HIV-1 p24 Antigen Detection by Immune Complex Dissociation and Neutralization in HIV-1 Infected Persons in Korea

Kang, Chun; Kim, Sung Soon; Kee, Mee Kyung; Nam, Jeong Gu; Choi, Byung Sun; Lee, Joo Shil; Lee, Yung Nok; Ryu, Jae Chun; Shin, Yung Oh

Abstract

BACKGROUND: HIV-1 p24 antigen assay is useful for the detection of circulating viruses, and infection prior to seroconversion. However, circulating HIV-1 p24 antigen may be complexed with HIV antibody and prevent it from being detected by antigen capture assay. To detect HIV-1 p24 antigen in the specimen, it is necessary to dissociate immune complexes and confirm the presence of HIV-1 p24 antigen after the neutralization with the specific antibody.
METHODS
We tested 32 sera from HIV-1 infected persons who were diagnosed from 1987 tO1996 in Korea for HIV-1 p24 antigen by enzyme linked immunosorbent assay (ELISA.) with or without the dissociation of immune complexes. And we confirmed the antigen assay results by the neutralization with HIV-1 specific antibody as a confirmatory test. We also calculated the concentration of HIV-1 p24 antigen in each specimen.
RESULTS
Eleven of 32 sera tested were initially positive for HIV-1 p24 antigen. After the dissociation of immune complexes for 29 sera except two of which signal/cutoff ratios were higher than 7.0 and except one which was not enough for the assay,13 were shown to be positive for HIV-1 p24 antigen and their signal/cutoff ratios were increased by 10 times. Five of antigen negative cases were turned to be positive after the immune complex dissociation. After neutralization with HIV-1specific p24 antibody for sera of 13 which were positive for HIV-1 p24 antigen with or without the immune complex dissociation, all were shown to be neutralized. We have observed more than 90% neutralization reduction for 12 sera and more than 50% less than 90% for one. The average concentration of HIV-1 p24 antigen was8.76pg/ml by antigen assay and was increased to 76.81~g/m~ after immune complex dissociation.
CONCLUSION
We concluded that the sensitivity and the specificity of HIV-1 p24 antigen assay could be increased by dissociation of the immune complexes and neutralization with the specific antibody.