Immunomodulation of water-in-oil-in-water (w/o/w) emulsion vaccines of killed Pasteurella multocida (P52) whole cells grown under iron-regulated conditions

Abstract

Immunization studies on 2 water-in-oil-in-water (w/o/w) vaccines incorporated with whole cells of Pasteurella multocida P52 grown in iron-sufficient (WCFe+) and iron-deficient (WCFe-) media were carried out in various groups of healthy adult rabbits with and without levamisole (s/c injections), vitamin E (incorporated in the external aqueous phase of w/o/w emulsion) and commerical immunomodulator (P/o) containing a combination of synergistically acting herbs Cissus quadrangularis, Uraria picta, Lepedium sativum elemental calcium 400mg and phosphorus 200mg/5g of the commercial product) as immunomodulators. Antibody response was monitored and active protection was observed by direct challenge of rabbits on 21st day of immunization. Cross-prtective immune-response against heterologous A: 3 and F:3 serotypes of P. multocida was observed by passive mouse protection test (PMPT) using 21st day pooled sera from respective immunized groups without immunomodulators. Both WCFe+ and WCFe- Vaccines showed a responsive rise in serum antibody titres from seventh day up to the 21st day of inoculation and more than 80% protection was onserved in rabbits immunized with either of the caccines and vaccines with commercial immunomodulator (CI). However, s/c injections of levamisole (2.5mg.kg:3 injections) and vitamin E incorporated in the external phase of w/o/w emulsion augmented the immune response not only in terms of antibody titres but also in terms of protection after direct challenge. Protection (100%) was achieved in respective groups of the 2 immunomodulators. Only WCFe vaccine showed a partial cross-protective response in PMPT against F:3 sertype. Possibilities for using external aqueous as a vehicle for incoporating immunomodulators and or same or other antigens can be exploited in future for improving the existing w/o based HS vaccines.