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Clinical and Vaccine Immunology, April 2008, p. 638-643, Vol. 15, No. 4
1071-412X/08/$08.00+0     doi:10.1128/CVI.00010-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Identification of Mycobacterium tuberculosis Ornithine Carboamyltransferase in Urine as a Possible Molecular Marker of Active Pulmonary Tuberculosis

Danielle R. Napolitano ,^1,, Nira Pollock,^2, Suely S. Kashino,^1, Virmondes Rodrigues Jr.,³ and Antonio Campos-Neto^1,4*

The Forsyth Institute, Boston, Massachusetts 02115,¹ Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215,² Federal University of Triângulo Mineiro, Uberaba, Minas Gerais, Brazil,³ University of Massachusetts Medical School, Worcester, Massachusetts 01655⁴

Received 9 January 2008/ Returned for modification 1 February 2008/ Accepted 13 February 2008

Although the antigen detection assay has the potential to discriminate active tuberculosis from latent infection, development of such a test for the accurate diagnosis of this serious disease has only recently become a matter of interest. Here we present evidence that a Mycobacterium tuberculosis protein (ornithine carboamyltransferase, coded for by MT_1694; Rv1656 [argF]) is an interesting candidate molecule for this test development. The protein was initially discovered by mass spectroscopy in urine of patients with pulmonary tuberculosis and shown by Western blot analysis to be present in M. tuberculosis crude cell extract as well as in the culture supernatant ("secreted" protein). In addition, a recombinant ornithine carboamyltransferase (rMT1694) produced in Escherichia coli was recognized by immunoglobulin G (IgG) antibodies from patients with active tuberculosis but not by IgG from uninfected healthy subjects. Moreover, rMT1694 was strongly recognized by peripheral blood mononuclear cells from both healthy tuberculin purified protein derivative (PPD)-positive individuals and patients with pulmonary tuberculosis. More importantly, a capture enzyme-linked immunosorbent assay formatted with rabbit IgG antibodies specific to rMT1694 was able to identify the presence of this antigen in urine samples from 6 of 16 patients with pulmonary tuberculosis and in none of 16 urine samples collected from healthy PPD⁺ controls. These results indicate that an improved antigen detection assay based on M. tuberculosis ornithine carboamyltransferase may represent an important new strategy for the development of a specific and accurate diagnostic test for tuberculosis.

Published ahead of print on 27 February 2008.

Present address: Federal University of Uberlândia, Uberlândia, Minas Gerais, Brazil.

D.R.N., N.P., and S.S.K. contributed equally to this work.