Immunoreactivity of the Mycobacterium avium subsp. paratuberculosis 19-kDa lipoprotein.
BACKGROUND
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 (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.


RESULTS
MAP0261c 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-gamma 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-gamma 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.


CONCLUSIONS
Collectively, these results demonstrate that while the 19-kDa protein from M. avium subsp. paratuberculosis stimulates a humoral immune response and weak IFN-gamma production in infected cattle, the elicited responses are not strong enough to be used in a sensitive diagnostic assay.
Huntley
Jason F J
JF
Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9048, USA. Jason.Huntley@UTSouthwestern.edu
Stabel
Judith R
JR
Bannantine
John P
JP
D000595:Amino Acid Sequence; D000818:Animals; D000907:Antibodies, Bacterial / Q000378:metabolism; D000917:Antibody Formation; D001426:Bacterial Proteins / Q000737:chemistry / Q000276:immunology*; D002417:Cattle; D005786:Gene Expression Regulation; D007371:Interferon-gamma / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D008074:Lipoproteins / Q000737:chemistry* / Q000276:immunology*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016927:Mycobacterium avium subsp. paratuberculosis / Q000145:classification* / Q000276:immunology*; D010283:Paratuberculosis / Q000276:immunology*; D017386:Sequence Homology, Amino Acid
D000907:Antibodies, Bacterial; D001426:Bacterial Proteins; D008074:Lipoproteins; D007371:Interferon-gamma