P43. Identification of blood-based signatures for spinal tuberculosis: a molecular insight from bench to bedside

BACKGROUND CONTEXT Tuberculosis (TB) runs rampant in the South-East Asian subcontinent. While demonstration of the pathogen (mycobacterium tuberculosis) in histopathology and culture remains the gold standard for diagnosis, a new age calls for newer methods of diagnosis. PURPOSE Our study aims to find biomarkers that can be used for diagnostic purposes in TB. STUDY DESIGN/SETTING This study was carried out in two phases: Phase-I was an experimental animal study, and Phase II was a prospective cohort clinical study. PATIENT SAMPLE For phase I, age, and sex matched KO (knock-out) mice and co-housed wild animals between 6-8 weeks of age were used. In phase 2 10 patients each for spinal TB, pulmonary TB, pyogenic osteomyelitis, and healthy subjects. METHODS For Phase I, age, and sex matched KO (knock-out) mice and co-housed wild animals between 6-8 weeks of age were used. Precursor macrophage cells from mice were infected with Mtb H37Rv-Gfp/AdosR strain, followed by quantification of the cytokine response and microarray analysis of the Mtb infected cells. Based on the results of phase I study, we measured the serum levels of TNF-α, IFN-γ, IL-10, IL-4, IL 12p70, IL-17A, IL-8, IL-6, IL-2 in patients with spinal TB, pulmonary TB, pyogenic osteomyelitis, and healthy subjects, in phase II. RESULTS Mtb infected mononuclear cells actively fused, resulting in the formation of larger osteoclasts. Mtb could substantially alter cellular programming to produce large osteoclast and the initial trigger of lineage commitment through RANKL was sufficient to produce mature bone resorbing cells. Analysis of TNF-α and hypoxia regulatory genes showed upregulation of approximately 90% genes in the pathway at either one or multiple time-points during infection. Mtb manifested its osteoclast potentiating function by diminishing RANK signaling and simultaneously activating TLR2-dependant MyD88 regulated TNF-α pathway via TNFR1 receptor. In phase II, barring IL-6 and IFN-γ, the extent of increase in the levels of the other 7 biomarkers was much more in patients with spinal TB, when compared to patients with pulmonary TB and non-TB, osteoarticular infection. CONCLUSIONS Our study reveals an interactive network consisting of TNF-α-HIF-1α-IL-10-RANK which may be a central axis operative in Mtb infected osteoclasts during spinal TB. Tissue-specific immune pathogenesis of spinal TB can help identify host serum biomarkers with potential diagnostic implications. FDA Device/Drug Status This abstract does not discuss or include any applicable devices or drugs. Tuberculosis (TB) runs rampant in the South-East Asian subcontinent. While demonstration of the pathogen (mycobacterium tuberculosis) in histopathology and culture remains the gold standard for diagnosis, a new age calls for newer methods of diagnosis. Our study aims to find biomarkers that can be used for diagnostic purposes in TB. This study was carried out in two phases: Phase-I was an experimental animal study, and Phase II was a prospective cohort clinical study. For phase I, age, and sex matched KO (knock-out) mice and co-housed wild animals between 6-8 weeks of age were used. In phase 2 10 patients each for spinal TB, pulmonary TB, pyogenic osteomyelitis, and healthy subjects. For Phase I, age, and sex matched KO (knock-out) mice and co-housed wild animals between 6-8 weeks of age were used. Precursor macrophage cells from mice were infected with Mtb H37Rv-Gfp/AdosR strain, followed by quantification of the cytokine response and microarray analysis of the Mtb infected cells. Based on the results of phase I study, we measured the serum levels of TNF-α, IFN-γ, IL-10, IL-4, IL 12p70, IL-17A, IL-8, IL-6, IL-2 in patients with spinal TB, pulmonary TB, pyogenic osteomyelitis, and healthy subjects, in phase II. Mtb infected mononuclear cells actively fused, resulting in the formation of larger osteoclasts. Mtb could substantially alter cellular programming to produce large osteoclast and the initial trigger of lineage commitment through RANKL was sufficient to produce mature bone resorbing cells. Analysis of TNF-α and hypoxia regulatory genes showed upregulation of approximately 90% genes in the pathway at either one or multiple time-points during infection. Mtb manifested its osteoclast potentiating function by diminishing RANK signaling and simultaneously activating TLR2-dependant MyD88 regulated TNF-α pathway via TNFR1 receptor. In phase II, barring IL-6 and IFN-γ, the extent of increase in the levels of the other 7 biomarkers was much more in patients with spinal TB, when compared to patients with pulmonary TB and non-TB, osteoarticular infection. Our study reveals an interactive network consisting of TNF-α-HIF-1α-IL-10-RANK which may be a central axis operative in Mtb infected osteoclasts during spinal TB. Tissue-specific immune pathogenesis of spinal TB can help identify host serum biomarkers with potential diagnostic implications.