CD3 downregulation identifies high-avidity, multipotent SARS-CoV-2 vaccine- and recall antigen-specific Th cells with distinct metabolism

Functional avidity is supposed to critically shape the quality of immune responses, thereby influencing host protection against infectious agents including SARS-CoV-2. Here we show that after human SARS-CoV-2 vaccination, a large portion of high-avidity spike-specific CD4+ T cells lost CD3 expression after in vitro activation. The CD3- subset was enriched for cytokine-positive cells, including elevated per-cell expression levels, and showed increased polyfunctionality. Assessment of key metabolic pathways by flow cytometry revealed that superior functionality was accompanied by a shift toward fatty acid synthesis at the expense of their oxidation, whereas glucose transport and glycolysis were similarly regulated in SARS-CoV-2-specific CD3- and CD3+ subsets. As opposed to their CD3+ counterparts, frequencies of vaccine-specific CD3- T cells positively correlated with both the size of the naive CD4+ T cell pool and vaccine-specific IgG levels. Moreover, their frequencies negatively correlated with advancing age and were impaired in patients under immunosuppressive therapy. Typical recall antigen-reactive T cells showed a comparable segregation into functionally and metabolically distinct CD3+ and CD3- subsets but were quantitatively maintained upon aging, likely due to earlier recruitment in life. In summary, our data identify CD3- T helper cells as correlates of high-quality immune responses that are impaired in at-risk populations.

Cytokine levels associated with favorable clinical outcome in the CAPSID randomized trial of convalescent plasma in patients with severe COVID-19

Objectives

To determine the profile of cytokines in patients with severe COVID-19 who were enrolled in a trial of COVID-19 convalescent plasma (CCP).

Methods

Patients were randomized to receive standard treatment and 3 CCP units or standard treatment alone (CAPSID trial, ClinicalTrials.gov NCT04433910). The primary outcome was a dichotomous composite outcome (survival and no longer severe COVID-19 on day 21). Time to clinical improvement was a key secondary endpoint. The concentrations of 27 cytokines were measured (baseline, day 7). We analyzed the change and the correlation between serum cytokine levels over time in different subgroups and the prediction of outcome in receiver operating characteristics (ROC) analyses and in multivariate models.

Results

The majority of cytokines showed significant changes from baseline to day 7. Some were strongly correlated amongst each other (at baseline the cluster IL-1ß, IL-2, IL-6, IL-8, G-CSF, MIP-1α, the cluster PDGF-BB, RANTES or the cluster IL-4, IL-17, Eotaxin, bFGF, TNF-α). The correlation matrix substantially changed from baseline to day 7. The heatmaps of the absolute values of the correlation matrix indicated an association of CCP treatment and clinical outcome with the cytokine pattern. Low levels of IP-10, IFN-γ, MCP-1 and IL-1ß on day 0 were predictive of treatment success in a ROC analysis. In multivariate models, low levels of IL-1ß, IFN-γ and MCP-1 on day 0 were significantly associated with both treatment success and shorter time to clinical improvement. Low levels of IP-10, IL-1RA, IL-6, MCP-1 and IFN-γ on day 7 and high levels of IL-9, PDGF and RANTES on day 7 were predictive of treatment success in ROC analyses. Low levels of IP-10, MCP-1 and high levels of RANTES, on day 7 were associated with both treatment success and shorter time to clinical improvement in multivariate models.

Conclusion

This analysis demonstrates a considerable dynamic of cytokines over time, which is influenced by both treatment and clinical course of COVID-19. Levels of IL-1ß and MCP-1 at baseline and MCP-1, IP-10 and RANTES on day 7 were associated with a favorable outcome across several endpoints. These cytokines should be included in future trials for further evaluation as predictive factors.

[Lupus and thrombophilia : Antiphospholipid syndrome]

Even early on thromboembolic events were observed in patients with systemic lupus erythematosus (SLE) until the antiphospholipid syndrome (APS) was described in the 1980s as an independent disorder. The APS is a systemic autoimmune disease often overlapping with SLE in which antiphospholipid autoantibodies, including lupus anticoagulant, can cause a hypercoagulation state, which clinically by definition is manifested as arterial and venous occlusions or pregnancy complications. The pathophysiology has not yet been entirely delineated and the clinical spectrum of associated concomitant manifestations is large. As the mortality is increased with SLE and simultaneous APS, focused diagnostics and risk assessment are indispensable. According to the recently published recommendations of the European League Against Rheumatism the therapeutic strategy comprises individualized secondary prevention of thromboembolic complications by means of anticoagulation (with unaltered importance of vitamin K antagonists) and thrombocyte aggregation inhibition, usually lifelong. Statins and antimalarial drugs are recommended for vascular protection while immunosuppressive treatment has not so far been sufficiently proven for APS but remains the subject of current research.

Human CD27+ memory B cells colonize a superficial follicular zone in the palatine tonsils with similarities to the spleen. A multicolor immunofluorescence study of lymphoid tissue

BACKGROUND

Memory B cell (mBC) induction and maintenance is one of the keys to long-term protective humoral immunity. MBCs are fundamental to successful medical interventions such as vaccinations and therapy in autoimmunity. However, their lifestyle and anatomic residence remain enigmatic in humans. Extrapolation from animal studies serves as a conceptual basis but might be misleading due to major anatomical distinctions between species.

METHODS AND FINDINGS

Multicolor immunofluorescence stainings on fixed and unfixed frozen tissue sections were established using primary antibodies coupled to haptens and secondary signal amplification. The simultaneous detection of five different fluorescence signals enabled the localization and characterization of human CD27+CD20+Ki67- mBCs for the first time within one section using laser scanning microscopy. As a result, human tonsillar mBCs were initially identified within their complex microenvironment and their relative location to naïve B cells, plasma cells and T cells could be directly studied and compared to the human splenic mBC niche. In all investigated tonsils (n = 15), mBCs appeared to be not only located in a so far subepithelial defined area but were also follicle associated with a previous undescribed gradual decline towards the follicular mantle comparable to human spleen. However, mBC areas around secondary follicles with large germinal centers (GCs) in tonsils showed interruptions and a general widening towards the epithelium while in spleen the mBC-containing marginal zones (MZ) around smaller GCs were relatively broad and symmetrical. Considerably fewer IgM+IgD+/- pre-switch compared to IgA+ or IgG+ post-switch mBCs were detected in tonsils in contrast to spleen.

CONCLUSIONS

This study extends existing insights into the anatomic residence of human mBCs showing structural similarities of the superficial follicular area in human spleen and tonsil. Our data support the debate of renaming the human splenic MZ to 'superficial zone' in order to be aware of the differences in rodents and, moreover, to consider this term equally for the human palatine tonsil.