GACPAT HIV-1- A SIMPLE, INEXPENSIVE ASSAY TO SCREEN FOR, AND DISCRIMINATE BETWEEN, ANTI-HIV-1 AND ANTI-HIV-2(2 )

A simple and cheap assay suitable for screening for anti-HIV 1 and ant i-HIV 2 and discriminating between them was evaluated. In it specimens are incubated in U-bottomed microplate wells coated with anti-human I gG for 30 min at room temperature. After washing, 100 mu l of a 1 in 5 0 dilution of HIV 1-coated gelatin particles (Serodia-HIV 1/2, Fujireb io) are added. Settling patterns are read on the second day: A positiv e reaction is indicated by adherence of the particles and a negative b y a button. The HIV 1 particles a re then washed away a nd HIV 2 parti cles added. Anti-HIV 2 reaction patterns are read on the third day. To assess the performance of the modified ''GACPAT HIV 1+2'' assay a pan el of 1,621 serum/plasma specimens was used. It comprised validated an ti-HIV 1 positive (n = 220), anti-HIV 2 positive (n = 214), dual anti- HIV 1/antiHIV 2 positive (n = 11), and anti-HIV negative (n = 1,176) s erum/plasma specimens. All 434 specimens that contained anti-HIV 1 or anti-HIV 2 reacted positively with the homologous particles. The 11 du ally positive specimens reacted positively with both HIV 1 and HIV 2 p articles. Five (2.3%) anti-HIV 1 and five (2.3%) anti-HIV 2 positive s pecimens gave positive reactions with both particle types, but none of the five cross-reactive anti-HIV 2 specimens were dually reactive whe n the order of particle addition was reversed. One repeat false positi ve reaction was recorded with the HIV 1 particles and none with the HI V 2 particles, giving specificities of 99.9% and 100%, respectively. T ype specificity was 98.8% after the results of the reverse assay had b een taken into account. The assay was sensitive for anti-HIV 1 in sero conversion series and for anti-HIV 2 in highly diluted specimens. GACP AT HIV 1 + 2 is an accurate anti-HIV assay applicable to serum/plasma. With few exceptions anti-HIV 1 positive specimens are reactive only o n the second day and anti-HIV 2 positive specimens only on the third d ay. It thus discriminates anti-HIV 2 from anti-HIV 1, probably through depletion of cross-reacting antibodies by the reaction with the parti cles initially added. (C) 1995 Wiley-Liss, Inc.