Recent studies have provided insights into the pathogenesis of coronavirus disease 2019 (COVID-19) 1 – 4 . However, the longitudinal immunological correlates of disease outcome remain unclear. Here we serially analysed immune responses in 113 patients with moderate or severe COVID-19. Immune profiling revealed an overall increase in innate cell lineages, with a concomitant reduction in T cell number. An early elevation in cytokine levels was associated with worse disease outcomes. Following an early increase in cytokines, patients with moderate COVID-19 displayed a progressive reduction in type 1 (antiviral) and type 3 (antifungal) responses. By contrast, patients with severe COVID-19 maintained these elevated responses throughout the course of the disease. Moreover, severe COVID-19 was accompanied by an increase in multiple type 2 (anti-helminths) effectors, including interleukin-5 (IL-5), IL-13, immunoglobulin E and eosinophils. Unsupervised clustering analysis identified four immune signatures, representing growth factors (A), type-2/3 cytokines (B), mixed type-1/2/3 cytokines (C), and chemokines (D) that correlated with three distinct disease trajectories. The immune profiles of patients who recovered from moderate COVID-19 were enriched in tissue reparative growth factor signature A, whereas the profiles of those with who developed severe disease had elevated levels of all four signatures. Thus, we have identified a maladapted immune response profile associated with severe COVID-19 and poor clinical outcome, as well as early immune signatures that correlate with divergent disease trajectories.

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Germinal centers (GCs), structures normally associated with B cell immunoglobulin (Ig) hypermutation and development of high-affinity antibodies upon infection or immunization, are present in gut-associated lymphoid organs of humans and mice under steady state. Gut-associated (ga)GCs can support antibody responses to enteric infections and immunization 1 . However, whether B cell selection and antibody affinity maturation can take place in face of the chronic and diverse antigenic stimulation characteristic of steady-state gaGCs is less clear 2 – 8 . Combining multicolor “Brainbow” fate-mapping and single-cell Ig sequencing, we find that 5–10% of gaGCs from specific pathogen-free (SPF) mice contained highly-dominant “winner” clones at steady state, despite rapid turnover of GC B cells. Monoclonal antibodies (mAbs) derived from these clones showed increased binding to commensal bacteria compared to their unmutated ancestors, consistent with antigen-driven selection and affinity maturation. Frequency of highly-selected gaGCs was markedly higher in germ-free (GF) than in SPF mice, and winner B cells in GF gaGCs were enriched in public IgH clonotypes found across multiple individuals, indicating strong B cell receptor (BCR)-driven selection in the absence of microbiota. Vertical colonization of GF mice with a defined microbial consortium (Oligo-MM 12 ) did not eliminate GF-associated clonotypes, yet induced a concomitant commensal-specific, affinity-matured B cell response. Thus, positive selection can take place in steady-state gaGCs, at a rate that is tunable over a wide range by the presence and composition of the microbiota.

Germinal centers (GCs) are the site of immunoglobulin somatic hypermutation and affinity maturation, processes essential to an effective antibody response. The formation of GCs has been studied in detail, but less is known about what leads to their regression and eventual termination, factors that ultimately limit the extent to which antibodies mature within a single reaction. We show that contraction of immunization-induced GCs is immediately preceded by an acute surge in GC-resident Foxp3+ T cells, attributed at least partly to up-regulation of the transcription factor Foxp3 by T follicular helper (TFH) cells. Ectopic expression of Foxp3 in TFH cells is sufficient to decrease GC size, implicating the natural up-regulation of Foxp3 by TFH cells as a potential regulator of GC lifetimes.

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Recent studies have provided insights into the pathogenesis of coronavirus disease 2019 (COVID-19)1-4. Yet, longitudinal immunological correlates of disease outcome remain unclear. Here, we serially analysed immune responses in 113 COVID-19 patients with moderate (non-ICU) and severe (ICU) disease. Immune profiling revealed an overall increase in innate cell lineages with a concomitant reduction in T cell number. We identify an association between early, elevated cytokines and worse disease outcomes. Following an early increase in cytokines, COVID-19 patients with moderate disease displayed a progressive reduction in type-1 (antiviral) and type-3 (antifungal) responses. In contrast, patients with severe disease maintained these elevated responses throughout the course of disease. Moreover, severe disease was accompanied by an increase in multiple type 2 (anti-helminths) effectors including, IL-5, IL-13, IgE and eosinophils. Unsupervised clustering analysis of plasma and peripheral blood leukocyte data identified 4 immune signatures, representing (A) growth factors, (B) type-2/3 cytokines, (C) mixed type-1/2/3 cytokines, and (D) chemokines that correlated with three distinct disease trajectories of patients. The immune profile of patients who recovered with moderate disease was enriched in tissue reparative growth factor signature (A), while the profile for those with worsened disease trajectory had elevated levels of all four signatures. Thus, we identified development of a maladapted immune response profile associated with severe COVID-19 outcome and early immune signatures that correlate with divergent disease trajectories.

During affinity maturation, germinal center (GC) B cells alternate between proliferation and somatic hypermutation in the dark zone (DZ) and affinity-dependent selection in the light zone (LZ). This anatomical segregation imposes that the vigorous proliferation that allows clonal expansion of positively selected GC B cells takes place ostensibly in the absence of the signals that triggered selection in the LZ, as if by “inertia.” We find that such inertial cycles specifically require the cell cycle regulator cyclin D3. Cyclin D3 dose-dependently controls the extent to which B cells proliferate in the DZ and is essential for effective clonal expansion of GC B cells in response to strong T follicular helper (Tfh) cell help. Introduction into the Ccnd3 gene of a Burkitt lymphoma–associated gain-of-function mutation (T283A) leads to larger GCs with increased DZ proliferation and, in older mice, clonal B cell lymphoproliferation, suggesting that the DZ inertial cell cycle program can be coopted by B cells undergoing malignant transformation.

Objective: Evaluation of the efficacy and safety of atezolizumab/bevacizumab in a real-world HCC cohort, including patients with impaired liver function and prior systemic therapy. Methods: Retrospective analysis of 147 HCC patients treated with atezolizumab/bevacizumab at six sites in Germany and Austria. Results: The overall response rate and disease control rate were 20.4% and 51.7%, respectively. Seventy-three patients (49.7%) met at least one major exclusion criterion of the IMbrave150 trial (IMbrave-OUT), whereas 74 patients (50.3%) were eligible (IMbrave-IN). Median overall survival (mOS) as well as median progression-free survival (mPFS) was significantly longer in IMbrave-IN versus IMbrave-OUT patients [mOS: 15.0 months (95% confidence interval (CI): 10.7–19.3] versus 6.0 months (95% CI: 3.2–8.9; p < 0.001) and mPFS: 8.7 months (95% CI: 5.9–11.5) versus 3.7 months (95% CI: 2.7–4.7; p < 0.001)]. Prior systemic treatment did not significantly affect mOS [hazard ratio (HR): 1.32 (95% CI: 0.78–2.23; p = 0.305)]. mOS according to ALBI grades 1/2/3 were 15.0 months (95% CI: not estimable), 8.6 months (95% CI: 5.4–11.7), and 3.2 months (95% CI: 0.3–6.1), respectively. ALBI grade and ECOG score were identified as independent prognostic factors [ALBI grade 2 versus 1; HR: 2.40 (95% CI: 1.34 – 4.30; p = 0.003), ALBI grade 3 versus 1; HR: 7.28 (95% CI: 3.30–16.08; p < 0.001), and ECOG ⩾2 versus 0; HR: 2.09 (95% CI: 1.03 – 4.23; p = 0.042)], respectively. Sixty-seven patients (45.6%) experienced an adverse event classified as CTCAE grade ⩾3. Patients in the IMbrave-OUT group were at increased risk of hepatic decompensation with encephalopathy (13.7% versus 1.4%, p = 0.004) and/or ascites (39.7% versus 9.5%; p < 0.001). Conclusion: In this real-world cohort, efficacy was comparable to the results of the IMbrave150 study and not affected by prior systemic treatment. ALBI grade and ECOG score were independently associated with survival. IMbrave-OUT patients were more likely to experience hepatic decompensation.