Background:
Immunization with inactivated vaccines is an effective strategy to control foot-and-mouth disease (FMD) in endemic countries. In India, inactivated trivalent vaccine against O, A and Asia1 has been used in the bi-annual vaccination program. Traces of viral non-structural proteins (NSPs) in the current inactivated vaccines interfere in the serology-based differentiation of infected from vaccinated animals (DIVA). Therefore, developing a DIVA compliant vaccine will facilitate in accurate sero-surveillance/sero-monitoring. To address this issue, research was initiated at ICAR-IVRI Bengaluru campus for the reverse genetics approach-based development of negative marker vaccine constituting Indian vaccine strains of FMDV serotypes O (IND R2/75), A (IND 40/2000) and Asia 1(IND 63/72) with deletion in portion of NSP (3A protein) of vaccine viruses. Preliminary studies on immunoreactivity of monovalent vaccines in guinea pigs demonstrated their suitability as vaccine candidates. Further, trivalent inactivated deletion marker vaccine formulation was successfully evaluated in a limited number of cattle, a natural host for FMD. This vaccine would be a promising alternative to currently used vaccine, especially as India advances towards achieving a disease-free status through a combined strategy of vaccination and rigorous disease surveillance:
Technology Details:
The innovation achieves the benefits of marker attribute of the Indian FMD vaccine strains in trivalent formulation. The negative marker FMD vaccine helps to rule out false- positive cases in a disease-free zone with vaccination, in the course of disease eradication:
Unique features:
i. Negative marker vaccine strains exhibit growth kinetics similar to their wildtype variants:
ii. Cattle immunized with negative marker vaccine demonstrated neutralizing antibody response comparable to those vaccinated with wild type vaccine, on day 28 post vaccination. Moreover, both groups exhibited similar protection efficacy against homologous live virus challenge:
iii. The deletion marker vaccine strains enable differentiation of infected from vaccinated animals (DIVA) through serological approaches. Specifically, an ELISA targeting the deleted portion of 3A protein is suitable as a companion diagnostic for DIVA. iv. After adapting the vaccine strains to suspension cell line, the FMD vaccine manufacturers can utilize their existing facility without requiring any alteration to grow the marker vaccine strains.