Acid Dissociation Increases the Sensitivity of p24 Antigen Detection for the Evaluation of Antiviral Therapy and Disease Progression in Asymptomatic Human Immunodeficiency Virus-Infected Persons

Because the time from primary infection to symptoms in human immunodeficiency virus type 1 (HIV-1) infection is typically 8–10 years, the use of surrogate markers to monitor disease progression and therapeutic efficacy is of interest. An acid dissociation procedure that disrupts the p24 antigen-antibody complexes found in early HIV-1 infection has greatly increased the sensitivity of p24 detection assays. The utility of p24 antigen after acid treatment as a surrogate marker of disease progression and therapeutic effect in asymptomatic HIV-infected subjects receiving zidovudine (AZT) was determined. After acid treatment, the sensitivity of p24 antigen detection increased fivefold. The proportion of subjects who were antigenemic increased over the 48-week follow-up in the placebo group; ∼50% of subjects who were p24 antigen-positive at entry and who received AZT showed clearance or a >50% reduction in baseline p24 antigen levels at 16 and 32 weeks. Thus, acid treatment of plasma may allow the use of p24 antigen as a marker of disease progression and therapeutic response.