Title : Zoonotic Tuberculosis: Characterization of Antibody Responses in Various Host Species for Improved Serodiagnosis
Bovine tuberculosis (bTB) has a broad range of mammalian host species including various livestock and wildlife animals. Ante-mortem testing for bTB traditionally relies on cell-mediated immune responses, such as tuberculin skin test reactions or in vitro interferon-gamma release. However, serological methods using novel antigens and advanced assay formats have recently emerged to offer attractive options for rapid identification of infected animals.
Using Dual-Path Platform (DPP) technology, IgM and IgG antibody responses to two antigens, MPB70/MPB83 and CFP10/ESAT6 fusion proteins, were studied in cattle and domestic pigs infected with Mycobacterium bovis. Both test antigens elicited IgM responses in pigs, whereas cattle produced IgM antibodies only to MPB70/MPB83. DPP assay detected robust IgG responses to both antigens in the vast majority of infected animals, with MPB70/MPB83 recognized more frequently than CFP10/ESAT6 in these host species. Detecting IgM antibody did not improve seroreactivity rates based on IgG antibody detection in cattle and pigs. CFP10/ESAT6 antigen showed limited value in identifying infected animals by DPP assay using MPB70/MPB83 antigen to measure IgG antibody responses. The overall diagnostic accuracy of DPP assay was estimated to be higher in pigs (sensitivity 98%, specificity 100%) than in cattle (sensitivity 78%, specificity 97%).
Characterization of the humoral immune responses to M. bovis in cattle and pigs reveals distinct patterns of antigen recognition by IgM and IgG antibodies. The findings suggest that development of improved serologic tests for various hosts will require further research on comparative bTB immunobiology focusing on inter-species differences in antibody profiles.