Protective immune response to liposome adjuvanted high potency foot-and-mouth disease vaccine in Indian cattle.

BACKGROUND

Foot-and-mouth disease (FMD) vaccines applied for prophylactic use in endemic areas provide short-lived immunity requiring regular boosters. Indian FMD control program recommends twice a year vaccination. Development of high potency vaccines that provide better immune response can singificantly contribute to control programme by reducing the frequency of vaccination. The present study explores new adjuvants to enhance the protective efficacy of inactivated trivalent FMD vaccines.

METHODOLOGY AND PRINCIPAL FINDINGS

VacciMax(®) is a novel adjuvant which uses a liposome-based oil emulsion platform. Cattle were immunized using VacciMax-A and VacciMax-B FMD vaccines and evaluated for protective efficacy. Similar groups of animals were also boosted after 6 months to study the effect of booster immunisation on protection against homologous challenge. Serum samples from immunized animals were tested by virus neutralization test (VNT) and liquid phase blocking ELISA (LPBE). After challenge, animals were screened for virus load by real-time PCR and reactivity in non-structural protein (3ABC) antibody detection ELISA to corroborate the protection data. A single dose of VacciMax-A formulation elicited higher percentage protection (63%) in VacciMax-A compared to 25% in VacciMax-B upon challenge at one-year post-vaccination. Upon boosting at 6 months also, VacciMax-A group showed higher levels of protection (100%) compared to VacciMax-B (86%), even though both the groups elicited comparable VNT titre (p=0.4964). The results also demonstrated that intramuscular route was preferrable over subcutaneous route of administration.

CONCLUSION

The study demonstrates that immunization with VacciMax-A-IM adjuvanted FMD vaccine with high antigen payload under boosting regimen could effectively be used as potent vaccine to maintain herd immunity.