A MULTI-CENTER, PLACEBO-CONTROLLED, DOUBLE-BLIND, RANDOMIZED TRIAL COMPARING THE VIROLOGIC AND IMMUNOLOGIC ACTIVITIES OF 400 MG NEVIRAPINE IN COMBINATION WITH ZIDOVUDINE VERSUS ZIDOVUDINE ALONE IN ASYMPTOMATIC HIV-1 INFECTED PATIENTS WITH 4-12 MONTHS OF PRIOR ZIDOVUDINE THERAPY AND 200-500 CD4+ CELL: