Differences in HIV Strains May Underlie Disease Patterns

Important note: Information in this article was accurate in 1995. The state of the art may have changed since the publication date.

Differences in HIV Strains May Underlie Disease Patterns

Science (10/06/95) Vol. 270, No. 5223, P. 30
Cohen, Jon

At the Third International Conference on AIDS in Asia and the Pacific, retrovirologist Max Essex of the Harvard School of Public Health presented data that may help explain why HIV is primarily transmitted through heterosexual intercourse in developing countries, while the virus is spread most often in the industrial world via anal intercourse and shared needles. Essex said the differences between the HIV strains in the two worlds could be the cause. He noted that 10 percent or fewer of HIV-1 infections are due to vaginal intercourse in the United States and Europe, but that the situation is completely opposite in Thailand. "That suggests that something is dramatically different," Essex said. In collaboration with teams from Mahidol University and Chiang Mai University, Essex and his colleagues at Harvard tested various virus subtypes on Langerhans' cells gathered from the vagina, cervix, breast, and penile foreskin. According to Essex, the research showed that HIV "subtype E"--the strain with which most Thai heterosexuals are infected--has "a clear propensity for better infection with those cells that line the female genital tract. However, "subtype B," the strain which dominates in Europe and the United States, had virtually no growth. This finding led Essex to suggest that there may be two separate HIV-1 epidemics--one in which subtype B predominates and that is spread by blood and homosexual sex, and a second involving the other HIV-1 subtypes and primarily vaginal sex. Although the proposal was received well by most, others had serious reservations. One researcher noted the overwhelming presence of subtype B in the Caribbean, Central America, and Brazil-- regions which all have primarily heterosexual epidemics.

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