The vulnerable spot is hidden in a protein essential for the Human Immunodeficiency Virus, the virus that causes Acquired Immune Deficiency Syndrome, to attach to host cells, the university said in a release.

An HIV vaccine doesn't exist because HIV is a mutating virus.

The scientists said they are focusing on a stretch of amino acids on HIV's envelope protein gp120.

"Unlike the changeable regions of its envelope, HIV needs at least one region that must remain constant to attach to cells. If this region changes, HIV cannot infect cells," said Sudhir Paul, a pathology professor at the UT Medical School.

Paul's group engineered antibodies with enzymatic activity, called abzymes, that can attack the virus's weakness.

"The abzymes recognize essentially all of the diverse HIV forms found across the world. This solves the problem of HIV changeability," Paul said. "The next step is to confirm our theory in human clinical trials."

The theory was in a recent issue of Autoimmunity Reviews and will be presented during the International AIDS Conference Aug. 3-8 in Mexico City.