SIMPLE MONITORING OF ANTIRETROVIRAL THERAPY WITH A SIGNAL-AMPLIFICATION-BOOSTED HIV-1 P24 ANTIGEN-ASSAY WITH HEAT-DENATURED PLASMA

Objective: Virus load determination has become indispensable for the m anagement of HIV patients, but depends on expensive assays of a low th roughput. We evaluated whether a highly improved HIV-1 p24 antigen det ection procedure which involves heat-mediated immune complex dissociat ion and signal-amplification-boosted enzyme-linked immunosorbent assay (ELISA) was suitable for antiretroviral treatment monitoring. Design and methods: Virus load in plasma was determined for 127 plasma sample s taken at 0, 2, 6, 12, 18, 24, 30 and 36 weeks from 23 patients with CD4+ T cells < 50 x 10(6)/l who received indinavir 800 mg three times daily in addition to prior antiretroviral treatment. Tests included po lymerase chain reaction (PCR) for viral RNA, measured prospectively wi th the Roche Amplicor kit, and retrospective batch testing of heat-den atured samples for p24 antigen by the DuPont HIV-1 p24 Core Profile EL ISA linked with a tyramide signal amplification step. Particle-associa ted reverse transcriptase (RT) by the product-enhanced RT (PERT) assay was determined as an independent third-opinion viral load marker. Res ults: p24 antigen was detected as sensitively as viral RNA. Overall de tection during a median observation time of 25 weeks (range, 0-39) amo unted to 75.6% for antigen and 73.6% for RNA. The antigen detection li mit was 0.2 pg/ml. Antigen was detectable in all 23 baseline samples, whereas RNA was undetectable in one. Antigen and RNA levels in 79 samp les positive for both markers correlated with r = 0.714 (P < 0.0001). Average changes in levels of p24 antigen and RNA at eight timepoints c orrelated with r = 0.982 (P < 0.0001). In individual patients, the two parameters behaved similarly, and in certain cases virtually identica lly. RT activity was measurable in all samples. Conclusions: The perfo rmance of this antigen detection procedure is comparable to RNA PCR, t hus providing a simple, high throughput alternative in monitoring the efficacy of antiretroviral treatment.