Scientists at Genelabs Technologies Inc. have developed a newway to track previously undetected levels of HIV at everystage of infection, according to a report in today's issue of thejournal Science.
The technique is up to 60,000 times more sensitive thancurrent methods and accurately reveals levels of virus present.The study of 66 patients indicates that HIV levels correlatewith severity of disease and treatment. The techniqueeventually may be used to monitor how well anti-viral agentsare working in seropositive patients.
"It will be particularly useful in clinical trials," said co-authorJeff Lifson, vice president of HIV and exploratory research atGenelabs (NASDAQ:GNLB) of Redwood City, Calif. Researchers atHarvard University developed a similar technique to tracklevels of the immune protein cytokines. Genelabs adapted thatmethod because the company has clinical trials of a potentialAIDS drug in which more than half the patients being studiedwould have tested negative for HIV at the start of treatment,Lifson said.
Current viral load tests involve culturing a patient's serum atvarying dilutions or measuring p24 antigen levels. Both are"sufficiently insensitive," Lifson said, and also quite variable.
The new method amplifies the amount of HIV RNA present inblood plasma through polymerase chain reaction (PCR) andincludes an internal yardstick consisting of known amounts of ashorter template. This strand is amplified along with thenucleotides from the virus, and is later separated inelectrophoresis. Comparing relative amounts of the amplifiedtemplate and HIV RNA indicates how much virus is present.
Genelabs has filed for a patent on the process, Lifson said, andwill continue to validate the method by working with academicinvestigators and using the assay in its own Phase II trial ofthe potential anti-AIDS drug GLQ223, trichosanthin. Thisproprietary formula of a protein-based compound derivedfrom plants apparently inhibits HIV replication in infected Tcells and macrophages.
The present study followed 66 patients and 10 healthyvolunteers recruited at the University of Alabama,Birmingham. Six patients were suffering from acute initial HIVinfection and had presented symptoms of viral infection withintwo weeks of initial exposure to the virus. Their HIV levels,tracked for months, could always be detected, indicating thevirus does not enter a latent stage.
Higher virus levels appeared to correlate with lower T celllevels and progression of the disease, while virus levelsdropped during the time patients were treated with AZT.
-- Nancy Garcia Associate Editor
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