Early clinical trial results on the potential AIDS vaccine beingdeveloped by Viral Technologies Inc. (VTI), the joint venturebetween Cel-Sci Corp. (NASDAQ:CELI) and Alpha 1 BiomedicalsInc. (NASDAQ:ALBM), were presented Friday at the NinthInternational Conference on AIDS in Berlin.
Not only is the HGP-30 vaccine, which is a synthetic peptideversion of HIV-1's p17 core protein, safe and well-tolerated involunteers, but it's able to elicit T-cell proliferation and CD8killer T-cell responses in some of those people.
Phase I clinical trials of HGP-30 were conducted in a total of 39HIV-negative volunteers at St. Stephen's Clinic & WestminsterHospital in London and at San Francisco General Hospital.
The results of both studies, which the company previously hadpresented separately, showed HGP-30 to be well-tolerated."Essentially, the two trials confirm each other," said GeertKersten, the chief operating officer of Cel-Sci of Alexandria, Va.
But the vaccine may also be able to elicit cytotoxic T-cellresponses, which are thought to be necessary to clear from thebody any HIV-infected cells. In fact, most researchers now feelthat the most important aspect of a vaccine is its ability to elicitcell-mediated immunity, explained Kersten. "But you have todifferentiate between the types of cytotoxic T-cells. The realkilling is done by the CD8 killer cells (not the CD4 helper cells),"he said.
The VTI researchers found a CTL response -- specifically of CD8cells -- in a small number of the vaccinated subjects whoparticipated in the California study. "We still see a CTLresponse in their blood a year after the vaccination," Kerstentold BioWorld.
Research collaborator Richard Markham at Johns HopkinsUniversity injected the blood of those vaccinated individualsinto SCID mice, followed 72 hours later by a "large dose" ofHIV-1: 10,000 TCID-50. The mice were protected from thisviral challenge as measured by both polymerase chain reaction(PCR) and culturing methods, Kersten told BioWorld. Incontrast, "nearly all the control mice got infected," he added.
"We knew we had a CTL response, but not if it was the CD8cells," Kersten said. So to abrogate CD8 cell activity theresearchers added an anti-CD8 monoclonal antibody to theblood before injecting it into the SCID mice. "The protection wasgone," Kersten said. "It looked as if (the human volunteers) hadnever been vaccinated."
Viral Technologies of Bethesda, Md., is working onstrengthening the immune response to its vaccine byimproving the present formulation. The current version ofHGP-30 uses alum as an adjuvant. "We plan to optimizeconditions for linking HGP-30 to carrier proteins and toevaluate various adjuvants, so as to be able to obtain T-cellproliferative and CTL responses in all the immunizedvolunteers," said Prem Sarin, vice president of research at VTI.041493HGP-30
-- Jennifer Van Brunt Senior Editor
(c) 1997 American Health Consultants. All rights reserved.