Biology subjects

Alves-Filho, J. C.

Publications and source records attributed to Alves-Filho, J. C..

18 recordsLinked to original sources

bioRxiv2026

Targeting soluble immunoglobulins ameliorates idiopathic multicentric Castleman disease in a mouse model

Idiopathic multicentric Castleman disease (iMCD) is a rare lymphoproliferative disorder that affects lymph nodes at multiple sites and can progress to life-threatening organ dysfunction. While curative therapies remain unavailable, largely due to a critical gap in understanding the diseases underlying etiology, the cytokine interleukin-6 (IL-6) is recognized as a major pathogenic driver, particularly in iMCD patients with plasmacytic lymphadenopathy. Here, we demonstrate the presence of Foxp3-expressing cells alongside plasma cells within germinal centers of lymph nodes from such iMCD patients. Based on this observation, we directed IL-6 overexpression specifically to Foxp3+ Treg cells and established a novel preclinical mouse model of iMCD. This targeted approach successfully recapitulated the key characteristics of iMCD in mice, including multifocal lymphadenopathy, splenomegaly, anemia, thrombocytopenia, marked plasmacytosis, and mortality in young adults. Advanced disease was characterized by renal pathology, including proteinuria and elevated creatinine levels. In this model, IL-6 directly promoted plasmacytosis, resulting in profound IgG1 hyperimmunoglobulinemia. Genetic ablation of soluble immunoglobulin production ameliorated iMCD symptoms, prevented renal dysfunction, and significantly extended survival. Our findings identify IL-6-driven IgG1 plasmacytosis as a critical pathogenic factor in iMCD, shedding light on the mechanisms underlying its development. Key pointsO_LITransgenic IL-6 expression in Foxp3+ cells models iMCD in mice and drives lethal IgG1 plasmacytosis C_LIO_LILoss of soluble immunoglobulins prevented renal impairment and prolonged survival in iMCD-like mice C_LI

immunology↗

bioRxiv2026

GALR2 W248L mutation exacerbates neuroinflammation through pro-inflammatory macrophage polarization and microglial activation in experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is a chronic neuroinflammatory disease characterized by demyelination, neurodegeneration, and progressive neurological disability. Galanin, a neuropeptide with immunomodulatory properties, signals through G protein-coupled receptors, among which galanin receptor 2 (GALR2) has been implicated with neuroprotective and anti-inflammatory functions. A rare homozygous single nucleotide variant in GALR2 (rs61745847; p.W249L) has been identified in a patient diagnosed with relapsing-remitting MS, however, the biological relevance of this variant in neuroinflammation remains unknown. Here, we investigated the impact of the orthologous GALR2 W248L mutation using a knock-in mouse model and experimental autoimmune encephalomyelitis (EAE). GALR2 W248L knock-in (KI) mice exhibited a more severe clinical course of EAE, accompanied by enhanced inflammatory infiltration, exacerbated demyelination, and increased microglial activation in the spinal cord compared with wild-type (WT) mice. Despite comparable lymphoid and myeloid cell frequencies in the central nervous system, alterations in microglial density and morphology suggested an important contribution of the innate immune system to disease exacerbation in the KI mice. Ex vivo analyses revealed that bone marrow-derived macrophages from KI animals exhibited a pronounced shift toward a pro-inflammatory phenotype, characterized by enhanced M1 polarization, impaired M2-associated responses, and increased NLRP3 inflammasome activation. In parallel, live-cell imaging of primary hippocampal neurons demonstrated reduced galanin binding in mutant cells, consistent with impaired GALR2 functional availability at the plasma membrane. Together, these findings identify GALR2 as a modulator of the neuroinflammatory response and indicate that disruption of galanin-GALR2 signaling promotes sustained innate immune activation, highlighting the relevance of this pathway for MS pathogenesis and its potential as a therapeutic target in neuroinflammatory disorders.

molecular biology↗

bioRxiv2026

Nav1.5 expressed in TrkB+ sensory neurons mediates paclitaxel-induced mechanical pain hypersensitivity

Chemotherapy-induced neuropathic pain (CINP) is a frequent and debilitating adverse effect of anti-tumor therapies, for which current treatments are largely non-specific and offer limited efficacy. Identifying molecular mechanisms that drive CINP may enable the development of targeted therapeutic strategies. Here, we demonstrate that paclitaxel-induced mechanical pain hypersensitivity in mice occurs independently of classical Nav1.8+ nociceptors but critically depends on TrkB+ sensory neurons. Transcriptomic analysis of TrkB+ sensory neurons revealed selective expression of Scn5a, which encodes the voltage-gated sodium channel Nav1.5, a channel classically associated with cardiac excitability. Importantly, SCN5A expression was also detected in human primary sensory neurons, indicating potential translational relevance. Functional studies further showed that Scn5a knockdown, using small interfering RNA, significantly attenuates paclitaxel-induced mechanical pain hypersensitivity. Together, these findings identify TrkB+ sensory neurons as key drivers of CINP and reveal Nav1.5 as a previously unrecognized contributor to chemotherapy-induced neuropathic pain. Targeting Nav1.5 in TrkB+ sensory neurons may therefore represent a novel therapeutic strategy for the treatment of CINP.

neuroscience↗

bioRxiv2026

Intestinal Barrier Loss Enables Microbiota-Mediated Purinergic Suppression During Malaria

The gut microbiota shapes malaria immunity and disease severity, but the mechanisms underlying these effects remain unclear. In a murine model, susceptibility to Plasmodium yoelii hyperparasitemia was associated with elevated regulatory T cells and diminished IFN-{gamma}. We demonstrate that the IgA-coated fraction of the microbiota is sufficient to transfer this susceptibility. Plasmodium infection disrupts the intestinal barrier regardless of microbiota composition. Mechanistically, barrier loss was associated with systemic adenosine persistence and an expansion of CD39+ plasmablasts in susceptible mice. Ugandan children with severe malaria exhibited a distinct purinergic immune signature compared to asymptomatic community children. Therapeutic reinforcement of the gut barrier or blockade of the downstream adenosine A2A receptor improved germinal centers and reduced disease severity in mice, independent of parasite burden, revealing a purinergic-dependent immunosuppression pathway that drives pathogenesis. This work defines an axis in which malaria-induced gut leakiness enables microbial-derived signals to trigger purinergic immunosuppression and severe disease.

immunology↗

bioRxiv2025

Escherichia coli-induced gut IL-33 release inhibits lung type 2 allergic responses

BackgroundThe incidence of lung allergies is reduced in countries with higher prevalence of infection and environmental exposure to microbes. However, enteric bacterial infections do not always correlate with lower incidence of allergic disorders and how lung immunity to allergens can be regulated by gut exposure to pathogens and their toxins is not fully understood. ObjectiveWe used mouse models of enterotoxigenic Escherichia coli (ETEC) infection and lung allergy to examine how gut exposure to bacteria, or their related toxins, affects allergic lung inflammation. MethodsNaive C57BL/6 mice were infected with enterotoxigenic Escherichia coli (ETEC) or orally treated with the ETEC LT toxin, to mimic enteric bacterial infections. After two weeks, these mice were treated intranasally with Ovalbumin (OVA) and Papain or IL-33, followed by challenge with OVA, to induce allergic lung inflammation that was assessed using multiple readouts. ResultsGut exposure to ETEC significantly inhibited allergic lung inflammation in a LT-dependent manner, as demonstrated by reduced tissue inflammation, less accumulation of type 2 cytokines, and reduced lung numbers of type 2 immune cells such as type 2 innate lymphoid cells (ILC2) and eosinophils. The anti-allergic capacity of LT was associated with reduced ability of lung ILC2s to recognize IL-33. Counterintuitively, deletion of either IL-33 or ILC2s significantly reverted the LT protective effect, suggesting the LT-mediated protection may occur through gut release and local sensing of IL-33. ConclusionsExposure to ETEC protects hosts against allergic lung inflammation through a negative feedback loop regulated by gut IL-33 release and sensing, suggesting a possible new immunological mechanism for reduced lung allergy incidence observed in areas with enteric bacterial infections. Key Messages- Enteric exposure to enterotoxigenic E. coli (ETEC) bacteria or its toxin LT significantly protects hosts against lung type 2 allergic inflammation. - ETEC and LT downregulate the capacity of lung ILC2s to respond to allergen-induced IL-33. - Deletion of IL-33 or ILC2s significantly impairs the protective effect of ETEC and LT, suggesting the presence of a negative feedback loop driven by toxin-induced gut IL-33 release.

immunology↗

bioRxiv2024

A central role for CCR2 in monocyte recruitment and blood-brain barrier disruption during Usutu virus encephalitis

Usutu virus (USUV) is an emerging neurotropic flavivirus capable of causing encephalitis in humans. Here, our main goal was to characterize the innate immune response in the brain during USUV encephalitis and to identify strategies to control disease severity. Using an immunocompetent mouse model of USUV encephalitis, we showed that microglia activation, blood-brain barrier (BBB) disruption and inflammatory monocyte recruitment are hallmarks of disease 6 days post infection. Activated microglia were in close association to USUV-infected cells, concomitantly with elevated levels of IL-6, IFN-{gamma}, CCL2, CCL5, CXCL10 and CXCL1 in the brain. Monocyte recruitment was CCR2-dependent and driven by IFN-{gamma} and CCL2 production beneath the brain vasculature. Moreover, CCR2 deficiency inhibited microglia activation and BBB disruption, showing the central role of CCR2 in USUV encephalitis. Accordingly, treatment with dexamethasone prevented pro-inflammatory mediator production and reduced leukocyte recruitment significantly, restraining encephalitis severity. Concluding, USUV encephalitis is driven by CCR2-mediated monocyte recruitment and BBB disruption, and blocked therapeutically by glucocorticoids. SUMMARYThe neurotropic Usutu virus can cause encephalitis driven by CCR2-mediated monocyte recruitment, microglia activation and blood-brain barrier disruption, all of which are inhibited by glucocorticoid treatment.

immunology↗

bioRxiv2024

PD-L1+ Neutrophils mediate Susceptibility during Systemic Inflammatory Response in Non-Alcoholic Fatty Liver Disease

Metabolic Dysfunction-Associated Steatotic Liver Disease (MAFLD) is a pathological condition affecting many individuals worldwide. Patients with MAFLD are more susceptible to systemic inflammation, including endotoxemia, which accelerates the progressive liver damage. However, the immunological mechanisms that trigger the hyper-inflammatory responses in individuals with MAFLD remain unknown. In the present study, we reported that short-term HFCD (Choline Deficient High Fat Diet)-fed mice, which did not show significant signs of hepatic damage and inflammation in the first two weeks, are more susceptible to a non-severe sepsis-like systemic inflammation induced by LPS challenge. Mechanistically, endotoxemic mice show an excessive accumulation of NK-producing IFN-{gamma} cells in liver tissue, which trigger the recruitment and polarization of a distinct subset of neutrophils, characterized by high expression of PD-L1 and massive release of TNF-. Remarkably, genetic inhibition of IFN-{gamma} or pharmacological blockade of PD-L1 effectively modulated the excessive recruitment of these neutrophils to the liver and TNF- production, thereby preventing hepatic damage and reducing the severity of host mortality. Thus, these results support the design of novel effective strategies to control hyperinflammatory responses in septic HFCD patients and consequently improve their survival.

immunology↗

bioRxiv2024

Differential action modes of Neutrophil Extracellular Trap-targeted drugs define T cell responses in SARS-CoV-2 infection.

Neutrophil extracellular traps (NETs) play a dual role in SARS-CoV-2 infection, aiding early immune defense but also contributing to lung damage. While NET targeting may improve clinical outcomes in SARS-CoV-2 infection, its impact on adaptive immunity, crucial for fighting the virus, remains unclear. Our study demonstrates that both recombinant human DNase (rhDNase), degrading NET structure, and GSK484, inhibiting NET formation, reduce lung NET concentration and improve clinical outcomes in infected mice, yet they differ in their influence on T cell responses. We show that rhDNase does not impact T cell responses, whereas GSK484 diminishes virus-specific T cell responses. In vitro, GSK484 decreases dendritic cell antigen presentation by impairing antigen uptake and reduces IL-2 signaling by affecting its production by T cells. In a model of lung inflammation, GSK484 diminishes antigen-specific T cell activation and proliferation, while rhDNase shows a potential to boost T cell responses via the presence of NET fragments that reduce T cell activation threshold. Our findings suggest that NET targeting with rhDNase or GSK484 holds therapeutic potential for treating SARS-CoV-2 infection, while their distinct modes of action shape T cell responses during the infection.

immunology↗

bioRxiv2024

Reprogramming of host energy metabolism mediated by the TNF-iNOS-HIF-1alpha axis plays a key role in host resistance to Plasmodium infection

TNF has a dual effect in Plasmodium infection, bolstering the hosts immune defense while also inducing sickness behavior. Here, we confirm that TNF signaling hampers physical activity, food intake, and energy expenditure while enhancing glucose uptake by the liver and spleen as well as controlling parasitemia in P. chabaudi (Pc)-infected mice. We also report that TNF is required for expression of inducible nitric oxide synthase (iNOS), stabilization of HIF-1, expression of glucose transporter GLUT1 and enhanced glycolysis in monocytic cells from Pc-infected mice. Importantly, Pc-infected iNOS-/-, TNFR{Delta}Lyz2 and HIF-1{Delta}Lyz2 mice show impaired release of TNF and glycolysis in monocytes, along with increased parasitemia and disease tolerance. Altogether, our results indicate that TNF-iNOS-HIF-1-induced glycolysis in monocytes plays a critical role in host defense and sickness behavior in Pc-infected mice. TeaseThe role of host energy metabolism and glycolysis in monocytes as determinant of host resistance to Plasmodium infection and tolerance to disease.

immunology↗

bioRxiv2022

T cell-specific P2RX7 favors lung parenchymal CD4+ T cell accumulation in response to severe lung infections

CD4+ T cells are key components of the immune response during lung infections and can mediate protection against tuberculosis (TB) or influenza. However, CD4+ T cells can also promote lung pathology during these infections, making it unclear how these cells control such discrepant effects. Using mouse models of hypervirulent TB and influenza, we observed that exaggerated accumulation of parenchymal CD4+ T cells promotes lung damage. Low numbers of lung CD4+ T cells, in contrast, are sufficient to protect against hypervirulent TB. In both situations, lung CD4+ T cell accumulation is mediated by CD4+ T cell-specific expression of the extracellular ATP (eATP) receptor P2RX7. P2RX7 upregulation in lung CD4+ T cells promotes expression of the chemokine receptor CXCR3 and favors in situ proliferation. Our findings suggest that direct sensing of lung eATP by CD4+ T cells is critical to induce tissue CD4+ T cell accumulation and pathology during lung infections. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=168 SRC="FIGDIR/small/508603v1_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@a4cdaborg.highwire.dtl.DTLVardef@1ba95e1org.highwire.dtl.DTLVardef@c60984org.highwire.dtl.DTLVardef@19ac0af_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2022

Targeting C5aR1 signaling reduced neutrophil extracellular traps and ameliorates COVID-19 pathology

Patients with severe COVID-19 develop acute respiratory distress syndrome (ARDS) that may progress to cytokine storm syndrome, organ dysfunction, and death. Considering that complement component 5a (C5a), through its cellular receptor C5aR1, has potent proinflammatory actions, and plays immunopathological roles in inflammatory diseases, we investigated whether C5a/C5aR1 pathway could be involved in COVID-19 pathophysiology. C5a/C5aR1 signaling increased locally in the lung, especially in neutrophils of critically ill COVID-19 patients compared to patients with influenza infection, as well as in the lung tissue of K18-hACE2 Tg mice (Tg mice) infected with SARS-CoV-2. Genetic and pharmacological inhibition of C5aR1 signaling ameliorated lung immunopathology in Tg-infected mice. Mechanistically, we found that C5aR1 signaling drives neutrophil extracellular trap (NET)s-dependent immunopathology. These data confirm the immunopathological role of C5a/C5aR1 signaling in COVID-19 and indicate that antagonist of C5aR1 could be useful for COVID-19 treatment.

immunology↗

bioRxiv2022

Complement receptor C5aR1 signaling in sensory neuron-associated macrophages drives neuropathic pain

Neuroimmune interactions across the pain pathway play a predominant role in the development of neuropathic pain. Previous reports demonstrated that complement driven effector systems including the C5a/C5aR1 axis contribute to these neuro-immune mechanisms. However, the cellular and molecular mechanisms underlying C5a/C5aR1 signaling-mediated neuropathic pain development remain ill-identified. Here we show that neuropathic pain following peripheral nerve injury was attenuated in C5aR1-deficient male and female mice as well as in wild type mice treated with a selective allosteric C5aR1 antagonist. Using two complementary cell-specific C5aR1 knockout mouse strains, we identified C5a/C5aR1 driven-activation of sensory neuron-associated macrophages (sNAMs) located in the sensory ganglia as the key site of peripheral nerve injury-induced neuropathic pain, whereas activation of macrophages of the local of peripheral nerve injury was not involved. Mechanistically, we uncovered IL-1b the main mediator of pain hypersensitivity in response to C5aR1 signaling in sNAMs. Our findings highlight a crucial role of C5a/C5aR1 axis activation in sNAMs for the development of neuropathic pain and identify this pathway as a promising novel target for neuropathic pain therapy.

pharmacology and toxicology↗

bioRxiv2022

Sensory neuron-associated macrophages proliferate in the sensory ganglia after peripheral nerve injury in a CX3CR1 signaling dependent manner

Resident macrophages are distributed across all tissues and are highly heterogeneous as a consequence of adaptation to different tissue-specific environments. The resident macrophages of the sensory ganglia (sensory neuron-associated macrophages, sNAMs) are in close contact with the cell body of primary sensory neurons and might play physiological and pathophysiological roles. After peripheral nerve injury, there is an increase in the population of macrophages in the sensory ganglia which have been involved in different conditions, especially in neuropathic pain development and nerve regeneration. However, it is still under debate whether macrophages accumulation in the sensor ganglia after peripheral nerve injury is due to the local proliferation of resident macrophages or as a result of blood monocytes infiltration. Here, we confirmed that the number of macrophages increased in the DRGs after spared nerve injury (SNI) model in mice. By using different approaches, we found that the increase in the number of macrophages in the DRGs after SNI is mainly in consequence of the proliferation of resident CX3CR1+ macrophages but not due to infiltration of CCR2+ blood monocytes. These proliferating macrophages are the source of the production of pro-inflammatory cytokines such as TNF and IL-1b. In addition, we found that CX3CR1 signaling is involved in the sNAMs proliferation after peripheral nerve injury. In summary, these results indicated that peripheral nerve injury leads to sNAMs proliferation in the sensory ganglia in a CX3CR1-dependent manner. In conclusion, sNAMs proliferation could be modulated to change pathophysiological conditions such as chronic neuropathic pain and/or nerve regeneration.

immunology↗

bioRxiv2022

IL-33 regulates age-dependency of long-term immune dysfunction induced by sepsis

Sepsis survival in adults is commonly followed by immunosuppression and increased susceptibility to secondary infections. However, the long-term immune consequences of pediatric sepsis are unknown. Here, we compared the frequency of Tregs, the activation of the IL-33/ILC2s axis in M2 macrophages, and the DNA methylation of epithelial lung cells from post-septic infant and adult mice. In contrast to adults, infant mice were resistant to secondary infection and did not show impairment in tumour controls upon melanoma challenge. Mechanistically, increased IL-33 levels, Tregs expansion, and activation of ILC2s and M2-macrophages were observed in post-septic adults but not infant mice. Impaired IL-33 production in post-septic infant mice was associated with increased DNA-methylation on lung epithelial cells. Notably, IL-33 treatment boosted the expansion of Tregs and induced immunosuppression in infant mice. Clinically, adults but not pediatric post-septic patients exhibited higher counts of Tregs and sera IL-33 levels. Hence, we describe a crucial and age-dependent role for IL-33 in post-sepsis immunosuppression.

immunology↗

bioRxiv2021

Vandetanib Reduces Inflammatory Cytokines and Ameliorates COVID-19 in Infected Mice

The portfolio of SARS-CoV-2 small molecule drugs is currently limited to a handful that are either approved (remdesivir), emergency approved (dexamethasone, baricitinib) or in advanced clinical trials. We have tested 45 FDA-approved kinase inhibitors in vitro against murine hepatitis virus (MHV) as a model of SARS-CoV-2 replication and identified 12 showing inhibition in the delayed brain tumor (DBT) cell line. Vandetanib, which targets the vascular endothelial growth factor receptor (VEGFR), the epidermal growth factor receptor (EGFR), and the RET-tyrosine kinase showed the most promising results on inhibition versus toxic effect on SARS-CoV-2-infected Caco-2 and A549-hACE2 cells (IC50 0.79 M) while also showing a reduction of > 3 log TCID50/mL for HCoV-229E. The in vivo efficacy of vandetanib was assessed in a mouse model of SARS-CoV-2 infection and statistically significantly reduced the levels of IL-6, IL-10, TNF-, and mitigated inflammatory cell infiltrates in the lungs of infected animals but did not reduce viral load. Vandetanib rescued the decreased IFN-1{beta} caused by SARS-CoV-2 infection in mice to levels similar to that in uninfected animals. Our results indicate that the FDA-approved vandetanib is a potential therapeutic candidate for COVID-19 positioned for follow up in clinical trials either alone or in combination with other drugs to address the cytokine storm associated with this viral infection.

immunology↗

bioRxiv2021

Pyronaridine Protects Against SARS-CoV-2 in Mouse

There are currently relatively few small-molecule antiviral drugs that are either approved or emergency approved for use against SARS-CoV-2. One of these is remdesivir, which was originally repurposed from its use against Ebola and functions by causing early RNA chain termination. We used this as justification to evaluate three molecules we had previously identified computationally with antiviral activity against Ebola and Marburg. Out of these we previously identified pyronaridine, which inhibited the SARS-CoV-2 replication in A549-ACE2 cells. Herein, the in vivo efficacy of pyronaridine has now been assessed in a K18-hACE transgenic mouse model of COVID-19. Pyronaridine treatment demonstrated a statistically significant reduction of viral load in the lungs of SARS CoV-2 infected mice. Furthermore, the pyronaridine treated group reduced lung pathology, which was also associated with significant reduction in the levels of pro-inflammatory cytokines/chemokine and cell infiltration. Notably, pyronaridine inhibited the viral PLpro activity in vitro (IC50 of 1.8 {micro}M) without any effect on Mpro, indicating a possible molecular mechanism involved in its ability to inhibit SARS-CoV-2 replication. Interestingly, pyronaridine also selectively inhibits the host kinase CAMK1 (IC50 of 2.4 {micro}M). We have also generated several pyronaridine analogs to assist in understanding the structure activity relationship for PLpro inhibition. Our results indicate that pyronaridine is a potential therapeutic candidate for COVID-19. One sentence summaryThere is currently intense interest in discovering small molecules with direct antiviral activity against the severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2). Pyronaridine, an antiviral drug with in vitro activity against Ebola, Marburg and SARS-CoV-2 has now statistically significantly reduced the viral load in mice along with IL-6, TNF-, and IFN-{beta} ultimately demonstrating a protective effect against lung damage by infection to provide a new potential treatment for testing clinically.

pharmacology and toxicology↗

bioRxiv2021

Neuroimmune-glial cells interactions elevate the kynurenine metabolic pathway to sustain neuropathic pain

Neuropathic pain is triggered by injury to the somatosensory system, and is one of the most important types of chronic pain. Nevertheless, critical pathophysiological mechanisms that maintain neuropathic pain are poorly understood. Here, we show that neuropathic pain is abrogated when the kynurenine metabolic pathway (KYNPATH) initiated by the enzyme indoleamine 2,3-dioxygenase (IDO) is ablated pharmacologically or genetically. Mechanistically, it was found that IDO upregulation in dendritic cells that accumulate in the dorsal root leptomeninges led to increased levels of kynurenine (Kyn) in the spinal cord, where Kyn is metabolized by astrocytes-expressed kynurenine-3-monooxygenase into a pro-nociceptive metabolite 3-hydroxykynurenine. In conclusion, these data reveal a novel role for KYNPATH as an important factor maintaining neuropathic pain during neuroimmune-glia cells interactions. This novel paradigm offers potential new targets for drug development against this type of chronic pain.

neuroscience↗

bioRxiv2020

Infection of human lymphomononuclear cells by SARS-CoV-2

Although SARS-CoV-2 severe infection is associated with a hyperinflammatory state, lymphopenia is an immunological hallmark, and correlates with poor prognosis in COVID-19. However, it remains unknown if circulating human lymphocytes and monocytes are susceptible to SARS-CoV-2 infection. In this study, SARS-CoV-2 infection of human peripheral blood mononuclear cells (PBMCs) was investigated both in vitro and in vivo. We found that in vitro infection of whole PBMCs from healthy donors was productive of virus progeny. Results revealed that monocytes, as well as B and T lymphocytes, are susceptible to SARS-CoV-2 active infection and viral replication was indicated by detection of double-stranded RNA. Moreover, flow cytometry and immunofluorescence analysis revealed that SARS-CoV-2 was frequently detected in monocytes and B lymphocytes from COVID-19 patients, and less frequently in CD4+T lymphocytes. The rates of SARS-CoV-2-infected monocytes in PBMCs from COVID-19 patients increased over time from symptom onset. Additionally, SARS-CoV-2-positive monocytes and B and CD4+T lymphocytes were detected by immunohistochemistry in post mortem lung tissue. SARS-CoV-2 infection of blood circulating leukocytes in COVID-19 patients may have important implications for disease pathogenesis, immune dysfunction, and virus spread within the host.

microbiology↗