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

GUADALUPE INÉS ALVAREZ; RODRIGO HERNÁNDEZ DEL PINO; ANGELA BARBERO; DOMINGO PALMERO; VERÓNICA GARCÍA; VIRGINIA PASQUINELLI

Buenos Aires

Congreso; LXIII Reunión Anual de Sociedad Argentina de Inmunología, IV Reunión de la Sociedad Latinoamericana de Inmunodeficiencias (LASID) y II Congreso Franco-Argentino de Inmunología (FAIC); 2015

Sociedad Argentina de Inmunología. Sociedad Latinoamericana de Inmunodeficiencias

When genetics meets epigenetics: deciphering the mechanisms controlling IFN-g expression andtuberculosis susceptibilityMillions of new tuberculosis (TB) cases are reported annually. Human geneticidentification is crucial for understanding TB pathogenesis. IFN-g is key in the protective immunityagainst M. tuberculosis (Mtb). We studied 7 Single Nucleotide Polymorphism (SNPs) on IFN-g 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). IFN-g +874 A/T SNP was studied by ARMS-PCR and we found the highest frequency of AA genotype in PTB vs HD and LTBI. Moreover, PTB with AA genotype had the lowest IFN-g levels in supernatants of Mtb-stimulated PBMC. We also studied -262 A/T, -188 A/G (PCR-RFLP) and +1343 G/T (sequencing) SNPs at the signaling lymphocytic activation molecule (SLAM, an inducer of IFN-g 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 IFN-g inhibitor were studied. We found an AA/GG/TT haplotype that was more frequent in PTB and LTBI, showing the lowest frequency in HD. IFN-g 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 IFN-g/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 IFN-g -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 IFN-g. Moreover treatment with a HDAC inhibitor significantly increased IFN-g in Mtb-stimulated cells, suggesting that Blimp1/TLE4 could be involved in the epigenetic control of IFN-g during Mtb infection.