New protein piece for AIDS puzzle.

New protein piece for AIDS puzzle

Experiments by two groups working independently have revealed a previously undetected gene and its protein product in the AIDS-causing virus HIV-1. The list of identified HIV-1 proteins now tallies nine. Because the protein's function remains unknown, the scientists say their results do not point to a way to eliminate AIDS. More likely, they say, the protein can help in AIDS diagnosis.

Both groups began by examining a region of the HIV-1 genetic material known to code for several viral proteins. They identified within this region a sequence of nucleotides -- the building blocks of genes -- that genetic rules indicated should code for a protein. They then added the chemical ingredients necessary for gene expression to the potential gene, vpu, and found it does produce a protein.

The scientists next looked for evidence that vpu actually produces a protein outside of the test tube. Analyzing blood sera from a total of more than 30 patients, the two teams detected antibodies to the synthesized vpu protein in people infected with HIV-1 but not in any of the uninfected individuals. This indicates "the protein is certainly made in AIDS patients," says Eric Cohen of the Dana-Farber Cancer Institute in Boston. However, not all infected patients had antibodies against the vpu protein -- a finding the researchers cannot yet explain.

The two groups then diverged in their investigations. Cohen, William Haseltine and their co-workers at Dana-farber went on to examine HIV-2, a virus that differs from HIV-1 in structure but still causes AIDS (SN: 3/7/87, p.151). Until now, scientists have known of only one genetic difference between the two viral forms: HIV-2 contains a gene that HIV-1 does not. The new results, reported in the Aug. 11 NATURE, show another difference: HIV-2 lacks the vpu gene. Cohen says vpu protein has potential to serve as a tool in distinguishing HIV-1 from HIV-2.

Approaching the project from a different angle, Klaus Strebel and his colleagues at the National Institute of Allergy and Infectious Diseases mutated HIV-1 so that it did not make vpu protein. In the Sept. 2 SCIENCE, they report that while the mutants produce fewer whole viruses, they kill as many of their host cells as do the nonmutants. Attempting to explain this paradox, Cohen says vpu protein's job may be to help construct whole HIV-1 from independent viral components, but without vpu protein, the yet-to-be-assembled HIV proteins still may destroy cells. "Vpu may be like a conductor in an orchestra," he says. "Without vpu, the orchestra can still play, but is uncoordinated."