Urine Soluble CD163 Is a Promising Biomarker for the Diagnosis and Evaluation of Lupus Nephritis.

Introduction: Urine-soluble CD163 (usCD163) is released from alternatively activated macrophages involved in the resolution of inflammation in glomeruli and plays an important role in glomerulonephritis. This study explored the role of usCD163 in patients with systemic lupus erythematosus (SLE). Materials and Methods: usCD163 concentrations were measured cross-sectionally in 261 SLE patients in Taiwan. Clinical and laboratory data were collected, and SLE disease activity scores were calculated to assess the correlation with usCD163. Results: SLE patients with high usCD163 levels tended to be younger, with a higher hospital admission rate, higher prednisolone dose, lower estimated glomerular filtration rate, higher urine protein creatinine ratio (UPCR), more pyuria and hematuria, higher levels of inflammatory markers, higher rates of anemia, neutropenia, and lymphopenia, lower complement 3 (C3) levels, higher anti-double-stranded DNA antibody (anti-dsDNA Ab) levels, and higher disease activity scores (p < 0.05). usCD163 levels were significantly higher in patients with active lupus nephritis (LN) than in those with extrarenal or inactive SLE and correlated with UPCR, disease activity, and anti-dsDNA Ab levels. SLE patients with high usCD163 levels tended to have a higher chronic kidney disease stage. Discussion and conclusion: The usCD163 level correlates with the severity of LN and disease activity in renal SLE.

ACE2 protein expression in lung tissues of severe COVID-19 infection.

Angiotensin-converting enzyme 2 (ACE2) is a key host protein by which severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) enters and multiplies within cells. The level of ACE2 expression in the lung is hypothesised to correlate with an increased risk of severe infection and complications in COrona VIrus Disease 2019 (COVID-19). To test this hypothesis, we compared the protein expression status of ACE2 by immunohistochemistry (IHC) in post-mortem lung samples of patients who died of severe COVID-19 and lung samples obtained from non-COVID-19 patients for other indications. IHC for CD61 and CD163 was performed for the assessment of platelet-rich microthrombi and macrophages, respectively. IHC for SARS-CoV-2 viral antigen was also performed. In a total of 55, 44 COVID-19 post-mortem lung samples were tested for ACE2, 36 for CD163, and 26 for CD61, compared to 15 non-covid 19 control lung sections. Quantification of immunostaining, random sampling, and correlation analysis were used to substantiate the morphologic findings. Our results show that ACE2 protein expression was significantly higher in COVID-19 post-mortem lung tissues than in controls, regardless of sample size. Histomorphology in COVID-19 lungs showed diffuse alveolar damage (DAD), acute bronchopneumonia, and acute lung injury with SARS-CoV-2 viral protein detected in a subset of cases. ACE2 expression levels were positively correlated with increased expression levels of CD61 and CD163. In conclusion, our results show significantly higher ACE2 protein expression in severe COVID-19 disease, correlating with increased macrophage infiltration and microthrombi, suggesting a pathobiological role in disease severity.

Up-regulated serum levels of soluble CD25 and soluble CD163 in pediatric patients with SARS-CoV-2.

Similar to hemophagocytic lymphohistiocytosis (HLH), some patients with SARS-CoV-2 have cytokine storm. Serum soluble interleukin-2 receptor (sCD25) and soluble CD163 (sCD163) are potential diagnostic biomarkers for HLH that help in guiding its treatment. This study was the first to investigate serum sCD25 and sCD163 levels in SARS-CoV-2. Serum sCD25 and sCD163 were measured by ELISA in 29 patients with SARS-CoV-2, aged between 2 months and 16 years (13 had COVID-19 and 16 had multisystem inflammatory syndrome in children (MIS-C)), in comparison to 30 age- and sex-matched healthy control children and 10 patients with HLH. Levels of these markers were re-measured in 21 patients with SARS-CoV-2 who were followed up 3 months after recovery. Patients with SARS-CoV-2 had significantly higher serum sCD25 and sCD163 than healthy control children (P < 0.001). SARS-CoV-2 patients had significantly higher sCD25 than patients with HLH (P < 0.05). Serum sCD25 was a good differentiating marker between patients with SARS-CoV-2 and HLH. Although there was a significant decrease of serum sCD25 and sCD163 of the 21 SARS-CoV-2 patients who were followed up, these levels were still significantly higher than the healthy controls levels (P < 0.001).  Conclusion: Serum sCD25 and sCD163 levels were up-regulated in SARS-CoV-2 patients. Serum sCD25 was a good differentiating marker between SARS-CoV-2 and HLH. This initial report requires further studies, on large scales, to investigate the relationship between SARS-CoV-2 and both sCD25 and sCD163, including the disease severity and outcome. The therapeutic role of sCD25 and sCD163 antagonists should also be studied in SARS-CoV-2 patients. What is Known: • Similar to hemophagocytic lymphohistiocytosis (HLH), some patients with COVID-19 have cytokine storm due to excessive pro-inflammatory host response. • Serum soluble interleukin-2 receptor (sCD25) and soluble CD163 (sCD163) are potential diagnostic biomarkers for HLH. Monitoring of serum sCD25 and sCD163 levels can also help in guiding the treatment. What is New: • Serum sCD25 and sCD163 levels are up-regulated in patients with COVID-19, including patients presenting with multisystem inflammatory syndrome in children (MIS-C). • Serum sCD25 is a good differentiating marker between SARS-CoV-2 and HLH.

RBD conjugate vaccine with a built-in TLR1/2 agonist is highly immunogenic against SARS-CoV-2 and variants of concern.

The coronavirus 2019 (COVID-19) pandemic is causing serious impacts in the world, and safe and effective vaccines and medicines are the best methods to combat the disease. The receptor-binding domain (RBD) of the SARS-CoV-2 spike protein plays a key role in interacting with the angiotensin-converting enzyme 2 (ACE2) receptor, and is regarded as an important target of vaccines. Herein, we constructed the adjuvant-protein conjugate Pam3CSK4-RBD as a vaccine candidate, in which the N-terminal of the RBD was site-selectively oxidized by transamination and conjugated with the TLR1/2 agonist Pam3CSK4. This demonstrated that the conjugation of Pam3CSK4 significantly enhanced the anti-RBD antibody response and cellular response. In addition, sera from the Pam3CSK4-RBD immunized group efficiently inhibited the binding of the RBD to ACE2 and protected cells from SARS-CoV-2 and four variants of concern (alpha, beta, gamma and delta), indicating that this adjuvant strategy could be one of the effective means for protein vaccine development.

SARS-CoV-2 infection triggers profibrotic macrophage responses and lung fibrosis.

COVID-19-induced "acute respiratory distress syndrome" (ARDS) is associated with prolonged respiratory failure and high mortality, but the mechanistic basis of lung injury remains incompletely understood. Here, we analyze pulmonary immune responses and lung pathology in two cohorts of patients with COVID-19 ARDS using functional single-cell genomics, immunohistology, and electron microscopy. We describe an accumulation of CD163-expressing monocyte-derived macrophages that acquired a profibrotic transcriptional phenotype during COVID-19 ARDS. Gene set enrichment and computational data integration revealed a significant similarity between COVID-19-associated macrophages and profibrotic macrophage populations identified in idiopathic pulmonary fibrosis. COVID-19 ARDS was associated with clinical, radiographic, histopathological, and ultrastructural hallmarks of pulmonary fibrosis. Exposure of human monocytes to SARS-CoV-2, but not influenza A virus or viral RNA analogs, was sufficient to induce a similar profibrotic phenotype in vitro. In conclusion, we demonstrate that SARS-CoV-2 triggers profibrotic macrophage responses and pronounced fibroproliferative ARDS.

Cell death and pathological findings of the spleen in COVID-19 patients.

The coronavirus disease 2019(COVID-19) is recognized as systemic inflammatory response syndrome. It was demonstrated that a rapid increase of cytokines in the serum of COVID-19 patients is associated with the severity of disease. However, the mechanisms of the cytokine release are not clear. By using immunofluorescence staining we found that the number of CD11b positive immune cells including macrophages in the spleens of died COVID-19 patients, was significantly higher than that of the control patients. The incidence of apoptosis as measured by two apoptotic markers, TUNEL and cleaved caspase-3, in COVID-19 patients' spleen cells is higher than that in control patients. By double immunostaining CD11b or CD68 and SARS-CoV-2 spike protein, it was found that up to 67% of these immune cells were positive for spike protein, suggesting that viral infection might be associated with apoptosis in these cells. Besides, we also stained the autophagy-related molecules (p-Akt、p62 and BCL-2) in spleen tissues, the results showed that the number of positive cells was significantly higher in COVID-19 group. And compared with non-COVID-19 patients, autophagy may be inhibited in COVID-19 patients. Our research suggest that SARS-CoV-2 may result in a higher rate of apoptosis and a lower rate of autophagy of immune cells in the spleen of COVID-19 patients. These discoveries may increase our understanding of the pathogenesis of COVID-19.

Hypopharyngeal Ulcers in COVID-19: Histopathological and Virological Analyses - A Case Report.

In coronavirus disease 2019 (COVID-19), ulcerative lesions have been episodically reported in various segments of the gastrointestinal (GI) tract, including the oral cavity, oropharynx, esophagus, stomach and bowel. In this report, we describe an autopsy case of a COVID-19 patient who showed two undiagnosed ulcers at the level of the anterior and posterior walls of the hypopharynx. Molecular testing of viruses involved in pharyngeal ulcers demonstrated the presence of severe acute respiratory syndrome - coronavirus type 2 (SARS-CoV-2) RNA, together with herpes simplex virus 1 DNA. Histopathologic analysis demonstrated full-thickness lympho-monocytic infiltration (mainly composed of CD68-positive cells), with hemorrhagic foci and necrosis of both the mucosal layer and deep skeletal muscle fibers. Fibrin and platelet microthrombi were also found. Cytological signs of HSV-1 induced damage were not found. Cells expressing SARS-CoV-2 spike subunit 1 were immunohistochemically identified in the inflammatory infiltrations. Immunohistochemistry for HSV1 showed general negativity for inflammatory infiltration, although in the presence of some positive cells. Thus, histopathological, immunohistochemical and molecular findings supported a direct role by SARS-CoV-2 in producing local ulcerative damage, although a possible contributory role by HSV-1 reactivation cannot be excluded. From a clinical perspective, this autopsy report of two undiagnosed lesions put the question if ulcers along the GI tract could be more common (but frequently neglected) in COVID-19 patients.

COVID-19 myocarditis: quantitative analysis of the inflammatory infiltrate and a proposed mechanism.

COVID-19 has a significant effect upon the cardiovascular system. While a number of different cardiovascular histopathologies have been described at post-mortem examination, the incidence of typical viral myocarditis in COVID-19 positive patients appears very low [1-3]. In this study, we further characterize and quantify the inflammatory cell infiltrate in a COVID-19 study cohort and compare the findings to both an age and disease matched control cohort and a cohort of patients diagnosed with typical inflammatory myocarditis. All study and control cohorts had 1 or more of the comorbidities most commonly associated with severe disease (hypertension, type II diabetes, obesity, or known cardiovascular disease). The results demonstrate a skewed distribution of the number of CD68+ cells in COVID-19 hearts, with upper quantiles showing a significant increase as compared to both matched control hearts, and those with myocarditis. In contrast, hearts from typical inflammatory myocarditis contained increased numbers of CD4+, and CD8+ cells compared to both COVID-19 and control cohorts. In conclusion, the presence of an increased number of CD68+ cells suggests that COVID-19 may incite a form of myocarditis different from typical viral myocarditis, and associated with diffusely infiltrative cells of monocytes/macrophage lineage.

Increased sCD163 and sCD14 Plasmatic Levels and Depletion of Peripheral Blood Pro-Inflammatory Monocytes, Myeloid and Plasmacytoid Dendritic Cells in Patients With Severe COVID-19 Pneumonia.

Background: Emerging evidence argues that monocytes, circulating innate immune cells, are principal players in COVID-19 pneumonia. The study aimed to investigate the role of soluble (s)CD163 and sCD14 plasmatic levels in predicting disease severity and characterize peripheral blood monocytes and dendritic cells (DCs), in patients with COVID-19 pneumonia (COVID-19 subjects). Methods: On admission, in COVID-19 subjects sCD163 and sCD14 plasmatic levels, and peripheral blood monocyte and DC subsets were compared to healthy donors (HDs). According to clinical outcome, COVID-19 subjects were divided into ARDS and non-ARDS groups. Results: Compared to HDs, COVID-19 subjects showed higher sCD163 (p<0.0001) and sCD14 (p<0.0001) plasmatic levels. We observed higher sCD163 plasmatic levels in the ARDS group compared to the non-ARDS one (p=0.002). The cut-off for sCD163 plasmatic level greater than 2032 ng/ml was predictive of disease severity (AUC: 0.6786, p=0.0022; sensitivity 56.7% [CI: 44.1-68.4] specificity 73.8% [CI: 58.9-84.7]). Positive correlation between plasmatic levels of sCD163, LDH and IL-6 and between plasmatic levels of sCD14, D-dimer and ferritin were found. Compared to HDs, COVID-19 subjects showed lower percentages of non-classical (p=0.0012) and intermediate monocytes (p=0.0447), slanDCs (p<0.0001), myeloid DCs (mDCs, p<0.0001), and plasmacytoid DCs (pDCs, p=0.0014). Compared to the non-ARDS group, the ARDS group showed lower percentages of non-classical monocytes (p=0.0006), mDCs (p=0.0346), and pDCs (p=0.0492). Conclusions: The increase in sCD163 and sCD14 plasmatic levels, observed on hospital admission in COVID-19 subjects, especially in those who developed ARDS, and the correlations of these monocyte/macrophage activation markers with typical inflammatory markers of COVID-19 pneumonia, underline their potential use to assess the risk of progression of the disease. In an early stage of the disease, the assessment of sCD163 plasmatic levels could have clinical utility in predicting the severity of COVID-19 pneumonia.

Do COVID-19 Infections Result in a Different Form of Secondary Hemophagocytic Lymphohistiocytosis.

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in significant morbidity and mortality across the world, with no current effective treatments available. Recent studies suggest the possibility of a cytokine storm associated with severe COVID-19, similar to the biochemical profile seen in hemophagocytic lymphohistiocytosis (HLH), raising the question of possible benefits that could be derived from targeted immunosuppression in severe COVID-19 patients. We reviewed the literature regarding the diagnosis and features of HLH, particularly secondary HLH, and aimed to identify gaps in the literature to truly clarify the existence of a COVID-19 associated HLH. Diagnostic criteria such as HScore or HLH-2004 may have suboptimal performance in identifying COVID-19 HLH-like presentations, and criteria such as soluble CD163, NK cell activity, or other novel biomarkers may be more useful in identifying this entity.

An open label trial of anakinra to prevent respiratory failure in COVID-19.

Background: It was studied if early suPAR-guided anakinra treatment can prevent severe respiratory failure (SRF) of COVID-19. Methods: A total of 130 patients with suPAR ≥6 ng/ml were assigned to subcutaneous anakinra 100 mg once daily for 10 days. Primary outcome was SRF incidence by day 14 defined as any respiratory ratio below 150 mmHg necessitating mechanical or non-invasive ventilation. Main secondary outcomes were 30-day mortality and inflammatory mediators; 28-day WHO-CPS was explored. Propensity-matched standard-of care comparators were studied. Results: 22.3% with anakinra treatment and 59.2% comparators (hazard ratio, 0.30; 95% CI, 0.20-0.46) progressed into SRF; 30-day mortality was 11.5% and 22.3% respectively (hazard ratio 0.49; 95% CI 0.25-0.97). Anakinra was associated with decrease in circulating interleukin (IL)-6, sCD163 and sIL2-R; IL-10/IL-6 ratio on day 7 was inversely associated with SOFA score; patients were allocated to less severe WHO-CPS strata. Conclusions: Early suPAR-guided anakinra decreased SRF and restored the pro-/anti-inflammatory balance. Funding: This study was funded by the Hellenic Institute for the Study of Sepsis, Technomar Shipping Inc, Swedish Orphan Biovitrum, and the Horizon 2020 Framework Programme. Clinical trial number: NCT04357366.

People infected with the SARS-CoV-2 virus, which causes COVID-19, can develop severe respiratory failure and require a ventilator to keep breathing, but this does not happen to every infected individual. Measuring a blood protein called suPAR (soluble urokinase plasminogen activator receptor) may help identify patients at the greatest risk of developing severe respiratory failure and requiring a ventilator. Previous investigations have suggested that measuring suPAR can identify pneumonia patients at highest risk for developing respiratory failure. The protein can be measured by taking a blood sample, and its levels provide a snapshot of how the body's immune system is reacting to infection, and of how it may respond to treatment. Anakinra is a drug that forms part of a class of medications called interleukin antagonists. It is commonly prescribed alone or in combination with other medications to reduce pain and swelling associated with rheumatoid arthritis. Kyriazopoulou et al. investigated whether treating COVID-19 patients who had developed pneumonia with anakinra could prevent the use of a ventilator and lower the risk of death. The findings show that treating COVID-19 patients with an injection of 100 milligrams of anakinra for ten days may be an effective approach because the drug combats inflammation. Kyriazopoulou et al. examined various markers of the immune response and discovered that anakinra was able to improve immune function, protecting a significant number of patients from going on a ventilator. The drug was also found to be safe and cause no significant adverse side effects. Administering anakinra decreased of the risk of progression into severe respiratory failure by 70%, and reduced death rates significantly. These results suggest that it may be beneficial to use suPAR as an early biomarker for identifying those individuals at highest risk for severe respiratory failure, and then treat them with anakinra. While the findings are promising, they must be validated in larger studies.

Increased Serum Levels of sCD14 and sCD163 Indicate a Preponderant Role for Monocytes in COVID-19 Immunopathology.

Background: Emerging evidence indicates a potential role for monocytes in COVID-19 immunopathology. We investigated two soluble markers of monocyte activation, sCD14 and sCD163, in COVID-19 patients, with the aim of characterizing their potential role in monocyte-macrophage disease immunopathology. To the best of our knowledge, this is the first study of its kind. Methods: Fifty-nine SARS-Cov-2 positive hospitalized patients, classified according to ICU or non-ICU admission requirement, were prospectively recruited and analyzed by ELISA for levels of sCD14 and sCD163, along with other laboratory parameters, and compared to a healthy control group. Results: sCD14 and sCD163 levels were significantly higher among COVID-19 patients, independently of ICU admission requirement, compared to the control group. We found a significant correlation between sCD14 levels and other inflammatory markers, particularly Interleukin-6, in the non-ICU patients group. sCD163 showed a moderate positive correlation with the time lapsed from admission to sampling, independently of severity group. Treatment with corticoids showed an interference with sCD14 levels, whereas hydroxychloroquine and tocilizumab did not. Conclusions: Monocyte-macrophage activation markers are increased and correlate with other inflammatory markers in SARS-Cov-2 infection, in association to hospital admission. These data suggest a preponderant role for monocyte-macrophage activation in the development of immunopathology of COVID-19 patients.

Elevated plasma sTIM-3 levels in patients with severe COVID-19.

BACKGROUND: The pathogenesis of coronavirus disease 2019 (COVID-19) is still incompletely understood, but it seems to involve immune activation and immune dysregulation. OBJECTIVE: We examined the parameters of activation of different leukocyte subsets in COVID-19-infected patients in relation to disease severity. METHODS: We analyzed plasma levels of myeloperoxidase (a marker of neutrophil activation), soluble (s) CD25 (sCD25) and soluble T-cell immunoglobulin mucin domain-3 (sTIM-3) (markers of T-cell activation and exhaustion), and sCD14 and sCD163 (markers of monocyte/macrophage activation) in 39 COVID-19-infected patients at hospital admission and 2 additional times during the first 10 days in relation to their need for intensive care unit (ICU) treatment. RESULTS: Our major findings were as follows: (1) severe clinical outcome (ICU treatment) was associated with high plasma levels of sTIM-3 and myeloperoxidase, suggesting activated and potentially exhausted T cells and activated neutrophils, respectively; (2) in contrast, sCD14 and sCD163 showed no association with need for ICU treatment; and (3) levels of sCD25, sTIM-3, and myeloperoxidase were inversely correlated with degree of respiratory failure, as assessed by the ratio of Pao2 to fraction of inspired oxygen, and were positively correlated with the cardiac marker N-terminal pro-B-type natriuretic peptide. CONCLUSION: Our findings suggest that neutrophil activation and, in particular, activated T cells may play an important role in the pathogenesis of COVID-19 infection, suggesting that T-cell-targeted treatment options and downregulation of neutrophil activation could be of importance in this disorder.

Association of Clonal Hematopoiesis of Indeterminate Potential With Inflammatory Gene Expression in Patients With Severe Degenerative Aortic Valve Stenosis or Chronic Postischemic Heart Failure.

Importance: Cytokine release syndrome is a complication of coronavirus disease 2019. Clinically, advanced age and cardiovascular comorbidities are the most important risk factors. Objective: To determine whether clonal hematopoiesis of indeterminate potential (CHIP), an age-associated condition with excess cardiovascular risk defined as the presence of an expanded, mutated somatic blood cell clone in persons without other hematological abnormalities, may be associated with an inflammatory gene expression sensitizing monocytes to aggravated immune responses. Design, Setting, and Participants: This hypothesis-generating diagnostic study examined a cohort of patients with severe degenerative aortic valve stenosis or chronic postinfarction heart failure, as well as age-matched healthy control participants. Single-cell RNA sequencing and analyses of circulating peripheral monocytes was done between 2017 and 2019 to assess the transcriptome of circulating monocytes. Exposures: Severe degenerative aortic valve stenosis or chronic postinfarction heart failure. Main Outcomes and Measures: CHIP-driver sequence variations in monocytes with a proinflammatory signature of genes involved in cytokine release syndrome. Results: The study included 8 patients with severe degenerative aortic valve stenosis, 6 with chronic postinfarction heart failure, and 3 healthy control participants. Their mean age was 75.7 (range, 54-89) years, and 6 were women. Mean CHIP-driver gene variant allele frequency was 4.2% (range, 2.5%-6.9%) for DNMT3A and 14.3% (range, 2.6%-37.4%) for TET2. Participants with DNMT3A or TET2 CHIP-driver sequence variations displayed increased expression of interleukin 1ß (no CHIP-driver sequence variations, 1.6217 normalized Unique Molecular Identifiers [nUMI]; DNMT3A, 5.3956 nUMI; P < .001; TET2, 10.8216 nUMI; P < .001), the interleukin 6 receptor (no CHIP-driver sequence variations, 0.5386 nUMI; DNMT3A, 0.9162 nUMI; P < .001;TET2, 0.5738 nUMI; P < .001), as well as the NLRP3 inflammasome complex (no CHIP-driver sequence variations, 0.4797 nUMI; DNMT3A, 0.9961 nUMI; P < .001; TET2, 1.2189 nUMI; P < .001), plus upregulation of CD163 (no CHIP-driver sequence variations, 0.5239 nUMI; DNMT3A, 1.4722 nUMI; P < .001; TET2, 1.0684 nUMI; P < .001), a cellular receptor capable of mediating infection, macrophage activation syndrome, and other genes involved in cytokine response syndrome. Gene ontology term analyses of regulated genes revealed that the most significantly upregulated genes encode for leukocyte-activation and interleukin-signaling pathways in monocytes of individuals with DNMT3A (myeloid leukocyte activation: log[Q value], -50.1986; log P value, -54.5177; regulation of cytokine production: log[Q value], -21.0264; log P value, -24.1993; signaling by interleukins: log[Q value], -18.0710: log P value, -21.1597) or TET2 CHIP-driver sequence variations (immune response: log[Q value], -36.3673; log P value, -40.6864; regulation of cytokine production: log[Q value], -13.1733; log P value, -16.3463; signaling by interleukins: log[Q value], -12.6547: log P value, -15.7977). Conclusions and Relevance: Monocytes of individuals who carry CHIP-driver sequence variations and have cardiovascular disease appear to be primed for excessive inflammatory responses. Further studies are warranted to address potential adverse outcomes of coronavirus disease 2019 in patients with CHIP-driver sequence variations.

CD163 and pAPN double-knockout pigs are resistant to PRRSV and TGEV and exhibit decreased susceptibility to PDCoV while maintaining normal production performance.

Porcine reproductive and respiratory syndrome virus (PRRSV) and transmissible gastroenteritis virus (TGEV) are two highly infectious and lethal viruses causing major economic losses to pig production. Here, we report generation of double-gene-knockout (DKO) pigs harboring edited knockout alleles for known receptor proteins CD163 and pAPN and show that DKO pigs are completely resistant to genotype 2 PRRSV and TGEV. We found no differences in meat-production or reproductive-performance traits between wild-type and DKO pigs, but detected increased iron in DKO muscle. Additional infection challenge experiments showed that DKO pigs exhibited decreased susceptibility to porcine deltacoronavirus (PDCoV), thus offering unprecedented in vivo evidence of pAPN as one of PDCoV receptors. Beyond showing that multiple gene edits can be combined in a livestock animal to achieve simultaneous resistance to two major viruses, our study introduces a valuable model for investigating infection mechanisms of porcine pathogenic viruses that exploit pAPN or CD163 for entry.

Pig epidemics are the biggest threat to the pork industry. In 2019 alone, hundreds of billions of dollars worldwide were lost due to various pig diseases, many of them caused by viruses. The porcine reproductive and respiratory virus (PRRS virus for short), for instance, leads to reproductive disorders such as stillbirths and premature labor. Two coronaviruses ­ the transmissible gastroenteritis virus (or TGEV) and the porcine delta coronavirus ­ cause deadly diarrhea and could potentially cross over into humans. Unfortunately, there are still no safe and effective methods to prevent or control these pig illnesses, but growing disease-resistant pigs could reduce both financial and animal losses. Traditionally, breeding pigs to have a particular trait is a slow process that can take many years. But with gene editing technology, it is possible to change or remove specific genes in a single generation of animals. When viruses infect a host, they use certain proteins on the surface of the host's cells to find their inside: the PRRS virus relies a protein called CD163, and TGEV uses pAPN. Xu, Zhou, Mu et al. used gene editing technology to delete the genes that encode the CD163 and pAPN proteins in pigs. When the animals were infected with PRRS virus or TGEV, the non-edited pigs got sick but the gene-edited animals remained healthy. Unexpectedly, pigs without CD163 and pAPN also coped better with porcine delta coronavirus infections, suggesting that CD163 and pAPN may also help this coronavirus infect cells. Finally, the gene-edited pigs reproduced and produced meat as well as the control pigs. These experiments show that gene editing can be a powerful technology for producing animals with desirable traits. The gene-edited pigs also provide new knowledge about how porcine viruses infect pigs, and may offer a starting point to breed disease-resistant animals on a larger scale.

Common determinants of severe Covid-19 infection are explicable by SARS-CoV-2 secreted glycoprotein interaction with the CD33-related Siglecs, Siglec-3 and Siglec-5/14.

SARS-CoV-2 interaction with the ACE-2 receptor cannot alone explain the demography and remarkable variation in clinical progression of Covid-19 infection. Unlike SARS-CoV, the cause of SARS, several SARS-CoV-2 spike glycans contain sialic acid residues. In contrast to the SARS secreted glycoprotein (SGP), SARS-CoV-2 SGP are thus potential ligands for Sialic acid-binding Siglecs on host immune cells, known to regulate immune function. Such SARS-CoV-2 glycoproteins would contribute to immune deviation. CD33-related Siglecs are important immune regulators. Siglec-5 and -14 are paired receptors with opposed actions on the NLRP3 inflammasome, which is critical in early viral clearance. SGP binding in persons of Siglec-14 null genotype (30-70% in Black, Asian and Minority Ethnic (BAME) persons, 10% in North Europeans) would induce unopposed inhibitory signalling, causing viral persistence through inflammasome inhibition. Siglec-3 (CD33) and Siglec-5 are expressed on CD33 myeloid derived suppressor cells (CD33 MDSC). Immunosuppressive CD33 MDSC populations are increased in all groups at risk of severe Covid-19 infection. CD33 expression is increased in persons with the CD33 rs3865444 CC allele, associated with Alzheimer's disease, who would thus show enhanced susceptibility. Viral SGP ligation of CD33, potentially in conjunction with Siglec-5, would promote expansion of CD33 MDSC cells, as occurs in cancers but at much greater scale. CD33 is expressed on CNS microglia, potentially activated by SGP penetration through the porous cribriform plate to cause anosmia. Genotyping of severe or fatal Covid-19 cases can confirm or refute this pathophysiological mechanism. Early data have confirmed extremely high-level increase of CD33 MDSC numbers in severe Covid-19 infection, consistent with the proposed mechanism.

Autopsy findings from the first known death from Severe Acute Respiratory Syndrome SARS-CoV-2 in Spain.

The new coronavirus SARS-CoV-2, first identified in Wuhan, China in December, 2019, can cause Severe Acute Respiratory Syndrome (SARS) with massive alveolar damage and progressive respiratory failure. We present the relevant autopsy findings of the first patient known to have died from COVID19 pneumonia in Spain, carried out on the 14th of February, 2020, in our hospital (Hospital Arnau de Vilanova-Lliria, Valencia). Histological examination revealed typical changes of diffuse alveolar damage (DAD) in both the exudative and proliferative phase of acute lung injury. Intra-alveolar multinucleated giant cells, smudge cells and vascular thrombosis were present. The diagnosis was confirmed by reverse real-time PCR assay on a throat swab sample taken during the patient's admission. The positive result was reported fifteen days subsequent to autopsy.