S.24. Studies on Microencapsulated Oral cell culture rabies vaccine in mice model

Rabies virus causes meningioencephalitis. Oral immunization is the best way to limit the spread of rabies virus, but it needed high concentrations of protein for oral immunization, so the use of adjuvants or gastrointestinal protectants are needed to reduce the protein dose and protect the antigen from gastrointestinal acidic environment. Hence in the present study Poly- Lactide- Co- Glycolide (PLG) biodegradable microspheres were used to achieve these ambitious goals. Microsphers were prepared with whole rabies virus antigen or glycoprotein by double emulsion or solvent evaporation technique was administered to mice by oral or intraperitoneal route. All microencapsulated vaccine groups showed eight fold higher IgG antibody response than only virus given orally. Microencapsulated intraperitoneally vaccinated groups showed highest sera IgA titer than other groups. Mucosal IgA response was significantly higher in groups orally vaccinated with encapsulated antigens. Mouse neutralization test also showed protective antibody titer of 8 in all i/p vaccinated groups (both microencapsulated and only antigen groups). In the challenge test 100% protection was observed in PLG + virus (i/p), PLG + GP (i/p) and virus (i/p) where as 75% protection was observed in PLG + virus (oral) and PLG + GP (oral), but only virus given orally showed 50% protection. The cell mediated immune response, which was assessed by LTT test, the mean stimulation index (S.I) value of microencapsulated virus antigen by both oral and intraperitoneal route was significantly higher (<1.87) than other groups. Microencapsulated virus groups showed significantly higher IgG2a titer (Th1 response) where as PLG + virus (i/p) group showed good IgG1 titer (Th2 response). All the intraperitoneally vaccinated groups expressed a significant level of IL-4 cytokine, which ranged from 4000–5000 pg/ml as assessed by Sandwich cytokine ELISA. PLG encapsulated virus groups showed higher level of IFN-gamma expression, which was estimated by reverse transcriptase PCR. Thus this encapsulation technique may be useful in mass oral immunization programme to control rabies in stray dogs using this encapsulated antigen in a suitable bait system. Further studies are warranted in natural host.