Abstract
Identification of pathogen-specific biomarkers present in patients' serum or urine samples can be a useful diagnostic approach. In efforts to discover Mycobacterium tuberculosis (Mtb) biomarkers we identified by mass spectroscopy a unique 21-mer Mtb peptide sequence (VVLGLTVPGGVELLPGVALPR) present in the urines of TB patients from Zimbabwe. This peptide has 100% sequence homology with the protein TBCG_03312 from the C strain of Mtb (a clinical isolate identified in New York, NY, USA) and 95% sequence homology with Mtb oxidoreductase (MRGA423_21210) from the clinical isolate MTB423 (identified in Kerala, India). Alignment of the genes coding for these proteins show an insertion point mutation relative to Rv3368c of the reference H37Rv strain, which generated a unique C-terminus with no sequence homology with any other described protein. Phylogenetic analysis utilizing public sequence data shows that the insertion mutation is apparently a rare event. However, sera from TB patients from distinct geographical areas of the world (Peru, Vietnam, and South Africa) contain antibodies that recognize a purified recombinant C-terminus of the protein, thus suggesting a wider distribution of isolates that produce this protein.
Highlights
Urinary excretion of antigens from pathogens that cause systemic diseases, known as “antigenuria,” has been known for decades to occur [1e5]
In search of specific molecular markers for TB diagnostics development we serendipitously found an M. tuberculosis (Mtb) polypeptide sequence that seems to be uniquely associated with defined clinical isolate of this pathogen
The peptide sequence was found in the urines of two TB patients from Zimbabwe
Summary
Urinary excretion of antigens from pathogens that cause systemic diseases, known as “antigenuria,” has been known for decades to occur [1e5]. Both polysaccharides and proteins from pathogens have been detected in the urine of diseased patients [6e10], and in most cases, the antigenuria is not reported to be associated with renal dysfunction. 2 Current address: Imam Abdulrahman Bin Faisal University, Saudi Arabia. We have discovered and validated protein biomarkers of M. tuberculosis (Mtb) and L. donovani in urine of patients with active tuberculosis (TB) and visceral leishmaniasis (VL), respectively [10,25,26,30,31,20]. The presence of these proteins in urine correlated well with clinical manifestations of active disease
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