Neutralizing Activity of Anti-interferon-γ Autoantibodies in Adult-Onset Immunodeficiency Is Associated With Their Binding Domains

Abstract

Adult-onset immunodeficiency (AOID) with anti-interferon-γ (IFN-γ) autoantibodies (autoAbs) is an emerging immunodeficiency syndrome in Asian countries. The presence of neutralizing anti-IFN-γ autoAbs are significantly associated with severe disseminated opportunistic infections. However, the characteristics of the neutralizing antibodies in patients are poorly defined. To better understand the properties of the anti-IFN-γ autoAbs in patients with opportunistic infections, a simplified competitive-binding ELISA was developed. The domains recognized by anti-IFN-γ autoAbs were assessed based on their competition with commercial neutralizing mouse anti-IFN-γ monoclonal antibodies (mAbs). First, the binding affinity and neutralizing capacity of these mAbs (clones B27, B133.5, and MD-1) were characterized. Kinetic analysis and epitope binning using bio-layer interferometry showed the comparable binding affinity of these mAbs to full-length IFN-γ and to the adjacent binding region. These mAbs did not recognize the synthetic 20-mer peptides and inhibited IFN-γ-mediated functions differently. In a competitive-binding ELISA, the anti-IFN-γ autoAbs in AOID serum blocked B27, B133.5, and MD-1 mAb binding. This evidence suggested that the autoAbs that competed with neutralizing mouse anti-IFN-γ mAbs recognized a discontinuous epitope of homodimeric IFN-γ as these mAbs. The patient autoAbs that recognized the B27 epitope exhibited strong neutralizing activity that was determined by the functional analysis. Our results demonstrated the heterogeneity of the autoAbs against IFN-γ in AOID patients and the different patterns among individuals. These data expand upon the fundamental knowledge of neutralizing anti-IFN-γ autoAbs in AOID patients.

Determination of a distinguished interferon gamma epitope recognized by monoclonal antibody relating to autoantibody associated immunodeficiency

“…To understand the mechanisms underlying the pathogenesis of AOID better, anti-IFN-γ autoAbs from patients should be characterized. In our previous study, the autoAbs of patients with AOID recognized the same epitope as B27 mAb 12 . Since B27 mAb did not recognize the C-terminal epitope identified by Lin et al 11 , the epitope for a particular autoAb in patients with AOID was investigated further.…”

“…However, the epitope recognized by the pathogenic autoAbs has not yet been thoroughly investigated. In a previous study, we had reported that autoAbs in patients with AOID competed with neutralizing mouse anti-IFN-γ monoclonal antibody (mAb) (clone B27) 12 . Epitope mapping using 20-mer synthetic peptides revealed that B27 mAb does not bind to the C-terminal epitope.…”

Minireview: Insights into anti-interferon-γ autoantibodies

“…8 Commercially available mouse anti-IFN-c monoclonal antibodies can bind to distinct epitopes of the IFN-c molecule with different neutralizing activity. 22 Competitivebinding ELISA using commercial neutralizing mouse anti-IFN-c monoclonal antibodies showed that anti-IFN-c AAbs in patients bind to discontinuous epitope of homodimeric IFN-c. This study also demonstrated the heterogeneity of the auto Abs against IFN-c in AOID patients and the diverse patterns among individuals.…”

Phenocopies: Mimics of Inborn Errors of Immunity

“…INF-ɣ is mainly produced by Th1 cells, the activation of its receptor (INF-ɣR) phosphorylates and activates molecules such as STAT1. [64] Some studies have shown that the ability of interferon inhibition by these autoantibodies is more important than the concentration to determine the predisposition to the disease, besides there is a heterogeneity between the types of autoantibodies in each individual [65] [66].…”