High levels (3116-8370 pg/ml) of HIV-1 p24 antigen were detected and confirmed in serum samples from 3 individuals that were referred to our laboratory for additional HIV serological testing after demonstrating repeated reactivity in the Abbott HIV-1/2 EIA. With one exception (Cambridge Biotech: Reombingen EIA; reactive) these samples were found to be non-reactive for HIV-1 or HIV-2 antibodies in several FDA licensed and non-licensed EIA's. All 3 of these samples were found to be negative for HIV-1 antibodies by an FDA licensed western blot assay (Cambridge Biotech) and in a modified HIV-1 western blot assay optimized to detect IgM responses. Additional specimens were obtained from one of these patients 28 days after the initial serum specimnen was collected. At that time HIV-1 was isolated from the PBMC'S and plasma of this patient and a complete serological profile indicative of HIV-1 seroconversion was demonstrated by IgG and IgM western blotting. These cases illustrate the importance of incorporating HIV-1 p24 antigen assays in testing algorithms to detect acute HIV-I infections when using Screening assays that have been proven to be more sensitive in detecting HIV-1 antibodies earlier in the course of HIV seroconversion than conventional W-l western blot confirmation assays.

Algorithms Blotting, Western Enzyme-Linked Immunosorbent Assay HIV Core Protein p24/*BLOOD HIV-1/*IMMUNOLOGY HIV-2/*IMMUNOLOGY Human IgG/IMMUNOLOGY IgM/IMMUNOLOGY ABSTRACT

www.aegis.org