protection against HIV-1 infection provided by HIV-2. Science 168(5217): 1612-1615. June 16, 1995.

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