Rapid serologic testing with immune-complex-dissociated HIV p24 antigen for early detection of HIV infection in neonates. Southern California Pediatric AIDS Consortium.

BACKGROUND: Serologic detection of human immunodeficiency virus (HIV) infection in neonates is complicated by the presence of immune complexes, consisting of passively transferred maternal antibodies and HIV antigens. A new, rapid assay has been designed to disrupt these immune complexes in order to permit the detection of a specific HIV antigen. We evaluated the efficacy of this assay in detecting HIV infection in neonates.
METHODS: We measured p24 antigen in blood samples from both infected and uninfected children of HIV-infected mothers. The samples were treated with glycine hydrochloride to dissociate the immune complexes, followed by neutralization with TRIS-hydrochloric acid. A commercial HIV p24 antigen assay was then used, with an optical density greater than 0.120 at a wavelength of 450 nm defined as indicating a positive result.
RESULTS: Of eight cord-blood samples from neonates with proved HIV infection, five were positive for immune-complex-dissociated p24 antigen. For two other neonates the first postnatal sample, obtained on days 12 and 18, was positive. There was no follow-up sample for the eighth neonate. Of 22 uninfected neonates, 20 were negative on the cord-blood assay. Two neonates had positive cord-blood samples, but the first postnatal sample was negative. Thus, the tests with early postnatal samples identified the HIV-infection status correctly for all 29 children who could be evaluated. In a separate group of 78 children (median age, 188 weeks), the specificity of the test was 100 percent and the sensitivity 81 percent.
CONCLUSIONS: The immune-complex-dissociated HIV p24 antigen assay is a rapid, simple serologic test that may be of value in diagnosing HIV infection in neonates born to HIV-infected women.