Relationship between Anti-p24 Antibody Levels and p24 Antigenemia in HIV-Infected Patients

We studied the influence of HIV p24 antigen immune complexing with anti-p24 antibodies on the assessment of their respective levels in HIV-positive sera. ELISAs were used to evaluate anti-p24 antibody levels and p24 antigenemia, with or without acid dissociation. Observations include the following: (1) p24 antigenemia usually coexisted with low anti-p24 levels; (2) the p24 antigen concentration inversely correlated with anti-p24 antibody levels; and (3) acid dissociation increased the percentage of p24 antigen-positive sera, mostly when anti-p24 was low. In contrast, (1) antigenemia and antibodies varied independently in antiretroviral-treated AIDS patients, undetectable p24 antigen coexisting then with low anti-p24; (2) after acid dissociation, antigen was still undetectable in 83% of sera with high antibody levels, and in 20% with low antibody levels; and (3) acid dissociation did not increase low anti-p24 levels. Whereas the first set of observations indicates that p24 antigen and anti-p24 antibodies can be engaged in immune complexes, the second set indicates that p24 antigen and antibodies were not inevitably linked in such complexes: they may actually be indicative of two distinct biological phenomena.