Characterization of foot-and-mouth disease virus antigen by surface-enhanced laser desorption ionization-time of flight-mass spectrometry in aqueous and oil-emulsion formulations

We have used a novel method, surface-enhanced laser desorption ionization-time of flight-mass spectrometry (SELDI-TOF-MS), to characterize foot-and-mouth disease virus (FMDV) vaccine antigens. Using specific capture with FMDV binding recombinant antibody fragments and tryptic digestion of FMDV antigens the spectral peaks representing the FMDV structural proteins VP1, VP2, VP3 and VP4 were identified. VP1 existed as 2 variants differing by 0.2 kDa and VP4 as 8 variants differing by 14–17 Da. Such heterogeneities have not been reported earlier. They could represent oxidation of VP4 and N-glycation of VP1. We also detected FMDV proteolysis upon incubation at elevated temperatures and impurities in FMDV antigen preparations. Finally, we could also characterize FMDV antigen present in emulsions with oil adjuvant by SELDI-TOF-MS. Such FMDV antigen retained the VP4 protein which is known to be specifically present in intact (146S) FMDV particles but absent from specific (12S) degradation products. This indicates that virions do not dissociate upon emulsification.