MONOCLONAL-ANTIBODIES TO IMMUNODOMINANT AND NEUTRALIZING DOMAINS OF THE ENVELOPE SURFACE PROTEIN OF FELINE IMMUNODEFICIENCY VIRUS

Hybridomas secreting monoclonal antibodies (MAbs) specific for the sur face protein (SU) of feline immunodeficiency virus were generated. Fou r MAbs were obtained which could be assigned to two groups based on th eir neutralization and competition behaviour. Using SU protein fragmen ts expressed in Escherichia coli the antigenic site recognized by one of the MAbs (2H11) could be mapped to the c terminus. The neutralizing MAb 1E1 did not bind to any of the SU protein fragments and was direc ted to a conformational epitope. Binding of the MAb 1E1 to native SU p rotein could be blocked with a rabbit serum raised against the SU3 fra gment (amino acids 361 to 445). These data indicate that at least part of the epitope is located on this SU3 domain. In competition experime nts most sera of naturally infected cats were able to inhibit binding of the MAbs. This shows the conserved and immunodominant nature of the epitopes involved.