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We examined the relationship between peripheral blood levels of SARS-CoV-2 S (Spike protein)1/M (Membrane protein)-reactive IFN-gamma-producing CD4+ and CD8+ T cells, serum levels of biomarkers of clinical severity, and mortality in critically ill COVID-19 patients. The potential association between SARS-CoV-2-S-Receptor Binding Domain (RBD)-specific IgG levels in sera and mortality was also investigated. SARS-CoV-2T cells and anti-RBD IgG levels were monitored in 71 non-consecutive patients (49 male and 22 female; median age, 65years) by whole-blood flow cytometry and Enzyme-linked immunosorbent assay (ELISA), respectively (326 specimens). SARS-CoV-2 RNA loads in paired tracheal aspirates [TA] (n=147) were available from 54 patients. Serum levels of interleukin-6, ferritin, D-Dimer, lactose dehydrogenase and C-reactive protein in paired sera were known. SARS-CoV-2 T cells (either CD4+, CD8+ or both) were detectable in 70 patients. SARS-CoV-2 IFN-gamma CD4+ T-cell responses were documented more frequently than their CD8+ counterparts (62 vs. 56 patients) and were of greater magnitude overall. Detectable SARS-CoV-2 S1/M-reactive CD8+ and CD4+ T-cell responses were associated with higher SARS-CoV-2 RNA loads in TA. SARS-CoV-2 RNA load in TA decreased over time, irrespective of the dynamics of SARS-CoV-2-reactive CD8+ and CD4+ T cells. No correlation was found between SARS-CoV-2 IFN-gamma T-cell counts, anti-RBD IgG concentrations and biomarker serum levels (Rho=0.3). The kinetics of both T cell subsets was comparable between those who died or survived, whereas anti-RBD IgG levels were higher across different time points in deceased patients than in survivors. Enumeration of peripheral blood levels of SARS-CoV-2-S1/M-reactive IFN-gamma CD4+ and CD8+ T cells does not predict viral clearance from the lower respiratory tract or poor clinical outcomes in critically ill COVID-19 patients. In contrast, anti-RBD IgG levels were directly associated with increased mortality. © 2022. The Author(s).

Whether immunosuppression impairs severe acute respiratory syndrome coronavirus 2-specific T cell-mediated immunity (SARS-CoV-2-CMI) after liver transplantation (LT) remains unknown. We included 31 LT recipients in whom SARS-CoV-2-CMI was assessed by intracellular cytokine staining (ICS) and interferon (IFN)-gamma FluoroSpot assay after a median of 103days from COVID-19 diagnosis. Serum SARS-CoV-2 IgG antibodies were measured by ELISA. A control group of nontransplant immunocompetent patients were matched (1:1 ratio) by age and time from diagnosis. Post-transplant SARS-CoV-2-CMI was detected by ICS in 90.3% (28/31) of recipients, with higher proportions for IFN-gamma-producing CD4+ than CD8+ responses (93.5% versus 83.9%). Positive spike-specific and nucleoprotein-specific responses were found by FluoroSpot in 86.7% (26/30) of recipients each, whereas membrane protein-specific response was present in 83.3% (25/30). An inverse correlation was observed between the number of spike-specific IFN-gamma-producing SFUs and time from diagnosis (Spearman's rho: -0.418; p value=.024). Two recipients (6.5%) failed to mount either T cell-mediated or IgG responses. There were no significant differences between LT recipients and nontransplant patients in the magnitude of responses by FluoroSpot to any of the antigens. Most LT recipients mount detectable-but declining over time-SARS-CoV-2-CMI after a median of 3months from COVID-19, with no meaningful differences with immunocompetent patients.

BACKGROUND: There is an imperative need to determine the durability of adaptive immunity to SARS-CoV-2. We enumerated SARS-CoV-2-reactive CD4+ and CD8+ T cells targeting S1 and M proteins and measured RBD-specific serum IgG over a period of 2-6 months after symptoms onset in a cohort of subjects who had recovered from severe clinical forms of COVID-19. PATIENTS AND METHODS: We recruited 58 patients (38 males and 20 females; median age, 62.5 years), who had been hospitalized with bilateral pneumonia, 60% with one or more comorbidities. IgG antibodies binding to SARS-CoV-2 RBD were measured by ELISA. SARS-CoV-2-reactive CD69+-expressing-IFNgamma-producing-CD4+ and CD8+ T cells were enumerated in heparinized whole blood by flow cytometry for ICS. RESULTS: Detectable SARS-CoV-2-S1/M-reactive CD69+-IFN-gamma CD4+ and CD8+ T cells were displayed in 17 (29.3%) and 6 (10.3%) subjects respectively, at a median of 84 days after onset of symptoms (range, 58-191 days). Concurrent comorbidities increased the risk (OR, 3.15; 95% CI, 1.03-9.61; P=0.04) of undetectable T-cell responses in models adjusted for age, sex and hospitalization ward. Twenty-one out of the 35 patients (60%) had detectable RBD-specific serum IgGs at a median of 118 days (range, 60-145 days) after symptoms onset. SARS-CoV-2 RBD-specific IgG serum levels were found to drop significantly over time. CONCLUSION: A relatively limited number of subjects who developed severe forms of COVID-19 had detectable SARS-CoV-2-S1/M IFNgamma CD4+ and CD8+ T cells at midterm after clinical diagnosis. Our data also indicated that serum levels of RBD-specific IgGs decline over time, becoming undetectable in some patients.

BACKGROUND: The magnitude and kinetics of severe acute respiratory syndrome coronavirus 2-specific cell-mediated immunity (SARS-CoV-2-CMI) in kidney transplant (KT) recipients remain largely unknown. METHODS: We enumerated SARS-CoV-2-specific interferon-gamma-producing CD69+ CD4+ and CD8+ T cells at months 4 and 6 from the diagnosis of coronavirus disease 2019 (COVID-19) in 21 KT recipients by intracellular cytokine staining. Overlapping peptides encompassing the SARS-CoV-2 spike (S) glycoprotein N-terminal 1- to 643-amino acid sequence and the membrane protein were used as stimulus. SARS-CoV-2 IgG antibodies targeting the S1 protein were assessed by ELISA at month 6. RESULTS: Detectable (=0.1%) SARS-CoV-2-specific CD4+ T-cell response was found in 57.1% and 47.4% of patients at months 4 and 6. Corresponding rates for CD8+ T cells were 19.0% and 42.1%, respectively. Absolute SARS-CoV-2-specific T-cell counts increased from month 4 to month 6 in CD8+ (P=0.086) but not CD4+ subsets (P=0.349). Four of 10 patients with any detectable response at month 4 had lost SARS-CoV-2-CMI by month 6, whereas 5 of 9 patients mounted SARS-CoV-2-CMI within this period. All but 2 patients (89.5%) tested positive for SARS-CoV-2 IgG. Patients lacking detectable SARS-CoV-2-specific CD4+ response by month 6 were more likely to be under tacrolimus (100.0% versus 66.7%; P=0.087) and to have received tocilizumab for the previous COVID-19 episode (40.0% versus 0.0%; P=0.087). CONCLUSIONS: Although still exploratory and limited by small sample size, the present study suggests that a substantial proportion of KT recipients exhibited detectable SARS-CoV-2-CMI after 6 months from COVID-19 diagnosis.

OBJECTIVES: The immunogenicity of the Comirnaty COVID-19 vaccine is understudied in elderly people with comorbidities. SARS-CoV-2-S-targeted antibody and T cell responses following full vaccination were assessed in nursing home residents. METHODS: Sixty nursing home residents (44 female; age, 53-100years), of whom 10 had previously been diagnosed of COVID-19, and 18 healthy controls (15 female; age, 27-54years) were recruited. Pre- and post-vaccination blood specimens were available for quantitation of total antibodies binding SARS-CoV-2 S protein and enumeration of SARS-CoV-2-S-reactive IFN-gamma CD4+ and CD8+ T cells by flow cytometry. RESULTS: The seroconversion rate in presumably SARS-CoV-2 naive nursing home residents (41/43; 95.3%), was similar to controls (17/18; 94.4%). A booster effect was documented in post vaccination samples of nursing home residents with prior COVID-19. Plasma antibody levels were higher (P

There is limited information on SARS-CoV-2 T-cell immune responses in patients with COVID-19. Both CD4+ and CD8+ T cells may be instrumental in resolution of and protection from SARS-CoV-2 infection. Here, we tested 25 hospitalized patients either with microbiologically documented COVID-19 (n=19) or highly suspected of having the disease (n=6) for presence of SARS-CoV-2-reactive CD69+ -expressing interferon-gamma (IFN-gamma) producing CD8+ T cells using flow-cytometry for intracellular cytokine staining assay. Two sets of overlapping peptides encompassing the SARS-CoV-2 Spike glycoprotein N-terminal 1-643 amino acid sequence and the entire sequence of SARS-CoV-2 M protein were used simultaneously as antigenic stimulus. Ten patients (40%) had detectable responses, displaying frequencies ranging from 0.15 to 2.7% (median of 0.57 cells/L; range, 0.43-9.98 cells/L). The detection rate of SARS-CoV-2-reactive IFN-gamma CD8+ T cells in patients admitted to intensive care was comparable (P=0.28) to the rate in patients hospitalized in other medical wards. No correlation was found between SARS-CoV-2-reactive IFN-gamma CD8+ T-cell counts and SARS-CoV-2 S-specific antibody levels. Likewise, no correlation was observed between either SARS-CoV-2-reactive IFN-gamma CD8+ T cells or S-specific IgG-antibody titers and blood cell count or levels of inflammatory biomarkers. In summary, in this descriptive, preliminary study we showed that SARS-CoV-2-reactive IFN-gamma CD8+ T cells can be detected in a non-negligible percentage of patients with moderate to severe forms of COVID-19. Further studies are warranted to determine whether quantitation of these T-cell subsets may provide prognostic information on the clinical course of COVID-19. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Cytomegalovirus (CMV) DNAemia and CMV disease have been reported as more frequent in patients undergoing haploidentical allogeneic hematopoietic stem cell transplantation (Haplo-HSCT) than in those receiving HLA-matched allografts. This could be due to impaired CMV-specific T-cell reconstitution. Here, we conducted a multicenter observational study to assess CMV pp65 and IE-1-specific T cells kinetics in patients undergoing unmanipulated Haplo-HSCT with posttransplant cyclophosphamide (PT/Cy-haplo) and compared it with patients allografted with HLA-matched donors. Plasma CMV DNA load was monitored by real-time PCR and enumeration of CMV-specific IFN-gamma-producing CD8(+) and CD4(+) T cells was performed by flow cytometry for intracellular cytokine staining at days +30, +60, +90, and +180 after transplantation. CMV DNAemia developed in 62 patients, occurring with comparable frequency in PT/Cy-haplo and MRD/MUD recipients (P = 0.14). There were no significant differences across groups in the number of patients either displaying detectable CMV-specific CD8(+) and CD4(+) T-cell responses or acquiring CMV-specific T-cell levels conferring protection against subsequent infection. CMV-specific T-cell counts were comparable between groups at most time points examined, irrespective of whether CMV DNAemia occurred or not prior to monitoring. Collectively the data suggest that PT/Cy-haplo recipients may reconstitute CMV-specific T-cell immunity to the same extent as patients undergoing HLA-matched allo-HSCT.