SUPERINFECTION OF HIV-2-PREINFECTED MACAQUES AFTER RECTAL EXPOSURE TOA PRIMARY ISOLATE OF SIVMAC251

To test the protection afforded by a weakly pathogenic HIV-2 isolate a gainst the superinfection or development of SIV-induced disease, we in trarectally challenged six HIV-P-preinfected rhesus monkeys with a pat hogenic Isolate of SIVmac251. At the time of SIV challenge, none of th ese HIV-2-infected animals was positive for virus isolation, p27-Gag a ntigenemla, or HIV-2 provirus detection in PBMCs or peripheral lymph n odes. However, all monkeys exhibited anti-HIV-2 antibody titers rangin g from 10(2) to 10(3). Neutralizing antibodies against the challenge S IV strain were also detected in two animals. After rectal exposure to SIVmac251, five of the six HIV-2-preinfected macaques were superinfect ed. SIVmac251 DNA sequences were detected repeatedly in the PBMCs of t he five superinfected animals and the two controls, whereas no HIV-2 p rovirus was detected for 14 months postchallenge. The one monkey that resisted superinfection was negative for all SIV infection criteria. T his monkey exhibited the highest anti-SIV ELISA and cross-neutralizing antibody titers on the day of SIV challenge. Preinfection with a weak ly pathogenic HIV-2 ROD isolate protected one of six macaques from inf ection with the closely related pathogenic SIVmac251 isolate, but no p rotection from the progression of disease was evidenced in the other f ive. (C) 1996 Academic Press, Inc.