Effect of Immunosuppression on the Immune Response to SARS-CoV-2 Infection and Vaccination

Abstract

Immunosuppressive treatment in patients with rheumatic diseases can maintain disease remission but also increase risk of infection. Their response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination is frequently blunted. In this study we evaluated the effect of immunosuppression exposure on humoral and T cell immune responses to SARS-CoV-2 infection and vaccination in two distinct cohorts of patients; one during acute SARS-CoV-2 infection and 3 months later during convalescence, and another prior to SARS-CoV-2 vaccination, with follow up sampling 6 weeks after vaccination. Results were compared between rituximab-exposed (in previous 6 months), immunosuppression-exposed (in previous 3 months), and non-immunosuppressed groups. The immune cell phenotype was defined by flow cytometry and ELISA. Antigen specific T cell responses were estimated using a whole blood stimulation interferon-γ release assay. A focused post-vaccine assessment of rituximab-treated patients using high dimensional spectral cytometry was conducted. Acute SARS-CoV-2 infection was characterised by T cell lymphopenia, and a reduction in NK cells and naïve CD4 and CD8 cells, without any significant differences between immunosuppressed and non-immunosuppressed patient groups. Conversely, activated CD4 and CD8 cell counts increased in non-immunosuppressed patients with acute SARS-CoV-2 infection but this response was blunted in the presence of immunosuppression. In rituximab-treated patients, antigen-specific T cell responses were preserved in SARS-CoV-2 vaccination, but patients were unable to mount an appropriate humoral response.

Keywords: COVID-19; SARS-CoV-2; immune response; immunosuppression; rituximab; vaccine.

Figure 1

Absolute circulating lymphocyte subset (naïve (A) and activated (B) CD4+, naïve (C) and activated (D) CD8+, and (E) effector CD8+) counts (median ± interquartile range) in patients with acute COVID-19 (Acute) and at 3 months post infection (Conv), stratified according to the presence of immunosuppression at the time of infection. The purple shading represents the interquartile range of healthy uninfected controls. * p < 0.5, ** p < 0.005, *** p < 0.001, Kruskal–Wallis test with Dunn’s post hoc test comparing individual groups against healthy controls.

Figure 2

Circulating monocyte subset (non-classical (A), intermediate (B), and classical (D)) fractions (median ± interquartile range) in patients with acute COVID-19 (Acute) and 3 months post infection (Conv), stratified according to the presence of immunosuppression at the time of infection. The CD10:CD16 WFI ratio was also determined on CD15+ neutrophils (C). The purple shading represents the interquartile range of healthy uninfected controls. ** p < 0.005, *** p < 0.001, **** p < 0.0001 Kruskal–Wallis test with Dunn’s post hoc test comparing individual groups against healthy controls.

Figure 3

Naïve CD4 (A), activated CD4 (B), naïve CD8 (C), activated CD8 (D) and effector CD8 (E) lymphocyte subsets in patients with AAV pre- and post-SARS-CoV-2 vaccination, stratified according to the presence or absence of immunosuppression at the time of vaccination (median ± interquartile range). The purple shading represents the interquartile range of healthy uninfected controls. ** p < 0.005, and *** p < 0.001, Kruskal–Wallis test with Dunn’s post hoc test comparing individual groups against healthy controls.

Figure 4

SARS-CoV-2-specific IgG (optical density (OD) ratio of test to irrelevant antigen, (A)) and whole blood interferon-γ release assay (COVID-IGRA, (B)) in patients vaccinated against SARS-CoV-2. “+” indicated presence of immunosuppressive therapies. The dotted line in (A) reflects the 5th centile in the healthy volunteer (HV) group and the grey bars reflect the median and interquartile range of neutralising antibody OD ratio. In (B), the white and grey bars reflect the IGRA median and interquartile range. (C) summarises the subject level IgG/IgA/IgM and IGRA responses. Pep = spike peptides (S, S1, S+ Peptivator; RTX = Rituximab; Other = other immunosuppression. *** p < 0.001, **** p < 0.0001 Kruskal–Wallis test with Dunn’s post hoc test comparing individual groups against healthy controls.

Figure 5

In depth T cell subset analysis of post-vaccine samples in patients exposed to rituximab (RTX+) and those on no immunosuppression (RTX-). (A) reflects the cell fraction and (B) the absolute cell count (median ± interquartile range). NK = natural killer cell; VD1 = Vδ1 γδ T cell; Vd2 = Vδ2 γδ T cell; iNKT = invariant natural killer T cell; T reg = regulatory T cell; Tn = naïve T cell; Tcm = central memory T cell; Tem = effector memory T cell; no significant differences between exposure groups were observed (mixed effects model with Šídák’s multiple comparisons test).