THE unnatural union of two molecules could provide a new way to treat AIDS
and prevent HIV infection.
By linking a viral protein to bacterial DNA, Anthony Horner and Eyal Raz of
the University of California, San Diego, and their colleagues have created a
bizarre molecule not normally seen in cells. This hybrid is very effective at
stimulating immunity in mice. 鈥淭he immune response has the elements you鈥檇 like
to see for an ideal HIV vaccine,鈥� says Horner.
Protein vaccines stimulate the immune system to produce antibodies, which
target free viruses in the blood. But most experts believe immunity against HIV
also requires the production of cytotoxic T lymphocytes (CTLs) that can seek out
and destroy cells invaded by the virus.
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Horner and Raz suspected that they could trick the immune system into
producing CTLs against a protein by adding a small piece of bacterial DNA.
Previous work by their lab and others has shown that the immune system is
programmed to respond to bacterial DNA with an arsenal of attack cells like
CTLs.
Mice injected with the two molecules simply mixed together did produce CTLs
against the viral protein. But the response was far greater when the protein
and DNA were chemically linked. Horner thinks this ensures that the same immune
cell that encounters the protein is also stimulated by the DNA.
Intriguingly, mice whose immune cells were depleted to resemble the ravaged
immune system of an AIDS patient still responded to the vaccine鈥攅ven
though they lacked key cells. 鈥淭he vaccine can bypass these crucial cells,鈥� says
Raz.
He says such vaccines might help AIDS patients to fight off secondary
infections, as well as providing a way to tackle HIV.
