Frontline Science: COVID-19 infection induces readily detectable morphologic and inflammation-related phenotypic changes in peripheral blood monocytes

The BCG vaccine and SARS-CoV-2: Could there be a beneficial relationship?

The COVID-19 disease continues to cause complications and deaths worldwide. Identifying effective immune protection strategies remains crucial to address this ongoing challenge. The Bacillus Calmette-Guérin (BCG) vaccine, developed initially to prevent pulmonary tuberculosis, has gained relevance due to its ability to induce cross-protection against other pathogens of the airways. This review summarizes research on the immunological protection provided by BCG, along with its primary clinical and therapeutic uses. It also explores the immunological features of COVID-19, the mechanisms implicated in host cell death, and its association with chronic pulmonary illnesses such as tuberculosis, which has led to complications in diagnosis and management. While vaccines against COVID-19 have been administered globally, uncertainty still exists about its effectiveness. Additionally, it is uncertain whether the utilization of BCG can regulate the immune response to pathogens such as SARS-CoV-2.

Interactions of SARS-CoV-2 with Human Target Cells-A Metabolic View

Viruses are obligate intracellular parasites, and they exploit the cellular pathways and resources of their respective host cells to survive and successfully multiply. The strategies of viruses concerning how to take advantage of the metabolic capabilities of host cells for their own replication can vary considerably. The most common metabolic alterations triggered by viruses affect the central carbon metabolism of infected host cells, in particular glycolysis, the pentose phosphate pathway, and the tricarboxylic acid cycle. The upregulation of these processes is aimed to increase the supply of nucleotides, amino acids, and lipids since these metabolic products are crucial for efficient viral proliferation. In detail, however, this manipulation may affect multiple sites and regulatory mechanisms of host-cell metabolism, depending not only on the specific viruses but also on the type of infected host cells. In this review, we report metabolic situations and reprogramming in different human host cells, tissues, and organs that are favorable for acute and persistent SARS-CoV-2 infection. This knowledge may be fundamental for the development of host-directed therapies.

SARS-CoV-2 Modulation of HIV Latency Reversal in a Myeloid Cell Line: Direct and Bystander Effects

Coronavirus disease 2019 (COVID-19) might impact disease progression in people living with HIV (PLWH), including those on effective combination antiretroviral therapy (cART). These individuals often experience chronic conditions characterized by proviral latency or low-level viral replication in CD4+ memory T cells and tissue macrophages. Pro-inflammatory cytokines, such as TNF-α, IL-1β, IL-6, and IFN-γ, can reactivate provirus expression in both primary cells and cell lines. These cytokines are often elevated in individuals infected with SARS-CoV-2, the virus causing COVID-19. However, it is still unknown whether SARS-CoV-2 can modulate HIV reactivation in infected cells. Here, we report that exposure of the chronically HIV-1-infected myeloid cell line U1 to two different SARS-CoV-2 viral isolates (ancestral and BA.5) reversed its latent state after 24 h. We also observed that SARS-CoV-2 exposure of human primary monocyte-derived macrophages (MDM) initially drove their polarization towards an M1 phenotype, which shifted towards M2 over time. This effect was associated with soluble factors released during the initial M1 polarization phase that reactivated HIV production in U1 cells, like MDM stimulated with the TLR agonist resiquimod. Our study suggests that SARS-CoV-2-induced systemic inflammation and interaction with macrophages could influence proviral HIV-1 latency in myeloid cells in PLWH.

Immune Response Dynamics and Biomarkers in COVID-19 Patients

BACKGROUND

The immune response dynamics in COVID-19 patients remain a subject of intense investigation due to their implications for disease severity and treatment outcomes. We examined changes in leukocyte levels, eosinophil activity, and cytokine profiles in patients hospitalized with COVID-19.

METHODS

Serum samples were collected within the first 10 days of hospitalization/confirmed infection and analyzed for eosinophil granule proteins (EGP) and cytokines. Information from medical records including comorbidities, clinical symptoms, medications, and complete blood counts were collected at the time of admission, during hospitalization and at follow up approximately 3 months later.

RESULTS

Serum levels of eotaxin, type 1 and type 2 cytokines, and alarmin cytokines were elevated in COVID-19 patients, highlighting the heightened immune response (p < 0.05). However, COVID-19 patients exhibited lower levels of eosinophils and eosinophil degranulation products compared to hospitalized controls (p < 0.05). Leukocyte counts increased consistently from admission to follow-up, indicative of recovery.

CONCLUSION

Attenuated eosinophil activity alongside elevated chemokine and cytokine levels during active infection, highlights the complex interplay of immune mediators in the pathogenesis COVID-19 and underscores the need for further investigation into immune biomarkers and treatment strategies.

Morphological Clues of Acute Monocytic Leukemia in COVID-19-Induced Transient Leukoerythroblastic Reaction with Monocytosis

Viral infections, including those caused by COVID-19, can produce striking morphologic changes in peripheral blood. Distinguishing between reactive changes and abnormal morphology of monocytes remains particularly difficult, with low consensus rates reported amongst hematopathologists. Here, we report a patient who developed transient monocytosis of 11.06 × 109/L with 32% promonocytes and 1% blasts during hospitalization that was secondary to severe COVID-19 infection. Three days later, the clinical status of the patient improved and the WBC had decreased to 8.47 × 109/L with 2.2 × 109/L monocytes. Flow cytometry studies did not reveal immunophenotypic findings specific for an overt malignant population. At no time during admission did the patient develop cytopenia(s), and she was discharged upon clinical improvement. However, the peripheral blood sample containing promonocytes was sent for molecular testing with an extended next-generation sequencing myeloid panel and was positive for pathogenic NPM1 Type A and DNMT3A R882H mutations. Subsequently, despite an essentially normal complete blood count, the patient underwent a bone marrow assessment that showed acute myeloid leukemia with 77% promonocytes. This case emphasizes the critical importance of a full work up to exclude acute leukemia when classical promonocyte morphology is encountered in the peripheral blood. Promonocytes are not a part of the reactive changes associated with COVID-19 and remain specific to myeloid neoplasia.

A generalizable and easy-to-use COVID-19 stratification model for the next pandemic via immune-phenotyping and machine learning

Introduction

The coronavirus disease 2019 (COVID-19) pandemic has affected billions of people worldwide, and the lessons learned need to be concluded to get better prepared for the next pandemic. Early identification of high-risk patients is important for appropriate treatment and distribution of medical resources. A generalizable and easy-to-use COVID-19 severity stratification model is vital and may provide references for clinicians.

Methods

Three COVID-19 cohorts (one discovery cohort and two validation cohorts) were included. Longitudinal peripheral blood mononuclear cells were collected from the discovery cohort (n = 39, mild = 15, critical = 24). The immune characteristics of COVID-19 and critical COVID-19 were analyzed by comparison with those of healthy volunteers (n = 16) and patients with mild COVID-19 using mass cytometry by time of flight (CyTOF). Subsequently, machine learning models were developed based on immune signatures and the most valuable laboratory parameters that performed well in distinguishing mild from critical cases. Finally, single-cell RNA sequencing data from a published study (n = 43) and electronic health records from a prospective cohort study (n = 840) were used to verify the role of crucial clinical laboratory and immune signature parameters in the stratification of COVID-19 severity.

Results

Patients with COVID-19 were determined with disturbed glucose and tryptophan metabolism in two major innate immune clusters. Critical patients were further characterized by significant depletion of classical dendritic cells (cDCs), regulatory T cells (Tregs), and CD4+ central memory T cells (Tcm), along with increased systemic interleukin-6 (IL-6), interleukin-12 (IL-12), and lactate dehydrogenase (LDH). The machine learning models based on the level of cDCs and LDH showed great potential for predicting critical cases. The model performances in severity stratification were validated in two cohorts (AUC = 0.77 and 0.88, respectively) infected with different strains in different periods. The reference limits of cDCs and LDH as biomarkers for predicting critical COVID-19 were 1.2% and 270.5 U/L, respectively.

Conclusion

Overall, we developed and validated a generalizable and easy-to-use COVID-19 severity stratification model using machine learning algorithms. The level of cDCs and LDH will assist clinicians in making quick decisions during future pandemics.

Spatiotemporal analysis of SARS-CoV-2 infection reveals an expansive wave of monocyte-derived macrophages associated with vascular damage and virus clearance in hamster lungs

IMPORTANCE

We present the first study of the 3D kinetics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the early host response in a large lung volume using a combination of tissue imaging and transcriptomics. This approach allowed us to make a number of important findings: Spatially restricted antiviral response is shown, including the formation of monocytic macrophage clusters and upregulation of the major histocompatibility complex II in infected epithelial cells. The monocyte-derived macrophages are linked to SARS-CoV-2 clearance, and the appearance of these cells is associated with post-infection endothelial damage; thus, we shed light on the role of these cells in infected tissue. An early onset of tissue repair occurring simultaneously with inflammatory and necrotizing processes provides the basis for longer-term alterations in the lungs.

Pyrogenic and inflammatory mediators are produced by polarized M1 and M2 macrophages activated with D-dimer and SARS-CoV-2 spike immune complexes

Lung macrophages are the first line of defense against invading respiratory pathogens including SARS-CoV-2, yet activation of macrophage in the lungs can lead to hyperinflammatory immune response seen in severe COVID-19. Here we used human M1 and M2 polarized macrophages as a surrogate model of inflammatory and regulatory macrophages and explored whether immune complexes (IC) containing spike-specific IgG can trigger aberrant cytokine responses in macrophages in the lungs and associated lymph nodes. We show that IC of SARS-CoV-2 recombinant S protein coated with spike-specific monoclonal antibody induced production of Prostaglandin E2 (PGE2) in non-polarized (M0) and in M1 and M2-type polarized human macrophages only in the presence of D-dimer (DD), a fibrinogen degradation product, associated with coagulopathy in COVID-19. Importantly, an increase in PGE2 was also observed in macrophages activated with DD and IC of SARS-CoV-2 pseudovirions coated with plasma from hospitalized COVID-19 patients but not from healthy subjects. Overall, the levels of PGE2 in macrophages activated with DD and IC were as follows: M1≫M2>M0 and correlated with the levels of spike binding antibodies and not with neutralizing antibody titers. All three macrophage subsets produced similar levels of IL-6 following activation with DD+IC, however TNFα, IL-1β, and IL-10 cytokines were produced by M2 macrophages only. Our study suggests that high titers of spike or virion containing IC in the presence of coagulation byproducts (DD) can promote inflammatory response in macrophages in the lungs and associated lymph nodes and contribute to severe COVID-19.

Aloe-derived vesicles enable macrophage reprogramming to regulate the inflammatory immune environment

Introduction: Bacterial pneumonia poses a significant global public health challenge, where unaddressed pathogens and inflammation can exacerbate acute lung injury and prompt cytokine storms, increasing mortality rates. Alveolar macrophages are pivotal in preserving lung equilibrium. Excessive inflammation can trigger necrosis in these cells, disrupting the delicate interplay between inflammation and tissue repair. Methods: We obtained extracellular vesicle from aloe and tested the biosafety by cell viability and hemolysis assays. Confocal microscopy and flow cytometry were used to detect the uptake and internalization of extracellular vesicle by macrophages and the ability of extracellular vesicle to affect the phenotypic reprogramming of macrophages in vitro. Finally, we conducted a clinical feasibility study employing clinical bronchoalveolar lavage fluid as a representative model to assess the effective repolarization of macrophages influenced by extracellular vesicle. Results: In our study, we discovered the potential of extracellular vesicle nanovesicles derived from aloe in reprograming macrophage phenotypes. Pro-inflammatory macrophages undergo a transition toward an anti-inflammatory immune phenotype through phagocytosing and internalizing these aloe vera-derived extracellular vesicle nanovesicles. This transition results in the release of anti-inflammatory IL-10, effectively curbing inflammation and fostering lung tissue repair. Discussion: These findings firmly establish the immunomodulatory impact of aloe-derived extracellular vesicle nanovesicles on macrophages, proposing their potential as a therapeutic strategy to modulate macrophage immunity in bacterial pneumonia.

Analysis of the Morphology of Monocytes and Lymphocytes from COVID-19 Patients Using Low-Voltage Scanning Electronic Microscopy

Severe course of COVID-19 is largely determined by hyperactivation of the immune system, or cytokine storm, in which immune cells (lymphocytes, monocytes, etc.) play a major role. Using low-voltage scanning electron microscopy, we studied the morphology of lymphocytes and monocytes during cytokine storm. Monocytes and lymphocytes were isolated by fluorescence sorting from the blood of healthy volunteers (n=6) and patients with COVID-19 (n=5) during cytokine storm (IL-6>23 ng/ml, smear positive for SARS-CoV-2). For each patient, 11-32 individual cells were analyzed at magnification of 18-32,000 times. Measurements showed that monocyte size was increased during cytokine storm (p=0.0001).

Morphological abnormalities of leukocytes in SARS-CoV-2 infection

Introduction

The causative agent of COVID-19 (Coronavirus Disease 2019) is an enveloped RNA (ribonucleic acid) virus of the SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus-2) family. The effects of SARS-CoV-2 on the differentiation and maturation of blood cells have been the subject of several studies, we report our experience of an investigation of the morphologic abnormalities of leukocytes observed during COVID-19.

Patients and methods

This is a prospective study of 5 months, from February 2021 to June 2021. Forty COVID-19 patients and 20 healthy controls were included in this study. We performed complete blood count and peripheral blood smear of all patients and control samples. Leukocytes abnormalities were quantified as a percentage of 100 leukocytes of the same lineage.

Results

The morphological abnormalities of the leukocytes found in percentage of patients have been mainly neutrophils bilobed 72,5%, hypogranulation 45%, acquired pseudo Pelger-Huet 35%, vacuolated neutrophils 42,5%, Apoptotic neutrophils 35,5 %, neutrophils with toxic granulations 30%, myelemia 45%, atypical lymphocytes 52,5%, lymphoplasmocytes 60% and vacuolated monocytes 27, 5%.

Conclusion

Our study revealed several morphological abnormalities of the different cells of the leukocyte lineage. The presence of toxic granulations in the cytoplasm of the myelocytes was specific to this study.

Monocytes subpopulations pattern in the acute respiratory syndrome coronavirus 2 virus infection and after long COVID-19

INTRODUTION AND OBJECTIVE

The present study sought to characterize the pattern of monocyte subpopulations in patients during the course of the infections caused by SARS-CoV-2 virus or who presented long COVID-19 syndrome compared to monocytes from patients with zika virus (Zika) or chikungunya virus (CHIKV).

CASUISTRY

Study with 89 peripheral blood samples from patients, who underwent hemogram and serology (IgG and IgM) for detection of Zika (Control Group 1, n = 18) or CHIKV (Control Group 2, n = 9), and from patients who underwent hemogram and reverse transcription polymerase chain reaction for detection of SARS-CoV-2 at the acute phase of the disease (Group 3, n = 19); and of patients who presented long COVID-19 syndrome (Group 4, n = 43). The monocyte and subpopulations counts were performed by flow cytometry.

RESULTS

No significant difference was observed in the total number of monocytes between the groups. The classical (CD14++CD16-) and intermediate (CD14+CD16+) monocytes counts were increased in patients with acute infection or with long COVID-19 syndrome. The monocytes subpopulations counts were lower in patients with infection Zika or CHIKV.

CONCLUSION

Increase in the monocyte subpopulations in patients with acute infection or with long COVID-19 syndrome may be an important finding of differentiated from the infection Zika or CHIKV.

Advantages and disadvantages of treatment of experimental ARDS by M2-polarized RAW 264.7 macrophages

Innate immunity reactions are core to any immunological process, including systemic inflammation and such extremes as acute respiratory distress syndrome (ARDS) and cytokine storm. Macrophages, the key cells of innate immunity, show high phenotypic plasticity: depending on microenvironmental cues, they can polarize into M1 (classically activated, pro-inflammatory) or M2 (alternatively activated, anti-inflammatory). The anti-inflammatory M2 macrophage polarization-based cell therapies constitute a novel prospective modality. Systemic administration of 'educated' macrophages is intended at their homing in lungs in order to mitigate the pro-inflammatory cytokine production and reduce the risks of 'cytokine storm' and related severe complications. Acute respiratory distress syndrome (ARDS) is the main mortality factor in pneumonia including SARS-CoV-associated cases. This study aimed to evaluate the influence of infusions of RAW 264.7 murine macrophage cell line polarized towards M2 phenotype on the development of LPS-induced ARDS in mouse model. The results indicate that the M2-polarized RAW 264.7 macrophage infusions in the studied model of ARDS promote relocation of lymphocytes from their depots in immune organs to the lungs. In addition, the treatment facilitates expression of M2-polarization markers Arg1, Vegfa and Tgfb and decreases of M1-polarization marker Cd38 in lung tissues, which can indicate the anti-inflammatory response activation. However, treatment of ARDS with M2-polarized macrophages didn't change the neutrophil numbers in the lungs. Moreover, the level of the Arg1 protein in lungs decreased throughtout the treatment with M2 macrophages, which is probably because of the pro-inflammatory microenvironment influence on the polarization of macrophages towards M1. Thus, the chemical polarization of macrophages is unstable and depends on the microenvironment. This adverse effect can be reduced through the use of primary autologous macrophages or some alternative methods of M2 polarization, notably siRNA-mediated.

Transport by circulating myeloid cells drives liposomal accumulation in inflamed synovium

The therapeutic potential of liposomes to deliver drugs into inflamed tissue is well documented. Liposomes are believed to largely transport drugs into inflamed joints by selective extravasation through endothelial gaps at the inflammatory sites, known as the enhanced permeation and retention effect. However, the potential of blood-circulating myeloid cells for the uptake and delivery of liposomes has been largely overlooked. Here we show that myeloid cells can transport liposomes to inflammatory sites in a collagen-induced arthritis model. It is shown that the selective depletion of the circulating myeloid cells reduces the accumulation of liposomes up to 50-60%, suggesting that myeloid-cell-mediated transport accounts for more than half of liposomal accumulation in inflamed regions. Although it is widely believed that PEGylation inhibits premature liposome clearance by the mononuclear phagocytic system, our data show that the long blood circulation times of PEGylated liposomes rather favours uptake by myeloid cells. This challenges the prevailing theory that synovial liposomal accumulation is primarily due to the enhanced permeation and retention effect and highlights the potential for other pathways of delivery in inflammatory diseases.

Navigating the Post-COVID-19 Immunological Era: Understanding Long COVID-19 and Immune Response

The COVID-19 pandemic has affected the world unprecedentedly, with both positive and negative impacts. COVID-19 significantly impacted the immune system, and understanding the immunological consequences of COVID-19 is essential for developing effective treatment strategies. The purpose of this review is to comprehensively explore and provide insights into the immunological aspects of long COVID-19, a phenomenon where individuals continue to experience a range of symptoms and complications, even after the acute phase of COVID-19 infection has subsided. The immune system responds to the initial infection by producing various immune cells and molecules, including antibodies, T cells, and cytokines. However, in some patients, this immune response becomes dysregulated, leading to chronic inflammation and persistent symptoms. Long COVID-19 encompasses diverse persistent symptoms affecting multiple organ systems, including the respiratory, cardiovascular, neurological, and gastrointestinal systems. In the post-COVID-19 immunological era, long COVID-19 and its impact on immune response have become a significant concern. Post-COVID-19 immune pathology, including autoimmunity and immune-mediated disorders, has also been reported in some patients. This review provides an overview of the current understanding of long COVID-19, its relationship to immunological responses, and the impact of post-COVID-19 immune pathology on patient outcomes. Additionally, the review addresses the current and potential treatments for long COVID-19, including immunomodulatory therapies, rehabilitation programs, and mental health support, all of which aim to improve the quality of life for individuals with long COVID-19. Understanding the complex interplay between the immune system and long COVID-19 is crucial for developing targeted therapeutic strategies and providing optimal care in the post-COVID-19 era.

A Review of Antibiotic Efficacy in COVID-19 Control

Severe acute respiratory disease is associated with chronic secondary infections that exacerbate symptoms and mortality. So far, many drugs have been introduced to treat this disease, none of which effectively control the coronavirus. Numerous studies have shown that mitochondria, as the center of cell biogenesis, are vulnerable to drugs, especially antibiotics. Antibiotics were widely prescribed during the early phase of the pandemic. We performed a literature review to assess the reasons, evidence, and practices on the use of antibiotics in coronavirus disease 2019 (COVID-19) in- and outpatients. The current research found widespread usage of antibiotics, mostly in an empirical context, among COVID-19 hospitalized patients. The effectiveness of this approach has not been established. Given the high death rate linked with secondary infections in COVID-19 patients and the developing antimicrobial resistance, further study is urgently needed to identify the most appropriate rationale for antibiotic therapy in these patients.

Morphofunctional Characteristics of Lung Macrophages in Rats with Acute Respiratory Distress Syndrome

A comprehensive morphofunctional study of the lungs and alveolar macrophages was carried out in Sprague-Dawley rats with acute respiratory distress syndrome (n=10) induced by intratracheal administration of E. coli LPS 0111:B4 in a dose of 15 mg/kg. On the first day after LPS administration, bronchopneumonia was observed in the lungs, the number of macrophages of the bone marrow origin and the number of M1 macrophages with the proinflammatory phenotype in the bronchoalveolar lavage increased, the expression of proinflammatory cytokines increased and the expression of anti-inflammatory cytokines decreased, which was accompanied by an increase in LPS and C-reactive protein in the blood serum. The revealed changes correspond to the development of acute respiratory distress syndrome in humans, and the decrease in the number of macrophages in the lungs and their predominant polarization to the M1-proinflammatory phenotype substantiate the use of cell therapy with reprogrammed M2 macrophages.

SARS-CoV-2 induced changes in the glycosylation pattern in the respiratory tract of Golden Syrian hamsters

Even after more than two years of intensive research, not all of the pathophysiological processes of Coronavirus Disease 2019 (COVID-19), induced by severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) infection, have been fully elucidated. The initial virus-host interaction at the respiratory epithelium plays a crucial role in the course and progression of the infection, and is highly dependent on the glycosylation pattern of the host cell and of the secreted mucins. Glycans are polysaccharides that can be attached to proteins and thereby add to their stability and functionality. Lectins are glycan-binding proteins that recognize specific glycan motifs, and lectin histochemistry is a suitable tool to visualize and examine glycosylation pattern changes in tissues. In this study we used lectins with different glycan-specificities for the visualization of glycosylation pattern changes in the respiratory tract of SARS-CoV-2 infected Golden Syrian hamsters. While some lectins (LEL, STL) enable the visualization of the damage to alveolar type 1 pneumocytes, other lectins, e.g., GSLI, visualized the loss and subsequent hyperplasia of type 2 pneumocytes. UEAI staining was co-localized with KI67, a proliferation marker. Double staining of lectins LEL, STL and WGA with specific immune cell markers (Iba1, CD68) showed co-localization and the dominant infiltration of monocyte-derived macrophages into infected alveolar tissue. The elucidation of the glycosylation pattern of the respiratory tract cells in uninfected and infected Golden Syrian hamsters revealed physiological and pathological aspects of the disease that may open new possibilities for therapeutic development.

The Role of Toll-like Receptor-4 in Macrophage Imbalance in Lethal COVID-19 Lung Disease, and Its Correlation with Galectin-3

To the current data, there have been 6,955,141 COVID-19-related deaths worldwide, reported to WHO. Toll-like receptors (TLRs) implicated in bacterial and virus sensing could be a crosstalk between activation of persistent innate-immune inflammation, and macrophage's sub-population alterations, implicated in cytokine storm, macrophage over-activation syndrome, unresolved Acute Respiratory Disease Syndrome (ARDS), and death. The aim of this study is to demonstrate the association between Toll-like-receptor-4 (TLR-4)-induced inflammation and macrophage imbalance in the lung inflammatory infiltrate of lethal COVID-19 disease. Twenty-five cases of autopsy lung tissues were studied by digital pathology-based immunohistochemistry to evaluate expression levels of TLR-4 (CD 284), pan-macrophage marker CD68 (clone KP1), sub-population marker related to alveolar macrophage Galectin-3 (GAL-3) (clone 9C4), and myeloid derived CD163 (clone MRQ-26), respectively. SARS-CoV-2 viral persistence has been evaluated by in situ hybridation (ISH) method. This study showed TLR-4 up-regulation in a subgroup of patients, increased macrophage infiltration in both Spike-1(+) and Spike-1(-) lungs (p < 0.0001), and a macrophage shift with important down-regulation of GAL-3(+) alveolar macrophages associated with Spike-1 persistence (p < 0.05), in favor of CD163(+) myeloid derived monocyte-macrophages. Data show that TLR-4 expression induces a persistent activation of the inflammation, with inefficient resolution, and pathological macrophage shift, thus explaining one of the mechanisms of lethal COVID-19.

Health disparities in COVID-19: immune and vascular changes are linked to disease severity and persist in a high-risk population in Riverside County, California

BACKGROUND

Health disparities in underserved communities, such as inadequate healthcare access, impact COVID-19 disease outcomes. These disparities are evident in Hispanic populations nationwide, with disproportionately high infection and mortality rates. Furthermore, infected individuals can develop long COVID with sustained impacts on quality of life. The goal of this study was to identify immune and endothelial factors that are associated with COVID-19 outcomes in Riverside County, a high-risk and predominantly Hispanic community, and investigate the long-term impacts of COVID-19 infection.

METHODS

112 participants in Riverside County, California, were recruited according to the following criteria: healthy control (n = 23), outpatients with moderate infection (outpatient, n = 33), ICU patients with severe infection (hospitalized, n = 33), and individuals recovered from moderate infection (n = 23). Differences in outcomes between Hispanic and non-Hispanic individuals and presence/absence of co-morbidities were evaluated. Circulating immune and vascular biomarkers were measured by ELISA, multiplex analyte assays, and flow cytometry. Follow-up assessments for long COVID, lung health, and immune and vascular changes were conducted after recovery (n = 23) including paired analyses of the same participants.

RESULTS

Compared to uninfected controls, the severe infection group had a higher proportion of Hispanic individuals (n = 23, p = 0.012) than moderate infection (n = 8, p = 0.550). Disease severity was associated with changes in innate monocytes and neutrophils, lymphopenia, disrupted cytokine production (increased IL-8 and IP-10/CXCL10 but reduced IFNλ2/3 and IFNγ), and increased endothelial injury (myoglobin, VCAM-1). In the severe infection group, a machine learning model identified LCN2/NGAL, IL-6, and monocyte activation as parameters associated with fatality while anti-coagulant therapy was associated with survival. Recovery from moderate COVID infection resulted in long-term immune changes including increased monocytes/lymphocytes and decreased neutrophils and endothelial markers. This group had a lower proportion of co-morbidities (n = 8, p = 1.0) but still reported symptoms associated with long COVID despite recovered pulmonary function.

CONCLUSION

This study indicates increased severity of COVID-19 infection in Hispanic individuals of Riverside County, California. Infection resulted in immunological and vascular changes and long COVID symptoms that were sustained for up to 11 months, however, lung volume and airflow resistance was recovered. Given the immune and behavioral impacts of long COVID, the potential for increased susceptibility to infections and decreased quality of life in high-risk populations warrants further investigation.

Initial immune response after exposure to Mycobacterium tuberculosis or to SARS-COV-2: similarities and differences

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb) and Coronavirus disease-2019 (COVID-19), whose etiologic agent is severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), are currently the two deadliest infectious diseases in humans, which together have caused about more than 11 million deaths worldwide in the past 3 years. TB and COVID-19 share several aspects including the droplet- and aerosol-borne transmissibility, the lungs as primary target, some symptoms, and diagnostic tools. However, these two infectious diseases differ in other aspects as their incubation period, immune cells involved, persistence and the immunopathological response. In this review, we highlight the similarities and differences between TB and COVID-19 focusing on the innate and adaptive immune response induced after the exposure to Mtb and SARS-CoV-2 and the pathological pathways linking the two infections. Moreover, we provide a brief overview of the immune response in case of TB-COVID-19 co-infection highlighting the similarities and differences of each individual infection. A comprehensive understanding of the immune response involved in TB and COVID-19 is of utmost importance for the design of effective therapeutic strategies and vaccines for both diseases.

COVID-19 Disease in Pediatric Solid Organ Transplantation from Alpha to Omicron: A High Monocyte Count in the Preceding Three Months Portends a Risk for Severe Disease

IMPORTANCE

Planning for future resurgences in SARS-CoV-2 infection is necessary for providers who care for immunocompromised patients.

OBJECTIVE

to determine factors associated with COVID-19 disease severity in immunosuppressed children.

DESIGN

a case series of children with solid organ transplants diagnosed with SARS-CoV-2 infection between 15 March 2020 and 31 March 2023.

SETTING

a single pediatric transplant center.

PARTICIPANTS

all children with a composite transplant (liver, pancreas, intestine), isolated intestine transplant (IT), isolated liver transplant LT), or simultaneous liver kidney transplant (SLK) with a positive PCR for SARS-CoV-2.

EXPOSURE

SARS-CoV-2 infection.

MAIN OUTCOME AND MEASURES

We hypothesized that children on the most immunosuppression, defined by the number of immunosuppressive medications and usage of steroids, would have the most severe disease course and that differential white blood cell count in the months preceding infection would be associated with likelihood of having severe disease. The hypothesis being tested was formulated during data collection. The primary study outcome measurement was disease severity defined using WHO criteria.

RESULTS

77 children (50 LT, 24 intestine, 3 SLK) were infected with SARS-CoV-2, 57.4 months from transplant (IQR 19.7-87.2). 17% were ≤1 year post transplant at infection. 55% were male, 58% were symptomatic and ~29% had severe disease. A high absolute lymphocyte count at diagnosis decreased the odds of having severe COVID-19 disease (OR 0.29; CI 0.11-0.60; p = 0.004). Conversely, patients with a high absolute monocyte count in the three months preceding infection had increased odds of having severe disease (OR 30.49; CI 1.68-1027.77; p = 0.033). Steroid use, higher tacrolimus level, and number of immunosuppressive medications at infection did not increase the odds of having severe disease.

CONCLUSIONS AND RELEVANCE

The significance of a high monocyte count as predictor of severe disease potentially confirms the importance of monocytic inflammasome-driven inflammation in COVID-19 pathogenesis. Our data do not support reducing immunosuppression in the setting of infection. Our observations may have important ramifications in resource management as vaccine- and infection-induced immunity wanes.

Hematocytological Clues of Peripheral Blood in Different Clinical Presentations of COVID-19

Background

To gain insight into the pathogenesis and clinical course of COVID-19 from a historical perspective, we reviewed paraclinical diagnostic tools of this disease and prioritized the patients with a more severe form of disease admitted to intensive care units (ICUs). The objective was to better predict the course and severity of the disease by collecting more paraclinical data, specifically by examining the relationship between hematological findings and cytological variation of blood neutrophils and monocytes.

Methods

This retrospective study was conducted on 112 patients with confirmed COVID-19 admitted to Imam Hossein Hospital (Tehran, Iran) from August to September 2020. Peripheral blood smears of these patients were differentiated according to several cytological variations of neutrophils and monocytes, and the correlation to the severity of the disease was specified.

Results

The mean percentages of degenerated monocytes, degenerated granulocytes, and spiky biky neutrophils were significantly different among critical and non-critical patients (P<0.05). Degenerated monocytes and granulocytes were higher in critical patients as opposed to spiky biky neutrophils, which were higher among non-critical ones. Comparing the peripheral blood smears of COVID-19 patients (regarding pulmonary involvement in chest computed tomography [CT] scans [subtle, mild, moderate, and severe groups]), the twisted form of neutrophils was significantly higher in the subtle group than in the mild and moderate groups (P=0.003).

Conclusion

Different cytological morphologies of neutrophils and monocytes, including degenerated monocytes, degenerated granulocytes, and spiky biky and twisted neutrophils, could help to predict the course and severity of the disease.

Coupled mechanical mapping and interference contrast microscopy reveal viscoelastic and adhesion hallmarks of monocyte differentiation into macrophages

Monocytes activated by pro-inflammatory signals adhere to the vascular endothelium and migrate from the bloodstream to the tissue ultimately differentiating into macrophages. Cell mechanics and adhesion play a crucial role in macrophage functions during this inflammatory process. However, how monocytes change their adhesion and mechanical properties upon differentiation into macrophages is still not well understood. In this work, we used various tools to quantify the morphology, adhesion, and viscoelasticity of monocytes and differentiatted macrophages. Combination of atomic force microscopy (AFM) high resolution viscoelastic mapping with interference contrast microscopy (ICM) at the single-cell level revealed viscoelasticity and adhesion hallmarks during monocyte differentiation into macrophages. Quantitative holographic tomography imaging revealed a dramatic increase in cell volume and surface area during monocyte differentiation and the emergence of round and spread macrophage subpopulations. AFM viscoelastic mapping showed important stiffening (increase of the apparent Young's modulus, E₀) and solidification (decrease of cell fluidity, β) on differentiated cells that correlated with increased adhesion area. These changes were enhanced in macrophages with a spread phenotype. Remarkably, when adhesion was perturbed, differentiated macrophages remained stiffer and more solid-like than monocytes, suggesting a permanent reorganization of the cytoskeleton. We speculate that the stiffer and more solid-like microvilli and lamellipodia might help macrophages to minimize energy dissipation during mechanosensitive activities. Thus, our results revealed viscoelastic and adhesion hallmarks of monocyte differentiation that may be important for biological function.

In vivo inhibition of nuclear ACE2 translocation protects against SARS-CoV-2 replication and lung damage through epigenetic imprinting

In vitro, ACE2 translocates to the nucleus to induce SARS-CoV-2 replication. Here, using digital spatial profiling of lung tissues from SARS-CoV-2-infected golden Syrian hamsters, we show that a specific and selective peptide inhibitor of nuclear ACE2 (NACE2i) inhibits viral replication two days after SARS-CoV-2 infection. Moreover, the peptide also prevents inflammation and macrophage infiltration, and increases NK cell infiltration in bronchioles. NACE2i treatment increases the levels of the active histone mark, H3K27ac, restores host translation in infected hamster bronchiolar cells, and leads to an enrichment in methylated ACE2 in hamster bronchioles and lung macrophages, a signature associated with virus protection. In addition, ACE2 methylation is increased in myeloid cells from vaccinated patients and associated with reduced SARS-CoV-2 spike protein expression in monocytes from individuals who have recovered from infection. This protective epigenetic scarring of ACE2 is associated with a reduced latent viral reservoir in monocytes/macrophages and enhanced immune protection against SARS-CoV-2. Nuclear ACE2 may represent a therapeutic target independent of the variant and strain of viruses that use the ACE2 receptor for host cell entry.

Phase 2, randomized, double-blind, placebo-controlled multi-center trial of the clinical and biological effects of anti-CD14 treatment in hospitalized patients with COVID-19 pneumonia

BACKGROUND

Severe COVID-19 is associated with innate immunopathology, and CD14, a proximal activator of innate immunity, has been suggested as a potential therapeutic target.

METHODS

We conducted the COVID-19 anti-CD14 Treatment Trial (CaTT), a Phase II randomized, double-blind, placebo-controlled trial at 5 US-sites between April 12, 2021 and November 30, 2021 (NCT04391309). Hospitalized adults with COVID-19 requiring supplemental oxygen (<30 LPM) were randomized 1:1 to receive 4 daily doses of intravenous IC14, an anti-CD14 monoclonal antibody, or placebo. All participants received remdesivir. The primary outcome was time-to-resolution of illness, defined as improvement on the 8-point NIH-Ordinal COVID-19 Scale to category ≤3. Secondary endpoints were safety and exploratory endpoints were pro-inflammatory and antiviral mediators in serum on days 0-5 & 7. The trial was stopped after 40 patients were randomized and treated due to slow enrollment.

FINDINGS

40 participants were randomized and treated with IC14 (n = 20) or placebo (n = 20). The median time-to-recovery was 6 days (95% CI, 5-11) in the IC14 group vs. 5 days (95% CI, 4-10) in the Placebo group (recovery rate ratio: 0.77 (95% CI, 0.40, 1.48) (log-rank p = 0.435). The number of adverse events was similar in each group, and no IC14-attributable secondary infections occurred. In repeated-measures mixed-effects analyses, IC14 treatment increased serum sCD14 concentrations, an expected pharmacodynamic effect. Pre-planned, exploratory analyses suggested that IC14 treatment decreased the trajectories of circulating MIP-1β and TNF-α.

INTERPRETATION

IC14 treatment did not improve time-to-resolution of illness in hypoxemic patients with COVID-19 in this small trial. Results of exploratory analyses suggested IC14 had biologic effects that warrant future clinical investigation.

FUNDING

National Institute of Allergy and Infectious Diseases.

Pathophysiological involvement of host mitochondria in SARS-CoV-2 infection that causes COVID-19: a comprehensive evidential insight

SARS-CoV-2 is a positive-strand RNA virus that infects humans through the nasopharyngeal and oral route causing COVID-19. Scientists left no stone unturned to explore a targetable key player in COVID-19 pathogenesis against which therapeutic interventions can be initiated. This article has attempted to review, coordinate and accumulate the most recent observations in support of the hypothesis predicting the altered state of mitochondria concerning mitochondrial redox homeostasis, inflammatory regulations, morphology, bioenergetics and antiviral signalling in SARS-CoV-2 infection. Mitochondria is extremely susceptible to physiological as well as pathological stimuli, including viral infections. Recent studies suggest that SARS-CoV-2 pathogeneses alter mitochondrial integrity, in turn mitochondria modulate cellular response against the infection. SARS-CoV-2 M protein inhibited mitochondrial antiviral signalling (MAVS) protein aggregation in turn hinders innate antiviral response. Viral open reading frames (ORFs) also play an instrumental role in altering mitochondrial regulation of immune response. Notably, ORF-9b and ORF-6 impair MAVS activation. In aged persons, the NLRP3 inflammasome is over-activated due to impaired mitochondrial function, increased mitochondrial reactive oxygen species (mtROS), and/or circulating free mitochondrial DNA, resulting in a hyper-response of classically activated macrophages. This article also tries to understand how mitochondrial fission-fusion dynamics is affected by the virus. This review comprehends the overall mitochondrial attribute in pathogenesis as well as prognosis in patients infected with COVID-19 taking into account pertinent in vitro, pre-clinical and clinical data encompassing subjects with a broad range of severity and morbidity. This endeavour may help in exploring novel non-canonical therapeutic strategies to COVID-19 disease and associated complications.

Effects of Different Types of Recombinant SARS-CoV-2 Spike Protein on Circulating Monocytes' Structure

This study investigated the biological effects on circulating monocytes after challenge with SARS-CoV-2 recombinant spike protein. Whole blood collected from seven ostensibly healthy healthcare workers was incubated for 15 min with 2 and 20 ng/mL final concentration of recombinant spike protein of Ancestral, Alpha, Delta, and Omicron variants. Samples were analyzed with Sysmex XN and DI-60 analyzers. Cellular complexity (i.e., the presence of granules, vacuoles and other cytoplasmic inclusions) increased in all samples challenged with the recombinant spike protein of the Ancestral, Alpha, and Delta variants, but not in those containing Omicron. The cellular content of nucleic acids was constantly decreased in most samples, achieving statistical significance in those containing 20 ng/mL of Alpha and Delta recombinant spike proteins. The heterogeneity of monocyte volumes significantly increased in all samples, achieving statistical significance in those containing 20 ng/mL of recombinant spike protein of the Ancestral, Alpha and Delta variants. The monocyte morphological abnormalities after spike protein challenge included dysmorphia, granulation, intense vacuolization, platelet phagocytosis, development of aberrant nuclei, and cytoplasmic extrusions. The SARS-CoV-2 spike protein triggers important monocyte morphological abnormalities, more evident in cells challenged with recombinant spike protein of the more clinically severe Alpha and Delta variants.

Persistent Exhausted T-Cell Immunity after Severe COVID-19: 6-Month Evaluation in a Prospective Observational Study

INTRODUCTION

Severe COVID-19 can result in a significant and irreversible impact on long-term recovery and subsequent immune protection. Understanding the complex immune reactions may be useful for establishing clinically relevant monitoring.

METHODS

Hospitalized adults with SARS-CoV-2 between March/October 2020 (n = 64) were selected. Cryopreserved peripheral blood mononuclear cells (PBMCs) and plasma samples were obtained at hospitalization (baseline) and 6 months after recovery. Immunological components' phenotyping and SARS-CoV-2-specific T-cell response were studied in PBMCs by flow cytometry. Up to 25 plasma pro/anti-inflammatory cytokines/chemokines were assessed by LEGENDplex immunoassays. The SARS-CoV-2 group was compared to matched healthy donors.

RESULTS

Biochemical altered parameters during infection were normalized at a follow-up time point in the SARS-CoV-2 group. Most of the cytokine/chemokine levels were increased at baseline in the SARS-CoV-2 group. This group showed increased Natural Killer cells (NK) activation and decreased CD16^high NK subset, which normalized six months later. They also presented a higher intermediate and patrolling monocyte proportion at baseline. T cells showed an increased terminally differentiated (TemRA) and effector memory (EM) subsets distribution in the SARS-CoV-2 group at baseline and continued to increase six months later. Interestingly, T-cell activation (CD38) in this group decreased at the follow-up time point, contrary to exhaustion markers (TIM3/PD1). In addition, we observed the highest SARS-CoV-2-specific T-cell magnitude response in TemRA CD4 T-cell and EM CD8 T-cell subsets at the six-months time point.

CONCLUSIONS

The immunological activation in the SARS-CoV-2 group during hospitalization is reversed at the follow-up time point. However, the marked exhaustion pattern remains over time. This dysregulation could constitute a risk factor for reinfection and the development of other pathologies. Additionally, high SARS-CoV-2-specific T-cells response levels appear to be associated with infection severity.

PM10 promotes an inflammatory cytokine response that may impact SARS-CoV-2 replication in vitro

Introduction

In the last decades, a decrease in air quality has been observed, mainly associated with anthropogenic activities. Air pollutants, including particulate matter (PM), have been associated with adverse effects on human health, such as exacerbation of respiratory diseases and infections. High levels of PM in the air have recently been associated with increased morbidity and mortality of COVID-19 in some regions of the world.

Objective

To evaluate the effect of coarse particulate matter (PM10) on the inflammatory response and viral replication triggered by SARS-CoV-2 using in vitro models.

Methods

Peripheral blood mononuclear cells (PBMC) from healthy donors were treated with PM10 and subsequently exposed to SARS-CoV-2 (D614G strain, MOI 0.1). The production of pro-inflammatory cytokines and antiviral factors was quantified by qPCR and ELISA. In addition, using the A549 cell line, previously exposed to PM, the viral replication was evaluated by qPCR and plaque assay.

Results

SARS-CoV-2 stimulation increased the production of pro-inflammatory cytokines in PBMC, such as IL-1β, IL-6 and IL-8, but not antiviral factors. Likewise, PM10 induced significant production of IL-6 in PBMCs stimulated with SARS-CoV-2 and decreased the expression of OAS and PKR. Additionally, PM10 induces the release of IL-1β in PBMC exposed to SARS-CoV-2 as well as in a co-culture of epithelial cells and PBMCs. Finally, increased viral replication of SARS-CoV-2 was shown in response to PM10.

Conclusion

Exposure to coarse particulate matter increases the production of pro-inflammatory cytokines, such as IL-1β and IL-6, and may alter the expression of antiviral factors, which are relevant for the immune response to SARS-CoV-2. These results suggest that pre-exposure to air particulate matter could have a modest role in the higher production of cytokines and viral replication during COVID-19, which eventually could contribute to severe clinical outcomes.

A low-cost, label-free microfluidic scanning flow cytometer for high-accuracy quantification of size and refractive index of particles

Flow cytometers and fluorescence activated cells sorters (FCM/FACS) represent the gold standard for high-throughput single-cell analysis, but their usefulness for label-free applications is limited by the unreliability of forward and side scatter measurements. Scanning flow cytometers represent an appealing alternative, as they exploit measurements of the angle-resolved scattered light to provide accurate and quantitative estimates of cellular properties, but the requirements of current setups are unsuitable for integration with other lab-on-chip technologies or for point-of-care applications. Here we present the first microfluidic scanning flow cytometer (μSFC), able to achieve accurate angle-resolved scattering measurements within a standard polydimethylsiloxane microfluidic chip. The system exploits a low cost linearly variable optical density (OD) filter to reduce the dynamic range of the signal and to increase its signal-to-noise ratio. We present a performance comparison between the μSFC and commercial machines for the label free characterization of polymeric beads with different diameters and refractive indices. In contrast to FCM and FACS, the μSFC yields size estimates linearly correlated with nominal particle sizes (R² = 0.99) and quantitative estimates of particle refractive indices. The feasibility of using the μSFC for the characterization of biological samples is demonstrated by analyzing a population of monocytes identified based on the morphology of a peripheral blood mononuclear cells sample, which yields values in agreement with the literature. The proposed μSFC combines low setup requirements with high performance, and has great potential for integration within other lab-on-chip systems for multi-parametric cell analysis and for next-generation point-of-care diagnostic applications.

Pregnancy-specific responses to COVID-19 revealed by high-throughput proteomics of human plasma

BACKGROUND

Pregnant women are at greater risk of adverse outcomes, including mortality, as well as obstetrical complications resulting from COVID-19. However, pregnancy-specific changes that underlie such worsened outcomes remain unclear.

METHODS

Plasma samples were collected from pregnant women and non-pregnant individuals (male and female) with (n = 72 pregnant, 52 non-pregnant) and without (n = 29 pregnant, 41 non-pregnant) COVID-19. COVID-19 patients were grouped as asymptomatic, mild, moderate, severe, or critically ill according to NIH classifications. Proteomic profiling of 7,288 analytes corresponding to 6,596 unique protein targets was performed using the SOMAmer platform.

RESULTS

Herein, we profile the plasma proteome of pregnant and non-pregnant COVID-19 patients and controls and show alterations that display a dose-response relationship with disease severity; yet, such proteomic perturbations are dampened during pregnancy. In both pregnant and non-pregnant state, the proteome response induced by COVID-19 shows enrichment of mediators implicated in cytokine storm, endothelial dysfunction, and angiogenesis. Shared and pregnancy-specific proteomic changes are identified: pregnant women display a tailored response that may protect the conceptus from heightened inflammation, while non-pregnant individuals display a stronger response to repel infection. Furthermore, the plasma proteome can accurately identify COVID-19 patients, even when asymptomatic or with mild symptoms.

CONCLUSION

This study represents the most comprehensive characterization of the plasma proteome of pregnant and non-pregnant COVID-19 patients. Our findings emphasize the distinct immune modulation between the non-pregnant and pregnant states, providing insight into the pathogenesis of COVID-19 as well as a potential explanation for the more severe outcomes observed in pregnant women.

The roles of critical pro-inflammatory cytokines in the drive of cytokine storm during SARS-CoV-2 infection

In patients with severe COVID-19, acute respiratory distress syndrome (ARDS), multiple organ dysfunction syndrome (MODS), and even mortality can result from cytokine storm, which is a hyperinflammatory medical condition caused by the excessive and uncontrolled release of pro-inflammatory cytokines. High levels of numerous crucial pro-inflammatory cytokines, such as interleukin-1 (IL-1), IL-2, IL-6, tumor necrosis factor-α, interferon (IFN)-γ, IFN-induced protein 10 kDa, granulocyte-macrophage colony-stimulating factor, monocyte chemoattractant protein-1, and IL-10 and so on, have been found in severe COVID-19. They participate in cascade amplification pathways of pro-inflammatory responses through complex inflammatory networks. Here, we review the involvements of these critical inflammatory cytokines in SARS-CoV-2 infection and discuss their potential roles in triggering or regulating cytokine storm, which can help to understand the pathogenesis of severe COVID-19. So far, there is rarely effective therapeutic strategy for patients with cytokine storm besides using glucocorticoids, which is proved to result in fatal side effects. Clarifying the roles of key involved cytokines in the complex inflammatory network of cytokine storm will help to develop an ideal therapeutic intervention, such as neutralizing antibody of certain cytokine or inhibitor of some inflammatory signal pathways.

COVID-19 and autoimmune diseases: is there a connection?

PURPOSE OF REVIEW

This review summarizes current evidence on the potential link between severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and autoimmunity.

RECENT FINDINGS

Several viral infections are potential triggers of reactive and autoimmune diseases by inducing type II and type IV hypersensitivity reactions. Recent evidence demonstrated that SARS-CoV-2 infection is not an exception, triggering the production of tissue-specific autoantibodies during the acute phase of coronavirus disease 2019 (COVID-19) and leading to autoimmune diseases development as long-term complication. The significant immune dysregulation with cytokine storm and organ damage observed in patients with severe to critical COVID-19 is considered the main mechanism explaining the high levels of autoantibodies, which are also implicated in disease severity and the need for an intensive care assessment. Multisystem inflammatory syndrome in children (MIS-C) is an immune-mediated disease where the recent viral infection leads to systemic inflammation, as already observed in other reactive and autoimmune diseases.

SUMMARY

Autoimmunity may be a complication of SAR-CoV-2 infection. Understanding the pathogenesis of autoimmune manifestations in COVID-19 might help prevent the incidence or exacerbation of autoimmune disorders and design better and more efficient treatment strategies in children and adult populations.

DEL-1 suppression attenuates atherosclerosis by modulating macrophagic GSK-3β/CEBP-β signaling pathway

OBJECTIVE

The study aims to investigate the effect of developmental endothelial locus-1(DEL-1) expression in atherosclerotic plaque formation and its mechanism.

METHODS

Human left coronary arteries were collected to detect the DEL-1 expression. The ApoE-/- mice were used to establish the atherosclerosis mice model. The left coronary artery and mouse aorta were stained with HE, Oil Red O, and Movat staining. The DEL-1 levels, chemokines CXC chemokine receptor 4 (CXCR4) and its ligand stromal cell-derived factor-1alpha (SDF-1α), pathway protein glycogen synthase kinase-3β (GSK-3β), CCAAT enhanced binding protein β (C/EBPβ), and downstream inflammatory factors (C-X-C motif chemokine 2 (MIP-2or CXCL2), macrophage inflammatory protein-1alpha (MIP-1α or CCL3),Tumor Necrosis Factor alpha (TNF-α) were detected by immunoblotting and immunohistochemistry. Pearson correlation coefficient was used to analyze the correlation between DEL-1 gene expression and inflammatory factors in the lesion group and the correlation between DEL-1 gene expression and structure-related indexes.

RESULTS

Compared with Control group(CON), the intravascular plaque area was widened, accompanied by narrowed lumens. The number of plaque foam cells was significantly increased in the high fat and high cholesterol (AS group) or AAV9-eGFP group (P < 0.05). Compared to CON, the enhanced fluorescence intensity of DEL-1 with CD68 in the AS or AAV9-eGFP groups. Diminished fluorescence of DEL-1 with CD68 expression in AAV9-CXCR4 group compared to AS group or AAV9-eGFP group. The DEL-1 and its downstream proteins in AS group or AAV9-eGFP group were mainly accumulated in the macrophage cytoplasm. The DEL-1 expression level was significantly and positively correlated with plaque area, lumen stenosis, plaque foam cell count, TNFα, CXCL2, and CCL3 levels.

CONCLUSION

DEL-1 inhibition decreases macrophagic inflammatory factors involved in atherosclerotic plaque formation.

Immunosenescence, Inflammaging, and Frailty: Role of Myeloid Cells in Age-Related Diseases

The immune system is the central regulator of tissue homeostasis, ensuring tissue regeneration and protection against both pathogens and the neoformation of cancer cells. Its proper functioning requires homeostatic properties, which are maintained by an adequate balance of myeloid and lymphoid responses. Aging progressively undermines this ability and compromises the correct activation of immune responses, as well as the resolution of the inflammatory response. A subclinical syndrome of "homeostatic frailty" appears as a distinctive trait of the elderly, which predisposes to immune debilitation and chronic low-grade inflammation (inflammaging), causing the uncontrolled development of chronic and degenerative diseases. The innate immune compartment, in particular, undergoes to a sequela of age-dependent functional alterations, encompassing steps of myeloid progenitor differentiation and altered responses to endogenous and exogenous threats. Here, we will review the age-dependent evolution of myeloid populations, as well as their impact on frailty and diseases of the elderly.

Relevance of TMPRSS2, CD163/CD206, and CD33 in clinical severity stratification of COVID-19

Background

Approximately 13.8% and 6.1% of coronavirus disease 2019 (COVID-19) patients require hospitalization and sometimes intensive care unit (ICU) admission, respectively. There is no biomarker to predict which of these patients will develop an aggressive stage that we could improve their quality of life and healthcare management. Our main goal is to include new markers for the classification of COVID-19 patients.

Methods

Two tubes of peripheral blood were collected from a total of 66 (n = 34 mild and n = 32 severe) samples (mean age 52 years). Cytometry analysis was performed using a 15-parameter panel included in the Maxpar® Human Monocyte/Macrophage Phenotyping Panel Kit. Cytometry by time-of-flight mass spectrometry (CyTOF) panel was performed in combination with genetic analysis using TaqMan® probes for ACE2 (rs2285666), MX1 (rs469390), and TMPRSS2 (rs2070788) variants. GemStone™ and OMIQ software were used for cytometry analysis.

Results

The frequency of CD163+/CD206- population of transitional monocytes (T-Mo) was decreased in the mild group compared to that of the severe one, while T-Mo CD163-/CD206- were increased in the mild group compared to that of the severe one. In addition, we also found differences in CD11b expression in CD14dim monocytes in the severe group, with decreased levels in the female group (p = 0.0412). When comparing mild and severe disease, we also found that CD45- [p = 0.014; odds ratio (OR) = 0.286, 95% CI 0.104–0.787] and CD14dim/CD33+ (p = 0.014; OR = 0.286, 95% CI 0.104–0.787) monocytes were the best options as biomarkers to discriminate between these patient groups. CD33 was also indicated as a good biomarker for patient stratification by the analysis of GemStone™ software. Among genetic markers, we found that G carriers of TMPRSS2 (rs2070788) have an increased risk (p = 0.02; OR = 3.37, 95% CI 1.18–9.60) of severe COVID-19 compared to those with A/A genotype. This strength is further increased when combined with CD45-, T-Mo CD163+/CD206-, and C14dim/CD33+.

Conclusions

Here, we report the interesting role of TMPRSS2, CD45-, CD163/CD206, and CD33 in COVID-19 aggressiveness. This strength is reinforced for aggressiveness biomarkers when TMPRSS2 and CD45-, TMPRSS2 and CD163/CD206, and TMPRSS2 and CD14dim/CD33+ are combined.

The utility of systemic immune-inflammation index and systemic immune-response index in the prediction of adverse outcomes in pregnant women with coronavirus disease 2019: Analysis of 2649 cases

AIM

To investigate the association of systemic immune-inflammation index (SII) and systemic immune-response index (SIRI) with adverse perinatal outcomes in pregnant women with coronavirus disease 2019 (COVID-19).

METHODS

The cases were divided into (1) the Mild-moderate COVID-19 group (n = 2437) and (2) the Severe-critical COVID-19 group (n = 212). Clinical characteristics, perinatal outcomes, SII (neutrophilXplatelet/lymphocyte), and SIRI (neutrophilXmonocyte/lymphocyte) were compared between the groups. Afterward, SII and SIRI values were compared between subgroups based on pregnancy complications, neonatal intensive care unit (NICU) admission, and maternal mortality. A receiver operator characteristic analysis was performed for the determination of optimal cutoff values for SII and SIRI in the prediction of COVID-19 severity, pregnancy complications, NICU admission, and maternal mortality.

RESULTS

Both SII and SIRI were significantly higher in complicated cases (p < 0.05). Cutoff values in the prediction of severe-critical COVID-19 were 1309.8 for SII, and 2.3 for SIRI. For pregnancy complications, optimal cutoff values were 973.2 and 1.6. Cutoff values of 1045.4 and 1.8 were calculated for the prediction of NICU admission. Finally, cut-off values of 1224.2 and 2.4 were found in the prediction of maternal mortality.

CONCLUSION

SII and SIRI might be used in combination with other clinical findings in the prediction of poor perinatal outcomes.

Label-free microfluidic cell sorting and detection for rapid blood analysis

Blood tests are considered as standard clinical procedures to screen for markers of diseases and health conditions. However, the complex cellular background (>99.9% RBCs) and biomolecular composition often pose significant technical challenges for accurate blood analysis. An emerging approach for point-of-care blood diagnostics is utilizing "label-free" microfluidic technologies that rely on intrinsic cell properties for blood fractionation and disease detection without any antibody binding. A growing body of clinical evidence has also reported that cellular dysfunction and their biophysical phenotypes are complementary to standard hematoanalyzer analysis (complete blood count) and can provide a more comprehensive health profiling. In this review, we will summarize recent advances in microfluidic label-free separation of different blood cell components including circulating tumor cells, leukocytes, platelets and nanoscale extracellular vesicles. Label-free single cell analysis of intrinsic cell morphology, spectrochemical properties, dielectric parameters and biophysical characteristics as novel blood-based biomarkers will also be presented. Next, we will highlight research efforts that combine label-free microfluidics with machine learning approaches to enhance detection sensitivity and specificity in clinical studies, as well as innovative microfluidic solutions which are capable of fully integrated and label-free blood cell sorting and analysis. Lastly, we will envisage the current challenges and future outlook of label-free microfluidics platforms for high throughput multi-dimensional blood cell analysis to identify non-traditional circulating biomarkers for clinical diagnostics.

SARS-CoV-2 triggers pericyte-mediated cerebral capillary constriction

The SARS-CoV-2 receptor, ACE2, is found on pericytes, contractile cells enwrapping capillaries that regulate brain, heart and kidney blood flow. ACE2 converts vasoconstricting angiotensin II into vasodilating angiotensin-(1-7). In brain slices from hamster, which has an ACE2 sequence similar to human ACE2, angiotensin II evoked a small pericyte-mediated capillary constriction via AT1 receptors, but evoked a large constriction when the SARS-CoV-2 receptor binding domain (RBD, original Wuhan variant) was present. A mutated non-binding RBD did not potentiate constriction. A similar RBD-potentiated capillary constriction occurred in human cortical slices, and was evoked in hamster brain slices by pseudotyped virions expressing SARS-CoV-2 spike protein. This constriction reflects an RBD-induced decrease in the conversion of angiotensin II to angiotensin-(1-7) mediated by removal of ACE2 from the cell surface membrane and was mimicked by blocking ACE2. The clinically used drug losartan inhibited the RBD-potentiated constriction. Thus, AT1 receptor blockers could be protective in COVID-19 by preventing pericyte-mediated blood flow reductions in the brain, and perhaps the heart and kidney.

Value of new advanced hematological parameters in early prediction of severity of COVID-19

INTRODUCTION

COVID-19 usually presents with upper respiratory tract infection in varying severity which can lead to sepsis. Early prediction of sepsis may reduce mortality by timely interventions. The intended purpose of this study was to determine whether the advanced parameters like the extended inflammation parameters (EIPs) can predict prognosis and early progression to sepsis as a sequel of COVID-19 infection and can be used as a screening profile. Also, to evaluate the Intensive Care Infection Score (ICIS) and the COVID-19 prognostic score and validate the scores for our population.

METHODS

Prospective observational study of 50 reverse transcription- polymerase chain reaction (RT-PCR) proven admitted COVID-19 patients. The data assessed included complete blood counts (CBC) with EIP measurements, from Day 1 of admission to Day 10. The following groups were studied: noncritical (NC) and critical illness (CI) in COVID-19 positive cases, COVID negative sepsis and nonsepsis cases, and healthy volunteers for reference range.

RESULTS

The parameters that showed statistically significant higher mean in CI group compared to the NC group are reactive lymphocyte number and percentage (RE-LYMPH#, RE-LYMPH%), antibody synthesizing lymphocyte number and percentage (AS-LYMPH#, AS-LYMPH%), Reactive monocyte count and percentage (RE-MONO#, RE-MONO%/M), ICIS, COVID-19 prognostic score (p-value <0.05). The AUC confirmed the diagnostic accuracy of all these parameters. From the multivariate logistic regression, the significant risk factor was RE-LYMPH# with cut-off >0.10 (p value: 0.011).

CONCLUSION

The new EIP parameters, RE-MONO#, RE-MONO%/M, ICIS score and COVID-19 prognostic score are useful for early prediction of critical illness. AS-LYMPH is the most useful predictor of critical illness on multivariate analysis. RE-MONO# and RE-MONO%/M parameter are useful in distinguishing critical and noncritical non-COVID and COVID-19 patients.

Specialized pro-resolving lipid mediators regulate inflammatory macrophages: A paradigm shift from antibiotics to immunotherapy for mitigating COVID-19 pandemic

The most severe clinical manifestations of the horrifying COVID-19 disease, that claimed millions of lives during the pandemic time, were Acute respiratory distress syndrome (ARDS), Coagulopathies, septic shock leading eventually to death. ARDS was a consequence of Cytokine storm. The viral SARS-COV2infection lead to avalanche of cytokines and eicosanoids causing "cytokine storm" and "eicosanoid storm." Cytokine storm is one of the macrophage-derived inflammatory responses triggered by binding of virus particles to ACE2 receptors of alveolar macrophages, arise mainly due to over production of various pro-inflammatory mediators like cytokines, e.g., interleukin (IL)-1, IL-2, and tumor necrosis factor (TNF)- α, causing pulmonary edema, acute respiratory distress, and multi-organ failure. Cytokine storm was regarded as the predictor of severity of the disease and was deemed one of the causes of the high mortality rates due to the COVID-19. The basis of cytokine storm is imbalanced switching between an inflammation increasing - pro-inflammatory (M1) and an inflammation regulating-anti-inflammatory (M2) forms of alveolar macrophages which further deteriorates if opportunistic secondary bacterial infections prevail in the lungs. Lack of sufficient knowledge regarding the virus and its influence on co-morbidities, clinical treatment of the diseases included exorbitant use of antibiotics to mitigate secondary bacterial infections, which led to the unwarranted development of multidrug resistance (MDR) among the population across the globe. Antimicrobial resistance (AMR) needs to be addressed from various perspectives as it may deprive future generations of the basic health immunity. Specialized pro-resolving mediators (SPMs) are generated from the stereoselective enzymatic conversions of essential fatty acids that serve as immune resolvents in controlling acute inflammatory responses. SPMs facilitate the clearance of injured tissue and cell debris, the removal of pathogens, and augment the concentration of anti-inflammatory lipid mediators. The SPMs, e.g., lipoxins, protectins, and resolvins have been implicated in exerting inhibitory influence on with cytokine storm. Experimental evidence suggests that SPMS lower antibiotic requirement. Therefore, in this review potential roles of SPMs in enhancing macrophage polarization, triggering immunological functions, hastening inflammation resolution, subsiding cytokine storm and decreasing antibiotic requirement that can reduce AMR load are discussed.

Immune responses in mildly versus critically ill COVID-19 patients

The current coronavirus pandemic (COVID-19), caused by SARS-CoV-2, has had devastating effects on the global health and economic system. The cellular and molecular mediators of both the innate and adaptive immune systems are critical in controlling SARS-CoV-2 infections. However, dysregulated inflammatory responses and imbalanced adaptive immunity may contribute to tissue destruction and pathogenesis of the disease. Important mechanisms in severe forms of COVID-19 include overproduction of inflammatory cytokines, impairment of type I IFN response, overactivation of neutrophils and macrophages, decreased frequencies of DC cells, NK cells and ILCs, complement activation, lymphopenia, Th1 and Treg hypoactivation, Th2 and Th17 hyperactivation, as well as decreased clonal diversity and dysregulated B lymphocyte function. Given the relationship between disease severity and an imbalanced immune system, scientists have been led to manipulate the immune system as a therapeutic approach. For example, anti-cytokine, cell, and IVIG therapies have received attention in the treatment of severe COVID-19. In this review, the role of immunity in the development and progression of COVID-19 is discussed, focusing on molecular and cellular aspects of the immune system in mild vs. severe forms of the disease. Moreover, some immune- based therapeutic approaches to COVID-19 are being investigated. Understanding key processes involved in the disease progression is critical in developing therapeutic agents and optimizing related strategies.

Deciphering the role of monocyte and monocyte distribution width (MDW) in COVID-19: an updated systematic review and meta-analysis

The SARS-CoV-2 infection is characterized by both systemic and organ hyper-thromboinflammation, with a clinical course ranging from mild up-to critical systemic dysfunction and death. In patients with coronavirus disease 2019 (COVID-19) the monocyte/macrophage population is deeply involved as both trigger and target, assuming the value of useful diagnostic/prognostic marker of innate cellular immunity. Several studies correlated morphological and immunophenotypic alterations of circulating monocytes with clinical outcomes in COVID-19 patients, concluding that monocyte distribution width (MDW) may retain clinical value in stratifying the risk of disease worsening. Through an electronic search in Medline and Scopus we performed an updated literature review and meta-analysis aimed to explore the association between increased MDW levels and illness severity in COVID-19 patients, deciphering role(s) and function(s) of monocytes in the harmful network underlining SARS-CoV-2 infection. We found that significantly elevated MDW values were frequently present in COVID-19 patients who developed unfavorable clinical outcomes, compounded by a significant association between monocyte anisocytosis and SARS-CoV-2 outcomes. These findings suggest that blood MDW index and its scatter plot could represent useful routine laboratory tools for early identification of patients at higher risk of unfavorable COVID-19 and for monitoring the progression of viral infection, clinical outcomes, and therapeutic efficacy throughout hospitalization. According to this evidence, therapeutic decisions in patients with SARS-CoV-2 infection could benefit from monitoring MDW value, with administration of drugs limiting thrombo-inflammation due to monocyte hyper-activation in patients with severe/critical COVID-19 disease.

Genetic predisposition to blood cell indices in relation to severe COVID-19

Despite considerable variation in disease manifestations observed among coronavirus disease 2019 (COVID-19) patients infected with severe acute respiratory syndrome coronavirus 2, the risk factors predicting disease severity remain elusive. Recent studies suggest that peripheral blood cells play a pivotal role in COVID-19 pathogenesis. Here, we applied two-sample Mendelian randomization (MR) analyses to evaluate the potential causal contributions of blood cell indices variation to COVID-19 severity, using single-nucleotide polymorphisms (SNPs) as instrumental variables for 17 indices from the UK Biobank and INTERVAL genome-wide association studies (N = 173 480). Data on the associations between the SNPs and very severe respiratory confirmed COVID-19 were obtained from the COVID-19 host genetics initiative (N = 8779/1 001 875). We observed significant negative association between hematocrit (HCT; odds ratio, OR = 0.775, 95% confidence interval, CI = 0.635-0.915, p = 3.48E-04) or red blood cell count (OR = 0.830, 95% CI = 0.728-0.932, p = 2.19E-03) and very severe respiratory confirmed COVID-19, as well as nominal negative association of hemoglobin concentration (OR = 0.808, 95% CI = 0.673-0.943, p = 3.95E-03) with very severe respiratory confirmed COVID-19 (no effect survived multiple correction). In conclusion, the MR study supports a protective effect of high HCT and red blood cell count from very severe respiratory confirmed COVID-19, suggesting potential strategies to ameliorate/treat clinical conditions in very severe respiratory confirmed COVID-19.

Bystander effect of SARS-CoV-2 spike protein on human monocytic THP-1 cell activation and initiation of prothrombogenic stimulus representing severe COVID-19

BACKGROUND

Hypercoagulable state and thromboembolic complications are potential life-threatening events in COVID-19 patients. Our previous studies demonstrated that SARS-CoV-2 infection as well as viral spike protein expressed epithelial cells exhibit senescence with the release of inflammatory molecules, including alarmins.

FINDINGS

We observed extracellular alarmins present in the culture media of SARS-CoV-2 spike expressing cells activate human THP-1 monocytes to secrete pro-inflammatory cytokines to a significant level. The release of THP-1 derived pro-inflammatory cytokine signature correlated with the serum of acute COVID-19 patient, but not in post-COVID-19 state. Our study suggested that the alarmins secreted by spike expressing cells, initiated phagocytosis property of THP-1 cells. The phagocytic monocytes secreted complement component C5a and generated an autocrine signal via C5aR1 receptor. The C5a-C5aR1 signal induced formation of monocyte mediated extracellular trap resulted in the generation of a prothrombogenic stimulus with activating platelets and increased tissue factor activity. We also observed an enhanced C5a level, platelet activating factor, and high tissue factor activity in the serum of acute COVID-19 patients, but not in recovered patients.

CONCLUSION

Our present study demonstrated that SARS-CoV-2 spike protein modulates monocyte responses in a paracrine manner for prothrombogenic stimulus by the generation of C5a complement component.

Neutralizing monoclonal antibody in patients with coronavirus disease 2019: an observational study

BACKGROUND

Clinical data on patients infected with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) delta variant are limited, especially on clinical status after the application of antibody therapy.

METHODS

We evaluated clinical status in patients with the SARS-CoV-2 delta variant after BRII-196 and BRII-198 treatment in an infectious disease hospital in China. We collected data on clinical symptoms, laboratory tests, radiological characteristics, viral load, anti-SARS-CoV-2 antibodies, treatment, and outcome.

RESULTS

In mid-June 2021, 36 patients with delta variant infection were identified in Shenzhen. The most common symptoms at illness onset were cough (30.6%), fever (22.2%), myalgia (16.7%), and fatigue (16.7%). A small number of patients in this study had underlying diseases, including diabetes (5.6%) and hypertension (8.3%). The application of BRII-196 and BRII-198 can rapidly increase anti-SARS-CoV-2 IgG. The median peak IgG levels in the antibody treatment group were 32 times higher than those in the control group (P < 0.001). The time from admission to peak IgG levels in the antibody treatment group (mean: 10.2 days) was significantly shorter than that in the control group (mean: 17.7 days). Chest CT score dropped rapidly after antibody therapy, with a mean duration of 5.74 days from admission to peak levels.

CONCLUSION

The results of this study suggest that the application of BRII-196 and BRII-198 antibody therapy improved clinical status in patients with SARS-CoV-2 delta variant infection.

Peripheral blood cell anomalies in COVID-19 patients in the United Arab Emirates: A single-centered study

Introduction

In this study, we aimed at exploring the morphologic and quantitative abnormalities in the peripheral blood counts of coronavirus disease 2019 (COVID-19) patients.

Methods

A cohort of 131 COVID-19 patients was recruited at University Hospital Sharjah (UHS), UAE. Their peripheral blood smears were examined for morphological evaluation. Also, their clinical laboratory investigations and radiological findings were retrieved from the medical records. Our cohort consisted of 63 males and 68 females with an age of 63.6 ± 18.6 years.

Results

The presence of atypical lymphocytes was observed in around 80% of the recruited COVID-19 patients. Further, monocytes with toxic cytoplasmic vacuoles were identified in 55% of the cases. Neutrophil-associated changes, including pseudo-Pelger-Huët, bands, and long nuclear endoplasm, were reported in around 25-35% of the patients. RBCs associated changes such as microcytic and hypochromic RBCs, as well as targetoid, dacrocytes, ovalocytes, echinocytes/burr cells, and schistocytes, were described. According to disease severity, RBCs chromicity was found to be significantly different between stable and critical patients. COVID-19 patients with CO-RADS 5 showed a similar change in RBCs as well as a decrease in the neutrophils with hypogranular cytoplasm.

Conclusion

Peripheral blood smear assessment in COVID-19 patients could provide information about the disease state and pulmonary involvement.

Integrated Analysis of Bulk RNA-Seq and Single-Cell RNA-Seq Unravels the Influences of SARS-CoV-2 Infections to Cancer Patients

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a highly contagious and pathogenic coronavirus that emerged in late 2019 and caused a pandemic of respiratory illness termed as coronavirus disease 2019 (COVID-19). Cancer patients are more susceptible to SARS-CoV-2 infection. The treatment of cancer patients infected with SARS-CoV-2 is more complicated, and the patients are at risk of poor prognosis compared to other populations. Patients infected with SARS-CoV-2 are prone to rapid development of acute respiratory distress syndrome (ARDS) of which pulmonary fibrosis (PF) is considered a sequelae. Both ARDS and PF are factors that contribute to poor prognosis in COVID-19 patients. However, the molecular mechanisms among COVID-19, ARDS and PF in COVID-19 patients with cancer are not well-understood. In this study, the common differentially expressed genes (DEGs) between COVID-19 patients with and without cancer were identified. Based on the common DEGs, a series of analyses were performed, including Gene Ontology (GO) and pathway analysis, protein-protein interaction (PPI) network construction and hub gene extraction, transcription factor (TF)-DEG regulatory network construction, TF-DEG-miRNA coregulatory network construction and drug molecule identification. The candidate drug molecules (e.g., Tamibarotene CTD 00002527) obtained by this study might be helpful for effective therapeutic targets in COVID-19 patients with cancer. In addition, the common DEGs among ARDS, PF and COVID-19 patients with and without cancer are TNFSF10 and IFITM2. These two genes may serve as potential therapeutic targets in the treatment of COVID-19 patients with cancer. Changes in the expression levels of TNFSF10 and IFITM2 in CD14+/CD16+ monocytes may affect the immune response of COVID-19 patients. Specifically, changes in the expression level of TNFSF10 in monocytes can be considered as an immune signature in COVID-19 patients with hematologic cancer. Targeting N6-methyladenosine (m6A) pathways (e.g., METTL3/SERPINA1 axis) to restrict SARS-CoV-2 reproduction has therapeutic potential for COVID-19 patients.

The role of lung macrophages in acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is an acute and diffuse inflammatory lung injury in a short time, one of the common severe manifestations of the respiratory system that endangers human life and health. As an innate immune cell, macrophages play a key role in the inflammatory response. For a long time, the role of pulmonary macrophages in ARDS has tended to revolve around the polarization of M1/M2. However, with the development of single-cell RNA sequencing, fate mapping, metabolomics, and other new technologies, a deeper understanding of the development process, classification, and function of macrophages in the lung are acquired. Here, we discuss the function of pulmonary macrophages in ARDS from the two dimensions of anatomical location and cell origin and describe the effects of cell metabolism and intercellular interaction on the function of macrophages. Besides, we explore the treatments for targeting macrophages, such as enhancing macrophage phagocytosis, regulating macrophage recruitment, and macrophage death. Considering the differences in responsiveness of different research groups to these treatments and the tremendous dynamic changes in the gene expression of monocyte/macrophage, we discussed the possibility of characterizing the gene expression of monocyte/macrophage as the biomarkers. We hope that this review will provide new insight into pulmonary macrophage function and therapeutic targets of ARDS.