Porcine deltacoronavirus (PDCoV) modulates calcium influx to favor viral replication

New perspective of small-molecule antiviral drugs development for RNA viruses

High variability and adaptability of RNA viruses allows them to spread between humans and animals, causing large-scale infectious diseases which seriously threat human and animal health and social development. At present, AIDS, viral hepatitis and other viral diseases with high incidence and low cure rate are still spreading around the world. The outbreaks of Ebola, Zika, dengue and in particular of the global pandemic of COVID-19 have presented serious challenges to the global public health system. The development of highly effective and broad-spectrum antiviral drugs is a substantial and urgent research subject to deal with the current RNA virus infection and the possible new viral infections in the future. In recent years, with the rapid development of modern disciplines such as artificial intelligence technology, bioinformatics, molecular biology, and structural biology, some new strategies and targets for antivirals development have emerged. Here we review the main strategies and new targets for developing small-molecule antiviral drugs against RNA viruses through the analysis of the new drug development progress against several highly pathogenic RNA viruses, to provide clues for development of future antivirals.

Calmodulin-like 5 promotes PEDV replication by regulating late-endosome synthesis and innate immune response

The infection caused by porcine epidemic diarrhea virus (PEDV) is associated with high mortality in piglets worldwide. Host factors involved in the efficient replication of PEDV, however, remain largely unknown. Our recent proteomic study in the virus-host interaction network revealed a significant increase in the accumulation of CALML5 (EF-hand protein calmodulin-like 5) following PEDV infection. A further study unveiled a biphasic increase of CALML5 in 2 and 12 ​h after viral infection. Similar trends were observed in the intestines of piglets in the early and late stages of the PEDV challenge. Moreover, CALML5 depletion reduced PEDV mRNA and protein levels, leading to a one-order-of-magnitude decrease in virus titer. At the early stage of PEDV infection, CALML5 affected the endosomal trafficking pathway by regulating the expression of endosomal sorting complex related cellular proteins. CALML5 depletion also suppressed IFN-β and IL-6 production in the PEDV-infected cells, thereby indicating its involvement in negatively regulating the innate immune response. Our study reveals the biological function of CALML5 in the virology field and offers new insights into the PEDV-host cell interaction.

The European Union prioritises economics over health in the rollout of radiofrequency technologies

The fifth generation of radiofrequency communication, 5G, is currently being rolled out worldwide. Since September 2017, the EU 5G Appeal has been sent six times to the EU, requesting a moratorium on the rollout of 5G. This article reviews the 5G Appeal and the EU's subsequent replies, including the extensive cover letter sent to the EU in September 2021, requesting stricter guidelines for exposures to radiofrequency radiation (RFR). The Appeal notes the EU's internal conflict between its approach to a wireless technology-led future, and the need to protect the health and safety of its citizens. It critiques the reliance of the EU on the current guidelines given by the International Commission on Non-Ionizing Radiation Protection (ICNIRP), that consider only heating and no other health relevant biological effects from RFR. To counteract the ICNIRP position, the 2021 cover letter briefly presented recent research from the EU's own expert groups, from a large collection of European and other international studies, and from previous reviews of the effects of RFR on humans and the environment. The 5G Appeal asserts that the majority of scientific evidence points to biological effects, many with the potential for harm, occurring below the ICNIRP public limits. Evidence to establish this position is drawn from studies showing changes to neurotransmitters and receptors, damage to cells, proteins, DNA, sperm, the immune system, and human health, including cancer. The 2021 Appeal goes on to warn that 5G signals are likely to additionally alter the behaviour of oxygen and water molecules at the quantum level, unfold proteins, damage skin, and cause harm to insects, birds, frogs, plants and animals. Altogether, this evidence establishes a high priority for the European Union towards (i) replacing the current flawed guidelines with protective thresholds, and (ii) placing a moratorium on 5G deployment so as to (iii) allow industry-independent scientists the time needed to propose new health-protective guidelines. This 2021 Appeal's relevance becomes even more pressing in the context of the EU plans to roll out the sixth generation of wireless technologies, 6G, further adding to the known risks of RFR technology for humans and the environment. This all leads to an important question: Do EU decision makers have the right to ignore EU´s own directives by prioritising economic gain over human and environmental health?

Porcine deltacoronavirus enters ST cells by clathrin-mediated endocytosis and does not require Rab5, Rab7, or Rab11

IMPORTANCE

Porcine deltacoronavirus (PDCoV) is a newly emerged enteric virus threatening pig industries worldwide. Our previous work showed that PDCoV enters porcine kidney (PK-15) cells through a caveolae-dependent pathway, but the entry mechanism for PDCoV into swine testicle (ST) cells remains unclear. Mechanisms of virus entry can be different with different virus isolates and cell types. Here, we determined that PDCoV enters ST cells via clathrin-mediated endocytosis. Additionally, we found that PDCoV entry does not require Rab5, Rab7, or Rab11. These findings provide additional understanding of the entry mechanisms of PDCoV and possible antiviral targets.

Lung transcriptomics of K18-hACE2 mice highlights mechanisms and genes involved in the MVA-S vaccine-mediated immune response and protection against SARS-CoV-2 infection

Unravelling the molecular mechanism of COVID-19 vaccines through transcriptomic pathways involved in the host response to SARS-CoV-2 infection is key to understand how vaccines work, and for the development of optimized COVID-19 vaccines that can prevent the emergence of SARS-CoV-2 variants of concern (VoCs) and future outbreaks. In this study, we investigated the effects of vaccination with a modified vaccinia virus Ankara (MVA)-based vector expressing the full-length SARS-CoV-2 spike protein (MVA-S) on the lung transcriptome from susceptible K18-hACE2 mice after SARS-CoV-2 infection. One dose of MVA-S regulated genes related to viral infection control, inflammation processes, T-cell response, cytokine production and IFN-γ signalling. Down-regulation of Rhcg and Tnfsf18 genes post-vaccination with one and two doses of MVA-S may represent a mechanism for controlling infection immunity and vaccine-induced protection. One dose of MVA-S provided partial protection with a distinct lung transcriptomic profile to healthy animals, while two doses of MVA-S fully protected against infection with a transcriptomic profile comparable to that of non-vaccinated healthy animals. This suggests that the MVA-S booster generates a robust and rapid antigen-specific immune response preventing virus infection. Notably, down-regulation of Atf3 and Zbtb16 genes in mice vaccinated with two doses of MVA-S may contribute to vaccine control of innate immune system and inflammation processes in the lungs during SARS-CoV-2 infection. This study shows host transcriptomic mechanisms likely involved in the MVA-S vaccine-mediated immune response against SARS-CoV-2 infection, which could help in improving vaccine dose assessment and developing novel, well-optimized SARS-CoV-2 vaccine candidates against prevalent or emerging VoCs.

Porcine reproductive and respiratory syndrome virus infection triggers autophagy via ER stress-induced calcium signaling to facilitate virus replication

Calcium (Ca2+), a ubiquitous second messenger, plays a crucial role in many cellular functions. Viruses often hijack Ca2+ signaling to facilitate viral processes such as entry, replication, assembly, and egress. Here, we report that infection by the swine arterivirus, porcine reproductive and respiratory syndrome virus (PRRSV), induces dysregulated Ca2+ homeostasis, subsequently activating calmodulin-dependent protein kinase-II (CaMKII) mediated autophagy, and thus fueling viral replication. Mechanically, PRRSV infection induces endoplasmic reticulum (ER) stress and forms a closed ER–plasma membrane (PM) contacts, resulting the opening of store operated calcium entry (SOCE) channel and causing the ER to take up extracellular Ca2+, which is then released into the cytoplasm by inositol trisphosphate receptor (IP3R) channel. Importantly, pharmacological inhibition of ER stress or CaMKII mediated autophagy blocks PRRSV replication. Notably, we show that PRRSV protein Nsp2 plays a dominant role in the PRRSV induced ER stress and autophagy, interacting with stromal interaction molecule 1 (STIM1) and the 78 kDa glucose-regulated protein 78 (GRP78). The interplay between PRRSV and cellular calcium signaling provides a novel potential approach to develop antivirals and therapeutics for the disease outbreaks.

Parkinson's Disease, SARS-CoV-2, and Frailty: Is There a Vicious Cycle Related to Hypovitaminosis D?

The literature has long established the association between aging and frailty, with emerging evidence pointing to a relationship between frailty and SARS-CoV-2 contagion. The possible neurological consequences of SARS-CoV-2 infection, associated with physical and cognitive frailty, could lead to a worsening of Parkinson's disease (PD) in infected patients or-more rarely-to an increase in the Parkinsonian symptomatology. A possible link between those clinical pictures could be identified in vitamin D deficiency, while the whole process would appear to be associated with alterations in the microbiota-intestine-brain axis that fall within the α-Synuclein Origin site and Connectome (SOC) model, and allow for the identification of a body-first PD and a brain-first PD. The model of care for this condition must consider intrinsic and extrinsic variables so that care by a multidisciplinary team can be successfully predicted. A multidimensional screening protocol specifically designed to identify people at risk or in the early stages of the disease should begin with the investigation of indices of frailty and microbiota-intestine-brain axis alterations, with a new focus on cases of hypovitaminosis D.

The GABA and GABA-Receptor System in Inflammation, Anti-Tumor Immune Responses, and COVID-19

GABA and GABA_A-receptors (GABA_A-Rs) play major roles in neurodevelopment and neurotransmission in the central nervous system (CNS). There has been a growing appreciation that GABA_A-Rs are also present on most immune cells. Studies in the fields of autoimmune disease, cancer, parasitology, and virology have observed that GABA-R ligands have anti-inflammatory actions on T cells and antigen-presenting cells (APCs), while also enhancing regulatory T cell (Treg) responses and shifting APCs toward anti-inflammatory phenotypes. These actions have enabled GABA_A-R ligands to ameliorate autoimmune diseases, such as type 1 diabetes (T1D), multiple sclerosis (MS), and rheumatoid arthritis, as well as type 2 diabetes (T2D)-associated inflammation in preclinical models. Conversely, antagonism of GABA_A-R activity promotes the pro-inflammatory responses of T cells and APCs, enhancing anti-tumor responses and reducing tumor burden in models of solid tumors. Lung epithelial cells also express GABA-Rs, whose activation helps maintain fluid homeostasis and promote recovery from injury. The ability of GABA_A-R agonists to limit both excessive immune responses and lung epithelial cell injury may underlie recent findings that GABA_A-R agonists reduce the severity of disease in mice infected with highly lethal coronaviruses (SARS-CoV-2 and MHV-1). These observations suggest that GABA_A-R agonists may provide off-the-shelf therapies for COVID-19 caused by new SARS-CoV-2 variants, as well as novel beta-coronaviruses, which evade vaccine-induced immune responses and antiviral medications. We review these findings and further advance the notions that (1) immune cells possess GABA_A-Rs to limit inflammation in the CNS, and (2) this natural "braking system" on inflammatory responses may be pharmacologically engaged to slow the progression of autoimmune diseases, reduce the severity of COVID-19, and perhaps limit neuroinflammation associated with long COVID.

Telmisartan Nanosuspension for Inhaled Therapy of COVID-19 Lung Disease and Other Respiratory Infections

Vaccine hesitancy and the occurrence of elusive variants necessitate further treatment options for coronavirus disease 2019 (COVID-19). Accumulated evidence indicates that clinically used hypertensive drugs, angiotensin receptor blockers (ARBs), may benefit patients by mitigating disease severity and/or viral propagation. However, current clinical formulations administered orally pose systemic safety concerns and likely require a very high dose to achieve the desired therapeutic window in the lung. To address these limitations, we have developed a nanosuspension formulation of an ARB, entirely based on clinically approved materials, for inhaled treatment of COVID-19. We confirmed in vitro that our formulation exhibits physiological stability, inherent drug activity, and inhibitory effect against SARV-CoV-2 replication. Our formulation also demonstrates excellent lung pharmacokinetics and acceptable tolerability in rodents and/or nonhuman primates following direct administration into the lung. Thus, we are currently pursuing clinical development of our formulation for its uses in patients with COVID-19 or other respiratory infections.

Discovery of SARS-CoV-2 antiviral synergy between remdesivir and approved drugs in human lung cells

SARS coronavirus 2 (SARS-CoV-2) has caused an ongoing global pandemic with significant mortality and morbidity. At this time, the only FDA-approved therapeutic for COVID-19 is remdesivir, a broad-spectrum antiviral nucleoside analog. Efficacy is only moderate, and improved treatment strategies are urgently needed. To accomplish this goal, we devised a strategy to identify compounds that act synergistically with remdesivir in preventing SARS-CoV-2 replication. We conducted combinatorial high-throughput screening in the presence of submaximal remdesivir concentrations, using a human lung epithelial cell line infected with a clinical isolate of SARS-CoV-2. This identified 20 approved drugs that act synergistically with remdesivir, many with favorable pharmacokinetic and safety profiles. Strongest effects were observed with established antivirals, Hepatitis C virus nonstructural protein 5A (HCV NS5A) inhibitors velpatasvir and elbasvir. Combination with their partner drugs sofosbuvir and grazoprevir further increased efficacy, increasing remdesivir's apparent potency > 25-fold. We report that HCV NS5A inhibitors act on the SARS-CoV-2 exonuclease proofreader, providing a possible explanation for the synergy observed with nucleoside analog remdesivir. FDA-approved Hepatitis C therapeutics Epclusa® (velpatasvir/sofosbuvir) and Zepatier® (elbasvir/grazoprevir) could be further optimized to achieve potency and pharmacokinetic properties that support clinical evaluation in combination with remdesivir.

Porcine deltacoronavirus accessory protein NS7a possesses the functional characteristics of a viroporin

Viroporins are virus-encoded proteins that mediate ion channel (IC) activity, playing critical roles in virus entry, replication, pathogenesis, and immune evasion. Previous studies have shown that some coronavirus accessory proteins have viroporin-like activity. Porcine deltacoronavirus (PDCoV) is an emerging enteropathogenic coronavirus that encodes three accessory proteins, NS6, NS7, and NS7a. However, whether any of the PDCoV accessory proteins possess viroporin-like activity, and if so which, remains unknown. In this study, we analyzed the biochemical properties of the three PDCoV-encoded accessory proteins and found that NS7a could enhance the membrane permeability of both mammalian cells and Escherichia coli cells. Indirect immunofluorescence assay and co-immunoprecipitation assay results further indicated that NS7a is an integral membrane protein and can form homo-oligomers. A bioinformation analysis revealed that a putative viroporin domain (VPD) is located within amino acids 69-88 (aa69-88) of NS7a. Experiments with truncated mutants and alanine scanning mutagenesis additionally demonstrated that the amino acid residues 69FLR71 of NS7a are essential for its viroporin-like activity. Together, our findings are the first to demonstrate that PDCoV NS7a possesses viroporin-like activity and identify its key amino acid residues associated with viroporin-like activity.

A GABA-receptor agonist reduces pneumonitis severity, viral load, and death rate in SARS-CoV-2-infected mice

Gamma-aminobutyric acid (GABA) and GABA-receptors (GABA-Rs) form a major neurotransmitter system in the brain. GABA-Rs are also expressed by 1) cells of the innate and adaptive immune system and act to inhibit their inflammatory activities, and 2) lung epithelial cells and GABA-R agonists/potentiators have been observed to limit acute lung injuries. These biological properties suggest that GABA-R agonists may have potential for treating COVID-19. We previously reported that GABA-R agonist treatments protected mice from severe disease induced by infection with a lethal mouse coronavirus (MHV-1). Because MHV-1 targets different cellular receptors and is biologically distinct from SARS-CoV-2, we sought to test GABA therapy in K18-hACE2 mice which develop severe pneumonitis with high lethality following SARS-CoV-2 infection. We observed that GABA treatment initiated immediately after SARS-CoV-2 infection, or 2 days later near the peak of lung viral load, reduced pneumonitis severity and death rates in K18-hACE2 mice. GABA-treated mice had reduced lung viral loads and displayed shifts in their serum cytokine/chemokine levels that are associated with better outcomes in COVID-19 patients. Thus, GABA-R activation had multiple effects that are also desirable for the treatment of COVID-19. The protective effects of GABA against two very different beta coronaviruses (SARS-CoV-2 and MHV-1) suggest that it may provide a generalizable off-the-shelf therapy to help treat diseases induced by new SARS-CoV-2 variants and novel coronaviruses that evade immune responses and antiviral medications. GABA is inexpensive, safe for human use, and stable at room temperature, making it an attractive candidate for testing in clinical trials. We also discuss the potential of GABA-R agonists for limiting COVID-19-associated neuroinflammation.

Potential of targeting host cell calcium dynamics to curtail SARS-CoV-2 infection and COVID-19 pathogenesis

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) infection and associated coronavirus disease 2019 (COVID-19) has severely impacted human well-being. Although vaccination programs have helped in reducing the severity of the disease, drug regimens for clinical management of COVID-19 are not well recognized yet. It is therefore important to identify and characterize the molecular pathways that could be therapeutically targeted to halt SARS-CoV-2 infection and COVID-19 pathogenesis. SARS-CoV-2 hijacks host cell molecular machinery for its entry, replication and egress. Interestingly, SARS-CoV-2 interacts with host cell Calcium (Ca²⁺) handling proteins and perturbs Ca²⁺ homeostasis. We here systematically review the literature that demonstrates a critical role of host cell Ca²⁺ dynamics in regulating SARS-CoV-2 infection and COVID-19 pathogenesis. Further, we discuss recent studies, which have reported that SARS-CoV-2 acts on several organelle-specific Ca²⁺ transport mechanisms. Moreover, we deliberate upon the possibility of curtailing SARS-CoV-2 infection by targeting host cell Ca²⁺ handling machinery. Importantly, we delve into the clinical trials that are examining the efficacy of FDA-approved small molecules acting on Ca²⁺ handling machinery for the management of COVID-19. Although an important role of host cell Ca²⁺ signaling in driving SARS-CoV-2 infection has emerged, the underlying molecular mechanisms remain poorly understood. In future, it would be important to investigate in detail the signaling cascades that connect perturbed Ca²⁺ dynamics to SARS-CoV-2 infection.

Identification and integrated analysis of lncRNAs and miRNAs in IPEC-J2 cells provide novel insight into the regulation of the innate immune response by PDCoV infection

Background

Noncoding RNAs (ncRNAs), including microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), are pivotal regulators involved in the pathogenic mechanism of multiple coronaviruses. Porcine deltacoronavirus (PDCoV) has evolved multiple strategies to escape the innate immune response of host cells, but whether ncRNAs are involved in this process during PDCoV infection is still unknown.

Results

In this study, the expression profiles of miRNAs, lncRNAs and mRNAs in IPEC-J2 cells infected with PDCoV at 0, 12 and 24 hours postinfection (hpi) were identified through small RNA and RNA sequencing. The differentially expressed miRNAs (DEmiRNAs), lncRNAs (DElncRNAs) and mRNAs (DEmRNAs) were screened from the comparison group of IPEC-J2 cells at 0 and 12 hpi as well as the comparison group of IPEC-J2 cells at 12 and 24 hpi. The target genes of these DEncRNAs were predicted. The bioinformatics analysis of the target genes revealed multiple significantly enriched functions and pathways. Among them, the genes that were associated with innate immunity were specifically screened. The expression of innate immunity-related ncRNAs and mRNAs was validated by RT–qPCR. Competing endogenous RNA (ceRNA) regulatory networks among innate immunity-related ncRNAs and their target mRNAs were established. Moreover, we found that the replication of PDCoV was significantly inhibited by two innate immunity-related miRNAs, ssc-miR-30c-3p and ssc-miR-374b-3p, in IPEC-J2 cells.

Conclusions

This study provides a data platform to conduct studies of the pathogenic mechanism of PDCoV from a new perspective and will be helpful for further elucidation of the functional role of ncRNAs involved in PDCoV escaping the innate immune response.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08722-2.

Hypocalcemia in COVID-19: Prevalence, clinical significance and therapeutic implications

COVID-19 extra-pulmonary features include several endocrine manifestations and these are becoming strongly clinically relevant in patients affected influencing disease severity and outcomes.At the beginning of COVID-19 pandemic no population data on calcium levels in patients affected were available and in April 2020 a first case of severe acute hypocalcemia in an Italian patient with SARS-CoV-2 infection was reported. Subsequently, several studies reported hypocalcemia as a highly prevalent biochemical abnormality in COVID-19 patients with a marked negative influence on disease severity, biochemical inflammation and thrombotic markers, and mortality. Also a high prevalence of vertebral fractures with worse respiratory impairment in patients affected and a widespread vitamin D deficiency have been frequently observed, suggesting an emerging "Osteo-Metabolic Phenotype" in COVID-19.To date, several potential pathophysiological factors have been hypothesized to play a role in determining hypocalcemia in COVID-19 including calcium dependent viral mechanisms of action, high prevalence of hypovitaminosis D in general population, chronic and acute malnutrition during critical illness and high levels of unbound and unsaturated fatty acids in inflammatory responses.Since hypocalcemia is a frequent biochemical finding in hospitalized COVID-19 patients possibly predicting worse outcomes and leading to acute cardiovascular and neurological complications if severe, it is reasonable to assess, monitor and, if indicated, replace calcium at first patient hospital evaluation and during hospitalization.

Contributing Factors for Calcium Changes During Hospitalization in COVID-19: A Longitudinal Study

BACKGROUND

Hypocalcemia is highly prevalent in Coronavirus disease 2019 (COVID-19). There is limited evidence about the course and roles of different parameters in the occurrence of new or worsening hypocalcemia.

OBJECTIVES

This prospective longitudinal study was conducted on hospitalized COVID-19 patients in Qazvin, Iran, in 2021.

METHODS

Serum levels of calcium, albumin, parathormone (PTH), 25(OH)D (vitamin D), magnesium, and phosphate were assessed on the first day (time one), as well as fourth to sixth days (time two) of hospitalization. Paired t-test, McNemar's test, and multivariate logistic regression test were used to compare data at two times and evaluating the independent roles of different variables in the occurrence or worsening of hypocalcemia.

RESULTS

Out of a total of 123 participants, 102 patients completed the study. The mean serum calcium level significantly decreased from 8.32 ± 0.52 mg/dL to 8.02 ± 0.55 mg/dL at time two compared to time one (P < 0.001). Also, we witnessed new or worsening hypocalcemia at time two in 44 (55%) patients with normal serum calcium or mild hypocalcemia at time one (P < 0.001). The PTH level decreased from 42.17 ± 27.20 pg/mL to 31.28 ± 23.42 pg/mL (P < 0.001). The decrease in albumin and PTH levels was an independent significant factor in the occurrence or worsening of hypocalcemia at time two (OR = 1.27; 95% CI: 1.10 - 1.46; P = 0.001 for each 1 g/L decrement in albumin and OR = 1.29; 95% CI: 1.03 - 1.62; P = 0.026 for each 10 pg/mL decrement in PTH). Vitamin D deficiency or changes during hospitalization did not have a significant role in new or worsening hypocalcemia.

CONCLUSIONS

Decreased PTH secretion and hypoalbuminemia have significant roles in the occurrence of new or worsening hypocalcemia during hospitalization due to COVID-19.

An Updated Review of Porcine Deltacoronavirus in Terms of Prevalence, Pathogenicity, Pathogenesis and Antiviral Strategy

The recent experience with SARS-COV-2 has raised our alarm about the cross-species transmissibility of coronaviruses and the emergence of new coronaviruses. Knowledge of this family of viruses needs to be constantly updated. Porcine deltacoronavirus (PDCoV), a newly emerging member of the genus Deltacoronavirus in the family Coronaviridae, is a swine enteropathogen that causes diarrhea in pigs and may lead to death in severe cases. Since PDCoV diarrhea first broke out in the United States in early 2014, PDCoV has been detected in many countries, such as South Korea, Japan and China. More importantly, PDCoV can also infect species other than pigs, and infections have even been reported in children, highlighting its potential for cross-species transmission. A thorough and systematic knowledge of the epidemiology and pathogenesis of PDCoV will not only help us control PDCoV infection, but also enable us to discover the common cellular pathways and key factors of coronaviruses. In this review, we summarize the current knowledge on the prevalence, pathogenicity and infection dynamics, pathogenesis and immune evasion strategies of PDCoV. The existing anti-PDCoV strategies and corresponding mechanisms of PDCoV infection are also introduced, aiming to provide suggestions for the prevention and treatment of PDCoV and zoonotic diseases.

Retrospective case-control study to evaluate hypocalcaemia as a distinguishing feature of COVID-19 compared with other infective pneumonias and its association with disease severity

OBJECTIVES

To investigate whether calcium derangement was a specific feature of COVID-19 that distinguishes it from other infective pneumonias, and its association with disease severity.

DESIGN

A retrospective observational case-control study looking at serum calcium on adult patients with COVID-19, and community-acquired pneumonia (CAP) or viral pneumonia (VP).

SETTING

A district general hospital on the outskirts of London, UK.

PARTICIPANTS

506 patients with COVID-19, 95 patients with CAP and 152 patients with VP.

OUTCOME MEASURES

Baseline characteristics including hypocalcaemia in patients with COVID-19, CAP and VP were detailed. For patients with COVID-19, the impact of an abnormally low calcium level on the maximum level of hospital care, as a surrogate of COVID-19 severity, was evaluated. The primary outcome of maximal level of care was based on the WHO Clinical Progression Scale for COVID-19.

RESULTS

Hypocalcaemia was a specific and common clinical finding in patients with COVID-19 that distinguished it from other respiratory infections. Calcium levels were significantly lower in those with severe disease. Ordinal regression of risk estimates for categorised care levels showed that baseline hypocalcaemia was incrementally associated with OR of 2.33 (95% CI 1.5 to 3.61) for higher level of care, superior to other variables that have previously been shown to predict worse COVID-19 outcome. Serial calcium levels showed improvement by days 7-9 of admission, only in survivors of COVID-19.

CONCLUSION

Hypocalcaemia is specific to COVID-19 and may help distinguish it from other infective pneumonias. Hypocalcaemia may independently predict severe disease and warrants detailed prognostic investigation. The fact that decreased serum calcium is observed at the time of clinical presentation in COVID-19, but not other infective pneumonias, suggests that its early derangement is pathophysiological and may influence the deleterious evolution of this disease.

TRIAL REGISTRATION NUMBER

20/HRA/2344.

Gene mapping, gene-set analysis, and genomic prediction of postpartum blood calcium in Holstein cows

The onset of lactation results in a sudden irreversible loss of Ca for colostrum and milk synthesis. Some cows are unable to quickly adapt to this demand and succumb to clinical hypocalcemia, whereas a larger proportion of cows develop subclinical hypocalcemia that predisposes them to other peripartum diseases. The objective of this study was to perform a comprehensive genomic analysis of blood total Ca concentration in periparturient Holstein cows. We first performed a genomic scan and a subsequent gene-set analysis to identify candidate genes, biological pathways, and molecular mechanisms affecting postpartum Ca concentration. Then, we assessed the prediction of postpartum Ca concentration using genomic information. Data consisted of 7,691 records of plasma or serum concentrations of Ca measured in the first, second, and third day after parturition of 959 primiparous and 1,615 multiparous cows that calved between December 2015 and June 2020 in 2 dairy herds. All cows were genotyped with 80k SNPs. The statistical model included lactation (1 to 5+), calf category (male, females, twins), and day as fixed effects, and season-treatment-experiment, animal, and permanent environmental as random effects. Model predictive ability was evaluated using 10-fold cross-validation. Heritability and repeatability estimates were 0.083 (standard error = 0.017) and 0.444 (standard error = 0.028). The association mapping identified 2 major regions located on Bos taurus autosome (BTA)6 and BTA16 that explained 1.2% and 0.7% of additive genetic variance of Ca concentration, respectively. Interestingly, the region on BTA6 harbors the GC gene, which encodes the vitamin D binding protein, and the region on BTA16 harbors LRRC38, which is actively involved in K transport. Other sizable peaks were identified on BTA5, BTA2, BTA7, BTA14, and BTA9. These regions harbor genes associated with Ca channels (CACNA1S, CRACR2A), K channels (KCNK9), bone remodeling (LRP6), and milk production (SOCS2). The gene-set analysis revealed terms related to vitamin transport, calcium ion transport, calcium ion binding, and calcium signaling. Genomic predictions of phenotypic and genomic estimated breeding values of Ca concentration yielded predictive correlations up to 0.50 and 0.15, respectively. Overall, the present study contributes to a better understanding of the genetic basis of postpartum blood Ca concentration in Holstein cows. In addition, the findings may contribute to the development of novel selection and management strategies for reducing periparturient hypocalcemia in dairy cattle.

Porcine deltacoronavirus enters porcine IPI-2I intestinal epithelial cells via macropinocytosis and clathrin-mediated endocytosis dependent on pH and dynamin

Porcine deltacoronavirus (PDCoV), an emerging enteropathogenic coronavirus, causes serious diarrhoea in suckling piglets and has the potential for cross-species transmission. Although extensive studies have been reported on the biology and pathogenesis of PDCoV, the mechanisms by which PDCoV enters cells are not well characterized. In this study, we investigated how PDCoV enters IPI-2I cells, a line of porcine intestinal epithelial cells derived from pig ileum. Immunofluorescence assays, siRNA interference, specific pharmacological inhibitors and dominant-negative mutation results revealed that PDCoV entry into IPI-2I cells depended on clathrin, dynamin and a low-pH environment, but was independent of caveolae. Specific inhibition of phosphatidylinositol 3-kinase (PI3K) and the Na⁺/H⁺ exchanger (NHE) revealed that PDCoV entry involves macropinocytosis and depends on NHE rather than on PI3K. Additionally, Rab5 and Rab7, but not Rab11, regulated PDCoV endocytosis. This is the first study to demonstrate that PDCoV uses clathrin-mediated endocytosis and macropinocytosis as alternative endocytic pathways to enter porcine intestinal epithelial cells. We also discussed the entry pathways of PDCoV into other porcine cell lines. Our findings reveal the entry mechanisms of PDCoV and provide new insight into the PDCoV life cycle. IMPORTANCE An emerging enteropathogenic coronavirus, PDCoV has the potential for cross-species transmission, attracting extensive attenuation. Characterizing the detailed process of PDCoV entry into cells will deepen our understanding of the viral infection and pathogenesis, and provide the clues for therapeutic intervention against PDCoV. With the objective, we used complementary approaches to dissect the process in PDCoV-infected IPI-2I cells, a line of more physiologically relevant intestinal epithelial cells to PDCoV infection in vivo. Here, we demonstrate that PDCoV enters IPI-2I cells via macropinocytosis that does not require a specific receptor and clathrin-mediated endocytosis that requires a low-pH environment and dynamin, while a caveola-mediated endocytic pathway is used by PDCoV to enter swine testicular (ST) cells and porcine kidney (LLC-PK1) cells. These findings provide a molecular detail of the cellular entry pathways of PDCoV and may direct us toward novel antiviral drug development.

Traditional Chinese Medicine and Western Medicine Share Similar Philosophical Approaches to Fight COVID-19

Though disciplines in the same field, modern medicine (Western medicine) and traditional medicine (Traditional Chinese medicine, TCM) have been viewed as two distinct and divergent fields of medicine and thus differ greatly in their ways of diagnosing, treating, and preventing disease. In brief, Western medicine is primarily an evidence (laboratory)-based science, whereas TCM is more of a healing art based on the theory of Yin and Yang and the five elements in the human body. Therefore, whether TCM and Western medicine could use similar philosophical approaches to treat disease remains unclear. It is well-known that vitamin D enhances immune function and reduces the spread of some viruses. Indeed, recent evidence shows that the blood calcium level is strongly associated with COVID-19 severity, and vitamin D supplementation has shown favorable effects in viral infections. According to TCM theory, the pathogenesis of COVID-19 is closely associated with cold-dampness, an etiological factor in TCM. Cold-dampness could be attenuated by sun exposure and Wenyang herbs, both of which can restore the vitamin D level in the blood in Western medicine. Therefore, TCM and Western medicine could share similar philosophical methods to fight COVID-19 and understanding their philosophical theories could achieve the maximum benefits for treatment of COVID-19 and other diseases.

Functions of Coronavirus Accessory Proteins: Overview of the State of the Art

Coronavirus accessory proteins are a unique set of proteins whose genes are interspersed among or within the genes encoding structural proteins. Different coronavirus genera, or even different species within the same coronavirus genus, encode varying amounts of accessory proteins, leading to genus- or species-specificity. Though accessory proteins are dispensable for the replication of coronavirus in vitro, they play important roles in regulating innate immunity, viral proliferation, and pathogenicity. The function of accessory proteins on virus infection and pathogenesis is an area of particular interest. In this review, we summarize the current knowledge on accessory proteins of several representative coronaviruses that infect humans or animals, including the emerging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), with an emphasis on their roles in interaction between virus and host, mainly involving stress response, innate immunity, autophagy, and apoptosis. The cross-talking among these pathways is also discussed.

Mechanisms of Nausea and Vomiting: Current Knowledge and Recent Advances in Intracellular Emetic Signaling Systems

Nausea and vomiting are common gastrointestinal complaints that can be triggered by diverse emetic stimuli through central and/or peripheral nervous systems. Both nausea and vomiting are considered as defense mechanisms when threatening toxins/drugs/bacteria/viruses/fungi enter the body either via the enteral (e.g., the gastrointestinal tract) or parenteral routes, including the blood, skin, and respiratory systems. While vomiting is the act of forceful removal of gastrointestinal contents, nausea is believed to be a subjective sensation that is more difficult to study in nonhuman species. In this review, the authors discuss the anatomical structures, neurotransmitters/mediators, and corresponding receptors, as well as intracellular emetic signaling pathways involved in the processes of nausea and vomiting in diverse animal models as well as humans. While blockade of emetic receptors in the prevention of vomiting is fairly well understood, the potential of new classes of antiemetics altering postreceptor signal transduction mechanisms is currently evolving, which is also reviewed. Finally, future directions within the field will be discussed in terms of important questions that remain to be resolved and advances in technology that may help provide potential answers.

GABAA-Receptor Agonists Limit Pneumonitis and Death in Murine Coronavirus-Infected Mice

There is an urgent need for new approaches to limit the severity of coronavirus infections. Many cells of the immune system express receptors for the neurotransmitter γ-aminobutyric acid (GABA), and GABA-receptor (GABA-R) agonists have anti-inflammatory effects. Lung epithelial cells also express GABA-Rs, and GABA-R modulators have been shown to limit acute lung injuries. There is currently, however, no information on whether GABA-R agonists might impact the course of a viral infection. Here, we assessed whether clinically applicable GABA-R agonists could be repurposed for the treatment of a lethal coronavirus (murine hepatitis virus 1, MHV-1) infection in mice. We found that oral GABA administration before, or after the appearance of symptoms, very effectively limited MHV-1-induced pneumonitis, severe illness, and death. GABA treatment also reduced viral load in the lungs, suggesting that GABA-Rs may provide a new druggable target to limit coronavirus replication. Treatment with the GABA_A-R-specific agonist homotaurine, but not the GABA_B-R-specific agonist baclofen, significantly reduced the severity of pneumonitis and death rates in MHV-1-infected mice, indicating that the therapeutic effects were mediated primarily through GABA_A-Rs. Since GABA and homotaurine are safe for human consumption, they are promising candidates to help treat coronavirus infections.

Association of Antihypertensive Agents with the Risk of In-Hospital Death in Patients with Covid-19

PURPOSE

The role of angiotensin receptor blockers (ARB), angiotensin-converting enzyme inhibitors (ACEi), or other antihypertensive agents in the case of Covid-19 remains controversial. We aimed to investigate the association between antihypertensive agent exposure and in-hospital mortality in patients with Covid-19.

METHODS

We performed a retrospective multicenter cohort study on patients hospitalized between February 1 and May 15, 2020. All patients had been followed up for at least 30 days.

RESULTS

Of the 8078 hospitalized patients for Covid-19, 3686 (45.6%) had hypertension and were included in the study. In this population, the median age was 75.4 (IQR, 21.5) years and 57.1% were male. Overall in-hospital 30-day mortality was 23.1%. The main antihypertensive pharmacological classes used were calcium channel blockers (CCB) (n=1624, 44.1%), beta-blockers (n=1389, 37.7%), ARB (n=1154, 31.3%), and ACEi (n=998, 27.1%). The risk of mortality was lower in CCB (aOR, 0.83 [0.70-0.99]) and beta-blockers (aOR, 0.80 [0.67-0.95]) users and non-significant in ARB (aOR, 0.88 [0.72-1.06]) and ACEi (aOR, 0.83 [0.68-1.02]) users, compared to non-users. These results remain consistent for patients receiving CCB, beta-blocker, or ARB as monotherapies.

CONCLUSION

This large multicenter retrospective of Covid-19 patients with hypertension found a reduced mortality among CCB and beta-blockers users, suggesting a putative protective effect. Our findings did not show any association between the use of renin-angiotensin-aldosterone system inhibitors and the risk of in-hospital death. Although they need to be confirmed in further studies, these results support the continuation of antihypertensive agents in patients with Covid-19, in line with the current guidelines.

Virus-Mediated Cell-Cell Fusion

Cell-cell fusion between eukaryotic cells is a general process involved in many physiological and pathological conditions, including infections by bacteria, parasites, and viruses. As obligate intracellular pathogens, viruses use intracellular machineries and pathways for efficient replication in their host target cells. Interestingly, certain viruses, and, more especially, enveloped viruses belonging to different viral families and including human pathogens, can mediate cell-cell fusion between infected cells and neighboring non-infected cells. Depending of the cellular environment and tissue organization, this virus-mediated cell-cell fusion leads to the merge of membrane and cytoplasm contents and formation of multinucleated cells, also called syncytia, that can express high amount of viral antigens in tissues and organs of infected hosts. This ability of some viruses to trigger cell-cell fusion between infected cells as virus-donor cells and surrounding non-infected target cells is mainly related to virus-encoded fusion proteins, known as viral fusogens displaying high fusogenic properties, and expressed at the cell surface of the virus-donor cells. Virus-induced cell-cell fusion is then mediated by interactions of these viral fusion proteins with surface molecules or receptors involved in virus entry and expressed on neighboring non-infected cells. Thus, the goal of this review is to give an overview of the different animal virus families, with a more special focus on human pathogens, that can trigger cell-cell fusion.

Conflicts over calcium and the treatment of COVID-19

Several recent studies have provided evidence that use of calcium channel blockers (CCBs), especially amlodipine and nifedipine, can reduce mortality from coronavirus disease 2019 (COVID-19). Moreover, hypocalcemia (a reduced level of serum ionized calcium) has been shown to be strongly positively associated with COVID-19 severity. Both effectiveness of CCBs as antiviral therapy, and positive associations of hypocalcemia with mortality, have been demonstrated for many other viruses as well. We evaluate these findings in the contexts of virus–host evolutionary conflicts over calcium metabolism, and hypocalcemia as either pathology, viral manipulation or host defence against pathogens. Considerable evidence supports the hypothesis that hypocalcemia represents a host defence. Indeed, hypocalcemia may exert antiviral effects in a similar manner as do CCBs, through interference with calcium metabolism in virus-infected cells. Prospective clinical studies that address the efficacy of CCBs and hypocalcemia should provide novel insights into the pathogenicity and treatment of COVID-19 and other viruses.

Is there a link between vitamin D status, SARS-CoV-2 infection risk and COVID-19 severity?

The outbreak of COVID-19 emerged in December 2019 rapidly spread across the globe and has become pandemic. Little is known about the protective factors of this infection, which is equally distributed between genders and different ages while severe and poor prognosis cases are strongly associated to old males and the presence of comorbidities. Thus, preventive measures aiming at reducing the number of infection and/or their severity are strongly needed. Vitamin D has got great attention and has been claimed as potentially protective against the infection since it may be associated with immunocompetence, inflammation, aging, and those diseases involved in determining the outcomes of COVID-19. This narrative review aims at collecting the literature available on the involvement of the vitamin D status in the pathogenesis of COVID-19 and the putative utility of vitamin D supplementation in the therapeutics. It emerges that a poor vitamin D status seems to associate with an increased risk of infection whereas age, gender and comorbidities seem to play a more important role in COVID-19 severity and mortality. While randomized control trials are needed to better inquire into this topic, vitamin D supplementation may be useful beside its potential effects on SARS-CoV-2 infection and COVID-19.

GABA administration prevents severe illness and death following coronavirus infection in mice

There is an urgent need for new treatments to prevent and ameliorate severe illness and death induced by SARS-CoV-2 infection in COVID-19 patients. The coronavirus mouse hepatitis virus (MHV)-1 causes pneumonitis in mice which shares many pathological characteristics with human SARS-CoV infection. Previous studies have shown that the amino acid gamma-aminobutyric acid (GABA) has anti-inflammatory effects. We tested whether oral treatment with GABA could modulate the MHV-1 induced pneumonitis in susceptible A/J mice. As expected, MHV-1-inoculated control mice became severely ill (as measured by weight loss, clinical score, and the ratio of lung weight to body weight) and >60% of them succumbed to the infection. In contrast, mice that received GABA immediately after MHV-1 inoculation became only mildly ill and all of them recovered. When GABA treatment was initiated after the appearance of illness (3 days post-MHV-1 infection), we again observed that GABA treatment significantly reduced the severity of illness and greatly increased the frequency of recovery. Therefore, the engagement of GABA receptors (GABA-Rs) prevented the MHV-1 infection-induced severe pneumonitis and death in mice. Given that GABA-R agonists, like GABA and homotaurine, are safe for human consumption, stable, inexpensive, and available worldwide, they are promising candidates to help prevent severe illness stemming from SARS-CoV-2 infection and other coronavirus strains.