Differential immune responses of red Deer (Cervus elaphus) following experimental challenge with Mycobacterium avium subsp. paratuberculosis.

Abstract

Immune responses of red deer (Cervus elaphus) that presented with different levels of paucibacillary pathology were profiled to detail immune changes during the progression of Johne's disease. Immune responses were monitored using an immunoglobulin G1 (IgG1) antibody enzyme-linked immunosorbent assay (ELISA), a gamma interferon (IFN-gamma) ELISA, and flow cytometry. Animals in the study were divided into outcome groups postmortem according to disease severity. All animals mounted IgG1 antibody and IFN-gamma responses to both the vaccination and experimental challenges. The Mycobacterium avium subsp. paratuberculosis-specific IgG1 antibody responses in the challenged group showed marked differences between infected and severely diseased animals. Slightly higher IFN-gamma responses were seen in infected animals compared with severely diseased animals. No significant changes were seen in the phenotype of lymphocyte populations investigated. Vaccination with killed M. avium subsp. paratuberculosis in mineral oil adjuvant reduced the level of severe disease; however, it obscured immunological differences between the infected and severely diseased groups. This suggests protection is not exclusively mediated via the presence of a type 1 response and, furthermore, the presence of a type 2 response is compatible with protection. These profiles provide information on the different immune processes in Johne's disease progression.