Rare neutralizing IFN-γ autoantibodies in HLA-DRB1* 15:02 or 16:02 individuals confer susceptibility to mycobacterial infections.

BACKGROUND: Weakly virulent environmental mycobacteria (EM) can cause severe disease in HLA-DRB1*15:02 or 16:02 adult individuals harboring neutralizing anti-IFN-γ autoantibodies (nAIGAs). The overall prevalence of nAIGA in a general population are unknown as is the the penetrance of nAIGA in HLA-DRB1*15:02 or 16:02 individuals, and the proportion of patients with unexplained, adult-onset EM infections carrying nAIGAs.

METHODS: This study analyzed the detection and neutralization of anti-IFN-γ autoantibodies (auto-Abs) from 8,430 healthy individuals of the general population, 257 HLA-DRB1*15:02 or 16:02 carriers, 1,063 patients with autoimmune disease, and 497 patients with unexplained severe disease due to EM.

RESULTS: We find that anti-IFN-γ autoantibodies detected in 4,148 of 8,430 healthy individuals (49.2%) from the general population of an unknown HLA-DRB1 genotype are not neutralizing. Moreover, we do not find nAIGAs in 257 individuals carrying HLA-DRB1* 15:02 or 16:02, including 71 individuals with detectable anti-IFN-g autoantibodies (27.6%). Additionally, nAIGA are absent in 1,063 patients with an autoimmune disease. Furthermore, we find only a few other autoantibodies in seven patients with nAIGAs tested. Finally, seven of 497 patients (1.4%) with unexplained severe disease due to EM harbored nAIGA. Yet, nAIGA are absent in the remaining 41 patients who are HLA-DRB1*15:02 or 16:02, the 45 patients with IFN-g autoantibodies, and the five patients with HLA-DRB1*15:02 or 16:02 and IFN-g autoantibodies .

CONCLUSION: These findings suggest that nAIGAs are isolated and that their penetrance in HLA-DRB1*15:02 or 16:02 individuals is low, implying that they may be triggered by rare germline or somatic variants. In contrast, the risk of mycobacterial disease in patients with nAIGAs is high, confirming that these nAIGAs are causal of EM disease.

FUNDING: The Laboratory of Human Genetics of Infectious Diseases is supported by the Howard Hughes Medical Institute, the Rockefeller University, the St. Giles Foundation, the National Institutes of Health (NIH) (R01AI095983), the National Center for Advancing Translational Sciences (NCATS), the NIH Clinical and Translational Science Award (CTSA) program (UL1 TR001866), and partly by French National Research Agency (ANR).