Appendix 23
Characterisation of monoclonal antibodies against foot-and-mouth disease vaccine strain C1 Oberbayern and their reactivity with field isolates N. Aggarwal*, S. J. Cox, R. J. Statham, P. V. Barnett International Vaccine Bank for FMD, Institute for Animal Health, Pirbright Laboratory Pirbright, Surrey GU24 0NF, U.K.
Introduction The 2001 epidemic of foot-and-mouth disease (FMD) in the U.K. and mainland Europe was a timely reminder of the devastating consequences of this disease. Although the epidemic was brought under control by slaughter of all infected/in-contact animals and traditional zoosanitary measures, vaccination was considered as an option, at-least in the early stages of the epidemic. The International Vaccine Bank (IVB) for FMD at Pirbright holds quantities of seven strains of inactivated FMD virus (FMDV) antigen over liquid Nitrogen, ready for immediate formulation into vaccine if required. These will protect against the viruses of serotypes that are most likely to threaten the livestock of the UK or other IVB member countries (i.e. serotypes A, O, C and Asia 1). The antigenicity of FMDV can change because of frequent mutations in it's genome, and thus evade the immunity provided by vaccines. It is therefore necessary to monitor the field isolates for their relatedness to vaccine strains to ensure that currently available vaccine will provide protection against any new isolate. Currently, an ELISA based on the use of polyclonal hyperimmune serum is used by the WRL for FMD for the antigenic profiling of field isolates. However, the inherent variation in the properties of polyclonal serum batches complicates the interpretation of results. An antigen profiling ELISA, based on monoclonal antibodies (MAbs) has also been described (Samuel et. al., 1991). We aim to refine this approach in order to have a more reliable ELISA that could ultimately alleviate the need for in-vivo testing of selected vaccine strains. As a first step towards this goal, we have started production and characterisation of monoclonal antibodies to cover the entire antigenic spectrum of vaccine strains held by the IVB. In this report results are presented of studies that have been done with the C1 Oberbayern vaccine strain of FMDV. Materials and Methods Cells and Viruses All the strains of FMDV were procured from WRL for FMD at Pirbright and were grown either in BHK-21 or IB-RS2 cells. Monoclonal antibody production Six-week old BALB/c mice were immunised by the sub-cutaneous route with 10 µg of C1 Oberbayern antigen that was received from the IVB. Immunisation was repeated at day 21 and 35 after first inoculation. Three days after the last immunisation, spleens were aseptically 190
