When genetics meets epigenetics: deciphering the mechanisms controlling IFN-g expression and tuberculosis susceptibility

ALVAREZ GI; HERNÁNDEZ DEL PINO RE; BARBERO AM; PALMERO DJ; GARCÍA VE; PASQUINELLI V

CAPITAL FEDERAL

Congreso; IV Congreso de la Sociedad Latinoamericana de Inmunodeficiencias (LASID), LXIII Reunión de la Sociedad Argentina de Inmunología (SAI) y II Reunión FAIC (French-Argentinean Immunology Congress); 2015

LASID, SAI, FAIC.

Millions of new tuberculosis (TB) cases are reported annually. Human genetic identification is crucial for understanding TB pathogenesis. IFNg is key in the protective immunity against M. tuberculosis (Mtb). We studied 7 Single Nucleotide Polymorphism (SNPs) on IFNg related genes, to find new genetic markers of TB susceptibility. DNA was obtained from whole blood of patients with TB (PTB), Healthy Donors (HD), and Latent TB Individuals (LTBI). IFNg +874 A/T SNP was studied by ARMSPCR and we found the highest frequency of AA genotype in PTB vs HD and LTBI. Moreover, PTB with AA genotype had the lowest IFNglevels in supernatants of Mtbstimulated PBMC. We also studied 262 A/T, 188A/G (PCRRFLP) and +1343 G/T (sequencing) SNPs at the signaling lymphocytic activation molecule (SLAM, an inducer of IFNg against Mtb). But they were not suitable as genetic markers of TB susceptibility, as the most frequent genotype for each SNP were overrepresented in all groups. 3 SNPs at the SLAM associated protein (SAP, 631 A/G, 494 A/G and 346 C/T), an IFNg inhibitor were studied. We found an AA/GG/TT haplotype that was more frequent in PTB and LTBI, showing the lowest frequency in HD. IFNg was significantly lower for the AA/GG/TT haplotype vs GG/AA/CC, while the opposite results were observed for SAP expression. Finally, we found an IFNg/SAP haplotype AA/AA/GG/TT that could be a strong marker of TB susceptibility in Argentina. We found, higher percentages of DNA methylation at the IFNg -53 CpG site in PTB compared with LTBI, showing epigenetic regulation. We also studied two gene repressors, Blimp1 and TLE4, which recruit to chromatin DNA Histone deacetylases (HDACs). After Mtb stimulation Blimp1 and TLE4 shown an expression pattern opposite to that observed for IFNg. Moreover treatment with a HDAC inhibitor significantly increased IFNg in Mtbstimulated cells, suggesting that Blimp1/TLE4 could be involved in the epigenetic control of IFNg during Mtb infection.TRABAJO PRESENTADO AL PREMIO LEONARDO SATZ DE LA SOCIEDAD ARGENTINA DE INMUNOLOGÍA.