Investigators from the University of Pennsylvania School of Medicine are reporting encouraging results from the preliminary human trial in which an HIV vector, loaded with genetic material that inhibits HIV replication, was found to decrease viral load in chronic HIV patients.
Viral loads of the patients remained stable or decreased during the study, and one subject showed a sustained decrease in viral load. T-cell counts remained steady or increased in four patients during the nine-month trial. Additionally, in four patients, immune function specific to HIV improved.
Overall, the study results are significant, say the researchers, because it is the first demonstration of safety in humans for a lentiviral vector (of which HIV is an example) for any disease. Additionally, the vector, called VRX496, produced encouraging results in some patients where other treatments have failed….
“The new vector is a lab-modified HIV that has been disabled to allow it to function as a Trojan horse, carrying a gene that prevents new infectious HIV from being produced,” says Levine. “Essentially, the vector puts a wrench in the HIV replication process.” Instead of chemical- or protein-based HIV replication blockers, this approach is genetic and uses a disabled AIDS virus to carry an anti-HIV genetic payload. The modified AIDS virus is added to immune cells that have been removed from the patients’ blood by apheresis, purified, genetically modified, and expanded by a process June and Levine developed. The modified immune cells are then returned to the patients’ body by simple intravenous infusion.
This approach enables patients’ own T cells, which are targets for HIV, to inhibit HIV replication — via the HIV vector and its anti-viral cargo. The HIV vector delivers an antisense RNA molecule that is the mirror image of an HIV gene called envelope to the T cells. When the modified T cells are given back to the patient, the antisense gene is permanently integrated into the cellular DNA. When the virus starts to replicate inside the host cell, the antisense gene prevents translation of the full-length HIV envelope gene, thereby shutting down HIV replication by preventing it from making essential building blocks for progeny virus. VRX496 was designed and produced by the Gaithersburg, Md. biotech company VIRxSYS Corp.