Abstract
BackgroundBovine tuberculosis, caused by Mycobacterium bovis, afflicts approximately 50 million cattle worldwide and is detected by the tuberculin skin test (TST). While it has long been recognized that purified protein derivative (PPD) tuberculin is composed of a mixture of M. bovis derived protein components, little is known about the quality, relative quantity and identity of the proteins that make up PPD tuberculin. We manufactured a sterile filtered PPD tuberculin (SF-PPD) from a nine-week-old M. bovis culture supernatant in order to characterise the culture filtrate proteins (CFP) which make up M. bovis PPD tuberculin and to compare the antibody response of M. bovis infected versus M. bovis sensitized cattle.ResultsSF-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.ConclusionsWe 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.
Highlights
Bovine tuberculosis, caused by Mycobacterium bovis, afflicts approximately 50 million cattle worldwide and is detected by the tuberculin skin test (TST)
This work suggested that M. bovis infected cattle and cattle artificially sensitized to M. bovis with an injection of heat-killed cells possess similar antibody response to selected M. bovis antigens
The main purpose of this study was to characterize the antigenic constituents of M. bovis culture filtrate proteins (CFP) and to compare the antibody response of M. bovis infected cattle to that of cattle artificially sensitized to M. bovis by 2D Western blot analysis
Summary
Bovine tuberculosis, caused by Mycobacterium bovis, afflicts approximately 50 million cattle worldwide and is detected by the tuberculin skin test (TST). While it has long been recognized that purified protein derivative (PPD) tuberculin is composed of a mixture of M. bovis derived protein components, little is known about the quality, relative quantity and identity of the proteins that make up PPD tuberculin. 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. The current accepted terminology for this complex mixture of tuberculo-proteins is culture filtrate proteins (CFP) and this includes secreted proteins, exported proteins and non-secreted, somatic components which are released into the culture medium due to autolysis, replication and bacterial leakage [12,13]. The protein profile of a CFP set is dependent on many factors including cultivation time, temperature, growth medium and culture agitation [13,14]
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