Twelve murine monoclonal antibodies (MAbs) to human immunodeficiency virus type 2 (isolate ROD) envelope glycoproteins have been generated and characterized. Nine MAbs were specific to the external gp125 and three reacted with the transmembrane gp36. A large majority of MAbs displayed a significant affinity for the native gp140 precursor and were shown to bind to viral antigens on the surface of fixed HIV-2-infected cells. In Western blot analysis, the 12 MAbs showed varying profiles of cross-reactivity, but none of the MAbs cross-reacted with the HIV-1LAI envelope. Six MAbs reacted exclusively with the homologous HIV-2ROD isolate whereas only two MAbs displayed cross-reactivity with HIV-2ROD, HIV-2EHO, and SIVmac251. The four other MAbs cross-reacted with either HIV-2EHO or SIVmac251. Results of competitive binding assays indicated that the three anti-gp36 MAbs shared the same competition group, whereas at least eight competition groups were defined with the nine anti-gp125 MAbs. The epitopes of the three anti-gp36 and four anti-gp125 MAbs have been delineated using synthetic peptides or by immunological screening of an SIVmac251 peptide library expressed in yeast. The anti-gp36 MAbs are directed against the same domain of the transmembrane gp36 corresponding to the major antigenic determinant of HIV-2 and HIV-1. The four anti-gp125 MAbs recognize four distinct epitopes localized in the V2, V3, and C1 domains. None of the 12 MAbs displayed neutralizing activity against HIV-2ROD, including the 2 MAbs directed against the V2 and V3 domains.(ABSTRACT TRUNCATED AT 250 WORDS)