Laboratory evaluation of the IFN-γ circuit for the molecular diagnosis of Mendelian susceptibility to mycobacterial disease

Abstract

The integrity of the interferon (IFN)-γ circuit is necessary to mount an effective immune response to intra-macrophagic pathogens, especially Mycobacteria. Inherited monogenic defects in this circuit that disrupt the production of, or response to, IFN-γ underlie a primary immunodeficiency known as Mendelian susceptibility to mycobacterial disease (MSMD). Otherwise healthy patients display a selective susceptibility to clinical disease caused by poorly virulent mycobacteria such as BCG (bacille Calmette-Guérin) vaccines and environmental mycobacteria, and more rarely by other intra-macrophagic pathogens, particularly Salmonella and M. tuberculosis. There is high genetic and allelic heterogeneity, with 19 genetic etiologies due to mutations in 10 genes that account for only about half of the patients reported. An efficient laboratory diagnostic approach to suspected MSMD patients is important, because it enables the establishment of specific therapeutic measures that will improve the patient’s prognosis and quality of life. Moreover, it is essential to offer genetic counseling to affected families. Herein, we review the various genetic and immunological diagnostic approaches that can be used in concert to reach a molecular and cellular diagnosis in patients with MSMD.

Keywords:

• Mycobacteria
• intracellular pathogens
• interferon gamma
• primary immunodeficiency
• diagnosis
• MSMD

Notes

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.

Notes

1 Approximate costs of the different techniques are calculated for each sample processed to which the cost of healthy (normal) control/s sample/s must be added; only reagent-derived costs are included. It is important to take into account that prices are approximate and that they may vary depending on the supplier/country or type of kit used. Moreover, when evaluating the costs of implementing these techniques, other costs need to be considered, such as sample preservation, including frozen PBMCs and plasma, DNA extraction and preservation, and general materials such as phosphate buffer saline, plastic materials, and culture media. As all laboratories may not have a flow cytometer, they may need to use flow cytometry facilities, which likely charge the users for the use of the cytometers and for technical assistance. This is an important variable to consider in all flow cytometry techniques as it may significantly increase the final cost.

2 Hands-on time is an estimation of the time needed to perform the technique; however, the response time (turn-around time) can vary depending on different factors including (i) the need to batch patient samples, (ii) the number of patient samples, and (iii) the time required for analysis (from receipt of specimen to reporting the result).

Additional information

Funding

All phases of this work were supported by the Plan Nacional de I+D+I and co-financed by the ISCIII – Subdirección General de Evaluación y Fomento de la Investigación Sanitaria – and the Fondo Europeo de Desarrollo Regional (FEDER) [PI12/01990 and PI15/01094 to LA; PI13/00676 to MJ and PI13/01456 and PI16/00759 to CRG]. The Laboratory of Human Genetics of Infectious Diseases is supported by grants from the National Institute of Allergy and Infectious Diseases [R01AI089970 and R37AI095983], the National Center for Research Resources and the National Center for Advancing Sciences of the National Institutes of Health [UL1TR001866 for J.L.C.], The Rockefeller University, the St. Giles Foundation, Institut National de la Santé et de la Recherche Médicale (INSERM), Paris Descartes University, the Integrative Biology of Emerging Infectious Diseases Laboratory of Excellence [ANR-10-LABX-62-IBEID], and the French National Research Agency (ANR) under the “Investments for the Future” program [ANR-10-IAHU-01 and ANR-GENMSMD for J.B.], SRC2017, support of Clinical research, Fondation du Souffle et du Fonds de Recherche en Santé Respiratoire, for J.B. RMB was supported by the European Molecular Biology Organization (EMBO). COQ was supported by ANR-14-CE15-006-01.