The Dynamic Changes in Cytokine Responses in COVID-19

meeting report

SARS-CoV-2 The dynamic changes in cytokine responses in COVID-19: a snapshot of the current state of knowledge “The role of cytokines in COVID-19” online symposium was presented on 18 June 2020 by the NIH/FDA Immunology and Cytokine Interest Groups and was purposed to discuss our rapidly changing understanding of COVID-19-related cytokine responses in diferent stages of infection, including the etiologies, downstream consequences and possible mitigation strategies. The recording is available at https://nci.rev.vbrick.com/ sharevideo/03106730-66cc-47ba-870b-f6e6274a998a.

he symposium was opened by address that underscored the broad variety serum cytokine concentrations with disease Anthony Fauci, Director of the of clinical presentations of COVID-19, outcome. Her data showed that IL-6, IL-8 TNational Institute of Allergy and thus highlighting the central role of the and TNF, and to a lesser extent, IL-1β, were Infectious Diseases at the US National immune response in this disease. She also elevated at the time of hospitalization, and Institutes of Health (NIAID, NIH), and remarked on the apparent geographic their concentrations correlated with disease Janet Woodcock, Director of the Center clusters of disease manifestations and the outcome and mortality, even after correcting of Drug Evaluation and Research, Food need to better understand possible factors for age, ethnicity, race and comorbidities, and Drug Administration (CDER, FDA) in host–pathogen interactions beyond those suggesting that they could be used to and currently leading the therapeutics health conditions already identified, such identify patients at risk of severe disease2. component of Operation Warp Speed. as prior innate immune experience and The proinflammatory cytokines Fauci briefly reviewed the current subtle differences in ACE2 expression in remained elevated throughout the disease status of the coronavirus disease 2019 the populations. Lastly, she discussed the course unless patients were treated with (COVID-19) pandemic, noting that complexity of the data emerging from the steroids or remdesivir, which reduced the worldwide incidence had grown to multiple clinical trials that are targeting the level of circulating IL-6. She also 8 million cases and more than 300,000 the inflammatory process underlying the stressed that IL-6 and TNF are regulated deaths, with >120,000 fatalities in the USA disease, emphasizing the importance of independently and thus could be targeted alone (incidence on June 18 2020). The establishing clinically relevant biomarkers to in parallel in patients with severe disease. causative virus, the severe acute respiratory guide the therapeutic course. Merad then described early results from syndrome coronavirus 2 (SARS-CoV-2), deep-profiling longitudinal studies using is a single-stranded RNA virus that uses Cytokine response and disease severity whole-blood proteomics that identified 23 angiotensin-converting enzyme 2 (ACE2) The first scientific session of the meeting clusters of cytokines that are differentially as a cellular receptor. The atomic-level focused on the changing cytokine response expressed in patients with mild disease, conformation of the prefusion spike protein over the course of COVID-19 and was severe disease without end organ damage of the virus was recently described by opened by Miriam Merad (Mount Sinai and severe disease with end organ damage. NIAID Vaccine Research Center scientists School of Medicine). Merad first reminded In this broader assessment, patients with and colleagues1. He also underscored us that the infection is asymptomatic severe disease had increased IL-6 and other the role of cytokines in the pathogenesis in 80% of adults and most children, but proinflammatory cytokines, while those of the different clinical presentations of 20% of patients require hospitalization with moderate disease had a pattern that COVID-19, ranging from asymptomatic to in the intensive care unit (ICU). The suggested T cell priming. Lastly, Merad pneumonia, neurological disorders, acute mortality rate for patients in the ICU is suggested that the pattern of cytokine respiratory distress syndrome (ARDS), 25%, with most deaths attributed to severe response in children with multisystem cardiomyopathies, sepsis, hypercoagulability, inflammation and embolic complications. inflammatory syndrome partly resembled multiorgan failure and death, as well as In agreement with Woodcock’s remarks that of adults with severe disease, as they had the multisystem inflammatory syndrome on the importance of biomarkers to better increased expression of proinflammatory seen in children. Also, the benefit of target therapeutic efforts, Merad described cytokines; however, they also had a variety dexamethasone treatment in severe COVID- studies using high-dimensional profiling to of autoantibodies, including some classical 19 cases requiring ventilation was discussed, identify early markers that predict disease autoantibodies, but also autoantibodies which is consistent with the central roles severity. In one study, her group selected directed to cardiac and endothelial of inflammation and a cytokine storm in a platform that monitors interleukin (IL)- antigens that might explain the disease causing serious pathology. Fauci ended 6, IL-8, IL-1β and tumor necrosis factor manifestations. Importantly, the cytokine his talk by calling attention to the multiple (TNF), which are well-established targets patterns that were present at the time of initiatives undertaken and supported by for anti-inflammatory therapeutics. They hospitalization in children as well as adults the NIAID to address the COVID-19 tested over 1,500 patients on the day of were maintained throughout the disease outbreak. Woodcock followed with an hospitalization and then correlated the course unless modified by treatment with

1146 Nature Immunology | VOL 21 | October 2020 | 1146–1151 | www.nature.com/natureimmunology meeting report steroids, remdesivir or immunomodulatory therapy and could be correlated with disease outcome, suggesting that they can be used to guide the therapeutic approach. John Tsang (NIAID, NIH) then spoke of Capillary the application of a systems immunology analysis of COVID-19. He described Alveolus studies employing cellular indexing of Pneumocyte type I transcriptomes and epitopes by sequencing Macrophage (CITE-seq), a single-cell analysis method B2 LMWK that combines highly multiplexed surface Tissue protein marker detection with transcriptome kallikrein profiling. The Tsang lab and collaborators SARS-CoV-2 ACE2 B1 Lys-bradykinin evaluated peripheral blood mononuclear IL-1 B1 Bradykinin cells (PBMCs) from a longitudinal cohort TNF of hospitalized patients with COVID-19 Leakage des-Arg9-BK Plasma ACE2 kallikrein from Brescia, Italy, taken at the height of Lys-des-Arg9-BK the outbreak in that region. The patients Plasma HMWK evaluated in this first experiment included Tissue kallikrein 13 severe or critical patients and 5 age- and sex-matched healthy controls. Two LMWK observations in particular emerged that differed from findings reported by other investigators. First, whereas previous studies suggested that the virus disrupted the type I Fig. 1 | Alveolus during severe COVID-19 hyperinflammation. ACE2 downregulation by SARS-CoV-2 interferon (IFN) signaling pathway, fueling is followed by the loss of neutralizing capacity of Lys-[des-Arg9]-bradykinin (BK) in the lung, leading speculation that the lack of an early type I to plasma leakage. Subsequently, plasma leakage results in more B1R ligands (des-Arg9-BK) and B2R (and III) IFN response permits rapid viral ligands (bradykinin), enhancing vascular permeability and angioedema. CPM, carboxypeptidase M; spread and induces hyperinflammatory CPN, carboxypeptidase N; HMWK, high-molecular-weight kininogen; LMWK, low-molecular-weight responses, this study identified a clear type kininogen. Figure reproduced with permission from ref. 4, eLife Sciences Publications. I IFN signature across major immune cell subsets in patients with COVID-19. These findings suggest that a careful evaluation of disease, with an initial focus on IL-1 biology patients with severe disease, which is of clear the patient populations scrutinized across and autoinflammation and a subsequent interest from a therapeutic standpoint. In the different studies should be performed, as the focus on the kallikrein–kinin system. IL-6 last part of his talk, van de Veerdonk focused timelines for the induction of such responses upregulation was prominent in patients on the reduced amounts of serpin family may differ according to disease stage and with severe disease, which van de Veerdonk A member 12 (SERPINA12) and DPP4 may be further influenced by genetic proposed was a manifestation of the (CD26) in patients in the ICU versus those and environmental factors. Furthermore, strong induction of an autoinflammatory not in the ICU. Since these factors suppress thus far, Tsang has found no evidence loop via IL-1β and the IL-1 receptor (IL- inflammation mediated by kallikreins of T cell exhaustion, as the expanded 1R). He proposed that, following SARS and it is expected that there is positive, CD8+ T cell clones were found to have CoV-2 binding to pathogen recognition coordinated stimulation of the kallikrein– decreased PD-1 expression in comparison receptors, pro-IL-1β is induced, processed kinin system from increases in IL-1 and with the non-expanded cells in patients. to IL-1β by activated inflammasomes and IL-6 as well as from activated complement, This observation again differs from other stimulates IL-6 and IL-18 production the upregulation of the kallikrein–kinin studies that found high amounts of PD-1 (from pro-IL-18). IL-1β binds to IL-1R on system was investigated. Most critically, expression on lymphocytes3, indicating monocytes/macrophages, generating the kininogens processed by kallikrein, a serine exhaustion and raising the possibility that autoinflammatory loop and recruitment protease, will generate bradykinin (BK) checkpoint blockade should be considered of polymorphonuclear leukocytes. He also or Lys-BK (Fig. 1), which can be further for treatment. noted that IL-1α released during tissue metabolized by tissue carboxypeptidases, The final seminar in this session was damage may further contribute to the producing des-Arg9-BK (DABK). DABK given by Frank van de Veerdonk (Radboud autoinflammatory loop by binding and binds to bradykinin 1 receptors (B1Rs) and University Medical Center). The main signaling through IL-1R, inducing more enhances vascular permeability, which can focus of his seminar regarded unique IL-1β. He further remarked that IL-1 is lead to local angioedema. Critically, DABK aspects of COVID-19 immune pathology; a difficult cytokine to measure (echoing is inactivated by ACE2. Because ACE2 is specifically, the role of ACE2 in modulation others) and that concentrations in plasma internalized by SARS-CoV-2, it is no longer of the kallikrein–kinin system. Preliminary likely do not reflect those in the lung, present to counter the downstream effects results suggested that this system has a suggesting that bronchoalveolar lavage of DABK, thus producing angioedema in role in the angioedema observed in the (BAL) measurements would be important the lung, which potentially explains the lungs of COVID-19 patients. Biological in verifying its upregulation at the site of early ARDS manifestation in these patients. pathways were evaluated via proteomic primary pathology. Lastly, he remarked on Furthermore, IL-1 and inflammation in analysis of serum from patients with the substantial reductions in IL-7R and stem general stimulate increased expression of severe (necessitating ICU care) versus cell factor and their potential relevance to B1Rs, thus upregulating these receptors in more moderate (not requiring ICU care) the commonly observed lymphopenia in the inflamed lung and boosting tissue-level

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this study, leaving open the question of the [ Anti-viral therapy ] contribution of antibodies in determining [ Anti-cytokine storm therapy ] disease progression. It is possible that a Infection point threshold level of antibody synergizes with Infection Respiratory Cytokine storm other features of immune (for example, T cell activation and memory formation) and inflammatory responses to affect Innate disease resolution. It also remains unclear to what extent neutralizing antibodies Adaptive persist in convalescent individuals and whether they will protect upon rechallenge with SARS-CoV-2. In this regard, another study reported that 40% of asymptomatic Illness severity individuals and 13% of symptomatic individuals became seronegative 8 weeks after discharge from hospital6. This apparently short-lived antibody response contrasts sharply with detectable SARS-CoV-specific IgG 2 years after Day 0 5 10 15 Fever, cough, Shortness of breath ARDS, shock, infection8. diarrhea MODS Notarangelo provided a comprehensive overview of cellular and cytokine changes Fig. 2 | The COVID-19 inflection point of illness. A graphic depiction of the course of illness for the in the context of disease course and severity up-to-20% of individuals with COVID-19 who develop cytokine storm syndrome (CSS) and respiratory in the Italian cohort. A recurring pattern 17 distress requiring hospitalization . Severity of illness is presented along the y axis and time in days along in COVID-19 is the increased expression the x axis. The participation of both the innate and adaptive immune responses is presented as orange of proinflammatory cytokines such as IL-6, and green triangles, respectively, during the different phases of disease. The early stages of infection TNF and IL-1β, as well as an IFN-γ signature (<5 days of symptoms) give rise to a more prominent respiratory phase in those with early signs of evidenced by expression of the downstream CSS, such that an inflection point of illness occurs typically between days 5 and 7 of illness. This interval cytokine CXCL9; similar observations is the time in which targeted immunomodulatory therapy will probably be most beneficial in lowering were also presented by Merad and Tsang mortality (dashed arrow). MODS, multiorgan dysfunction syndrome. Figure adapted with permission in Session 1. Serum concentrations of 17 from ref. , the Journal of Rheumatology Publishing. soluble biomarkers of endothelial cell activation (ICAM-1 and VCAM-1) and of septic shock (lipopolysaccharide binding angioedema. The ensuing plasma leakage IgG1 and IgM antibodies that recognized protein (LBP) and sIL-33R) were also into the alveolar space allows activation recombinant SARS-CoV-2 nucleoprotein significantly elevated in patients with of plasma kallikrein–kinin at the site and the receptor-binding domain of the COVID-19 and more so in those with of infection. Subsequent production of spike protein (S-RBD) in patient sera critical disease who eventually died. In bradykinin results in persistent angioedema as compared to serum from healthy an interesting twist, Notarangelo showed via bradykinin activation of the bradykinin 2 individuals. In general, antigen-specific that, during the course of disease, certain receptor (B2R). antibody concentrations were higher in inflammatory markers, such as IL-6, did not This observation led to the hypothesis individuals recently released from hospital change significantly, whereas others, such that the kallikrein–kinin system was (8 patients) as compared to those assayed 2 as soluble IL-33R (sIL-33R) and CXCL10, critically involved in lung pathology in weeks after release (6 patients). Longitudinal decreased in patients who eventually COVID-19, which was tested by treating studies on larger patient cohorts will be recovered but remained persistently elevated patients with hypoxia and enhanced oxygen needed to determine the time course and in those who succumbed to COVID- requirements with icatibant, an approved duration of humoral responses during 19. Additionally, cytokines associated B2R blocker for hereditary angioedema COVID-19. Somewhat consistent with with myeloid differentiation positively (HAE). Promising effects were observed, these observations, Luigi Notarangelo correlated with disease severity, suggesting which will be published soon. This finding (NIAID, NIH) noted in a study of more a contribution of de novo myelopoiesis. suggests the need for expanded trials as well than 300 patients from Brescia and Monza A striking observation in this study was as the investigation of a longer lasting agent, in northern Italy that the proportion of the reduced numbers of CD4+ and CD8+ lanadelumab, which blocks plasma kallikrein plasmablasts in blood was highest in the T cells in patients with COVID-19. T activity and is approved for HAE. In light early stages of COVID-19 and decreased lymphopenia was evident even in patients of the findings of this study and data from with disease course6. Using a pseudovirus with mild symptoms, and it reached extreme other sources, a treatment protocol based on particle-based neutralization assay, Dong deficits in those with severe disease9. The disease stage was proposed4. found that 13 out of 14 patients developed underlying cause of T cell loss is not known varying levels of neutralizing antibodies with and will be an important area of future Cellular origins of cytokines specificity for S-RBD. In an independent research. Notarangelo also pointed out the The second session commenced with Chen study, 94% of 175 patients developed surprising decrease in soluble Fas ligand Dong (Tsinghua University), who discussed neutralizing antibodies, suggesting that such (sFasL) and sCD62L, contrasting with high his recently published work5 on humoral humoral responses are a consistent feature concentrations of sCD25, a biomarker of responses in patients with COVID-19. In of COVID-197. Importantly, antibody titers T cell activation. A preprint in bioRxiv also a small cohort, his group readily detected did not correlate with disease duration in reported profound antigen-specific T cell

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–10 1.00 ARB IFN p = 7.7 × 10

300

0.75 100

0.50 30 IL–6 (pg/mL)

Proportion virus positive 10

0.25 p = 0.002

0.00 Normal

0 10 20 30 40 0–2 3–5 6–8 9–11 Days from symptom onset to viral clearance 12–14 15–17 18–20 21–23 24–26 27–29 30–32 33–35 36–38 39–41 42–44 45–47 48–50 51–53 54–56 57–59 60–62 63–65 Days from symptom onset to viral clearance

Fig. 3 | IFN-α2b treatment accelerates viral clearance and reduces inflammatory IL-6. Patients with confirmed COVID-19 were treated with either ARB alone (ARB; 24 patients) or IFN-α2b with or without ARB (IFN; 53 patients). Left, upper respiratory samples were assessed by PCR for the presence of SARS-CoV-2. Shown is the proportion of patients who had detectable virus as a function of the day of sampling from symptom onset. The P value for treatment effect was assessed using a Cox proportional-hazards model that included age and comorbidities as covariates. Right, patients were serially sampled for assessment of IL-6 from the day of symptom onset. Values recorded were aggregated across 3 day intervals and shown as the mean ± s.e. P value was assessed using R v.3.6.0, and analysis of variance (ANOVA) was used to test for treatment effect, adjusting for age and comorbidities. Figure reproduced with permission from ref. 15, International Union of Immunological Societies. activation and cytotoxic responses even in with disease severity11,12. Recruited for peripheral priming in generating the seronegative individuals7. Further studies are macrophages primarily expressed high phenotype. required to understand the contributions of amounts of chemokines such as CCL2, such contrasting immune responses to the CCL7 and CCL8 and, with increasing Cytokine-targeted mitigation course of COVID-19. Finally, Notarangelo disease severity, CXCL10 and CCL3. By strategies provided evidence that reduced expression contrast, typical proinflammatory cytokines The symposium concluded with a session of HLA-DR and CD4 on peripheral blood such as IL-6 and IL-8 that were elevated that discussed the recent advances in monocytes (the former a biomarker of in the periphery were not markedly managing both the virus infection and the antigen-presenting capacity) correlated upregulated in these cells. The distinct associated cytokine storm using biologics with disease severity9. By impairing lung-specific responses may contribute and drugs to treat the disease and how antigen presentation and the consequent to COVID-19 lung pathophysiology, for such approaches significantly ameliorated activation of T cells, this cellular phenotype example, by CCL2-mediated recruitment of disease outcomes. Randy Cron (University could attenuate effective responses during macrophages11. of Alabama at Birmingham) started off this SARS-CoV-2 infection. The predictive The basis for the dichotomy between session by reminding us that, long before potential of this biomarker remains to be the chemokine-dominated lung COVID-19 came into the limelight, the determined. macrophage response and the peripheral cytokine storm was already recognized The final speaker in this session, Xiaoyu prevalence of more classical inflammatory as a major issue in the field of immune Hu (Tsinghua University), elaborated cytokines is not clear. One possibility is homeostasis. Cytokine storm is an umbrella specifically on the nature and origins of that the lung microenvironment skews term for several hyperinflammatory cytokine responses in COVID-19, focusing macrophage responses toward chemokine immune responses that include cytokine on the lung myeloid compartment of gene expression. In this scenario, lung release syndrome, culture-negative sepsis, patients. Previous studies have shown that macrophage responses in other acute macrophage activation syndrome and the largest population of lung-resident respiratory syndromes should also be hemophagocytic lymphohistiocytosis alveolar macrophages are of fetal origin and similarly skewed. However, it should be (HLH), among others. Therefore, there are are maintained by proliferation in situ10. noted that resident alveolar macrophages several causes of cytokine storm, which can Single-cell RNA sequencing studies of do not exhibit this pattern, indicating be triggered by genetic factors, cancer, viral BAL fluid from patients with COVID-19 that it is not solely a microenvironment infections and other insults and that need to showed a substantial influx of peripheral issue. Alternatively, SARS-CoV-2 infection be managed accordingly. Consequently, the monocyte-derived macrophages to the may generate a unique inflammatory COVID-19-triggered cytokine storm should lungs, with a proportionate reduction in milieu that promotes the observed gene be manageable using knowledge amassed the frequency of alveolar macrophages; expression pattern. That it is restricted in the past based on the management of these changes in cell populations correlated to recruited macrophages hints at a role similar viral infections (Fig. 2). In the course

Nature Immunology | VOL 21 | October 2020 | 1146–1151 | www.nature.com/natureimmunology 1149 meeting report

of his brief but cutting-edge overview of IFN-α) and that such an effect was further considered a collateral effect of BTK the literature, Cron cited a previous study reproduced in a clinical trial when SARS inhibition, resulting in impaired fungal wherein the inability of perforin-deficient patients were subcutaneously injected immunity as demonstrated by the CD8+ CTLs to eliminate LCMV-infected with IFN alfacon-1, resulting in rapid lung susceptibility to fungal infections in target cells resulted in the death of infected clearance and substantial improvements a subset of ibrutinib-treated patients. mice by hyperactivation, but not when in various clinical parameters. Translating Notably, ibrutinib has been reported to IFN-γ was neutralized13. those findings to COVID-19, a clinical trial suppress macrophages by inhibiting the Along these lines, the disruption of other was designed involving 77 hospitalized activation of both the inflammasome and genes involved in the cytolytic pathway patients with confirmed cases of COVID- NF-κB, precisely the two downstream also results in a cytokine storm and lethal 19 in Wuhan, China. In this trial, patients pathways of the cytokine storm in severe hyperinflammation. For example, the were treated with either the antiviral drug COVID-19. These findings led Lionakis Cron group performed whole-exome arbidol (ARB), nebulized IFN-α2b or a and his colleagues to hypothesize sequencing of patients who succumbed to combination of the two agents. While the that BTK inhibitors would ameliorate H1N1 influenza infection and found that investigators did not observe any differences hyperinflammation and thus prevent 36% of the 14 individuals in the study had among patients in the treatment groups clinical deterioration in patients with mutations in the genes encoding either with respect to body temperature, oxygen severe COVID-19. The Lionakis group perforin or the lysosomal trafficking saturation or blood biochemistry, there was hypothesized that the overt immune regulator (LYST). Thus, cytokine storm is a significant difference in viral clearance, as response of SARS-CoV-2-infected alveolar evidently associated with the failure to clear IFN-treated patients cleared the virus much macrophages could be inhibited at the virus-infected target cells and persistent faster. Notably, IFN-treated patients also proximal signaling level by the off-label T cell stimulation. As a solution, Cron showed significantly reduced concentrations use of a second generation BTK inhibitor, summarized a few approaches focused of serum IL-6 and C-reactive protein (CRP) acalabrutinib. Such an approach could on targeting IL-6, IL-1 or JAK/STAT (Fig. 3)15. Thus, with the caveat that this trial be superior to employing neutralizing proteins to suppress the cytokine storm. He was a non-randomized, small-cohort study, antibodies specific to individual concluded his talk by offering alternative the data advocated for using type I IFN as proinflammatory cytokines because it could strategies to reduce hyperinflammation, an early intervention agent in COVID-19. potentially suppress the effect of multiple such as JAK inhibitors and glucocorticoids. Moreover, type I IFN treatment may prove cytokines. In addition, because BTK is not Specifically, the World Health Organization to be more beneficial than other treatments expressed in T cells, BTK inhibition would initially recommended against the use of because it did not trigger a cytokine storm limit the effect to macrophages without corticosteroids for COVID-19 based on the or severe adverse events. Furthermore, it impacting anti-viral T cell effector function. experiences of SARS and MERS, but recent may be advantageous over treatment with The results from the first clinical study data showed a clear reduction in the need for type III IFN, given the systemic spread with 19 patients were in line with the ventilation and in mortality in patients with of SARS-CoV-2 from the lungs to the hypothesis, and some remarkable effects COVID-19 treated with dexamethasone14. vasculature and other organs, as type I IFN were observed for patients with COVID- Steroids are widely available and affordable, receptors are expressed on virtually all cells, 19 in the pre-ICU setting16. While patients and, with careful dosing and timing, these whereas type III IFN receptor expression is with severe COVID-19 symptoms had agents could become powerful tools in largely restricted to epithelial cells. increased production of IL-6 by CD14+ fighting the cytokine storm triggered by Michail Lionakis (NIAID, NIH) monocytes in blood, acalabrutinib SARS-CoV-2. presented his recent work utilizing a kinase treatment substantially improved In the next seminar, Eleanor Fish inhibitor to antagonize the COVID-19 oxygenation, decreased inflammation (University of Toronto) put the COVID- cytokine storm16. The hyperinflammatory (for example, reduced production of CRP 19 pandemic into greater perspective response in COVID-19 features activation and IL-6) and also significantly increased by pointing out two other coronavirus of NF-κB and the inflammasome (Nlrp3), lymphocyte numbers in the majority of outbreaks that had preceded SARS-CoV-2, as evidenced by the increased levels of patients. Mechanistically, it was found namely SARS-CoV in 2002 and MERS-CoV proinflammatory cytokines and chemokines, that monocytes but not B cells in patients in 2012. To control viral infections, the first including IL-1β, TNF, IL-6, CCL2 and with COVID-19 contained higher basal 24–72 hours are the most critical, and Fish CCL3, among others. Consequently, he levels of phosphorylated BTK, validating emphasized that the type I IFN response hypothesized that neutralizing these that monocyte/macrophage-directed by innate cells plays a pivotal role in this cytokines or their downstream signaling BTK inhibition provides the basis of process. Type I IFNs are powerful because would be an effective strategy to suppress suppressing the cytokine storm14. Currently, they not only act directly on infected cells the COVID-19-associated cytokine storm. three different BTK inhibitors, including to suppress viral replication but also recruit Using mouse models of Bruton’s acalabrutinib, zanubrutinib and ibrutinib, and activate immune cells to clear the virus. tyrosine kinase (BTK) deficiency and are in clinical trials for treatment of severe Notably, the SARS-CoV-2 genome encodes pharmacological inhibitors of BTK, the COVID-19. Further studies will be required genes that suppresses IFN production, such Lionakis group previously pinpointed the to validate these clinical findings, which, as Nsp1, Nsp3, ORF6 and the M proteins. target population of BTK inhibition in if confirmed, would potentially point to a Thus, it is evident that viruses are equipped antifungal host defense to be macrophages, broader use for BTK inhibitors in managing with tools to dampen host IFN production, not B cells. Ibrutinib is an effective and hyperinflammatory responses. and both SARS-CoV-2 and SARS-CoV fail well-tolerated BTK inhibitor that blocks Collectively, the talks in this session to trigger a good type I IFN response. B cell receptor signaling and is used highlighted the multifaceted approaches Along these lines, the Fish group as a treatment for B cell malignancies to neutralize cytokine storm in patients demonstrated that SARS-CoV replication and inflammatory conditions such as with COVID-19, and they showcased in vitro could be effectively suppressed graft-versus-host disease. Thus, the initial successes. Moreover, the results by IFN alfacon-1 treatment (a synthetic suppression of macrophages has been further illustrated the necessity of nimble

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approaches in applying interventional on COVID-19 with the international References strategies, depending on the severity or stage community. ❐ 1. Wrapp, D. et al. Science 367, 1260–1263 (2020). 2. Del Valle, D. M. et al. Nat. Med. https://doi.org/10.1038/s41591- of the diseases. Thus, the dosing, timing 020-1051-9 (2020). 1 2 and the selection of the patient group must Maja Buszko , Jung-Hyun Park , 3. Diao, B. et al. Front. Immunol. 11, 827 (2020). be considered carefully and in the context Daniela Verthelyi 3, Ranjan Sen4, 4. van de Veerdonk, F. L. et al. Elife https://doi.org/10.7554/ Howard A. Young 5 and eLife.57555 (2020). of disease progression. Dexamethasone 5. Ni, L. et al. Immunity 52, 971–977.e3 (2020). 6 ✉ treatment, for example, should be reserved Amy S. Rosenberg 6. Long, Q.-X. et al. Nat. Med. https://doi.org/10.1038/s41591-020- for late-stage patients because of its 1Cellular Immunology Section, Laboratory of 0965-6 (2020). Immune System Biology, National Institute of Allergy 7. Sekine, T. et al. Cell https://doi.org/10.1016/j.cell.2020.08.017 immunosuppressive function, whereas type (2020). I IFNs are clearly suitable for investigation and Infectious Diseases, National Institutes of Health, 8. Wu, L.-P. et al. Emerg. Infect. Dis. 13, 1562–1564 (2007). in immediate early treatment. Targeted Bethesda, MD, USA. 2Experimental Immunology 9. Moratto, D. et al. J. Clin. Immunol. https://doi.org/10.1007/ suppression of immune cell activities by Branch, Center for Cancer Research, National Cancer s10875-020-00806-6 (2020). 10. Ginhoux, F. & Guilliams, M. Immunity 44, 439–449 (2016). BTK inhibitors has been tested in patients Institute, National Institutes of Health, Bethesda, 11. Liao, M. et al. Nat. Med. 26, 842–844 (2020). requiring oxygen supplementation, but it MD, USA. 3Laboratory of Innate Immunity, Division 12. Bost, P. et al. Cell 181, 1475–1488.e12 (2020). remains unclear whether treatment at earlier of Biotechnology Review and Research-III, Ofce of 13. Jordan, M. B., Hildeman, D., Kappler, J. & Marrack, P. Blood 104, 735–743 (2004). stages would be even more effective. Biotechnology Products, Center for Drug Evaluation 14. Recovery Collaborative Group et al. N. Engl. J. Med. https://doi. and Research, US Food and Drug Administration, org/10.1056/NEJMoa2021436 (2020). Concluding remarks Silver Spring, MD, USA. 4Laboratory of Molecular 15. Zhou, Q. et al. Front. Immunol. 11, 1061 (2020). 16. Roschewski, M. et al. Sci. Immunol. https://doi.org/10.1126/ This conference brought together over Biology and Immunology, National Institute on sciimmunol.abd0110 (2020). 1,600 scientists from different countries Aging, Baltimore, MD, USA. 5Laboratory of Cancer 17. Chatham, W. W. & Cron, R. Q. J. Rheumatol. https://doi. and different time zones, demonstrating the Immunometabolism, Center for Cancer Research, org/10.3899/jrheum.200679 (2020). power of running a virtual conference but National Cancer Institute-Frederick, Frederick, also documenting the immense worldwide MD, USA. 6Laboratory of Immunology, Division of Acknowledgements interest in COVID-19 biology. Because of its Biotechnology Review and Research-III, Ofce of We thank the speakers for their useful feedback in preparing this Meeting Report. The views expressed in great success and the enthusiastic feedback Biotechnology Products, Center for Drug Evaluation this article are those of the authors and do not necessarily that was received, the next COVID-19 and Research, U.S. Food and Drug Administration, reflect the official policy or position of the United States conference organized by the NIH/FDA Silver Spring, MD, USA. Food and Drug Administration and the Department of Immunology Interest Group and Cytokine ✉e-mail: [email protected] Health and Human Services, nor does mention of trade Interest Group is already being scheduled, names, commercial products, or organizations imply endorsement by the United States Government. and we look forward to broad participation in cyberspace in November 2020 to share Published online: 27 August 2020 Competing interests the newest and most exciting research https://doi.org/10.1038/s41590-020-0779-1 The authors declare no competing interests.

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