Background:
FMD viral particles is remarkably thermo-labile in nature and moderate heat induces the dissociation of intact virions (146S) into the pentameric subunits (12S). Out of the seven immunologically distinct serotypes of FMDV, serotype O has been considered to be more thermo-labile than other serotypes. In addition, the majority of FMDV outbreaks (90-95%) in India have been caused by serotype O. As the potency of the FMD vaccine has been directly related to the preservation of the structural integrity of the intact virion, it is essential to maintain continuous cold chain from vaccine production to its use in animals. However, there are many challenges to maintain the fault-less cold chain for the vaccines from the production site to the field vaccination site. Therefore, a thermotolerant vaccine strain can tolerate transient break in cold-chain conditions for a limited period of time while retaining the potency of the viral antigen/vaccine:
Technology Details:
The present innovation addresses the above problem by developing a genetically defined thermotolerant FMDV serotype O Indian vaccine strain O IND R2/1975 using reverse genetics technology. An enhanced thermal stability was observed for the thermotolerant vaccine strain at different incubating temperature as compared to the parental O IND R2/1975 vaccine strain. In addition, through cattle-challenge experiment it was observed that the oil adjuvanted vaccine formulated with thermotolerant antigen (either monovalent or trivalent form) elicited significantly higher neutralizing antibody response for longer duration and equivalent protective immunity in cattle when compared with the parent virus vaccine. The innovation demonstrated that the vaccine candidate with the enhanced thermostability of the capsids not only elicits higher amplitude and longer duration of neutralizing antibody response, but also increases the stability of vaccine for longer period, signifying its effectiveness as an antigen in the vaccine formulations for sub-tropical climatic conditions.