Expression and field evaluation of new Mycobacterium bovis antigens

Abstract

Bovine tuberculosis (bTB) represents a threat to livestock production. Mycobacteriumbovis is the main causative agent of bTB and a pathogen capable of infecting wildlifeand humans. Eradication programs based on surveillance in slaughterhouses withmandatory testing and culling of reactive cattle have failed to eradicate bTB in manyregions worldwide. Therefore, developing effective tools to control this disease iscrucial. Using a computational tool, we identified proteins in the M. bovis proteome thatcarry predictive binding peptides to BoLADRB3.2 and selected Mb0309, Mb1090,Mb1810 and Mb3810 from all the identified proteins. The expression of these proteinsin a baculovirus-insect cell expression system was successful only for Mb0309 andMb3810. In parallel, we expressed the ESAT-6 family proteins EsxG and EsxH in thissystem. Among the recombinant proteins, Mb0309 and EsxG exhibited moderateperformance in distinguishing between cattle that test positive and negative to bTBusing the official test, the intradermal tuberculin test (IDT), when used to stimulateinterferon-gamma production in blood samples from cattle. However, when combinedas a protein cocktail, Mb0309 and EsxG were reactive in 50% of positive cattle. Furtherassessments in cattle that evade the IDT (false negative) and cattle infected withMycobacterium avium paratuberculosis are necessary to determine the potential utilityof this cocktail as an additional tool to assist the accurate diagnosis of bTB.