Mycobacterium tuberculosis LprA is a lipoprotein agonist of TLR2 that regulates innate immunity and APC function.
TLR2 recognizes components of Mycobacterium tuberculosis (Mtb) and initiates responses by APCs that influence both innate and adaptive immunity. Mtb lipoproteins are an important class of TLR2 ligand, but only two, LpqH and LprG, have been characterized to date. In this study, we characterize a third Mtb lipoprotein, LprA, and determine its effects on host macrophages and dendritic cells. LprA is a cell wall-associated lipoprotein with no homologs outside the slow-growing mycobacteria. Using Mycobacterium smegmatis as an expression host, we purified 6x His-tagged LprA both with and without its acyl modifications. Acylated LprA had agonist activity for both human and murine TLR2 and induced expression of TNF-alpha, IL-10, and IL-12. LprA also induced dendritic cell maturation as shown by increased expression of CD40, CD80, and class II MHC (MHC-II). In macrophages, prolonged (24 h) incubation with LprA decreased IFN-gamma-induced MHC-II Ag processing and presentation, consistent with an observed decrease in MHC-II expression (macrophage viability was not affected and apoptosis was not induced by LprA). Reduced MHC-II Ag presentation may represent a negative feedback mechanism for control of inflammation that may be subverted by Mtb for immune evasion. Thus, Mtb LprA is a TLR2 agonist that induces cytokine responses and regulates APC function.
Pecora
Nicole D
ND
Department of Pathology, Case Western Reserve University, 2103 Cornell Road, Cleveland, OH 44106-7288, USA.
Gehring
Adam J
AJ
Canaday
David H
DH
Boom
W Henry
WH
Harding
Clifford V
CV
D000215:Acylation; D000595:Amino Acid Sequence; D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology*; D001426:Bacterial Proteins / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology*; D002460:Cell Line; D016207:Cytokines / Q000096:biosynthesis; D005260:Female; D006031:Glycosylation; D006801:Humans; D007113:Immunity, Innate; D007155:Immunologic Factors / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology; D008024:Ligands; D008074:Lipoproteins / Q000302:isolation & purification / Q000378:metabolism / Q000502:physiology*; D008264:Macrophages / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D051195:Toll-Like Receptor 2 / Q000819:agonists*
D001426:Bacterial Proteins; D016207:Cytokines; D007155:Immunologic Factors; D008024:Ligands; D008074:Lipoproteins; C512257:LprA protein, Mycobacterium tuberculosis; C495342:TLR2 protein, human; C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2