Prospective Registry of Outcomes, Treatment, and Clinical Trajectories for Anti-IFN-γ Immunodeficiency

Autoantibodies against interferon-γ (AIGA) impair the IFN-γ-interleukin 12 pathway. The disease is underrecognized, leading to profound diagnostic and therapeutic delays. Evidence on treatment strategies, particularly B-cell depletion, remains limited.

To evaluate the utility of Stat1 phosphorylation (pStat1) neutralization assays to guide management of AIGA immunodeficiency.

This ambispective longitudinal cohort study of patients with confirmed AIGA immunodeficiency was performed at Queen Mary Hospital, as the only center performing AIGA testing under Hong Kong's unified public health care system. The AIGA Prospective Registry of Outcomes, Treatment and Evaluating Clinical Trajectories (PROTECT) reviews patients with AIGA immunodeficiency in Hong Kong, with a focus on rituximab response. Participants included patients with AIGA immunodeficiency demonstrated by positive enzyme-linked immunosorbent assay findings with pStat1 inhibition recruited into the AIGA-PROTECT registry. Demographic, clinical, and laboratory data were collected longitudinally from January 1, 2021, to November 30, 2024.

All patients diagnosed with AIGA immunodeficiency were evaluated for rituximab therapy by the attending immunologist on a case-by-case basis. Treatment decisions were guided by clinical severity, infection burden, and patient preference, following detailed counselling on potential benefits and risks.

Demographic characteristics, medical history (with detailed documentation of prior and incident hospitalizations), physical examination findings, laboratory investigations including serial pStat1 neutralizing assays, and longitudinal clinical progress were collected. For patients treated with rituximab, their laboratory and clinical parameters before and after treatment were compared.

A total of 38 patients with AIGA immunodeficiency were recruited. Patients experienced disseminated infections from multiple pathogens. Twenty-one patients (55.3%) received rituximab, which was associated with reduced patient hospitalizations (odds ratio, 25.00 [95% CI, 1.48-422.26]; P < .001) and annual hospitalization rates (median difference, -3.0 [95% CI, -5.0 to -1.0]; P = .008). Serial monitoring of pStat1 neutralization aligned with clinical events.

This cohort study presents a detailed analysis of clinical features, course of disease, and outcomes of rituximab treatment in patients with AIGA immunodeficiency in a clinical setting. These findings suggest that serial monitoring via pStat1 assays is a valuable tool for monitoring treatment response and guiding clinical management.