Evaluation of the immunogenicity of a recombinant glycoprotein-based Chandipura vaccine in combination with commercially available DPT vaccine.

Chandipura virus (CHPV) belongs to family Rhabdovoridae and has emerged as an encephalitis causing pathogen with high mortality among pediatric population from three Indian states. The recombinant glycoprotein (rGp) was shown to be an excellent vaccine candidate as evaluated in a murine model. As the disease is predominantly rural, to ensure maximum coverage for Chandipura vaccine, an attempt was made to evaluate combination of rGp and a commercially available DPT vaccine (CHP-DPT). When CHP-DPT was used for immunization of mice, 90% seroconversion against rGp with high antibody titers (1:1200 by ELISA and 1:320 by neutralization test) was observed and did not differ from mice immunized with rGp alone (P>0.05). Similarly seroconversions and antibody titers against DPT were comparable in mice immunized with DPT alone or in combination with rGp. Seroconversions and antibody titers ranged from 90 to 100% and 1:1200 to 1:2400 respectively. Intracerebral challenge with homologous CHPV strain resulted in 90% survival in rGp alone and CHP-DPT groups. Lymphocyte proliferative responses were also comparable. Thus, neither components of the candidate combination vaccine inhibited immune response to the other component. Substantial decrease of CHPV RNA and absence of histopathological changes in the brains of surviving immunized mice after challenge than the unimmunized controls further confirm efficacy of the vaccine even after intracerebral challenge. In conclusion, a combination vaccine seems feasible for use in a restricted area where the disease is endemic and should be subjected to additional studies required for future use in humans.