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Journal of Clinical Microbiology, August 1999, p. 2568-2575, Vol. 37, No. 8
Department of Pathology, University of Texas
Medical Branch, Galveston, Texas,1 and
MRL Diagnostics, Cypress, California 906302
Received 1 February 1999/Returned for modification 16 March
1999/Accepted 27 April 1999
Diagnosis of human monocytotropic ehrlichiosis (HME) generally
depends on serology that detects the antibody response to
immunodominant proteins of Ehrlichia chaffeensis. Protein
immunoblotting was used to evaluate the reaction of the antibodies in
patients' sera with the recombinant E. chaffeensis 120- and 28-kDa proteins as well as the 106- and the 37-kDa proteins. The
cloning of the genes encoding the latter two proteins is described in
this report. Immunoelectron microscopy demonstrated that the 106-kDa
protein is located at the surfaces of ehrlichiae and on the
intramorular fibrillar structures associated with E. chaffeensis. The 37-kDa protein is homologous to the iron-binding
protein of gram-negative bacteria. Forty-two serum samples from
patients who were suspected to have HME were tested by
immunofluorescence (IFA) using E. chaffeensis antigen and
by protein immunoblotting using recombinant E. chaffeensis proteins expressed in Escherichia coli. Thirty-two serum
samples contained IFA antibodies at a titer of 1:64 or greater. The
correlation of IFA and recombinant protein immunoblotting was 100% for
the 120-kDa protein, 41% for the 28-kDa protein, 9.4% for the 106-kDa protein, and 0% for the 37-kDa protein. None of the recombinant antigens yielded false-positive results. All the sera reactive with the
recombinant 28- or the 106-kDa proteins also reacted with the
recombinant 120-kDa protein.
0095-1137/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Comparison of Ehrlichia chaffeensis
Recombinant Proteins for Serologic Diagnosis of Human
Monocytotropic Ehrlichiosis
*
Corresponding author. Mailing address: Department of
Pathology, 301 University Blvd., University of Texas Medical Branch, Galveston, TX 77555-0609. Phone: (409) 772-2856. Fax: (409) 772-2500. E-mail: dwalker{at}utmb.edu.
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