Humoral Immune Response of Inactivated Bivalent <i>Leptospira</i> Vaccine among Dogs in Tiruchirappalli, Tamilnadu, India

Abstract

Leptospirosis has been recognized as the disease of the dogs. The prevention of canine leptospirosis can block the transmission of the etiological agent to humans. Commercial vaccines prevent not only clinical leptospirosis but also the renal carrier state in dogs. Thus in this present investigation, the humoral immune response of the vaccinated dogs with the multivalent vaccine (Megavac-6) was analyzed. Enzyme linked immunosorbent assay (ELISA) with preparations of 2 whole cell lysate, 2 leptospiral LPS, 4 purified recombinant proteins were used to test sera from 30 dogs vaccinated with MEGAVAC-6, a commercial vaccine practiced by the animal husbandary Departments in Tamilnadu. All 30 sera were positive by ELISA with whole cell lysate of Canicola and Icterohaemorrhagiae, and ELISA with Canicola LPS, Icterohaemorrhagiae LPS; antibody titres ranged from 20 to ≥10,240. Although there was less frequent reactivity of sera with recombinant antigens, antibodies to LipL32 and LigA were detected in 25 (83.3%) serum samples. Less frequent reactivity was noted when recombinant GroEl, LK73.5 antigens were included separately in ELISAs. The highest MAT titre was observed against the serovar Canicola and Icterohaemorrhagiae. The more reactivity against LPS may be due to the dominance of serovar specific leptospiral LPS, which may be the dominant immunogenic antigen in inactivated bivalent leptospiral vaccines. Eventhough LPS is the dominant antigen. It is serovars specific and hence recommends the incorporation of the locally circulating serovars in vaccine for its efficient use. The efficiency at this point can be increased by the use of subunit vaccines rather than recombinant proteins as such. The present study has proposed certain epitopes with increased antigenic potency.