Leprosy is a bacterial disease of the skin and the nerves, caused by Mycobacterium leprae. Ever since the introduction of a multi-drug therapy in the 1970’s, worldwide incidence has been decreasing and the disease has been eradicated in many countries. However, in recent years occurrence of new cases remains stable at around 200,000 per year. Most new cases are reported in developing countries, and India accounts for more than half of new cases registered every year. In my thesis, I investigated how innate immunity plays an important role in regulating the disease outcome during multi-drug-therapy. This is addressed by examining the transcriptome profile of specific cells of the innate immunity, namely the Natural Killer (NK) cells. Secondly, I investigated innate immunity-associated genes of the human host that are believed to play a significant role in regulating the disease outcome. The thesis is structured into four different chapters. In chapter I of my thesis, published as an original study, I evaluated four specific functional variants in three different genes that are part of the NOD-2 signaling pathway: NOD2 (rs9302752A/G), LRRK2 (rs1873613A/G), and RIPK2 (rs40457A/G and rs42490G/A). I utilized 211 clinically classified Indian leprosy patients with 230 ethnically matched controls. The genetic variants were chosen for their role in innate immunity and because they had been found to be associated to leprosy in an earlier study carried out in a Han Chinese population. The LRRK2 locus proved to be associated with leprosy outcome. The LRRK2 rs1873613A minor allele and respective rs1873613AA genotype were significantly associated with an increased risk whereas the LRRK2 rs1873613G major allele and rs1873613GG genotypes conferred protection. Also, the reconstructed GA haplotype from the RIPK2 rs40457A/G and rs42490G/A variants was observed to contribute towards increased risk. In chapter II, also published as an original study, I investigated loci in the heterodimeric transporter associated with antigen processing (TAP) gene, which is known to play a vital role in immune surveillance. Functional variants both in TAP1 (rs1057141 Iso333Val and rs1135216 Asp637Gly) and TAP2 (rs2228396 Ala565Thr and rs241447 Ala665Thr) were genotyped using a study group of clinically classified Indian leprosy patients (n = 222) and ethnically matched controls (n = 223). The minor allele of TAP1 6 (637G) contributed to an increased risk of leprosy. In the dominant model, two of the researched genotypes of TAP1, rs1135216AG and rs1135216GG, contributed to an increased risk of leprosy as well. In the unpublished chapter III of my thesis, I investigated the interactions of M. leprae antigen with monocytes and monocyte-derived macrophages by fluorescenceactivated cell sorting. M. leprae whole cell antigen up-regulated L-Selectin expression in monocytes by 20%. This is a strong indicator of increased migration of phagocytic cells into the tissue upon identification of a threat by Mycobacterium leprae. Additionally, the CD163 expression is increased by 30% in macrophages. As CD163 is an indicator of M2-macrophage activity this underlines the role of possible immunoevasion by the pathogen through alternative activation of macrophages. In chapter IV, also unpublished, peripheral blood mononuclear cells were extracted from fresh blood of 9 Indian leprosy patients (5 paucibacillary and 4 multibacillary) and three healthy, ethnically matched controls. The cells were then incubated and afterwards mRNA was isolated from them. The Natural Killer-cell transcriptome profile was investigated using microarray technology. LCN2 and APOBEC3 transcription was predominantly up-regulated in paucibacillary cases, while multibacillary cases were mostly unchanged and controls were down-regulated. A comparison of paucibacillary and multibacillary patients with controls as a baseline revealed that multibacillary patients generally showed a higher transcription of genes associated to cell-cellcommunication, a phenomenon not repeated in paucibacillary patients, which actually presented a down-regulation in comparison with healthy controls. Further, multibacillary patients also showed an up-regulation in gene-products involved in immunity. However, some notable exceptions emerged, such as CD70 and TNFRSF9. In conclusion, utilizing a combination of molecular genetics, cell-culture experiments, and microarray technology, a number of promising findings can be presented here which could serve in deepening our understanding of host-bacterial interactions in leprosy.
}, year = {2015}, pages = {104 p.}, publisher = {Universität Tübingen}, address = {Tübingen}, url = {https://publikationen.uni-tuebingen.de/xmlui/handle/10900/67180}, language = {eng}, }