S. Parida - Improving the duration of immunity for FMD vaccines

Session: Improving conventional vaccines

Open Session of the EuFMD – 2018 – Increasing Global Security in the supply of effective vaccines – 29-31 October 2018 -Borgo Egnazia, Italy

Introduction
Chemically inactivated, oil adjuvanted FMD vaccines are a critical element in FMD control in developing countries. Although these vaccines are effective in pigs and ruminants, protective immunity is not reached quickly, is short-lived (~3 months) and is serotype- and sometimes strain-specific. More appropriate vaccine strains that induce broader protection, together with identification of novel adjuvants that provide a greater duration of immunity and simplified methods to measure vaccine quality would make a significant contribution to FMD control and to livestock development in developing countries.Oil adjuvant vaccines induce variable T cell responses, whilst novel adjuvants can prime greater and more consistent T cell and humoral responses that may give longer duration of protection.

Materials and methods
In our CIDLID funded grant, we had selected 8 new adjuvants as potent immune enhancers, including ligands for TLR receptors that enhanced Th1 priming in various human or animal vaccines. The aim was to supplement the oil component of the adjuvant with a novel immunostimulant that impacts on TLR or related signaling pathways. These eight new adjuvanted vaccines were tested in a pilot study in cattle at IIL, India. The four most efficacious ones (MPLA, Poly I:C, Abisco 300 and R848) were retested for Serotype A in a larger number of cattle at Pirbright, UK. The vaccinated cattle were challenged on 21 days post-vaccination. The most efficacious adjuvant, poly: I:C, tested further in cattle for serotype O FMD vaccine for 7.5 months to assess its impact on the duration of immunity.


Results and Discussion
The enhanced humoral and cellular responses were observed by incorporating poly I:C in FMD vaccine that increased the duration of immunity in comparison to the conventional oil adjuvant vaccine . Therefore we conclude that there is a measurable T cell component to vaccine-induced protection in addition to humoral antibody component and strengthening this would improve efficacy and duration of immunity.

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