IMMUNOGENICITY OF NEF PROTEIN OF SIVSMM(PBJ14) EXPRESSED IN A LIVE VACCINE STRAIN OF SALMONELLA SPECIES

The nef gene of an infectious molecular clone of SIVSMM isolate PBjl4 was fused to the glutathione S-transferase gene of Schistosoma japonic um to generate plasmid pEMC100. The recombinant plasmid was placed in an aroA live vaccine Salmonella dublin strain, and the production of G ST-Nef protein was induced by exposure to IPTG. The fusion protein was purified and administered as vaccine to BALB/c mice by i.p. injection . Several doses of the purified fusion protein produced an earlier ant i-GST-Nef response, without an anti-GST response, than did IPTG-induce d Salmonella live vaccine containing an equal amount (0.1 mu g) of fus ion protein, apparently because of the transient immunosuppressive eff ect of live vaccine given by injection. The highest anti-GST-Nef titer s were obtained by a third immunization schedule in which mice were tr eated with a priming inoculum of induced live vaccine followed, after the predicted immunosuppressed interval, by two i.p. doses of 1 mu g o f purified GST-Nef protein with Ribi adjuvant. The data presented here demonstrate that SL5928 aroA, an attenuated S. dublin strain, can be used as a live vaccine carrier to express Nef protein of SIVSMM-PBj14, one of the most acutely pathogenic primate lentiviruses so far descri bed.