MONOCLONAL ANTIBODY-MEDIATED INHIBITION OF RNA-BINDING AND ANNEALING ACTIVITIES OF HIV TYPE-1 NUCLEOCAPSID PROTEIN

Retroviral nucleocapsid (NC) proteins are highly basic, with one or tw o zinc fingers, and are required for virion formation, genomic RNA dim erization and packaging, and replication primer tRNA annealing to the viral RNA. We report here the first characterization of monoclonal ant ibodies directed against a retroviral nucleocapsid protein and their u se to study the structure-function relationships of the nucleocapsid p rotein NCp7 of HIV-1. Four anti-NCp7 monodonal antibodies (MAbs) have been generated by using NCp7 of HIV-1. The epitope targets of these MA bs were mapped using ELISA and BIAcore techniques. Whereas three of th em are specific for epitopes located in the N and C termini of NCp7, t he fourth one appears to be conformation specific. Interestingly, only two of these MAbs, the conformation-specific one and the MAb recogniz ing an N-terminal epitope are able to inhibit the RNA-binding and anne aling activities of NCp7 as well as strong-stop DNA synthesis in vitro . The binding of the two other MAbs onto NCp7 either has no effect or enhances the NCp7-RNA interactions. These MAbs also display a differen tial recognition of the Gag polyprotein precursor, which makes them us eful tools for studying NC protein maturation in the course of virion morphogenesis.