Novel mutations in genes of the IL-12/IFN-γ axis cause susceptibility to tuberculosis.

BACKGROUND: The IL-12/23/ISG15-IFN-γ pathway is the main immunological pathway for controlling intra-macrophagic microorganisms such as Mycobacteria, Salmonella, and Leishmania spp. Consequently, upon mutations in genes of the IL-12/23/ISG15-IFN-γ pathway cause increased susceptibility to intra-macrophagic pathogens, particularly to Mycobacteria. Therefore, the purpose of this study was to characterize the mutations in genes of the IL-12/23/ISG15-IFN-γ pathway in severe tuberculosis (TB) patients. METHODS: Clinically suspected TB was initially confirmed in four patients (P) (P1, P2, P3, and P4) using the GeneXpert MTB/RIF and culturing techniques. The patients' Peripheral blood mononuclear cells (PBMCs) were then subjected to ELISA to measure Interleukin 12 (IL-12) and interferon gamma (IFN-γ). Flow cytometry was used to detect the surface expressions of IFN-γR1 and IFN-γR2 as well as IL-12Rß1and IL-12Rß2 on monocytes and T lymphocytes, respectively.The phosphorylation of signal transducer and activator of transcription 1(STAT1) on monocytes and STAT4 on T lymphocytes were also detected by flow cytometry. Sanger sequencing was used to identify mutations in the IL-12Rß1, STAT1, NEMO, and CYBB genes. RESULTS: P1's PBMCs exhibited reduced IFN-γ production, while P2's and P3's PBMCs exhibited impaired IL-12 induction. Low IL-12Rß1 surface expression and reduced STAT4 phosphorylation were demonstrated by P1's T lymphocytes, while impaired STAT1 phosphorylation was detected in P2's monocytes. The impaired IκB-α degradation and abolished H2O2 production in monocytes and neutrophils of P3 and P4 were observed, respectively. Sanger sequencing revealed novel nonsense homozygous mutation: c.191 G>A/p.W64 * in exon 3 of the IL-12Rß1 gene in P1, novel missense homozygous mutation: c.107 A>T/p.Q36L in exon 3 of the STAT1 gene in P2, missense hemizygous mutation:: c.950 A>C/p.Q317P in exon 8 of the NEMO gene in P3, and nonsense hemizygous mutation: c.868 C>T/p.R290X in exon 8 of CYBB gene in P4. CONCLUSION: Our findings broaden the clinical and genetic spectra associated with IL-12/23/ISG15-IFN-γ axis anomalies. Additionally, our data suggest that TB patients in Pakistan should be investigated for potential genetic defects due to high prevalence of parental consanguinity and increased incidence of TB in the country.

Association between pulmonary tuberculosis and Type 2 diabetes in Sudanese patients.

INTRODUCTION: Tuberculosis (TB) and diabetes mellitus (DM) are both important health issues, and the association between DM and TB may be the next challenge for global TB control worldwide, type 2 DM (T2DM) responsible for 90% of DM cases. Persons with diabetes have a significantly increased risk of active TB, which is two to three times higher than in persons without diabetes. The aim of this study was to determine the association between pulmonary tuberculosis (PTB) and T2DM among Sudanese patients and also to determine the association between hemoglobin A1c (HbA1c) percentage in diabetic patients and development of PTB and effect of duration of T2DM in developing PTB. MATERIALS AND METHODS: A total of 120 sputum samples were collected from patients during 6 months in Ribat University Hospital, Khartoum, Sudan. Sixty of them were known type 2 diabetic patients categorized as study group and sixty were nondiabetic patients categorized as control group. Ziehl-Neelsen smear preparation and DNA were extracted from sputum for detection of Mycobacterium tuberculosis by polymerase chain reaction (PCR). RESULTS: Among the 120 sputum specimens, 72 (60%) were males and 48 (40%) were females. Fourteen (19.4%) males and 6 (12.5%) females had PTB, the difference was not statistically significant according to gender P = 0.229. According to treatment modalities, diabetic patients were treated with injectable insulin (36.7%), PCR positive was 4(33.3%) P value (0.853), oral hypoglycemic drugs (51.7%) PCR positive 7 (58.3%) P value (0.849) and dietary control (11.7%) PCR positive (1 (8.3%) P value (1.000) Were insignificant differences. The frequency of HbA1c of 58 patients with diabetes was 24 (41.4%) who had controlled DM (HbA1c level ≤ 6.5%) and 34 (58.6%) had uncontrolled DM. Of the 60 patients with diabetes, 12 had PTB with uncontrolled DM, with significant difference (P=0.000). The mean duration of diabetes mellitus was (6.92 years ± Std 6.801) and the frequency of diabetes mellitus in first 10 years was 47 (78.3%), in (11-20) years was 10 (16.7%) and in (21-30) years was 3 (5%), the PCR positive PTB showed 10(21.3%) for the first 10 years, (11-20) years was 2 (20%) and zero (0.0%) for (21-30) years, P-value (0.480) insignificant different. CONCLUSIONS: In summary, we found consistent evidence for an increased risk of TB among patients with uncontrolled DM (high-level HbA1c).