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Infection and Immunity, December 1999, p. 6510-6517, Vol. 67, No. 12
Department of Pathology and Laboratory
Medicine,1 Department of
Medicine,2 and Molecular Biology
Institute,3 University of California, Los
Angeles, California 90095, and Inflammatory Bowel Disease
Research Center, Cedars-Sinai Medical Center, Los Angeles,
California 900484
Received 24 June 1999/Returned for modification 28 July
1999/Accepted 20 September 1999
pANCA is a marker antibody associated with inflammatory bowel
disease (IBD), including most patients with ulcerative colitis and a
subset with Crohn's disease. This study addressed the hypothesis that
pANCA reacts with an antigen(s) of microbial agents potentially relevant to IBD pathogenesis. Using a pANCA monoclonal antibody, we
have previously identified the C-terminal basic random-coil domain of
histone H1 as a pANCA autoantigen. BLAST analysis of the peptide
databases revealed H1 epitope homologues in open reading frames of the
Mycobacterium tuberculosis genome. Western analysis of
extracts from six mycobacterial species directly demonstrated reactivity to a single, conserved ~32-kDa protein. Direct protein sequencing, followed by gene cloning, revealed a novel 214-amino-acid protein, an iron-regulated protein recently termed HupB. Sequence analysis demonstrated its homology with the mammalian histone H1 gene
family, and recombinant protein expression confirmed its reactivity
with the 5-3 pANCA monoclonal antibody. Binding activity of patient
serum immunoglobulin G (IgG) to HupB did not correlate with reactivity
to histone H1 or pANCA, indicating the complex character of the pANCA
antigen. However, anti-HupB IgA was strongly associated with Crohn's
disease (P < 0.001). These findings indicate that the
5-3 pANCA monoclonal antibody detects a structural domain recurrent
among mycobacteria and cross-reactive with a DNA-binding domain of
histone H1. The association of HupB-binding serum IgA with IBD provides
new evidence for the association of a mycobacterial species with
Crohn's disease.
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Identification of a Novel Mycobacterial Histone H1
Homologue (HupB) as an Antigenic Target of pANCA Monoclonal Antibody
and Serum Immunoglobulin A from Patients with Crohn's
Disease
*
Corresponding author. Mailing address: Department of
Pathology and Lab Medicine, UCLA School of Medicine, Box 173216, CHS 13-222, Los Angeles, CA 90095-1732. Phone: (310) 794 7953. Fax: (310)
825 5674. E-mail: jbraun{at}mednet.ucla.edu.
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