Characterization of the Apa antigen from M. avium subsp. paratuberculosis: A conserved

GIOFFRÉ, ANDREA KARINA; ECHAVARRÍA VALENCIA, GABRIELA; ARESE, ALICIA; MORSELLA, CLAUDIA; GARBACCIO, SERGIO; DELGADO, FERNANDO; ZUMÁRRAGA, MARTÍN JOSÉ; PAOLICCHI, FERNANDO; CATALDI, ANGEL; ROMANO, MARÍA ISABEL

VETERINARY IMMUNOLOGY AND IMMUNOPATHOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2009 vol. 15 p. 199 - 208

0165-2427

Johne?s disease or paratuberculosis is widespread in almost all countries and remainsdifficult to eradicate. Nowadays, diagnosis of Mycobacterium avium subsp. paratuberculosis(MPTB) infection is one of the main concerns. In this work, we evaluated the expression,biochemical properties and antigenicity of the Apa antigen, encoded by the geneannotated as MAP1569, in the MPTB genome.We confirmed its expression in MPTB and itsglycosylation by the ConA binding assay. Although the MPTB-Apa is not an immunodominantantigen, MPTB-infected cattle showed a strong humoral response torecombinant Apa by Western blot and ELISA. Milk was also a suitable sample to betested by ELISA. We comparatively analysed the humoral cross-reactivity to the Apa fromMPTB (MPTB-Apa) and the orthologue from Mycobacterium tuberculosis (MT-Apa, identicalto that from Mycobacterium bovis) in both infected and control cows. Response of M. bovisandMPTB-infected animals against MT-Apa was similar (P = 0.6985) but the response ofthe M. bovis-infected ones to MPTB-Apa was differential, being significantly diminished(P < 0.0001). Although 6 out 45 animals from MPTB-infected herds responded to MPTBApastimulation in the IFNg release assay, we found no significant differences whencompared infected herds with non-infected ones (P = 0.34). This antigen, in contrast tobovine Purified Protein Derivative (PPDb), was strongly represented in avian PPD (PPDa),as shown by the recognition of BALB/c mice hyperimmune sera against MPTB-Apa by Dotblotimmunoassay. We therefore demonstrated the antigenicity of Apa in MPTB-infectedanimals and a differential response to the recombinant antigen when compared to M.bovis-infected animals. These traits herein described, added to the usefulness of milksamples to detect IgG anti-Apa, could be important for routine screening in dairy cattle,considering a multiantigenic approach to overcome the lack of immunodominance.