Low IFN-α2 Avidity Linked to Neurologic Complications in COVID-19

Key Takeaways

• Among patients with severe COVID-19 and confirmed anti-type I interferon autoantibodies, low anti-IFN-α2 avidity was associated with more neurological complications than high avidity.
• The anti-IFN-ω signal pointed in the same direction but was not statistically significant.
• Avidity and neutralizing capacity overlapped only partially, indicating related but non-interchangeable functional features in severe COVID-19.
• Agreement between anti-IFN-α2 and anti-IFN-ω avidity classes was modest, with 62% concordance and Cohen’s κ = 0.24.

Severe COVID-19 has been linked to autoantibodies against type I interferons, yet functional characterization has centered on whether those antibodies neutralize signaling. It remained unclear whether binding avidity captures a different dimension of autoantibody behavior in patients already known to carry anti-type I interferon reactivity, particularly when neurological complications emerge during severe illness. Investigators therefore measured avidity alongside neutralization-related features in patients with severe COVID-19 and confirmed anti-type I interferon autoantibodies.

In the anti-type I interferon autoantibody avidity analysis in severe COVID-19, investigators evaluated 95 patients with severe COVID-19 and confirmed anti-type I interferon autoantibodies. They measured immunoglobulin G (IgG) avidity against interferon-alpha-2 (IFN-α2) and interferon-omega (IFN-ω) with a urea-dissociation enzyme-linked immunosorbent assay (ELISA) and classified avidity as high when the avidity index was greater than 0.6 and low when it was 0.6 or lower.

Low anti-IFN-α2 avidity had a higher crude neurological-complication rate than high avidity (6/24 [25%] vs 3/51 [6%]; p = 0.026); the paper also reports an odds ratio of 0.21 (95% CI, 0.05-0.84), apparently using high versus low avidity as the comparison. The low-avidity plus non-neutralizing anti-IFN-α2 subgroup had the highest neurological complication rate at 6/18 (33%), while anti-IFN-ω showed a same-direction, non-significant trend. High avidity had low positive predictive value for neutralization for both antibody types, at 47% for anti-IFN-α2 and 16% for anti-IFN-ω.

These findings describe associations within the reported cohort rather than a causal pathway between avidity and neurological injury. The anti-IFN-ω pattern is best interpreted as a same-direction, non-significant trend rather than a confirmed association.

Within this cohort, avidity appeared to add information beyond antibody detection or neutralization alone. The authors concluded that combined avidity and neutralization profiling identified higher neurological risk than either feature alone.

Clinician Questions

How was anti-type I IFN autoantibody avidity defined in severe COVID-19 patients?

Investigators measured IgG autoantibody avidity against IFN-α2 and IFN-ω by urea-dissociation ELISA in severe COVID-19 patients with confirmed anti-type I IFN autoantibodies and classified avidity as high when the avidity index was greater than 0.6 and low when it was 0.6 or lower.

Did avidity and neutralizing capacity identify the same anti-type I IFN autoantibody pattern in severe COVID-19?

No. The data suggest that avidity and neutralizing capacity were related but not equivalent, so the authors treated them as overlapping rather than interchangeable functional features.

Which subgroup had the highest neurological complication burden among severe COVID-19 patients with anti-type I IFN autoantibodies?

The subgroup with low-avidity plus non-neutralizing anti-IFN-α2 autoantibodies carried the greatest neurological burden in this cohort.