Submitted to: American Association of Veterinary Laboratory Diagnosticians
Publication Type: Abstract Only
Publication Acceptance Date: 10/22/2004
Publication Date: 10/22/2004
Citation: Waters, W.R., Palmer, M.V., Nonnecke, B.J., Minion, F.C. 2004. Differentiation of mycobacterium bovis infection of cattle from m. avium subsp. avium and m. avium subsp. paratuberculosis infection using reombinant esat-6:cfp-10 fusion protein [abstract]. American Association of Veterinary Laboratory Diagnosticians. p. 203
Technical Abstract: Immunological diagnosis of Mycobacterium bovis infection of cattle often is confounded by cross-reactive responses resulting from exposure to other mycobacterial species, especially Mycobacterium avium. Early secretory antigenic target-6 (ESAT-6) and culture filtrate protein-10 (CFP-10) are dominant interferon (IFN)-gamma-inducing antigens of tuberculous mycobacteria; and, they are absent from many environmental non-tuberculous mycobacteria. Because M. avium exposure is the primary confounding factor in the diagnosis of M. bovis-infected animals, in vitro responses to a recombinant ESAT-6:CFP-10 fusion protein by blood leukocytes from cattle naturally-exposed to M. avium or experimentally-challenged with M. avium subsp. avium or M. avium subsp. paratuberculosis (Map) were compared to responses by M. bovis-infected cattle. Responses to heterogeneous mycobacterial antigens [i.e., purified protein derivatives (PPD) and whole cell sonicates (WCS)] were also evaluated. Tumor necrosis factor (TNF)-alpha, IFN-gamma, and nitric oxide responses by M. bovis-infected cattle to rESAT-6:CFP-10 exceeded (P<0.05) corresponding responses by cattle sensitized naturally to M. avium. Experimental infection with M. bovis, M. avium, or Map induced significant (P<0.05) IFN-gamma and nitric oxide production to WCS and PPD antigens, regardless of the mycobacterial species used for the preparation of the antigen. Responses to homologous crude antigens generally exceeded responses to heterologous antigens. Nitric oxide and IFN-gamma responses to rESAT-6:CFP-10 by blood leukocytes from M. bovis-infected calves exceeded (P<0.05) corresponding responses of non-infected, M. avium-infected, and Map-infected calves. Despite the reported potential for secretion of immunogenic ESAT-6 and CFP-10 proteins by M. avium and Map, it appears that use of the rESAT-6:CFP-10 fusion protein will be useful for the detection of tuberculous cattle in herds with pre-existing sensitization to M. avium and/or Map.