Sudhanshu Abhishek
PGIMER, India
Title: Transcriptional signatures of Mycobacterium tuberculosis in mouse model of experimental intraocular tuberculosis
Biography
Biography: Sudhanshu Abhishek
Abstract
Statement of the Problem: Intraocular tuberculosis (IOTB), one of the extrapulmonary form of tuberculosis (TB), is a significant cause of inflammation and visual morbidity in TB endemic countries. Studies on IOTB are extremely challenging due to lack of appropriate human IOTB specimens, hence animal models of IOTB are required. Methodology & Theoretical Orientation: In the present study, a mouse model of IOTB was established by infecting the animals with Mycobacterium tuberculosis (M. tb; H37Rv) via intravenous (i.v.) route. Bacteriological evidence, histopathological changes and whole genome microarray study was done to identify the M. tb transcriptional signatures in mouse eye. Findings: At 45 days, post-infection (dpi), M. tb bacilli were observed in the eyes of 5 out of 12 (45%) M. tb challenged mice, whereas all the 12 animals showed positivity for M. tb RNA. Apart, histopathology of one CFU positive eye demonstrated intraretinal granuloma and moderate tissue damage in comparison to CFU negative eye that showed mild disease condition with no granuloma. Mycobacterium tuberculosis transcriptome analysis through microarray platform in the infected eyes, showed upregulation (≥ 1.5-fold) of 12 M. tb genes, where top three upregulated transcripts included Rv0962c, Rv2612, and Rv0984. Real-time validation of these top three genes showed an average of 7.40, 4.13 and 3.47 Log2 fold upregulation (p<0.05), respectively. Conclusion & Significance: Although, ocular bacterial load was low, but detection of M. tb RNA with undetectable tubercle bacilli in the animals confirmed the paucibacillary nature of IOTB developed under experimental conditions, similar to that observed in human IOTB patients. Upregulation of mycobacterial genes, suggest that the adaptation of M. tb in ocular environment, an immune-privileged site, may be associated with enhanced transcription of genes whose products are required for virulence and survival in intraocular environment. These genes/gene products could be important candidates for understanding the pathogenesis as well as development of new diagnostics/therapeutics for IOTB.