Consanguineous marriages increase the incidence of recurrent tuberculosis: Evidence from whole exome sequencing

Background: In this study, we have identified multiple mutations in the IL-12R1 gene among Pakistani patients who have inherited them through consanguineous marriages. These patients have experienced severe BacilleCalmette-Guerin (BCG) infection as well as recurrent tuberculosis. We will demonstrate the pivotal role of interleukin (IL)-12/interferon (IFN)-gamma axis in the regulation of mycobacterial diseases. Methodology: First, we checked the patients' medical records, and then afterward, we assessed interferon-gamma (IFN-gamma) production through ELISA. Following that, DNA was extracted to investigate IL-12/IFN- abnormalities. Whole exome sequencing was conducted through Sanger sequencing. Secretory cytokine levels were compared from healthy control of the same age groups and they were found to be considerably less in the disease cohort. To evaluate the probable functional impact of these alterations, an in silico study was performed. Results: The study found that the patients' PBMCs produced considerably less IFN-gamma than expected. Analysis using flow cytometry showed that activated T cells lacked surface expression of IL-12R beta 1. Exon 7 of the IL-12R beta 1 gene, which encodes a portion of the cytokine binding region (CBR), and exon 10, which encodes the fibronectin-type III (FNIII) domain, were found to have the mutations c.641 A > G; p.Q214R and c.1094 T > C; p.M365T, respectively. In silico analysis showed that these mutations likely to have a deleterious effect on protein function. Conclusion: Our findings indicate the significant contribution of the IL-12/IFN-gamma is in combating infections due to mycobacterium. Among Pakistani patients born to consanguineous marriages, the identified mutations in the IL12R beta-1 gene provide insights into the genetic basis of severe BCG infections and recurrent tuberculosis. The study highlights the potential utility of newborn screening in regions with mandatory BCG vaccination, enabling early detection and intervention for primary immunodeficiencies associated with mycobacterial infections. Moreover, the study suggests at the potential role of other related genes such as IL-23R beta 1, TYK2, or JAK2 in IFN-gamma production, warranting further investigation.