Novel Purification Method for Recombinant 3AB1 Nonstructural Protein of Foot-and-Mouth Disease Virus for Use in Differentiation between Infected and Vaccinated Animals
2005
Nanni, Mariana | Alegre, Mariana | Compaired, Diego | Taboga, Oscar | Fondevila, Norberto
An indirect enzyme-linked immunosorbent assay (ELISA) was developed for differentiation of animals infected with foot-and-mouth disease virus (FMDV) from vaccinated animals. The test was based on a highly pure and concentrated preparation of recombinant 3AB1 protein obtained by expression in a prokaryotic system, protein separation by sodium dodecyl sulfate–polyacrylamide gel electrophoresis, and electro elution. Experimental- and field-serum samples from naive, vaccinated, and infected cattle were tested for anti3AB1 antibody using the ELISA. A cutoff level was set at 35% of the maximum absorbance obtained with a positive control serum (FMDV-infected animal, 21 days postinfection [dpi]). This assay could detect antibodies from sera of animals experimentally infected by contact (n = 118) with a sensitivity of 97.5%. The specificity was 100%, based on negative test results obtained on 109 sera from naive animals. Remarkably, all sera from animals vaccinated either once (n = 102) or twice (n = 30) were negative. In addition, this 3AB1-ELISA could detect seroconversion at 7 dpi in animals inoculated intradermolingually. This assay constitutes an important tool for the rapid detection of FMDV outbreaks in a vaccinated population. In addition, it presents a reliable, economical, and simple method for testing large numbers of serum samples.
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