LENTIVIRUS CROSS-REACTIVE DETERMINANTS PRESENT IN THE CAPSID PROTEIN OF EQUINE INFECTIOUS-ANEMIA VIRUS

In this study we used immune sera from equine infectious anaemia virus (EIAV)-infected horses which uniquely display broad reactivity with d ifferent lentivirus capsid proteins (CA) to characterize the cross-rea ctive determinants of lentivirus CA proteins. In particular, the role of the major homology region (MHR) of lentivirus CA proteins in this s erological cross-reactivity was evaluated using both equine immune ser um and murine monoclonal antibodies (MAbs) directed against the MHR se gment of different lentiviruses. The results of our studies indicate t hat about 80% of sera from long-term experimentally infected ponies or naturally infected horses react with human immunodeficiency virus typ e 1 CA in Western immunoblot assays. In addition, the cross-reactive d eterminants on the EIAV CA were localized within the immunodominant ca rboxyl terminus of the protein (residues 277 to 367). However, the cro ss-reactive determinants recognized by the equine sera do not appear t o correlate with linear peptides from the carboxyl terminus of the EIA V CA, including the MHR. These results suggest cross-reactivity betwee n more distant lentiviruses is associated with non-linear determinants . In contrast, MHR-specific MAbs did react with linear peptides by ELI SA and distinguished the primate lentiviruses from EIAV and feline imm uno-deficiency virus. These data support the concept of a highly conse rved structural and antigenic organization among the CA proteins of le ntiviruses from different species.