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Severe COVID-19 represents an undiagnosed primary immunodeficiency in a high proportion of infected individuals


Since the emergence of the COVID-19 pandemic in early 2020, a key challenge has been to define risk factors, other than age and pre-existing comorbidities, that predispose some people to severe disease, while many other SARS-CoV-2-infected individuals experience mild, if any, consequences. One explanation for intra-individual differences in susceptibility to severe COVID-19 may be that a growing percentage of otherwise healthy people have a pre-existing asymptomatic primary immunodeficiency (PID) that is unmasked by SARS-CoV-2 infection. Germline genetic defects have been identified in individuals with life-threatening COVID-19 that compromise local type I interferon (IFN)-mediated innate immune responses to SARS-CoV-2. Remarkably, these variants - which impact responses initiated through TLR3 and TLR7, as well as the response to type I IFN cytokines - may account for between 3% and 5% of severe COVID-19 in people under 70 years of age. Similarly, autoantibodies against type I IFN cytokines (IFN-alpha, IFN-omega) have been detected in patients' serum prior to infection with SARS-CoV-2 and were found to cause c. 20% of severe COVID-19 in the above 70s and 20% of total COVID-19 deaths. These autoantibodies, which are more common in the elderly, neutralise type I IFNs, thereby impeding innate antiviral immunity and phenocopying an inborn error of immunity. The discovery of PIDs underlying a significant percentage of severe COVID-19 may go some way to explain disease susceptibility, may allow for the application of targeted therapies such as plasma exchange, IFN-alpha or IFN-beta, and may facilitate better management of social distancing, vaccination and early post-exposure prophylaxis.

Type Journal
ISBN 2050-0068 (Print) 2050-0068 (Linking)
Authors Gray, P. E.; Bartlett, A. W.; Tangye, S. G.
Publisher Name Clinical & Translational Immunology
Published Date 2022-04-30
Published Volume 11
Published Issue 4
Published Pages e1365
Status Published in-print
DOI 10.1002/cti2.1365
URL link to publisher's version