Effect of different adjuvants in equines for the production of equine rabies immunoglobulin.

ABSTRACT

BACKGROUND: Implementation of the recommended post-exposure prophylaxis by vaccination and specific immunoglobulin therapy for rabies is largely hampered by its high cost and inadequate production. Therefore, the development and availability of an economic preparation of rabies immunoglobulin is a high priority for India, where rabies is a major cause of death. We studied the efficacy of four different adjuvants in raising antibodies to rabies antigen in older, discarded equines. METHODS: Eleven equines, 23-26 years old, were divided into 4 groups to receive four different adjuvants in small amounts (1-2 ml)-Freund complete adjuvant with Mycobacterium tuberculosis, Freund complete adjuvant with M. butyricum, Freund incomplete adjuvant and bentonite--along with purified chick embryo cell vaccine. The immunization schedule was spread over 105 days and the antibody titres were measured on days 56, 91 and 119. RESULTS: On day 119 (third sampling), Freund complete adjuvant with M. tuberculosis provided a geometric mean titre of 654.03 IU/ml in comparison with a titre of 459.19 IU/ml with Freund complete adjuvant with M. butyricum, 630.95 IU/ ml with Freund incomplete adjuvant and 172.18 IU/ml with bentonite. CONCLUSION: Purified chick embryo cell vaccine in combination with Freund complete adjuvant containing M. tuberculosis and Freund incomplete adjuvant were better at eliciting an immune response. The low quantity of adjuvants used possibly helped by causing very few side-effects but without compromising the antibody titres.