Detection Of P24 Antigen Research Articles

Hemophiliacs With HIV Antibody Are Actively Infected

Cultures of peripheral blood mononuclear cells for human immunodeficiency virus type 1 (HIV-1) and assays for the p24 antigen were performed for a group of 75 unselected hemophiliacs to determine whether patients positive for HIV-1 antibody are actively infected rather than immunized by viral proteins in non-heat-treated factor VIII or IX concentrates. Fifty-six (75%) of the 75 hemophiliacs were antibody positive and 55 (98%) of the 56 with antibodies also had positive cultures. The one culture-negative individual had detectable HIV-1 proviral DNA sequences in three separate samples of peripheral blood mononuclear cell DNA, as detected by a polymerase chain reaction assay. Detection of serum p24 antigen and the time to development of a positive culture were significantly more frequent and shorter, respectively, in symptomatic vs asymptomatic patients. None of the 19 hemophiliacs negative for HIV-1 antibody had positive cultures, detectable p24 serum antigen, or symptoms of HIV-1 infection. Moreover, latent HIV-1 infection was not detected in 16 female sexual partners of hemophiliacs positive for HIV-1 antibody using Western blot testing, assays for p24 antigen, HIV-1 cultures, and polymerase chain reaction assays, despite repeated unprotected sexual exposure. We conclude that antibody-positive hemophiliacs have been actively infected by HIV-1 and that a long period of latent HIV-1 infection prior to overt seroconversion is unlikely.

Detection of human immunodeficiency virus by antigen capture ELISA in culture fluids and blood specimens

A newly developed HIV p24 antigen capture ELISA was compared with the reverse transcriptase assay (RT) for the detection of human immunodeficiency virus (HIV) in culture fluids of virus-infected lymphocytes. The comparison was made by testing 350 culture fluids derived from lymphocyte cultures of 88 patients and collected 7, 14, 21 and 28 days after co-cultivation with lymphocytes from healthy donors. For 87 out of 88 patients there was agreement in the results of the two methods (98·9%) but the antigen capture assay gave positive results 7–14 days earlier than the RT assay with culture fluid specimens from five patients; specimens from only one patient gave discrepant results with a constantly negative RT activity but positive HIV p24 antigen detection at the second and third passage in culture. We also investigated the ability of the antigen capture assay to detect the antigen directly in 246 clinical specimens (including serum, plasma, lymphocytes and cerebrospinal fluid) from 100 seropositive patients, and found that 16% of the patients were positive. These and the former results compared well with those obtained using commercial antigen capture assays. A similar percentage of positivity (16·2%) was observed in a panel of 37 serum specimens from seropositive patients whose antibody response pattern was evaluated by Western blot analysis. Besides, a higher percentage of positivity (66·6%) was observed in a panel of 12 plasma specimens from hemophiliac children for whom virus isolation was also performed.

Shedding of Leukemia-Associated P24 Antigen by Lymphoblastoid Cell Lines

We report the development of a unique enzyme-linked immunosorbent assay (ELISA) which makes possible the detection of leukemia-associated P24 antigen, utilizing its ability to bind the Ricinus communis agglutinin (RCA1) and a monoclonal antibody, SJ-9A4 simultaneously. Using the RCA1/SJ-9A4-ELISA, P24 antigen, as few as 50 X 10(3) cells from a common acute lymphoblastic leukemia (C-ALL) cell line could be detected. The presence of D-galactose gave complete and specific inhibition of P24 antigen binding to RCA1. Matched concentrations of D-glucose and D-sucrose had no effect on binding. The release of the P24 antigen into the culture medium by a C-ALL cell line maintained at 37 degrees C could be detected; however, no P24 antigen was present in the culture medium when the cells were maintained at 4 degrees C. Sequential analysis of the culture medium for soluble P24 antigen revealed that release of the P24 antigen associated with cell growth. Molecular sieve chromatography of concentrated culture medium indicated that shed P24 antigen was eluted in the macromolecule fraction. P24 antigen was detected in the cerebrospinal fluid (CSF) of four patients with P24 positive ALL at the time of relapse of the central nervous system (CNS) and was undetectable while in complete remission. The CSF from three patients with P24 negative ALL and three patients with aseptic meningitis had no detectable activity.