Antibody response to a sterile filtered PPD tuberculin in M. bovis infected and M. bovis sensitized cattle

SF-PPD resolved into approximately 200 discrete spots using two-dimensional polyacrylamide gel electrophoresis (2-DE) while fewer than 65 spots could be discerned from 2-DE gels of tuberculin derived from autoclaved culture supernatant. Two dimensional Western blot analyses indicated that sera from M. bovis sensitized cattle recognized additional SF-PPD antigens as compared to M. bovis infected cattle at seven weeks post infection/sensitization. However, application of a comparative tuberculin skin test resulted in an antibody boosting response to the same set of M. bovis CFPs in both the M. bovis infected and M. bovis sensitized cattle.We concluded that it is the heat sterilization of the M. bovis CFPs that causes severe structural changes to the M. bovis proteins. This work suggests that M. bovis infected cattle and cattle artificially sensitized to M. bovis with an injection of heat killed cells exhibit similar antibody responses to M. bovis antigens.Bovine tuberculosis, caused by Mycobacterium bovis infection, is a major global health threat, with approximately 50 million cattle currently infected worldwide [1]. The primary method used to detect tuberculosis in cattle is the single intradermal test (SIT). Although the SIT is the most widely used diagnostic test for M. bovis infections in cattle, little is known about the quality, relative quantity and identity of the proteins that make up purified protein derivative (PPD) tuberculin.PPD tuberculin is a crude and complex mixture of tuberculo-proteins which has changed little since its conception and original application by Dr. Robert Koch in 1890 [2]. The original tuberculin, Koch's old tuberculin, was prepared from a heat sterilized liquid culture medium containing 8 - 12 week old M. tuberculosis (M. tb) cultures concentrated to one-tenth the original volume by evaporation [2]. While it has long been recognised that PPD tuberculin is composed of M. bovis derived protein components, early efforts to accurately ch