INDUCTION OF FELINE IMMUNODEFICIENCY VIRUS-SPECIFIC ANTIBODIES IN CATS WITH AN ATTENUATED SALMONELLA STRAIN EXPRESSING THE GAG PROTEIN

Salmonella typhimurium aroA strains (SL3261), expressing high levels o f the Gag protein of feline immunodeficiency virus (FIV) fused with ma ltose binding protein (SL3261-MFG), were constructed using an invertib le promoter system that allows the stable expression of heterologous a ntigens at levels toxic for bacteria. A SL3261 strain expressing the B subunit of cholera toxin by a similar system (SL3261-CtxB) served as a control in FIV-immunization experiments. Cats immunized once orally or intraperitoneally with SL3261-MFG or SL3261-CtxB all developed seru m antibodies to SL3261 lipopolysaccharide and against maltose binding protein or the B subunit of cholera toxin, respectively. Two intraperi toneal immunizations with SL3261-MFG also resulted in the development of Gag specific serum antibodies. Two oral immunisations with SL3261-M FG primed for a Gag specific response, which was demonstrated upon MV challenge, All challenged cars became infected and no significant diff erences in viral loads were found between SL3261-MFG and SL3261-CtxB i mmunized cats. (C) 1997 Elsevier Science Ltd.