Abstract
BackgroundThe Mycobacterium tuberculosis 19-kDa lipoprotein has been reported to stimulate both T and B cell responses as well as induce a number of Th1 cytokines. In order to evaluate the Mycobacterium avium subsp. paratuberculosis (M. avium subsp. paratuberculosis) 19-kDa lipoprotein as an immunomodulator in cattle with Johne's disease, the gene encoding the 19-kDa protein (MAP0261c) was analyzed.ResultsMAP0261c is conserved in mycobacteria, showing a 95% amino acid identity in M. avium subspecies avium, 84% in M. intracellulare and 76% in M. bovis and M. tuberculosis. MAP0261c was cloned, expressed, and purified as a fusion protein with the maltose-binding protein (MBP-19 kDa) in Escherichia coli. IFN-γ production was measured from 21 naturally infected and 9 control cattle after peripheral blood mononuclear cells (PBMCs) were stimulated with a whole cell lysate (WCL) of M. avium subsp. paratuberculosis or the recombinant MBP-19 kDa. Overall, the mean response to MBP-19 kDa was not as strong as the mean response to the WCL. By comparison, cells from control, non-infected cattle did not produce IFN-γ after stimulation with either WCL or MBP-19 kDa. To assess the humoral immune response to the 19-kDa protein, sera from cattle with clinical Johne's disease were used in immunoblot analysis. Reactivity to MBP-19 kDa protein, but not MBP alone, was observed in 9 of 14 infected cattle. Antibodies to the 19-kDa protein were not observed in 8 of 9 control cows.ConclusionsCollectively, these results demonstrate that while the 19-kDa protein from M. avium subsp. paratuberculosis stimulates a humoral immune response and weak IFN-γ production in infected cattle, the elicited responses are not strong enough to be used in a sensitive diagnostic assay.
Highlights
The Mycobacterium tuberculosis 19-kDa lipoprotein has been reported to stimulate both T and B cell responses as well as induce a number of Th1 cytokines
Sequence analysis of the mycobacterial 19-kDa coding region The 19-kDa coding sequence was identified from the M. avium subsp. paratuberculosis genome project as MAP0261c
A majority of the research on individual mycobacterial proteins has been performed in M. tuberculosis, whereas little is known about the M. avium subsp. paratuberculosis proteome
Summary
The Mycobacterium tuberculosis 19-kDa lipoprotein has been reported to stimulate both T and B cell responses as well as induce a number of Th1 cytokines. In order to evaluate the Mycobacterium avium subsp. Paratuberculosis (Johne's disease) is caused by Mycobacterium avium subsp. In the United States alone the economic burden of Johne's disease is estimated at over $200 million in lost annual revenue to the dairy industry [1]. BMC Microbiology 2005, 5:3 http://www.biomedcentral.com/1471-2180/5/3 dairy herds are infected with M. avium subsp. During the subclinical stage of infection, the host cell-mediated immune response is robust and appears to control the infection. As the disease progresses from the subclinical to the clinical stage, the cell-mediated response diminishes, and a humoral immune response predominates [6]. Vaccines are not completely protective, but have been reported to reduce fecal shedding and delay the onset of clinical disease [7,8,9]
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