SARS-CoV-2 T Cell Response in Severe and Fatal COVID-19 in Primary Antibody Deficiency Patients Without Specific Humoral Immunity

Abstract

Morbidity and mortality of COVID-19 is increased in patients with inborn errors of immunity (IEI). Age and comorbidities and also impaired type I interferon immunity were identified as relevant risk factors. In patients with primary antibody deficiency (PAD) and lack of specific humoral immune response to SARS-CoV-2, clinical disease outcome is very heterogeneous. Despite extensive clinical reports, underlying immunological mechanisms are poorly characterized and levels of T cellular and innate immunity in severe cases remain to be determined. In the present study, we report clinical and immunological findings of 5 PAD patients with severe and fatal COVID-19 and undetectable specific humoral immune response to SARS-CoV-2. Reactive T cells to SARS-CoV-2 spike (S) and nucleocapsid (NCAP) peptide pools were analyzed comparatively by flow cytometry in PAD patients, convalescents and naïve healthy individuals. All examined PAD patients developed a robust T cell response. The presence of polyfunctional cytokine producing activated CD4⁺ T cells indicates a memory-like phenotype. An analysis of innate immune response revealed elevated CD169 (SIGLEC1) expression on monocytes, a surrogate marker for type I interferon response, and presence of type I interferon autoantibodies was excluded. SARS-CoV-2 RNA was detectable in peripheral blood in three severe COVID-19 patients with PAD. Viral clearance in blood was observed after treatment with COVID-19 convalescent plasma/monoclonal antibody administration. However, prolonged mucosal viral shedding was observed in all patients (median 67 days) with maximum duration of 127 days. PAD patients without specific humoral SARS-CoV-2 immunity may suffer from severe or fatal COVID-19 despite robust T cell and normal innate immune response. Intensified monitoring for long persistence of SARS-CoV-2 viral shedding and (prophylactic) convalescent plasma/specific IgG as beneficial treatment option in severe cases with RNAemia should be considered in seronegative PAD patients.

Keywords: convalescent plasma (CP); coronavirus disease 2019 (COVID-19); innate immunity; primary antibody deficiency (PAD); primary immunodeficiencies (PID); severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); type I interferons.

Figure 1

CD154⁺CD137⁺CD4⁺ T cell response to SARS-CoV-2 Spike and NCAP peptide pools and SEB positive control. PBMCs of PAD (n = 4, red), CHC (n = 6, blue) and naïve HC (n = 6, grey) were stimulated with 1 µg/ml SARS-CoV-2 peptides or 3 µg/ml SEB. Frequencies of activated CD154⁺CD137⁺CD4⁺ (A) T cells after stimulation with the different SARS-CoV-2 peptides and SEB (B). Only T cell responses above the threshold of 20% above background activation are shown. Median and interquartile range (IQR) are indicated. Statistical analysis was performed by non-parametric one-tailed Mann–Whitney-U test for comparison of control and patient groups. A p-value ≤0.05 was considered as statistically significant. p ≤0. 05 = *; p ≤0.001 = **. PAD patients are depicted by the following symbols: patient #1 *; patient #2 ▲; patient #3 ■; patient #4 ▼.

Figure 2

Triple and double cytokine producing activated CD4⁺ T cell subsets in response to SARS-CoV-2 specific peptide stimulation. PBMCs of PAD (n = 4, red), CHC (n = 6, blue) and naïve HC (n = 6, grey) were stimulated with 1 µg/ml SARS-CoV-2 peptides or 3 µg/ml SEB. IFNγ, TNFα and IL-2 tp activated CD4⁺ T cells were analyzed by Boolean combination gating strategy. Cytokine expression profile in tp activated CD4⁺CD154⁺CD137⁺ (A) T cells, and also TNFα + IL-2 dp (B) activated CD4⁺ T cells in response to SARS-CoV-2 peptide pools are shown. Median and interquartile range (IQR) are indicated. Statistical analysis was performed by non-parametric one-tailed Mann–Whitney-U test for comparison of control and patient groups. A p-value ≤0.05 was considered as statistically significant. p ≤0. 05 = *; p ≤0.001 = **. PAD patients are depicted by the following symbols: patient #1 *; patient #2 ▲; patient #3 ■; patient #4 ▼.