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| |  HIV Plasma Viral Load Can Predict the Risk of AIDS and Death PITTSBURGH, May 23, 1996 -- Viral load, the amount of human immunodeficiency virus (HIV) RNA in the plasma of infected individuals, can accurately predict how quickly people with HIV infection will progress to AIDS and, ultimately, their survival, according to a study published in the May 24, 1996 issue of Science. The study, led by John W. Mellors, M.D., associate professor of medicine, University of Pittsburgh Medical Center (UPMC), and co-investigator of the Pittsburgh site for the Multi-center AIDS Cohort Study (MACS), demonstrates that direct quantification of HIV-1 RNA by branched DNA (bDNA) predicts HIV disease progression earlier and more accurately than CD4+ T-cell counts, the most commonly used marker, regardless of an individual's disease stage at measurement. "Our findings confirm that baseline HIV RNA levels measured by bDNA can accurately predict the risk of AIDS and death," said Dr. Mellors. "The data also indicate that we can predict disease progression as far as 10 years into the future." The study results indicate that a baseline viral load measurement provides an excellent marker of both time to AIDS and time to death. Using the bDNA assay developed by Chiron Diagnostics, investigators measured baseline viral load in plasma samples from 180 HIV-infected individuals. The risk of progression to AIDS after five years was 8 percent among those whose HIV RNA measurements were in the study's lowest quartile. On the other hand, 62 percent of individuals whose viral load was in the highest quartile progressed to AIDS within five years. Estimated survival time in the lowest through highest viral load quartiles was greater than 10 years, 9.5 years, 7.4 years and 5.1 years, respectively. Conversely, among the three quartiles with the highest CD4+ T-cell counts, no differences were observed for either time to development of AIDS or time to death. Dr. Mellors' findings indicate that prognosis in HIV infection is directly related to viral load. Further, other completed studies indicate that reduction in viral load in response to therapy improves prognosis. "These simple principles may help us to individualize patient therapy and provide better information to guide therapeutic research," said Dr. Mellors. "Measuring HIV viral load with bDNA provides us with a prognostic tool that is similar to that of surgical staging procedures for cancer, which has important implications for both management of HIV-infected individuals and therapeutic research," Dr. Mellors continued. Currently, a significant drop in CD4+ T-cell counts is considered an indication of disease progression and is used to gauge a patient's response to anti-viral therapies. Unfortunately, changes in CD4+ T-cell counts can occur later than increases in viral load. "Measuring viral load with the bDNA assay predicts disease progression and death better than the CD4 count because the level of HIV in plasma most likely drives the CD4 cell decline, which is a marker for the deterioration of the immune system," said Dr. Lawrence A. Kingsley, associate professor of epidemiology and microbiology at the University of Pittsburgh, and epidemiologist for the study. The authors were able to conduct the study because of the resources available through the Pitt Men's Study, the Pittsburgh arm for MACS. "We were able to select specimens from the thousands of blood samples in our repository that were contributed during the last 12 years by more than 1,000 gay and bisexual male volunteers in the study," said Charles Rinaldo, Ph.D., professor of pathology and microbiology at the UPMC and principal investigator of the Pitt Men's Study. The bDNA assay, the Quantiplex(R) HIV RNA assay, is currently under review by the Food and Drug Administration. In the meantime, HIV RNA viral load measurement by bDNA is available to physicians from the Chiron Reference Testing Laboratory, a service of Chiron Diagnostics.
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