DEVELOPMENT OF A HIV-1 NUCLEOCAPSID (p7) PROTEIN CAPTURE ASSAY

Abstract

The p24 antigen capture assay, the current immunoassay used to detect and quantitate human immunodeficiency virus, is an undesirable assay when analyzing plasma or serum from an HIV-1 infected person because anti-p24 antibodies interfere with the assay. Before development of an antigen capture assay that may be useful in analyzing samples from HIV-1 infected people, sera from HIV-1 positive people were tested for antibodies to the nucleocapsid protein of HIV-1, p7. Of 801 HIV-1 antibody positive sera tested, 100 (12.5%) were positive for anti-p7, indicating low anti-p7 seroprevalence in infected persons. An antigen capture assay for p7 was developed and compared to the p24 antigen capture assay in reconstruction experiments. HIV-1 diluted in normal plasma was readily detected by both the p7 and p24 antigen capture assays. The p7 antigen capture assay detected virus diluted in the HIV-1 positive plasma as efficiently as from normal plasma. However, the p24 capture assay was ineffective in detecting virus diluted in HIV-1 positive plasma, even at p24 input concentrations as high as 460 ng/ml. Even though the p7 antigen capture assay currently lacks the sensitivity to detect virus in the plasma if HIV-1 infected people, the reconstruction experiments indicate that with increased sensitivity the assay may prove to be useful in assessing viral quantity in HIV-1 infected individuals. The p7 antigen capture assay will be useful in neutralization studies even at the current level of sensitivity.