AIDSWEEKLY Plus, Monday, 3 March 1997
Daniel J. DeNoon, Senior Editor
CD4 count - long used by AIDS clinicians to track HIV disease progression - is still the best surrogate marker for immune function.
Sensitive new measures of HIV viral load provide a wealth of information on disease progression. These new tests may be the most sensitive measure of how well an individual is doing in his or her struggle with the AIDS virus.
But data obtained in a Phase II clinical trial of the Genentech candidate HIV vaccine show that a patient's CD4 count remains the best mark of immune function.
"Although HIV replication drives CD4-cell loss, CD4 count is a better marker of immunologic function than plasma HIV-1 RNA level," wrote Donald R. Kuritzkes of the University of Colorado, Denver, and colleagues in the abstract of their presentation to the Fourth Conference on Retroviruses and Opportunistic Infections, held January 22-26, 1997, in Washington, D.C.
The trial obtained baseline measures of immune function from the 164 study participants. These measures included microbial and HIV specific lymphocyte proliferative assays (LPA); HIV specific cytotoxic lymphocyte (CTL) activity; CD4 counts; plasma HIV-1 RNA levels (RT-PCR); and quantitative HIV-1 cultures.
Subjects were stratified by CD4 counts and by whether or not they had received antiretroviral drugs. These strata were: A1 (antiretroviral naive, CD4 350-500 cells/(micro)L); A (ARV-treated, CD4 350-500 cells/(micro)L); B (ARV-treated, CD4 200-349 cells/(micro)L); and C (ARV-treated, CD4 50-199 cells/(micro)L).
Positive lymphocyte proliferation assays to at least one microbial antigen were seen in 18 percent of stratum A1 patients, 60 percent of stratum A patients, 33 percent of stratum B patients, and in seven percent of stratum C patients.
Positive lymphocyte proliferation assays to one or more microbial antigen were seen in five percent of stratum A1 patients, 14 percent of stratum A patients, four percent of stratum B patients, and in two percent of stratum C patients.
"CD4 count and LPA responses to microbial antigens were significantly correlated," Kuritzkes et al. wrote.
Specific lysis of HIV-1[MN] envelope targets was detectable in six percent of stratum A1 patients, 15 percent of stratum A patients, eight percent of stratum B patients, and in none of the stratum C patients.
HIV Gag-protein specific lysis was detectable in 42 percent of stratum A1 patients, 34 percent of stratum A patients, 26 percent of stratum B patients, and in 14 percent of stratum C patients.
As seen in other studies, there was a very strong (r=0.46, P=0.0001) negative correlation between CD4 count and HIV-1 viral RNA level.
Multiple regression analysis, however, showed that CD4 count - and not viral RNA level - significantly (albeit weakly) correlated with lymphoproliferative responses to microbial antigens.
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