Submitted to: Research Workers in Animal Diseases Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 10/25/2006
Publication Date: 12/4/2006
Citation: Zsak, L., Pisano, M., Neilan, J.G. 2006. Genomic and biological variability of foot and mouth disease virus serotype A: Exploration of the 'quasispecies' nature of RNA viruses and characterization of A24 variants in naive and vaccinated cattle [abstract]. In: Proceedings of the 87th Conference of Research Workers in Animal Diseases, December 3-5, 2006, Chicago, Illinois. p. 127. Interpretive Summary:
Technical Abstract: Foot-and-mouth disease (FMD) is an acute, systemic disease of domestic and wild cloven-hoofed animal species and is caused by FMDV. The quasispecies nature of FMDV, and other RNA viruses is a hallmark of RNA virus genetics. Thus, investigation of the potential hypervariability of FMDV is relevant to the development of novel vaccines and antiviral treatments. The objective of these studies was to assess the hypervariability of the FMDV A24 virus VP1 capsid region following experimental direct challenge of naïve and FMD vaccinated cattle. In the first study, non-immunized cattle (n=5) and cattle previously immunized with an experimental non-replicating human adenovirus-vectored A24 vaccine (Ad5A24) (n=4) or 21 (n=5) days earlier, were challenged via the intradermal-lingual route with FMDV subtype A24 Cruzeiro. In the second study, non-immunized cattle (n=6) and cattle previously immunized with either an inactivated A24 (n=5) or experimental Ad5A24 (n=5) vaccine 4 or 7 days earlier, were similarly challenged. At various timepoints post-challenge, tongue epithelial tissue and vesicular fluid was collected, viral RNA extracted, cDNA prepared and FMDV A24 capsid-specific primers used to amplify and sequence PCR products. Comparative sequence analysis using ClustalW and EMBOSS-Align software was conducted to determine if there were variations within the VP1 region between the original A24 Cruzerio challenge virus and the new isolates obtained from naïve and vaccinated animals. Results demonstrate 97 to 99 percent identity in the VP1 coding region between A24 Cruzerio challenge virus and A24 virus isolates obtained from tongue epithelial or vesicular fluid. Importantly, there was a similar degree of identity between A24 virus isolates obtained from naïve, nonprotected, vaccinated, protected and vaccinated, non-protected animals. These data suggest that cattle previously immunized with either current inactivated A24 vaccine or experimental Ad5A24 vaccine do not appear to produce new FMD escape variants that could emerge as a consequence of antibody-mediated selective pressure.