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Antibody Lowers HIV Transmission Risk

Antibody Protects Against Infection -- Maybe Both Ways
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WebMD Health News

Feb. 10, 2003 -- Placed in the vagina, an HIV-blocking antibody protects monkeys from AIDS virus infection. The finding points to a powerful way to slow the wildfire spread of HIV.

Sex is by far the most common way a person gets HIV from another person. Condoms can block HIV transmission, but not enough people use them. One problem is that it's up to a man to choose condom use -- and many men choose not to. What's needed is a covert way for women to protect themselves.

Most experts say a safe vaginal microbicide would do that. It's a substance a woman could put in her vagina that would kill or neutralize HIV. Several potential agents are now being tested. Now there's a new idea. It's based on the recent development of several lab-created antibodies that block most HIV strains. They are able to attack only the strains for which they are designed.

What if a woman could put these antibodies into her vagina before she had sex? Cornell University researcher John P. Moore, PhD, led a team of researchers that looked into this question.

Moore's team used a human antibody called b12. First, they mixed together some of the antibodies with an infectious AIDS virus. When they put the mixture into the vaginas of monkeys, none got infected.

Next, they put the antibody into a liquid or gel and applied it to the monkey's vaginas. Up to two hours later, they then applied an infectious AIDS virus. Without antibody protection, this infects nearly every monkey. But only three of 12 monkeys with antibody protection got infected.

Moore and colleagues know that b12 doesn't protect against all HIV strains. But there are other lab-created antibodies besides b12. A combination of several of these antibodies would protect against virtually every known HIV strain, they suggest.

"A particular advantage of neutralizing ... antibodies is that they might not only reduce male-to-female transmission, but could also neutralize virus within vaginal secretions of an infected women," Moore and colleagues suggest in the March issue of Nature Medicine.

The authors note that these antibodies are not likely to affect fertility. This suggests that couples in which one partner has HIV and the other doesn't could use the antibodies if they want to get pregnant without the risk of infecting their partner.

SOURCE: Nature Medicine, March 2003.

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