Urine Lipoarabinomannan as a Biomarker for Mycobacterium tuberculosis and non-tuberculous mycobacterial infections v1

Lipoarabinomannan (LAM) is a unique cell wall component containing a fatty acid region with a large mannan core attached to poly-arabinan chains, sometimes followed by mannose capping in Actinomyces species. The hydrophobic region made of tuberculostearic acid (TBSA) and two palmitic acid chains linked to a phosphoinositol, anchors LAM to the mycobacterial cell wall. As a major constituent of all mycobacteria, includingMycobacterium tuberculosis(M.tb),LAM has been shown to be a useful diagnostic biomarker in the identification of MTB infection in HIV positive (HIV+) patients. The size of LAM makes it difficult to analyze on GC-MS when using complex matrices such as urine, therefore chemical processing and derivatization is required. Two methods have been developed to quantify urine-LAM amounts, one by measuring D-arabinose and the other TBSA. Both components are unique and not metabolized through basic pathways in mammalian cells and can therefore serve as LAM surrogates. Using either chemical assay, urine-LAM can be detected in low quantities with sensitive GC-MS, providing a diagnostic tool for clinical assessment of infection. These methods are robust and have been applied to a significant number of TB and non-tuberculous mycobacterial (NTM) urine samples. These protocols provide additional sensitivity beyond what is required for assays of MTB in HIV+ patients, allowing for identification of both M.tb and NTM infections in immunocompetent hosts.