AUGMENTED SERUM NEUTRALIZING ACTIVITY AGAINST PRIMARY HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 (HIV-1) ISOLATES IN 2 GROUPS OF HIV-1-INFECTED LONG-TERM NONPROGRESSORS

Neutralizing activity against primary human immunodeficiency virus typ e 1 (HIV-1) isolates from 17 persons who were long-term disease nonpro gressors (LTNPs) and 13 persons who were fast progressors (FPs) was co mpared, Sera from LTNPs showed higher neutralizing activity both in ti ter and in host spectrum than did sera from FPs, However, LTNP sera ha d limited neutralizing activity against HIV-1 subtypes from different geographic areas, Sera collected 6 years earlier from both groups had limited neutralizing activity, indicating that early responses are not predictive for disease progression. LTNPs had very low virus loads, a s reflected by only one positive isolation, which was an MT-2-negative phenotype. Virus was isolated from all FPs, and the isolates showed a phenotype switch from MT-2 negative to MT-2 positive, Development of high-titer, broadly cross-reactive neutralizing antibodies is associat ed with control of virus replication and low virus load in HIV-1-infec ted LTNPs.