University of Texas scientist creates promising HIV vaccine candidate

Jul 21 2010

The Abzyme Research Foundation announces today that Dr. Sudhir Paul, a scientist at University of Texas Houston Medical School, has identified an important immunological deficiency in HIV-infected patients and has created a promising HIV vaccine candidate that rectifies the deficiency.  The discoveries were presented on July 19th and 20th, 2010 at the XVII International AIDS Society Conference in Vienna, Austria.

The HIV vaccine candidate has been tested in mice and rabbits.  It was effective in inducing the production of protective antibodies that stopped the HIV from infecting human blood cells in laboratory tests.

Dr. Paul and his colleagues discovered that HIV patients do not produce sufficient protective antibodies of a type called IgG that are capable of attacking the vulnerable CD4 binding site on the HIV.  The virus binds to human host cells through this site to cause infection. The CD4 binding site is a small part of gp120, a protein found on the surface of HIV.  Studies of mice injected with gp120 confirmed an insufficient IgG response to the CD4 binding site. Previous vaccine tests by other researchers used the gp120 protein itself without success in protecting against infection.

"Using an electron-seeking form of gp120, we triggered the production of the crucial IgG antibodies to the CD4 binding site in animals," said Dr. Paul. "We believe this method is the key to developing an HIV vaccine."

Dr. Paul's team has found that chemical stimulation of the immune system by electron-seeking (electrophilic) proteins is the central step for rectifying the defective antibody response to the CD4 binding site. Since the structure of the CD4 binding site is very similar in all HIV strains throughout the world, a globally effective HIV vaccine may be possible.

Lead E-VAC Candidate

The researchers have developed a synthetic electrophilic vaccine candidate, or E-VAC, which works by focusing the antibody response at the CD4 binding site. The E-VAC is a synthetic portion of gp120 that successfully mimics the shape of the CD4 binding site expressed by the HIV virus. Administration of E-VAC to animals induces antibodies with enzymatic activity, or abzymes. Unlike traditional antibodies that neutralize the target on a 1:1 basis, abzymes are significantly more efficacious because each abzyme molecule can neutralize thousands of target molecules.

E-VAC administered to mice and rabbits induced the production of blood-borne IgG antibodies that blocked the infection of human cells by genetically divergent HIV-1 strains from across the world.

"We are backing the research of Dr. Paul's team because his approach using abzymes shows enormous progress in creating an HIV vaccine," said Alan Kleiman, chairman of the board for the Abzyme Research Foundation. "Our foundation aims to drive discovery and innovation in the field of HIV research in hopes of one day eliminating the HIV/AIDS pandemic."

The lead E-VAC was developed from recent proof-of-concept studies that validated targeting of the CD4 binding site and chemical stimulation of the immune system as published recently by Dr. Paul's team in the journals AIDS and The Journal of Biological Chemistry. The work is being conducted at the University of Texas Houston Medical School and California Department of Public Health with support from the National Institutes of Health.