REMOVAL OF THE CLEAVAGE SITE OF RECOMBINANT FELINE IMMUNODEFICIENCY VIRUS ENVELOPE PROTEIN FACILITATES INCORPORATION OF THE SURFACE GLYCOPROTEIN IN IMMUNE-STIMULATING COMPLEXES

Recombinant vaccinia viruses were constructed that expressed the compl ete env gene of feline immunodeficiency virus with or without the nucl eotide sequence encoding the cleavage site between the surface (SU) pr otein and the transmembrane (TM) protein. The removal of this cleavage site resulted in the expression of a 150K protein that was processed into a 130K protein and was not cleaved into the SU and the TM protein s. Removal of the cleavage site also facilitated incorporation of the SU protein in immune-stimulating complexes (iscoms). Antibody response s to both an SU and a TM peptide representing two immunodominant B cel l epitopes were measured. These were higher in cats immunized with isc oms prepared from the cleavage site-deleted envelope protein than in c ats immunized with iscoms prepared from the native envelope protein or immunized with the envelope protein and the adjuvant Quil A.