Characterization of the Apa antigen from M. avium subsp. paratuberculosis: A conserved Mycobacterium antigen that elicits a strong humoral response in cattle

GIOFFRE; AA ECHEVERRIA-VALENCIAIA, G. ARESEE AA MORSELLALA, C. GARBACCIOO SS DELGADODO, F. ZUMARRAGAA MM PAOLICCHIHI, F. CATALDII AA AND ROMANO O, M.I.

VETERINARY IMMUNOLOGY AND IMMUNOPATHOLOGY

ELSEVIER SCIENCE BV

Año: 2009 vol. 132 p. 199 - 208

0165-2427

Johne’s disease or paratuberculosis is widespread in almost all countries and remains difficult to eradicate. Nowadays, diagnosis of M. avium subsp. paratuberculosis (MPTB) infection is one of the main concerns. We evaluated the expression, biochemical properties and antigenicity of the Apa antigen, encoded by the gene annotated as MAP1569 in the MPTB genome. We confirmed its expression in MPTB and the glycosylation of the antigen by the Con-A binding assay. MPTB-infected cattle showed a strong humoral response to recombinant Apa (rApa) by Western blot and ELISA. Milk was also a suitable sample to be tested by ELISA. We comparatively analysed the recognition of the rApa with the orthologue from M. tuberculosis (MT-Apa) in both infected and control cows. Response of M. bovis and MPTB-infected animals against MT-Apa was similar (P = 0.6985) but response of M. bovis infected animals to MPTB-Apa was differential, being significantly diminished (P < 0.0001). Although 6 out 45 animals from MPTB-infected herds responded to rApa stimulation in the ãIFN release assay there was no significant difference with control herds (P=0.34). This antigen, in contrast to bovine Purified Protein Derivative (PPD), was strongly represented in avian PPD, as shown by the recognition of BALB/c mice hyperimmune sera against MPTB-Apa by Western blot. We therefore demonstrated the antigenicity of Apa in paratuberculosis-infected animals and a differential response to the recombinant antigen when compared to MT-infected animals. These facts, added to the usefulness of milk samples to detect IgG anti-Apa could be important for routine screening in dairy cattle.