Circulating human immunodeficiency virus (HIV) p24 antigen-positive lymphocytes: a flow cytometric measure of HIV infection.

Asymptomatic individuals seropositive for human immunodeficiency virus (HIV) progress in a heterogeneous fashion toward AIDS. To facilitate monitoring of disease progression and response to therapy, a rapid, new flow cytometric assay (FCA) lymphocyte p24-FCA, has been devised to quantify peripheral blood lymphocytes expressing cell-associated HIV-1 p24 antigen. Results from 55 asymptomatic, HIV-1-seropositive, serum p24 antigen-negative individuals ranged from undetectable (less than 0.1%) to 13.6% p24+ lymphocytes (mean, 2.0%). Mean values for three other groups studied were 0.1% for seronegative, viral culture-negative laboratory workers (n = 24); 4.2% for untreated patients with AIDS (n = 16); and 0.3% for AIDS patients receiving zidovudine (n = 11). Lymphocyte p24-FCA values were inversely related to the number of days to positive viral cultures and to levels of CD4+ lymphocytes. The ratio of p24+ lymphocytes to CD4+ lymphocytes may reflect the fraction of infected CD4+ lymphocytes. Lymphocyte p24-FCA determination may provide a method for monitoring response to antiretroviral therapy regardless of serum p24 antigen status.