Re: Why can't antibodies against HIV defeat the virus?

Your question about antibodies and HIV is a very good one. Some vaccine efforts are aimed at finding a way to generate antibodies against HIV which would block infection. These antibodies are often directed at the surface proteins of the virus which are required for it to enter into cells. This seems like a good strategy, although in practice I don't think it will be the full answer. Any virus particle that manages to get past the antibody and into a cell would then likely be unaffected by the presence of these antibodies. The virus would replicate inside the infected cell, and probably continue to spread to other cells.

Many people think that an effective HIV vaccine will need to induce strong anti-virus cell mediated immunity. This term refers to cytotoxic T lymphocytes which can identify virally infected cells and kill them ["cytotoxic" means just what its name sounds like - toxic to cells]. By killing all of the virally infected cells, one would rid the body of the virus. The key challenge to this idea is to figure out a way to make a vaccine that best stimulates these killer T cells.

Here is a website that has a bunch more information on the HIV vaccine effort. http://www.iavi.org/newpage/iscience.html

Hope this helps.