Induction of B Cell Responses upon Experimental Infection of Neonatal Calves with Mycobacterium avium subsp. paratuberculosis

Abstract

ABSTRACTThe objective of this study was to determine if experimental infection of neonatal calves withMycobacterium aviumsubsp.paratuberculosiswould invoke changes in the percentages of total B cells in the peripheral blood mononuclear cell population and of subpopulations of B cells as determined by CD5, CD25, and CD45RO markers during a 12-month period. Experimental infection groups included control (noninfected), oral (infected withM. aviumsubsp.paratuberculosisstrain K-10), oral/DXM (pretreatment with dexamethasone before oral inoculation), i.p. (intraperitoneal inoculation), and oral/M (oral inoculation with mucosal scrapings from a cow with clinical disease) groups. Over the course of the study, the percentages of total B cells in nonstimulated and antigen-stimulated cell cultures increased for oral and i.p. group calves, with the highest percentages noted at 3 and 6 months. Oral/M group calves had increased percentages of activated B cells, as determined by CD5dimand CD5brightmarkers, at 9 and 12 months. Experimental infection by all methods resulted in increased expression of CD25+and CD45RO+B cells early in the study, but the most significant results were observed at 12 months for oral/DXM and oral/M group calves. Immunoblot analyses with a whole-cell sonicate ofM. aviumsubsp.paratuberculosisdemonstrated the most reactivity with sera from i.p. group calves and the least reactivity with sera from oral group calves. Further evidence ofM. aviumsubsp.paratuberculosis-specific antibody responses in the i.p. group calves was demonstrated using the ethanol vortex enzyme-linked immunosorbent assay (EvELISA) method. In summary, an induction of B cell responses was noted after experimental infection withM. aviumsubsp.paratuberculosis, with differences in responses noted according to the method of experimental inoculation.