Tissue distribution of ACE2 protein, the functional receptor for SARS coronavirus. A first step in understanding SARS pathogenesis

Pathogenesis and virulence of coronavirus disease: Comparative pathology of animal models for COVID-19

Animal models that can replicate clinical and pathologic features of severe human coronavirus infections have been instrumental in the development of novel vaccines and therapeutics. The goal of this review is to summarize our current understanding of the pathogenesis of coronavirus disease 2019 (COVID-19) and the pathologic features that can be observed in several currently available animal models. Knowledge gained from studying these animal models of SARS-CoV-2 infection can help inform appropriate model selection for disease modelling as well as for vaccine and therapeutic developments.

The lethal K18-hACE2 knock-in mouse model mimicking the severe pneumonia of COVID-19 is practicable for antiviral development

Animal models of COVID-19 facilitate the development of vaccines and antivirals against SARS-CoV-2. The efficacy of antivirals or vaccines may differ in different animal models with varied degrees of disease. Here, we introduce a mouse model expressing human angiotensin-converting enzyme 2 (ACE2). In this model, ACE2 with the human cytokeratin 18 promoter was knocked into the Hipp11 locus of C57BL/6J mouse by CRISPR - Cas9 (K18-hACE2 KI). Upon intranasal inoculation with high (3 × 105 PFU) or low (2.5 × 102 PFU) dose of SARS-CoV-2 wildtype (WT), Delta, Omicron BA.1, or Omicron BA.2 variants, all mice showed obvious infection symptoms, including weight loss, high viral loads in the lung, and interstitial pneumonia. 100% lethality was observed in K18-hACE2 KI mice infected by variants with a delay of endpoint for Delta and BA.1, and a significantly attenuated pathogenicity was observed for BA.2. The pneumonia of infected mice was accompanied by the infiltration of neutrophils and pulmonary fibrosis in the lung. Compared with K18-hACE2 Tg mice and HFH4-hACE2 Tg mice, K18-hACE2 KI mice are more susceptible to SARS-CoV-2. In the antivirals test, REGN10933 and Remdesivir had limited antiviral efficacies in K18-hACE2 KI mice upon the challenge of SARS-CoV-2 infections, while Nirmatrelvir, monoclonal antibody 4G4, and mRNA vaccines potently protected the mice from death. Our results suggest that the K18-hACE2 KI mouse model is lethal and stable for SARS-CoV-2 infection, and is practicable and stringent to antiviral development.

Proton pump inhibitors and gastrointestinal symptoms among patients with COVID-19 infection

INTRODUCTION

The administration of proton pump inhibitors (PPIs) is anticipated to elevate an individual's susceptibility to enteric infections as a result of altering the gut flora. The influence of PPIs on the clinical manifestation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is still uncertain. This study aims to investigate the impact of PPI usage on the clinical manifestation of COVID-19, namely its gastrointestinal symptoms.

METHODS

This is a cross-sectional cohort study involving COVID-19 patients. Patients were interviewed using a predesigned questionnaire that asked about their demographics, clinical manifestations of COVID-19 infection, and the extent and type of PPIs in use. PPI usage was confirmed by reviewing patients' electronic medical records. The primary outcome was to establish any association between the use of PPI and the symptoms and clinical presentation of COVID-19.

RESULTS

Out of a total of 254 participants, 69 (27.2%) were considered PPI users. Patients who were on PPI medications reported a significantly lower rate of myalgia (27.5% vs 51.9%; p = 0.0006) and heartburn (5.7% vs 15.6%; p = 0.03) but had a significantly higher rate of abdominal pain (27.5% vs 13.5%; p = 0.001) and diarrhoea (28.9% vs 14.5%, p = 0.02) when compared to those who were not using PPIs. Patients on PPIs were also shown to have significantly higher odds of developing diarrhoea (OR 2.0, 95% CI: 1.08 to 3.93, p = 0.02) and abdominal pain (OR 2.0, 95% CI: 1.22 to 3.93, p = 0.03), but a lower risk of developing myalgia (OR 0.5, 95% CI: 0.3 to 0.9, p = 0.02) when compared to non-PPI users.

CONCLUSION

This study shows that the use of PPIs could impact COVID-19 clinical presentation toward more gastrointestinal manifestations. Further studies investigating the link between other acid suppression medications and COVID-19 manifestations and severity should be carried out.

Hepatic angiotensin-converting enzyme 2 expression in metabolic dysfunction-associated steatotic liver disease and in patients with fatal COVID-19

BACKGROUND

Metabolic dysfunction-associated steatotic liver disease (MASLD), characterised by hepatic lipid accumulation, causes inflammation and oxidative stress accompanied by cell damage and fibrosis. Liver injury (LI) is also frequently reported in patients hospitalised with coronavirus disease 2019 (COVID-19), while pre-existing MASLD increases the risk of LI and the development of COVID-19-associated cholangiopathy. Mechanisms of injury at the cellular level remain unclear, but it may be significant that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which causes COVID-19, uses angiotensin-converting expression enzyme 2 (ACE2), a key regulator of the ‘anti-inflammatory’ arm of the renin-angiotensin system, for viral attachment and host cell invasion.

AIM

To determine if hepatic ACE2 levels are altered during progression of MASLD and in patients who died with severe COVID-19.

METHODS

ACE2 protein levels and localisation, and histological fibrosis and lipid droplet accumulation as markers of MASLD were determined in formalin-fixed liver tissue sections across the MASLD pathological spectrum (isolated hepatocellular steatosis, metabolic dysfunction-associated steatohepatitis (MASH) +/- fibrosis, end-stage cirrhosis) and in post-mortem tissues from patients who had died with severe COVID-19, using ACE2 immunohistochemistry and haematoxylin and eosin and picrosirius red staining of total collagen and lipid droplet areas, followed by quantification using machine learning-based image pixel classifiers.

RESULTS

ACE2 staining is primarily intracellular and concentrated in the cytoplasm of centrilobular hepatocytes and apical membranes of bile duct cholangiocytes. Strikingly, ACE2 protein levels are elevated in non-fibrotic MASH compared to healthy controls but not in the progression to MASH with fibrosis and in cirrhosis. ACE2 protein levels and histological fibrosis are not associated, but ACE2 and liver lipid droplet content are significantly correlated across the MASLD spectrum. Hepatic ACE2 levels are also increased in COVID-19 patients, especially those showing evidence of LI, but are not correlated with the presence of SARS-CoV-2 virus in the liver. However, there is a clear association between the hepatic lipid droplet content and the presence of the virus, suggesting a possible functional link.

CONCLUSION

Hepatic ACE2 levels were elevated in nonfibrotic MASH and COVID-19 patients with LI, while lipid accumulation may promote intra-hepatic SARS-CoV-2 replication, accelerating MASLD progression and COVID-19-mediated liver damage.

Organophosphate pesticide exposure and risk of SARS-CoV-2 infection

Several studies have reported immune modulation by organophosphate (OP) pesticides, but the relationship between OP exposure and SARS-CoV-2 infection is yet to be studied. We used two different measures of OP pesticide exposure (urinary biomarkers (N = 154) and residential proximity to OP applications (N = 292)) to examine the association of early-childhood and lifetime exposure to OPs and risk of infection of SARS-CoV-2 using antibody data. Our study population consisted of young adults (ages 18-21 years) from the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) Study, a longitudinal cohort of families from a California agricultural region. Urinary biomarkers reflected exposure from in utero to age 5 years. Residential proximity reflected exposures between in utero and age 16 years. SARS-CoV-2 antibodies in blood samples collected between June 2022 and January 2023 were detected via two enzyme linked immunosorbent assays, each designed to bind to different SARS-CoV-2 antigens. We performed logistic regression for each measure of pesticide exposure, adjusting for covariates from demographic data and self-reported questionnaire data. We found increased odds of SARS-CoV-2 infection among participants with higher urinary biomarkers of OPs in utero (OR = 1.94, 95% CI: 0.71, 5,58) and from age 0-5 (OR = 1.90, 95% CI: 0.54, 6.95).

SARS-CoV-2-induced disruption of a vascular bed in a microphysiological system caused by type-I interferon from bronchial organoids

Blood vessels show various COVID-19-related conditions including thrombosis and cytokine propagation. Existing in vitro blood vessel models cannot represent the consequent changes in the vascular structure or determine the initial infection site, making it difficult to evaluate how epithelial and endothelial tissues are damaged. Here, we developed a microphysiological system (MPS) that co-culture the bronchial organoids and the vascular bed to analyze infection site and interactions. In this system, virus-infected organoids caused damage in vascular structure. However, vasculature was not damaged or infected when the virus was directly introduced to vascular bed. The knockout of interferon-related genes and inhibition of the JAK/STAT pathway reduced the vascular damage, indicating the protective effect of interferon response suppression. The results demonstrate selective infection of bronchial epithelial cells and vascular damage by cytokines and also indicate the applicability of MPS to investigate how the infection influences vascular structure and functions.

Endothelial dysfunction and cardiovascular risk in post-COVID-19 patients after 6- and 12-months SARS-CoV-2 infection

INTRODUCTION

SARS-CoV-2 infection causes severe endothelial damage, an essential step for cardiovascular complications. Endothelial-colony forming cells (ECFCs) act as a biomarker of vascular damage but their role in SARS-CoV-2 remain unclear. The aim of this study was to assess whether the number of ECFCs and angiogenic biomarkers remained altered after 6 and 12-months post-infection and whether this imbalance correlated with the presence of long-COVID syndrome and other biological parameters measured.

METHODS

Seventy-two patients were recruited at different time-points after overcoming COVID-19 and thirty-one healthy controls. All subjects were matched for age, gender, BMI, and comorbidities. ECFCs were obtained from peripheral blood and cultured with specific conditions.

RESULTS

The results confirm the presence of a long-term sequela in post-COVID-19 patients, with an abnormal increase in ECFC production compared to controls (82.8% vs. 48.4%, P < 0.01) that is maintained up to 6-months (87.0% vs. 48.4%, P < 0.01) and 12-months post-infection (85.0% vs. 48.4%, P < 0.01). Interestingly, post-COVID-19 patients showed a significant downregulation of angiogenesis-related proteins compared to controls indicating a clear endothelial injury. Troponin, NT-proBNP and ferritin levels, markers of cardiovascular risk and inflammation, remained elevated up to 12-months post-infection. Patients with lower numbers of ECFC exhibited higher levels of inflammatory markers, such as ferritin, suggesting that ECFCs may play a protective role. Additionally, long-COVID syndrome was associated with higher ferritin levels and with female gender.

CONCLUSIONS

These findings highlight the presence of vascular sequela that last up to 6- and 12-months post-infection and point out the need for preventive measures and patient follow-up.

A Comprehensive Analysis of NRP1 in Malignancies Provide Therapeutic Implication for Treating Cancer Patients Infected with SARS-CoV-2

COVID-19 (Coronavirus disease 2019) is caused by SARS-CoV-2 (severe acute respiratory syndrome coronavirus-2), which can lead to pneumonia, cytokine storms, and lymphopenia. Patients with cancer are more susceptible to SARS-CoV-2 infection and severe COVID-19 due to immunosuppression. Recent studies have indicated that NRP1 (Neuropilin 1) may act as a novel mediator of SARS-CoV-2 entry into the host cell. As no systematic review has been performed investigating the characteristics of NRP1 in pan-carcinoma, we comprehensively analyzed NRP1 in patients with pan-cancer. Using a bioinformatics approach, we aimed to systematically examine NRP1 expression profiles in both pan-carcinoma and healthy tissues. We found that lung and genitourinary cancers have a relatively higher NRP-1 expression than other cancer patients, suggesting that these patients may be more susceptible to SARS-CoV-2. Our analysis further revealed that NRP1 expression was downregulated in Vero E6 cells, whole blood, lung organoids, testis tissue, and alveolospheres infected with SARS-CoV-2. Notably, NRP1 was associated with immune cell infiltration, immune checkpoint genes, and immune-related genes in most patients with cancer. These findings suggest that, in patients with specific types of cancer, especially lung and genitourinary, high expression of NRP1 contributes to greater susceptibility to SARS-CoV-2 infection and an increased risk of damage due to cytokine storms. Overall, NRP1 appears to play a critical role in regulating immunological properties and metabolism in many tumor types. Specific inhibitors of the NRP1 antigen (pegaptanib, EG00229, or MNRP1685A) combined with other anti-SARS-CoV-2 strategies may aid in treating patients with lung and genitourinary cancers following SARS-CoV-2 infection.

Wastewater monitoring of SARS-CoV-2 gene for COVID-19 epidemiological surveillance in Tucumán, Argentina

Wastewater-based epidemiology provides temporal and spatial information about the health status of a population. The objective of this study was to analyze and report the epidemiological dynamics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the province of Tucumán, Argentina during the second and third waves of coronavirus disease 2019 (COVID-19) between April 2021 and March 2022. The study aimed to quantify SARS-CoV-2 RNA in wastewater, correlating it with clinically reported COVID-19 cases. Wastewater samples (n = 72) were collected from 16 sampling points located in three cities of Tucumán (San Miguel de Tucumán, Yerba Buena y Banda del Río Salí). Detection of viral nucleocapsid markers (N1 gene) was carried out using one-step reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Viral loads were determined for each positive sample using a standard curve. A positive correlation (p < 0.05) was observed between viral load (copies/mL) and the clinically confirmed COVID-19 cases reported at specific sampling points in San Miguel de Tucumán (SP4, SP7, and SP8) in both months, May and June. Indeed, the high viral load concurred with the peaks of COVID-19 cases. This method allowed us to follow the behavior of SARS-CoV-2 infection during epidemic outbreaks. Thus, wastewater monitoring is a valuable epidemiological indicator that enables the anticipation of increases in COVID-19 cases and tracking the progress of the pandemic. SARS-CoV-2 genome-based surveillance should be implemented as a routine practice to prepare for any future surge in infections.

Immune Response and Risk of Decompensation following SARS-CoV-2 Infection in Outpatients with Advanced Chronic Liver Disease

Advanced chronic liver disease (ACLD) is associated with a wide spectrum of immune dysfunction. The clinical impact of SARS-CoV-2 on the development of decompensation and immune response in unvaccinated outpatients has not as yet been clearly defined. This study aimed to evaluate the clinical and immunological impact of SARS-CoV-2 on outpatients with ACLD. This is an observational case-control study, in which ACLD outpatients were included prospectively and consecutively and classified into two groups: SARS-CoV-2 infected and non-infected. Patients' baseline characteristics and infection data were collected and analyzed. Immunoglobulin G (IgG) levels against Spike 1 were evaluated. The primary endpoint was risk of liver decompensation during follow-up, assessed after propensity score matching and adjusted by Cox regression. Between October 2020 and July 2021, ACLD outpatients (n = 580) were identified, and 174 patients with clinical follow-up were included. SARS-CoV-2 infection incidence was 7.6% (n = 44). Risk of liver decompensation was significantly higher after infection (HR = 2.43 [1.01-5.86], p = 0.048) vs. non-infection. The time of IgG evaluation was similar in all patients (n = 74); IgG concentrations were significantly higher in compensated vs. decompensated patients (1.02 ± 0.35 pg/mL vs. 0.34 ± 0.16 pg/mL, p < 0.0001) and correlated with hemoglobin levels. The dysregulation of the innate immune response in patients with decompensated liver disease increased the risk of further decompensation following SARS-CoV-2, mainly due to a worsening of ascites.

Cardiovascular Comorbidities in COVID-19: Comprehensive Analysis of Key Topics

BACKGROUND

The interrelation between COVID-19 and various cardiovascular and metabolic disorders has been a critical area of study. There is a growing need to understand how comorbidities such as cardiovascular diseases (CVDs) and metabolic disorders affect the risk and severity of COVID-19.

OBJECTIVE

The objective of this study is to systematically analyze the association between COVID-19 and cardiovascular and metabolic disorders. The focus is on comorbidity, examining the roles of CVDs such as embolism, thrombosis, hypertension, and heart failure, as well as metabolic disorders such as disorders of glucose and iron metabolism.

METHODS

Our study involved a systematic search in PubMed for literature published from 2000 to 2022. We established 2 databases: one for COVID-19-related articles and another for CVD-related articles, ensuring all were peer-reviewed. In terms of data analysis, statistical methods were applied to compare the frequency and relevance of MeSH (Medical Subject Headings) terms between the 2 databases. This involved analyzing the differences and ratios in the usage of these terms and employing statistical tests to determine their significance in relation to key CVDs within the COVID-19 research context.

RESULTS

The study revealed that "Cardiovascular Diseases" and "Nutritional and Metabolic Diseases" were highly relevant as level 1 Medical Subject Headings descriptors in COVID-19 comorbidity research. Detailed analysis at level 2 and level 3 showed "Vascular Disease" and "Heart Disease" as prominent descriptors under CVDs. Significantly, "Glucose Metabolism Disorders" were frequently associated with COVID-19 comorbidities such as embolism, thrombosis, and heart failure. Furthermore, iron deficiency (ID) was notably different in its occurrence between COVID-19 and CVD articles, underlining its significance in the context of COVID-19 comorbidities. Statistical analysis underscored these differences, highlighting the importance of both glucose and iron metabolism disorders in COVID-19 research.

CONCLUSIONS

This work lays the foundation for future research that utilizes a knowledge-based approach to elucidate the intricate relationships between these conditions, aiming to develop more effective health care strategies and interventions in the face of ongoing pandemic challenges.

An ex vivo human precision-cut lung slice platform provides insight into SARS-CoV-2 pathogenesis and antiviral drug efficacy

Coronavirus disease 2019 (COVID-19) has claimed millions of lives since the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and lung disease appears the primary cause of death in COVID-19 patients. However, the underlying mechanisms of COVID-19 pathogenesis remain elusive, and there is no existing model where human disease can be faithfully recapitulated and conditions for the infection process can be experimentally controlled. Herein we report the establishment of an ex vivo human precision-cut lung slice (hPCLS) platform for studying SARS-CoV-2 pathogenicity and innate immune responses, and for evaluating the efficacy of antiviral drugs against SARS-CoV-2. We show that while SARS-CoV-2 continued to replicate during the course of infection of hPCLS, infectious virus production peaked within 2 days, and rapidly declined thereafter. Although most proinflammatory cytokines examined were induced by SARS-CoV-2 infection, the degree of induction and types of cytokines varied significantly among hPCLS from individual donors. Two cytokines in particular, IP-10 and IL-8, were highly and consistently induced, suggesting a role in the pathogenesis of COVID-19. Histopathological examination revealed focal cytopathic effects late in the infection. Transcriptomic and proteomic analyses identified molecular signatures and cellular pathways that are largely consistent with the progression of COVID-19 in patients. Furthermore, we show that homoharringtonine, a natural plant alkaloid derived from Cephalotoxus fortunei, not only inhibited virus replication but also production of pro-inflammatory cytokines, and thus ameliorated the histopathological changes caused by SARS-CoV-2 infection, demonstrating the usefulness of the hPCLS platform for evaluating antiviral drugs.

IMPORTANCE

Here, established an ex vivo human precision-cut lung slice platform for assessing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, viral replication kinetics, innate immune response, disease progression, and antiviral drugs. Using this platform, we identified early induction of specific cytokines, especially IP-10 and IL-8, as potential predictors for severe coronavirus disease 2019 (COVID-19), and uncovered a hitherto unrecognized phenomenon that while infectious virus disappears at late times of infection, viral RNA persists and lung histopathology commences. This finding may have important clinical implications for both acute and post-acute sequelae of COVID-19. This platform recapitulates some of the characteristics of lung disease observed in severe COVID-19 patients and is therefore a useful platform for understanding mechanisms of SARS-CoV-2 pathogenesis and for evaluating the efficacy of antiviral drugs.

Exploring the role of the ocular surface in the lung-eye axis: Insights into respiratory disease pathogenesis

Chronic respiratory diseases (CRDs) represent a significant proportion of global health burden, with a wide spectrum of varying, heterogenic conditions largely affecting the pulmonary system. Recent advances in immunology and respiratory biology have highlighted the systemic impact of these diseases, notably through the elucidation of the lung-eye axis. The current review focusses on understanding the pivotal role of the lung-eye axis in the pathogenesis and progression of chronic respiratory infections and diseases. Existing literature published on the immunological crosstalk between the eye and the lung has been reviewed. The various roles of the ocular microbiome in lung health are also explored, examining the eye as a gateway for respiratory virus transmission, and assessing the impact of environmental irritants on both ocular and respiratory systems. This novel concept emphasizes a bidirectional relationship between respiratory and ocular health, suggesting that respiratory diseases may influence ocular conditions and vice versa, whereby this conception provides a comprehensive framework for understanding the intricate axis connecting both respiratory and ocular health. These aspects underscore the need for an integrative approach in the management of chronic respiratory diseases. Future research should further elucidate the in-depth molecular mechanisms affecting this axis which would pave the path for novel diagnostics and effective therapeutic strategies.

Next-generation nanovaccine induces durable immunity and protects against SARS-CoV-2

While first generation SARS-CoV-2 vaccines were effective in slowing the spread and severity of disease during the COVID-19 pandemic, there is a need for vaccines capable of inducing durable and broad immunity against emerging variants of concern. Nanoparticle-based vaccines (i.e., "nanovaccines") composed of polyanhydride nanoparticles and pentablock copolymer micelles have previously been shown to protect against respiratory pathogens, including influenza A virus, respiratory syncytial virus, and Yersinia pestis. In this work, a nanovaccine containing SARS-CoV-2 spike and nucleocapsid antigens was designed and optimized. The optimized nanovaccine induced long-lived systemic IgG antibody responses against wild-type SARS-CoV-2 virus. In addition, the nanovaccine induced antibody responses capable of neutralization and cross-reactivity to multiple SARS-CoV-2 variants (including B.1.1.529) and antigen-specific CD4+ and CD8+ T cell responses. Finally, the nanovaccine protected mice against a lethal SARS-CoV-2 challenge, setting the stage for advancing particle-based SARS-CoV-2 nanovaccines. STATEMENT OF SIGNIFICANCE: First-generation SARS-CoV-2 vaccines were effective in slowing the spread and limiting the severity of COVID-19. However, current vaccines target only one antigen of the virus (i.e., spike protein) and focus on the generation of neutralizing antibodies, which may be less effective against new, circulating strains. In this work, we demonstrated the ability of a novel nanovaccine platform, based on polyanhydride nanoparticles and pentablock copolymer micelles, to generate durable and broad immunity against SARS-CoV-2. These nanovaccines induced long-lasting (> 62 weeks) serum antibody responses which neutralized binding to ACE2 receptors and were cross-reactive to multiple SARS-CoV-2 variants. Additionally, mice immunized with the SARS-CoV-2 nanovaccine showed a significant increase of antigen-specific T cell responses in the draining lymph nodes and spleens. Together, these nanovaccine-induced immune responses contributed to the protection of mice against a lethal challenge of live SARS-CoV-2 virus, indicating that this nanovaccine platform is a promising next-generation SARS-CoV-2 vaccine.

Wastewater surveillance for viral pathogens: A tool for public health

A focus on water quality has intensified globally, considering its critical role in sustaining life and ecosystems. Wastewater, reflecting societal development, profoundly impacts public health. Wastewater-based epidemiology (WBE) has emerged as a surveillance tool for detecting outbreaks early, monitoring infectious disease trends, and providing real-time insights, particularly in vulnerable communities. WBE aids in tracking pathogens, including viruses, in sewage, offering a comprehensive understanding of community health and lifestyle habits. With the rise in global COVID-19 cases, WBE has gained prominence, aiding in monitoring SARS-CoV-2 levels worldwide. Despite advancements in water treatment, poorly treated wastewater discharge remains a threat, amplifying the spread of water-, sanitation-, and hygiene (WaSH)-related diseases. WBE, serving as complementary surveillance, is pivotal for monitoring community-level viral infections. However, there is untapped potential for WBE to expand its role in public health surveillance. This review emphasizes the importance of WBE in understanding the link between viral surveillance in wastewater and public health, highlighting the need for its further integration into public health management.

Neurological symphony: post-acute COVID-19 syndrome, an innovative pathophysiological exploration from neuraltherapeutic medicine

The SARS-CoV-2 pandemic has affected 771 million people and caused 6.9 million confirmed deaths as of November 2023. Beyond the adversity, a crucial and less-explored chapter unfolds: adaptive sequelae. These have altered social, mental, and emotional conditions, leaving an imprint on biological systems. While some cases fully resolve the pathological process post-acute infection, others persist with symptoms, posing a challenge that underscores the need to comprehend pathophysiology from innovative perspectives. The article delves into “Long COVID” or Post-Acute COVID-19 Syndrome (PACS), where symptoms persist for ≥4 weeks irrespective of initial severity. Risk factors include a history of severe illness, in-hospital management, and intensive care. This article also explores theories, derived from various experimental models, that have demonstrated the involvement of the nervous system in coordination with the psychoneuroimmunoendocrine axes in the expression of inflammation. It is posited that PACS involves processes of peripheral and central sensitization (corticalization), facilitating dishomeostasis and the chronicity of the inflammatory process. In this context, various therapeutic strategies grounded in modulating the inflammatory reflex are reviewed, primarily through the infiltration of local anesthetics via linear and non-linear approaches. Neural therapeutic use is considered to stimulate the regulatory inflammatory circuits coordinated by the neuroimmune-endocrine system.

Perfusion deficits may underlie lung and kidney injury in severe COVID-19 disease: insights from a multicenter international cohort study

BACKGROUND

Lung perfusion defects, mainly due to endothelial and coagulation activation, are a key contributor to COVID-19 respiratory failure. COVID-19 patients may also develop acute kidney injury (AKI) because of renal perfusion deficit. We aimed to explore AKI-associated factors and the independent prediction of standardized minute ventilation (MV)-a proxy of alveolar dead space-on AKI onset and persistence in COVID-19 mechanically ventilated patients.

METHODS

This is a multicenter observational cohort study. We enrolled 157 COVID-19 patients requiring mechanical ventilation and intensive care unit (ICU) admission. We collected clinical information, ventilation, and laboratory data. AKI was defined by the 2012 KDIGO guidelines and classified as transient or persistent according to serum creatinine criteria persistence within 48 h. Ordered univariate and multivariate logistic regression analyses were employed to identify variables associated with AKI onset and persistence.

RESULTS

Among 157 COVID-19 patients on mechanical ventilation, 47% developed AKI: 10% had transient AKI, and 37% had persistent AKI. The degree of hypoxia was not associated with differences in AKI severity. Across increasing severity of AKI groups, despite similar levels of paCO2, we observed an increased MV and standardized MV, a robust proxy of alveolar dead space. After adjusting for other clinical and laboratory covariates, standardized MV remained an independent predictor of AKI development and persistence. D-dimer levels were higher in patients with persistent AKI.

CONCLUSIONS

In critically ill COVID-19 patients with respiratory failure, increased wasted ventilation is independently associated with a greater risk of persistent AKI. These hypothesis-generating findings may suggest that perfusion derangements may link the pathophysiology of both wasted ventilation and acute kidney injury in our population.

SARS-CoV-2 Infection Positively Correlates with Hyperglycemia and Inflammatory Markers in COVID-19 Patients: A Clinical Research Study

Diabetes mellitus (DM) is a common comorbidity in COVID-19 subjects. Hyperglycemia at hospital admission identified as a major risk factor and is responsible for poor prognosis. Hematological and inflammatory parameters have been recognized as predictive markers of severity in COVID-19. In this clinical study, we aimed to assess the impact of hyperglycemia at hospital admission on hematological and several inflammatory parameters in COVID-19 patients. A total of 550 COVID-19 subjects were primarily categorized into two major groups (normoglycemic and hyperglycemic) based on random blood sugar levels. On the first day of hospitalization, subjects' oxygen saturation, random blood sugar, hematological variables, and inflammatory parameters were recorded. The hyperglycemic group exhibited higher levels of serum ferritin, total leukocyte count (TLC), lactate dehydrogenase (LDH), neutrophil count, and neutrophil-to-lymphocyte ratio (NLR). In contrast, oxygen saturation and lymphocyte count were lower compared to the normoglycemic group. Significantly elevated levels of hematological variables (TLC, neutrophil count, NLR) and inflammatory parameters (serum ferritin) were observed in the hyperglycemic group. Among inflammatory parameters, only serum ferritin levels showed statistical significance. This study supports the clinical association between hyperglycemia and an increased severity of COVID-19. Consequently, the identification of these parameters is a crucial and valuable prognostic indicator for assessing disease severity in hyperglycemic subjects.

SARS-CoV-2-associated lymphopenia: possible mechanisms and the role of CD147

T lymphocytes play a primary role in the adaptive antiviral immunity. Both lymphocytosis and lymphopenia were found to be associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). While lymphocytosis indicates an active anti-viral response, lymphopenia is a sign of poor prognosis. T-cells, in essence, rarely express ACE2 receptors, making the cause of cell depletion enigmatic. Moreover, emerging strains posed an immunological challenge, potentially alarming for the next pandemic. Herein, we review how possible indirect and direct key mechanisms could contribute to SARS-CoV-2-associated-lymphopenia. The fundamental mechanism is the inflammatory cytokine storm elicited by viral infection, which alters the host cell metabolism into a more acidic state. This "hyperlactic acidemia" together with the cytokine storm suppresses T-cell proliferation and triggers intrinsic/extrinsic apoptosis. SARS-CoV-2 infection also results in a shift from steady-state hematopoiesis to stress hematopoiesis. Even with low ACE2 expression, the presence of cholesterol-rich lipid rafts on activated T-cells may enhance viral entry and syncytia formation. Finally, direct viral infection of lymphocytes may indicate the participation of other receptors or auxiliary proteins on T-cells, that can work alone or in concert with other mechanisms. Therefore, we address the role of CD147-a novel route-for SARS-CoV-2 and its new variants. CD147 is not only expressed on T-cells, but it also interacts with other co-partners to orchestrate various biological processes. Given these features, CD147 is an appealing candidate for viral pathogenicity. Understanding the molecular and cellular mechanisms behind SARS-CoV-2-associated-lymphopenia will aid in the discovery of potential therapeutic targets to improve the resilience of our immune system against this rapidly evolving virus.

The Interplay of HIV and Long COVID in Sub-Saharan Africa: Mechanisms of Endothelial Dysfunction

PURPOSE OF REVIEW

Long COVID affects approximately 5 million people in Africa. This disease is characterized by persistent symptoms or new onset of symptoms after an acute SARS-CoV-2 infection. Specifically, the most common symptoms include a range of cardiovascular problems such as chest pain, orthostatic intolerance, tachycardia, syncope, and uncontrolled hypertension. Importantly, these conditions appear to have endothelial dysfunction as the common denominator, which is often due to impaired nitric oxide (NO) mechanisms. This review discusses the role of mechanisms contributing to endothelial dysfunction in Long COVID, particularly in people living with HIV.

RECENT FINDINGS

Recent studies have reported that increased inflammation and oxidative stress, frequently observed in Long COVID, may contribute to NO dysfunction, ultimately leading to decreased vascular reactivity. These mechanisms have also been reported in people living with HIV. In regions like Africa, where HIV infection is still a major public health challenge with a prevalence of approximately 26 million people in 2022. Specifically, endothelial dysfunction has been reported as a major mechanism that appears to contribute to cardiovascular diseases and the intersection with Long COVID mechanisms is of particular concern. Further, it is well established that this population is more likely to develop Long COVID following infection with SARS-CoV-2. Therefore, concomitant infection with SARS-CoV-2 may lead to accelerated cardiovascular disease. We outline the details of the worsening health problems caused by Long COVID, which exacerbate pre-existing conditions such as endothelial dysfunction. The overlapping mechanisms of HIV and SARS-CoV-2, particularly the prolonged inflammatory response and chronic hypoxia, may increase susceptibility to Long COVID. Addressing these overlapping health issues is critical as it provides clinical entry points for interventions that could improve and enhance outcomes and quality of life for those affected by both HIV and Long COVID in the region.

Insight into COVID-19 associated liver injury: Mechanisms, evaluation, and clinical implications

COVID-19 has affected millions worldwide, causing significant morbidity and mortality. While predominantly involving the respiratory tract, SARS-CoV-2 has also caused systemic illnesses involving other sites. Liver injury due to COVID-19 has been variably reported in observational studies. It has been postulated that liver damage may be due to direct damage by the SARS-CoV-2 virus or multifactorial secondary to hepatotoxic therapeutic options, as well as cytokine release syndrome and sepsis-induced multiorgan dysfunction. The approach to a COVID-19 patient with liver injury requires a thorough evaluation of the pattern of hepatocellular injury, along with the presence of underlying chronic liver disease and concurrent medications which may cause drug-induced liver injury. While studies have shown uneventful recovery in the majority of mildly affected patients, severe COVID-19 associated liver injury has been associated with higher mortality, prolonged hospitalization, and greater morbidity in survivors. Furthermore, its impact on long-term outcomes remains to be ascertained as recent studies report an association with metabolic-fatty liver disease. This present review provides insight into the subject by describing the postulated mechanism of liver injury, its impact in the presence of pre-existing liver disease, and its short- and long-term clinical implications.

Optic nerve head alterations after COVID-19: an optical coherence tomography angiography-based longitudinal study

OBJECTIVE

To evaluate longitudinal changes in peripapillary vessel density (VD) following coronavirus disease 2019 (COVID-19) using optical coherence tomography angiography.

METHODS

As part of a prospective longitudinal observational study, we studied healthy individuals with a history of mild COVID-19 confirmed via real-time polymerase chain reaction. After recovery, we used the Optovue RTVue XR Avanti machine to perform optic nerve head (ONH) imaging. We also assessed the VD of all vessels and of small vessels in the disc and the radial peripapillary capillary (RPC) network at 1 and 3 months post-recovery.

RESULTS

We included 17 patients (34 eyes; mean age: 36.9 ± 10.2 years, range: 24-62 years) who had recovered from COVID-19. No changes were observed in the ONH parameters. However, there was a noticeable trend of increased small vessel VD values in the RPC. These increases were significant for the peripapillary whole, superior hemifield, inferior-temporal, temporal-superior, and superior-temporal small vessels. Moreover, the evaluation of all vessel VD values in the RPC revealed a significant decrease in the inside disc and a significant increase in a grid-based inferior region.

CONCLUSION

COVID-19 may affect VD of the RPC in the ONH, and should be considered in ONH evaluations.

SARS-CoV-2 infection induces thymic atrophy mediated by IFN-γ in hACE2 transgenic mice

Pathogenic infections cause thymic atrophy, perturb thymic T-cell development, and alter immunological response. Previous studies reported dysregulated T-cell function and lymphopenia in coronavirus disease-19 (COVID-19). However, immunopathological changes in the thymus associated with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection have not been elucidated. Here, we report that SARS-CoV-2 infects thymocytes, and induces CD4+CD8+ (double positive; DP) T-cell apoptosis leading to thymic atrophy and loss of peripheral TCR repertoire in K18-hACE2 transgenic mice. Infected thymus led to increased CD44+CD25- T-cells, indicating an early arrest in the T-cell maturation pathway. Thymic atrophy was notably higher in male hACE2-Tg mice than in females and involved an upregulated de-novo synthesis pathway of thymic glucocorticoid. Further, IFN-γ was crucial for thymic atrophy, as anti-IFN-γ -antibody neutralization blunted thymic involution. Therapeutic use of Remdesivir also rescued thymic atrophy. While the Omicron variant and its sub-lineage BA.5 variant caused marginal thymic atrophy, the delta variant of SARS-CoV-2 exhibited severe thymic atrophy characterized by severely depleted DP T-cells. Recently characterized broadly SARS-CoV-2 neutralizing monoclonal antibody P4A2 was able to rescue thymic atrophy and restore the thymic maturation pathway of T-cells. Together, we report SARS-CoV-2-associated thymic atrophy resulting from impaired T-cell maturation pathway which may contribute to dyregulated T cell response during COVID-19.

Persistent SARS-CoV-2 infection: significance and implications

SARS-CoV-2 causes persistent infections in a subset of individuals, which is a major clinical and public health problem that should be prioritised for further investigation for several reasons. First, persistent SARS-CoV-2 infection often goes unrecognised, and therefore might affect a substantial number of people, particularly immunocompromised individuals. Second, the formation of tissue reservoirs (including in non-respiratory tissues) might underlie the pathophysiology of the persistent SARS-CoV-2 infection and require new strategies for diagnosis and treatment. Finally, persistent SARS-CoV-2 replication, particularly in the setting of suboptimal immune responses, is a possible source of new, divergent virus variants that escape pre-existing immunity on the individual and population levels. Defining optimal diagnostic and treatment strategies for patients with persistent virus replication and monitoring viral evolution are therefore urgent medical and public health priorities.

Progress in SARS-CoV-2, diagnostic and clinical treatment of COVID-19

Background

Corona Virus Disease 2019(COVID-19)is a global pandemic novel coronavirus infection disease caused by Severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2). Although rapid, large-scale testing plays an important role in patient management and slowing the spread of the disease. However, there has been no good and widely used drug treatment for infection and transmission of SARS-CoV-2.

Key findings

Therefore, this review updates the body of knowledge on viral structure, infection routes, detection methods, and clinical treatment, with the aim of responding to the large-section caused by SARS-CoV-2. This paper focuses on the structure of SARS-CoV-2 viral protease, RNA polymerase, serine protease and main proteinase-like protease as well as targeted antiviral drugs.

Conclusion

In vitro or clinical trials have been carried out to provide deeper thinking for the pathogenesis, clinical diagnosis, vaccine development and treatment of SARS-CoV-2.

Recovery from Severe COVID-19 Is an Independent Predictor of Electrocardiographic Abnormal P-Wave Axis

AIM

Abnormal P-wave axis (aPwa) have been correlated with an increased risk of supraventricular arrhythmias. The aim of this study was to analyze whether infection with COVID-19 may cause a predisposition for supraventricular arrhythmia in the long term, following recovery.

MATERIALS AND METHODS

In this study, a total of 252 subjects with a confirmed history of COVID-19 (recovered COVID-19) and 251 healthy subjects without a history of COVID-19 were included. The recovered COVID-19 group was divided into three subgroups designated as mild, moderate, and severe according to the severity score of their chest CT. The aPwa data were obtained using 12-lead electrocardiography (ECG) and compared between the healthy subjects and the recovered COVID-19 subgroups.

RESULTS

This study showed that in the recovered severe COVID-19 subgroup the prevalence of aPwa was significantly increased compared to the controls and the other COVID-19 subgroups. No correlation could be detected in Spearman's Rho correlation between the existence of aPwa and the number of positive PCR tests for COVID-19 and the time elapsed after infection with COVID-19. The binary logistic regression analysis showed that recovery from severe COVID-19, the severity score of the chest CT in the recovered from COVID-19 subjects, and the existence of hypertension (HT) were all independent predictors of aPwa (hazard ratio: 3.542, 95% confidence interval: 1.398-8.969, p: 0.01; hazard ratio: 0.896, 95% confidence interval: 0.840-0.955, p < 0.001; hazard ratio: 2.710, 95% confidence interval: 1.079-6.804, p: 0.03, respectively).

CONCLUSIONS

Individuals who have recovered from severe COVID-19 have shown an increased prevalence of aPwa. The existence of aPwa was not associated with the number of positive PCR tests for COVID-19 or the time elapsed after infection with COVID-19. Therefore, recovery from severe COVID-19 is an independent predictor of electrocardiographic abnormal P-wave axis.

Association between gut microbiota dysbiosis and poor functional outcomes in acute ischemic stroke patients with COVID-19 infection

Acute ischemic stroke (AIS) patients with active COVID-19 infection often have more severe symptoms and worse recovery. COVID-19 infection can cause gut microbiota dysbiosis, which is also a risk factor for poor outcomes in AIS patients. However, the association between gut microbiota and functional outcomes among AIS patients with COVID-19 infection has not been fully clarified yet. In this study, we performed 16S rRNA gene sequencing to characterize the gut microbial community among AIS patients with acute COVID-19 infection, AIS patients with post-acute COVID-19 infection, and AIS patients without COVID-19 infection. We found that AIS patients with acute COVID-19 experienced poorer recovery and significant gut dysbiosis, characterized by higher levels of Enterobacteriaceae and lower levels of Ruminococcaceae and Lachnospiraceae. Furthermore, a shorter time window (less than 28 days) between COVID-19 infection and stroke was identified as a risk factor for poor functional outcomes in AIS patients with COVID-19, and the enrichment of Enterobacteriaceae was indicated as a mediator in the relationship between infection time window and poor stroke outcomes. Our findings highlight the importance of early intervention after COVID-19 infection, especially by regulating the gut microbiota, which plays a role in the prognosis of AIS patients with COVID-19 infection.IMPORTANCEThe gut microbiota plays an important role in the association between respiratory system and cerebrovascular system through the gut-lung axis and gut-brain axis. However, the specific connection between gut bacteria and the functional outcomes of acute ischemic stroke (AIS) patients with COVID-19 is not fully understood yet. In our study, we observed a significant decrease in bacterial diversity and shifts in the abundance of key bacterial families in AIS patients with acute COVID-19 infection. Furthermore, we identified that the time window was a critical influence factor for stroke outcomes, and the enrichment of Enterobacteriaceae acted as a mediator in the relationship between the infection time window and poor stroke outcomes. Our research provides a new perspective on the complex interplay among AIS, COVID-19 infection, and gut microbiota dysbiosis. Moreover, recognizing Enterobacteriaceae as a potential mediator of poor stroke prognosis offers a novel avenue for future exploration and therapeutic interventions.

The relationship between SARS-CoV-2 infection and type 1 diabetes mellitus

Environmental factors, in particular viral infections, are thought to have an important role in the pathogenesis of type 1 diabetes mellitus (T1DM). The COVID-19 pandemic reinforced this hypothesis as many observational studies and meta-analyses reported a notable increase in the incidence of T1DM following infection with SARS-CoV-2 as well as an association between SARS-CoV-2 infection and the risk of new-onset T1DM. Experimental evidence suggests that human β-cells express SARS-CoV-2 receptors and that SARS-CoV-2 can infect and replicate in β-cells, resulting in structural or functional alterations of these cells. These alterations include reduced numbers of insulin-secreting granules, impaired pro-insulin (or insulin) secretion, and β-cell transdifferentiation or dedifferentiation. The inflammatory environment induced by local or systemic SARS-CoV-2 infection might result in a set of signals (such as pro-inflammatory cytokines) that lead to β-cell alteration or apoptosis or to a bystander activation of T cells and disruption of peripheral tolerance that triggers autoimmunity. Other mechanisms, such as viral persistence, molecular mimicry and activation of endogenous human retroviruses, are also likely to be involved in the pathogenesis of T1DM following SARS-CoV-2 infection. This Review addresses the issue of the involvement of SARS-CoV-2 infection in the development of T1DM using evidence from epidemiological, clinical and experimental studies.

Controlling spatial distribution of functional lipids in a supported lipid bilayer prepared from vesicles

Conjugating biomolecules, such as antibodies, to bioconjugate moieties on lipid surfaces is a powerful tool for engineering the surface of diverse biomaterials, including cells and nanoparticles. We developed supported lipid bilayers (SLBs) presenting well-defined spatial distributions of functional moieties as models for precisely engineered functional biomolecular-lipid surfaces. We used quartz crystal microbalance with dissipation (QCM-D) and atomic force microscopy (AFM) to determine how vesicles containing a mixture of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[azido(polyethylene glycol)-2000] (DSPE-PEG-N3) form SLBs as a function of the lipid phase transition temperature (Tm). Above the DPPC Tm, DPPC/DSPE-PEG-N3 vesicles form SLBs with functional azide moieties on SiO2 substrates via vesicle fusion. Below this Tm, DPPC/DSPE-PEG-N3 vesicles attach to SiO2 intact. Intact DPPC/DSPE-PEG-N3 vesicles on the SiO2 surfaces fuse and rupture to form SLBs when temperature is brought above the DPPC Tm. AFM studies show uniform and complete DPPC/DSPE-PEG-N3 SLB coverage of SiO2 surfaces for different DSPE-PEG-N3 concentrations. As the DSPE-PEG-N3 concentration increases from 0.01 to 6 mol%, the intermolecular spacing of DSPE-PEG-N3 in the SLBs decreases from 4.6 to 1.0 nm. The PEG moiety undergoes a mushroom to brush transition as DSPE-PEG-N3 concentration varies from 0.1 to 2.0 mol%. Via copper-free click reaction, IgG was conjugated to SLB surfaces with 4.6 nm or 1.3 nm inter-DSPE-PEG-N3 spacing. QCM-D and AFM data show; 1) uniform and complete IgG layers of similar mass and thickness on the two types of SLB; 2) a higher-viscosity/less rigid IgG layer on the SLB with 4.6 nm inter-DSPE-PEG-N3 spacing. Our studies provide a blueprint for SLBs modeling spatial control of functional macromolecules on lipid surfaces, including surfaces of lipid nanoparticles and cells.

Histopathological impact of SARS-CoV-2 on the liver: Cellular damage and long-term complications

Coronavirus disease 2019 (COVID-19), caused by the highly pathogenic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), primarily impacts the respiratory tract and can lead to severe outcomes such as acute respiratory distress syndrome, multiple organ failure, and death. Despite extensive studies on the pathogenicity of SARS-CoV-2, its impact on the hepatobiliary system remains unclear. While liver injury is commonly indicated by reduced albumin and elevated bilirubin and transaminase levels, the exact source of this damage is not fully understood. Proposed mechanisms for injury include direct cytotoxicity, collateral damage from inflammation, drug-induced liver injury, and ischemia/hypoxia. However, evidence often relies on blood tests with liver enzyme abnormalities. In this comprehensive review, we focused solely on the different histopathological manifestations of liver injury in COVID-19 patients, drawing from liver biopsies, complete autopsies, and in vitro liver analyses. We present evidence of the direct impact of SARS-CoV-2 on the liver, substantiated by in vitro observations of viral entry mechanisms and the actual presence of viral particles in liver samples resulting in a variety of cellular changes, including mitochondrial swelling, endoplasmic reticulum dilatation, and hepatocyte apoptosis. Additionally, we describe the diverse liver pathology observed during COVID-19 infection, encompassing necrosis, steatosis, cholestasis, and lobular inflammation. We also discuss the emergence of long-term complications, notably COVID-19-related secondary sclerosing cholangitis. Recognizing the histopathological liver changes occurring during COVID-19 infection is pivotal for improving patient recovery and guiding decision-making.

SARS-CoV-2 Spike Protein Enhances Carboxypeptidase Activity of Angiotensin-Converting Enzyme 2

In this study, we investigated whether severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) spike protein may modify angiotensin-converting enzyme 2 (ACE2) activity in the plasma, heart, kidney, liver, lung, and six brain regions (amygdala, brain stem, cortex, hippocampus, hypothalamus, and striatum) of diabetic and hypertensive rats. We determine ACE2 activity in the plasma and lysates of heart, kidney, liver, lung, and six brain regions. MLN-4760 inhibits ACE2 activity in the plasma and all organs. On the other hand, soluble ACE2 (sACE2) activity increased in the plasma of diabetic rats, and there was no change in the plasma of hypertensive rats. ACE2 activity was augmented in the liver, brain stem, and striatum, while it decreased in the kidney, amygdala, cortex, and hippocampus of diabetic rats. ACE2 activity increased in the kidney, liver, and lung, while it decreased in the heart, amygdala, cortex, and hypothalamus of hypertensive rats. We measured the ACE2 content via enzyme-linked immunosorbent assay and found that ACE2 protein levels increased in the heart, while it decreased in the plasma, kidney, brain stem, cortex, hippocampus, hypothalamus, and striatum of diabetic rats. ACE2 protein levels decreased in the brain stem, cortex, hippocampus, and hypothalamus of hypertensive rats. Our data showed that the spike protein enhanced ACE2 activity in the liver and lungs of diabetic rats, as well as in the heart and three of the brain regions (cortex, hypothalamus, and striatum) of hypertensive rats.

The impact of hypertension on clinical manifestations of Omicron variant BA.1 infection in adult patients

COVID-19 caused by Omicron BA.1 has resulted in a global humanitarian crisis. In this COVID-19 pandemic era, hypertension has been receiving increased attention. Omicron BA.1 infection combined with hypertension created a serious public health problem and complicated the treatment and prognosis of COVID-19. The aim of our study was to assess the implications of hypertension for the clinical manifestations of adult patients (APs) infected with Omicron BA.1. This single-center retrospective cohort study enrolled consecutive COVID-19 APs, who were admitted to Tianjin First Central Hospital from 01 August 2022 to 30 November 2022. All included APs were divided into two groups: hypertension and non-hypertension group. The APs' baseline demographic, laboratory, clinical, and radiological characteristics were collected and analyzed. Of 512 APs admitted with PCR proven COVID-19, 161 (31.45%) APs had comorbid hypertension. Hypertension APs have older age, higher body mass index, lower Ct-values of the viral target genes at admission, and longer hospital stay than non-hypertension APs. Furthermore, hypertension aggravates the clinical classification, impairs liver, kidney, and myocardium function, and abnormalizes the coagulation system in Omicron BA.1- infected APs. Moreover, hypertension elevates inflammation levels and lung lesion involvement while weakened virus-specific IgM level in APs with Omicron BA.1 infection. Hypertension APs tend to have worse clinical conditions at baseline than those non-hypertension APs. This study indicates that hypertension is a contributor to the poor clinical manifestations of Omicron BA.1-infected APs and supports that steps to control blood pressure should be a vital consideration for reducing the burden of Omicron BA.1 infection in hypertension individuals.

IMPORTANCE

This study provided inclusive insight regarding the relationship between hypertension and Omicron BA.1 infection and supported that hypertension was an adverse factor for COVID-19 APs. In conclusion, this study showed that hypertension was considered to be associated with severe conditions, and a contributor to poor clinical manifestations. Proper medical management of hypertension patients is an imperative step in mitigating the severity of Omicron BA.1 variant infection.

Olive Leaf Extract Downregulates the Protein Expression of Key SARS-CoV-2 Entry Enzyme ACE-2, TMPRSS2, and Furin

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) poses ongoing global health challenges due to its propensity for mutations, which can undermine vaccine efficacy. With no definitive treatment available, urgent research into affordable and biocompatible therapeutic agents is extremely urgent. Angiotensin converting enzyme-2 (ACE-2), transmembrane protease serine subtype 2 (TMPRSS2), and Furin enzymes, which allow the virus to enter cells, are particularly important as potential drug targets among scientists. Olive leaf extract (OLE) has garnered attention for its potential against Coronavirus Disease-9 (COVID-19), yet its mechanism remains understudied. In this study, we aimed to investigate the effects of OLE on ACE-2, TMPRSS2, and Furin protein expressions by cell culture study. Total phenol, flavonoid content, and antioxidant capacity were measured by photometric methods, and oleuropein levels were measured by liquid LC-HR-MS. Cell viability was analyzed by ATP levels using a luminometric method. ACE-2, TMPRSS2, and Furin expressions were analyzed by the Western Blotting method. ACE-2, TMPRSS2, and Furin protein expression levels were significantly lower in a dose dependent manner and the highest inhibition was seen at 100 μg/ml OLE. The results showed that OLE may be a promising treatment candidate for COVID-19 disease. However, further studies need to be conducted in cells co-infected with the virus.

Sex hormones in COVID-19 severity: The quest for evidence and influence mechanisms

Studies have reported variable effects of sex hormones on serious diseases. Severe disease and mortality rates in COVID-19 show marked gender differences that may be related to sex hormones. Sex hormones regulate the expression of the viral receptors ACE2 and TMPRSS2, which affect the extent of viral infection and consequently cause variable outcomes. In addition, sex hormones have complex regulatory mechanisms that affect the immune response to viruses. These hormones also affect metabolism, leading to visceral obesity and severe disease can result from complications such as thrombosis. This review presents the latest researches on the regulatory functions of hormones in viral receptors, immune responses, complications as well as their role in COVID-19 progression. It also discusses the therapeutic possibilities of these hormones by reviewing the recent findings of clinical and assay studies.

Risk factors for severe COVID-19 disease increase SARS-CoV-2 infectivity of endothelial cells and pericytes

Coronavirus disease 2019 (COVID-19) was initially considered a primarily respiratory disease but is now known to affect other organs including the heart and brain. A major route by which COVID-19 impacts different organs is via the vascular system. We studied the impact of apolipoprotein E (APOE) genotype and inflammation on vascular infectivity by pseudo-typed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viruses in mouse and human cultured endothelial cells and pericytes. Possessing the APOE4 allele or having existing systemic inflammation is known to enhance the severity of COVID-19. Using targeted replacement human APOE3 and APOE4 mice and inflammation induced by bacterial lipopolysaccharide (LPS), we investigated infection by SARS-CoV-2. Here, we show that infectivity was higher in murine cerebrovascular pericytes compared to endothelial cells and higher in cultures expressing APOE4. Furthermore, increasing the inflammatory state of the cells by prior incubation with LPS increased infectivity into human and mouse pericytes and human endothelial cells. Our findings provide insights into the mechanisms underlying severe COVID-19 infection, highlighting how risk factors such as APOE4 genotype and prior inflammation may exacerbate disease severity by augmenting the virus's ability to infect vascular cells.

Prevalence of new onset erectile dysfunction among Damietta governorate men after contracting COVID-19

BACKGROUND

Several reports showed that sexual function was affected during and after the COVID-19 pandemic.

AIMS

The objective of the study was to demonstrate whether a realistic association exists between the COVID-19 pandemic and erectile dysfunction (ED) among a sampled Egyptian population in Damietta governorate.

METHODS

This cross-sectional study consisted of 330 adult males diagnosed with COVID-19 infection. They were categorized in three age groups (18-29, 30-39, and 40-50 years, respectively). COVID-19-confirmed cases were assessed by the Arabic version of the International Index of Erectile Function questionnaire (IIEF) scores.

RESULTS

The prevalence of ED according to the IIEF was 55.1%. The ED was categorized into mild ED which represents 25.8% of the patients, mild to moderate which represents 22.4% of the patients, moderate which represents 7% of the patients, and severe which represents 0% of the patients. We found a significant negative correlation between the age of the patients and the IIEF score. Also, we found an association between the severity of COVID-19 infection and the IIEF score.

CONCLUSION

An association of new-onset ED in men who suffered COVID-19 infection was established. This may be due to virus-induced endothelial cell dysfunction; however, an underlying mechanism and causation have not yet been clearly elucidated. While it appears that COVID-19 infection may be a risk factor for ED, additional research is needed to establish causality.

Molecular cross-talk between long COVID-19 and Alzheimer's disease

The long COVID (coronavirus disease), a multisystemic condition following severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection, is one of the widespread problems. Some of its symptoms affect the nervous system and resemble symptoms of Alzheimer's disease (AD)-a neurodegenerative condition caused by the accumulation of amyloid beta and hyperphosphorylation of tau proteins. Multiple studies have found dependence between these two conditions. Patients with Alzheimer's disease have a greater risk of SARS-CoV-2 infection due to increased levels of angiotensin-converting enzyme 2 (ACE2), and the infection itself promotes amyloid beta generation which enhances the risk of AD. Also, the molecular pathways are alike-misregulations in folate-mediated one-carbon metabolism, a deficit of Cq10, and disease-associated microglia. Medical imaging in both of these diseases shows a decrease in the volume of gray matter, global brain size reduction, and hypometabolism in the parahippocampal gyrus, thalamus, and cingulate cortex. In some studies, a similar approach to applied medication can be seen, including the use of amino adamantanes and phenolic compounds of rosemary. The significance of these connections and their possible application in medical practice still needs further study but there is a possibility that they will help to better understand long COVID.

The interplay of aging, adipose tissue, and COVID-19: a potent alliance with implications for health

Obesity has emerged as a significant public health challenge. With the ongoing increase in life expectancy, the prevalence of obesity is steadily growing, particularly among older age demographics. The extension of life expectancy frequently results in additional years of vulnerability to chronic health issues associated with obesity in the elderly.The concept of SARS-CoV-2 directly infecting adipose tissue stems from the fact that both adipocytes and stromal vascular fraction cells express ACE2, the primary receptor facilitating SARS-CoV-2 entry. It is noteworthy that adipose tissue demonstrates ACE2 expression levels similar to those found in the lungs within the same individual. Additionally, ACE2 expression in the adipose tissue of obese individuals surpasses that in non-obese counterparts. Viral attachment to ACE2 has the potential to disturb the equilibrium of renin-angiotensin system homeostasis, leading to an exacerbated inflammatory response.Consequently, adipose tissue has been investigated as a potential site for active SARS-CoV-2 infection, suggesting its plausible role in virus persistence and contribution to both acute and long-term consequences associated with COVID-19.This review is dedicated to presenting current evidence concerning the presence of SARS-CoV-2 in the adipose tissue of elderly individuals infected with the virus. Both obesity and aging are circumstances that contribute to severe health challenges, heightening the risk of disease and mortality. We will particularly focus on examining the mechanisms implicated in the long-term consequences, with the intention of providing insights into potential strategies for mitigating the aftermath of the disease.

Long COVID Definition, Symptoms, Risk Factors, Epidemiology and Autoimmunity: A Narrative Review

The virus called SARS-CoV-2 emerged in 2019 and quickly spread worldwide, causing COVID-19. It has greatly impacted on everyday life, healthcare systems, and the global economy. In order to save as many lives as possible, precautions such as social distancing, quarantine, and testing policies were implemented, and effective vaccines were developed. A growing amount of data collected worldwide allowed the characterization of this new disease, which turned out to be more complex than other common respiratory tract infections. An increasing number of convalescents presented with a variety of nonspecific symptoms emerging after the acute infection. This possible new global health problem was identified and labelled as long COVID. Since then, a great effort has been made by clinicians and the scientific community to understand the underlying mechanisms and to develop preventive measures and effective treatment. The role of autoimmunity induced by SARS-CoV-2 infection in the development of long COVID is discussed in this review. We aim to deliver a description of several conditions with an autoimmune background observed in COVID-19 convalescents, including Guillain-Barré syndrome, antiphospholipid syndrome and related thrombosis, and Kawasaki disease highlighting a relationship between SARS-CoV-2 infection and the development of autoimmunity. However, further studies are required to determine its true clinical significance.

Generation of a humanized mAce2 and a conditional hACE2 mouse models permissive to SARS-COV-2 infection

The Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) remains a public health concern and a subject of active research effort. Development of pre-clinical animal models is critical to study viral-host interaction, tissue tropism, disease mechanisms, therapeutic approaches, and long-term sequelae of infection. Here, we report two mouse models for studying SARS-CoV-2: A knock-in mAce2F83Y,H353K mouse that expresses a mouse-human hybrid form of the angiotensin-converting enzyme 2 (ACE2) receptor under the endogenous mouse Ace2 promoter, and a Rosa26 conditional knock-in mouse carrying the human ACE2 allele (Rosa26hACE2). Although the mAce2F83Y,H353K mice were susceptible to intranasal inoculation with SARS-CoV-2, they did not show gross phenotypic abnormalities. Next, we generated a Rosa26hACE2;CMV-Cre mouse line that ubiquitously expresses the human ACE2 receptor. By day 3 post infection with SARS-CoV-2, Rosa26hACE2;CMV-Cre mice showed significant weight loss, a variable degree of alveolar wall thickening and reduced survival rates. Viral load measurements confirmed inoculation in lung and brain tissues of infected Rosa26hACE2;CMV-Cre mice. The phenotypic spectrum displayed by our different mouse models translates to the broad range of clinical symptoms seen in the human patients and can serve as a resource for the community to model and explore both treatment strategies and long-term consequences of SARS-CoV-2 infection.

Understanding long COVID myocarditis: A comprehensive review

Infectious diseases are a cause of major concern in this twenty-first century. There have been reports of various outbreaks like severe acute respiratory syndrome (SARS) in 2003, swine flu in 2009, Zika virus disease in 2015, and Middle East Respiratory Syndrome (MERS) in 2012, since the start of this millennium. In addition to these outbreaks, the latest infectious disease to result in an outbreak is the SARS-CoV-2 infection. A viral infection recognized as a respiratory illness at the time of emergence, SARS-CoV-2 has wreaked havoc worldwide because of its long-lasting implications like heart failure, sepsis, organ failure, etc., and its significant impact on the global economy. Besides the acute illness, it also leads to symptoms months later which is called long COVID or post-COVID-19 condition. Due to its ever-increasing prevalence, it has been a significant challenge to treat the affected individuals and manage the complications as well. Myocarditis, a long-term complication of coronavirus disease 2019 (COVID-19) is an inflammatory condition involving the myocardium of the heart, which could even be fatal in the long term in cases of progression to ventricular dysfunction and heart failure. Thus, it is imperative to diagnose early and treat this condition in the affected individuals. At present, there are numerous studies which are in progress, investigating patients with COVID-19-related myocarditis and the treatment strategies. This review focuses primarily on myocarditis, a life-threatening complication of COVID-19 illness, and endeavors to elucidate the pathogenesis, biomarkers, and management of long COVID myocarditis along with pipeline drugs in detail.

JAK inhibition during the early phase of SARS-CoV-2 infection worsens kidney injury by suppressing endogenous antiviral activity in mice

Coronavirus disease 2019 (COVID-19) induces respiratory dysfunction as well as kidney injury. Although the kidney is considered a target organ of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and affected by the COVID-19-induced cytokine storm, the mechanisms of renal reaction in SARS-CoV-2 infection are unknown. In this study, a murine COVID-19 model was induced by nasal infection with mouse-adapted SARS-CoV-2 (MA10). MA10 infection induced body weight loss along with lung inflammation in mice 4 days after infection. Serum creatinine levels and the urinary albumin/creatinine ratio increased on day 4 after MA10 infection. Measurement of the urinary neutrophil gelatinase-associated lipocalin/creatinine ratio and hematoxylin and eosin staining revealed tubular damage in MA10-infected murine kidneys, indicating kidney injury in the murine COVID-19 model. Interferon (IFN)-γ and interleukin-6 upregulation in the sera of MA10-infected mice, along with the absence of MA10 in the kidneys, implied that the kidneys were affected by the MA10 infection-induced cytokine storm rather than by direct MA10 infection of the kidneys. RNA-sequencing analysis revealed that antiviral genes, such as the IFN/Janus kinase (JAK) pathway, were upregulated in MA10-infected kidneys. Upon administration of the JAK inhibitor baricitinib on days 1-3 after MA10 infection, an antiviral pathway was suppressed, and MA10 was detected more frequently in the kidneys. Notably, JAK inhibition upregulated the hypoxia response and exaggerated kidney injury. These results suggest that endogenous antiviral activity protects against SARS-CoV-2-induced kidney injury in the early phase of infection, providing valuable insights into the pathogenesis of COVID-19-associated nephropathy.NEW & NOTEWORTHY Patients frequently present with acute kidney injury or abnormal urinary findings after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Here, we investigated how the kidneys respond during SARS-CoV-2 infection using a murine coronavirus disease 2019 (COVID-19) model and showed that Janus kinase-mediated endogenous antiviral activity protects against kidney injury in the early phase of SARS-CoV-2 infection. These findings provide valuable insights into the renal pathophysiology of COVID-19.

The murine metastatic microenvironment of experimental brain metastases of breast cancer differs by host age in vivo: a proteomic study

Breast cancer in young patients is known to exhibit more aggressive biological behavior and is associated with a less favorable prognosis than the same disease in older patients, owing in part to an increased incidence of brain metastases. The mechanistic explanations behind these findings remain poorly understood. We recently reported that young mice, in comparison to older mice, developed significantly greater brain metastases in four mouse models of triple-negative and luminal B breast cancer. Here we have performed a quantitative mass spectrometry-based proteomic analysis to identify proteins potentially contributing to age-related disparities in the development of breast cancer brain metastases. Using a mouse hematogenous model of brain-tropic triple-negative breast cancer (MDA-MB-231BR), we harvested subpopulations of tumor metastases, the tumor-adjacent metastatic microenvironment, and uninvolved brain tissues via laser microdissection followed by quantitative proteomic analysis using high resolution mass spectrometry to characterize differentially abundant proteins potentially contributing to age-dependent rates of brain metastasis. Pathway analysis revealed significant alterations in signaling pathways, particularly in the metastatic microenvironment, modulating tumorigenesis, metabolic processes, inflammation, and neuronal signaling. Tenascin C (TNC) was significantly elevated in all laser microdissection (LMD) enriched compartments harvested from young mice relative to older hosts, which was validated and confirmed by immunoblot analysis of whole brain lysates. Additional in vitro studies including migration and wound-healing assays demonstrated TNC as a positive regulator of tumor cell migration. These results provide important new insights regarding microenvironmental factors, including TNC, as mechanisms contributing to the increased brain cancer metastatic phenotype observed in young breast cancer patients.

Neuropathological lesions in intravenous BCG-stimulated K18-hACE2 mice challenged with SARS-CoV-2

In the wake of the COVID-19 pandemic caused by SARS-CoV-2, questions emerged about the potential effects of Bacillus Calmette-Guérin (BCG) vaccine on the immune response to SARS-CoV-2 infection, including the neurodegenerative diseases it may contribute to. To explore this, an experimental study was carried out in BCG-stimulated and non-stimulated k18-hACE2 mice challenged with SARS-CoV-2. Viral loads in tissues determined by RT-qPCR, histopathology in brain and lungs, immunohistochemical study in brain (IHC) as well as mortality rates, clinical signs and plasma inflammatory and coagulation biomarkers were assessed. Our results showed BCG-SARS-CoV-2 challenged mice presented higher viral loads in the brain and an increased frequency of neuroinvasion, with the greatest differences observed between groups at 3-4 days post-infection (dpi). Histopathological examination showed a higher severity of brain lesions in BCG-SARS-CoV-2 challenged mice, mainly consisting of neuroinflammation, increased glial cell population and neuronal degeneration, from 5 dpi onwards. This group also presented higher interstitial pneumonia and vascular thrombosis in lungs (3-4 dpi), BCG-SARS-CoV-2 mice showed higher values for TNF-α and D-dimer values, while iNOS values were higher in SARS-CoV-2 mice at 3-4 dpi. Results presented in this study indicate that BCG stimulation could have intensified the inflammatory and neurodegenerative lesions promoting virus neuroinvasion and dissemination in this experimental model. Although k18-hACE2 mice show higher hACE2 expression and neurodissemination, this study suggests that, although the benefits of BCG on enhancing heterologous protection against pathogens and tumour cells have been broadly demonstrated, potential adverse outcomes due to the non-specific effects of BCG should be considered.

Susceptibility to recombinant SARS-CoV-2 spike protein entry in the lungs of high-fat diet-induced obese mice

Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Obesity is a major risk factor for the development of COVID-19. Angiotensin-converting enzyme 2 (ACE2) is an essential receptor for cell entry of SARS-CoV-2. The receptor-binding domain of the S1 subunit (S1-RBD protein) in the SARS-CoV-2 spike glycoprotein binds to ACE2 on host cells, through which the virus enters several organs, including the lungs. Considering these findings, recombinant ACE2 might be utilized as a decoy protein to attenuate SARS-CoV-2 infection. Here, we examined whether obesity increases ACE2 expression in the lungs and whether recombinant ACE2 administration diminishes the entry of S1-RBD protein into lung cells. We observed that high-fat diet-induced obesity promoted ACE2 expression in the lungs by increasing serum levels of LPS derived from the intestine. S1-RBD protein entered the lungs specifically through ACE2 expressed in host lungs and that the administration of recombinant ACE2 attenuated this entry. We conclude that obesity makes hosts susceptible to recombinant SARS-CoV-2 spike proteins due to elevated ACE2 expression in lungs, and this model of administering S1-RBD protein can be applied to new COVID-19 treatments.

ADAM-17 Activity and Its Relation to ACE2: Implications for Severe COVID-19

There is a lack of studies aiming to assess cellular a disintegrin and metalloproteinase-17 (ADAM-17) activity in COVID-19 patients and the eventual associations with the shedding of membrane-bound angiotensin-converting enzyme 2 (mACE2). In addition, studies that investigate the relationship between ACE2 and ADAM-17 gene expressions in organs infected by SARS-CoV-2 are lacking. We used data from the Massachusetts general hospital COVID-19 study (306 COVID-19 patients and 78 symptomatic controls) to investigate the association between plasma levels of 33 different ADAM-17 substrates and COVID-19 severity and mortality. As a surrogate of cellular ADAM-17 activity, an ADAM-17 substrate score was calculated. The associations between soluble ACE2 (sACE2) and the ADAM-17 substrate score, renin, key inflammatory markers, and lung injury markers were investigated. Furthermore, we used data from the Genotype-Tissue Expression (GTEx) database to evaluate ADAM-17 and ACE2 gene expressions by age and sex in ages between 20-80 years. We found that increased ADAM-17 activity, as estimated by the ADAM-17 substrates score, was associated with COVID-19 severity (p = 0.001). ADAM-17 activity was also associated with increased mortality but did not reach statistical significance (p = 0.06). Soluble ACE2 showed the strongest positive correlation with the ADAM-17 substrate score, follow by renin, interleukin-6, and lung injury biomarkers. The ratio of ADAM-17 to ACE2 gene expression was highest in the lung. This study indicates that increased ADAM-17 activity is associated with severe COVID-19. Our findings also indicate that there may a bidirectional relationship between membrane-bound ACE2 shedding via increased ADAM-17 activity, dysregulated renin-angiotensin system (RAS) and immune signaling. Additionally, differences in ACE2 and ADAM-17 gene expressions between different tissues may be of importance in explaining why the lung is the organ most severely affected by COVID-19, but this requires further evaluation in prospective studies.

Diverse roles of SARS-CoV-2 Spike and Nucleocapsid proteins in EndMT stimulation through the TGF-β-MRTF axis inhibited by aspirin

BACKGROUND

The SARS-CoV-2 virus causes severe COVID-19 in one-fifth of patients. In addition to high mortality, infection may induce respiratory failure and cardiovascular complications associated with inflammation. Acute or prolonged inflammation results in organ fibrosis, the cause of which might be endothelial disorders arising during the endothelial-mesenchymal transition (EndMT).

METHODS

HUVECs and HMEC-1 cells were stimulated with SARS-CoV-2 S (Spike) and N (Nucleocapsid) proteins, and EndMT induction was evaluated by studying specific protein markers via Western blotting. Wound healing and tube formation assays were employed to assess the potential of SARS-CoV-2 to stimulate changes in cell behaviour. MRTF nuclear translocation, ROS generation, TLR4 inhibitors, TGF-β-neutralizing antibodies, and inhibitors of the TGF-β-dependent pathway were used to investigate the role of the TGF-β-MRTF signalling axis in SARS-CoV-2-dependent EndMT stimulation.

RESULTS

Both viral proteins stimulate myofibroblast trans-differentiation. However, the N protein is more effective at EndMT induction. The TGF-β-MRTF pathway plays a critical role in this process. The N protein preferentially favours action through TGF-β2, whose secretion is induced through TLR4-ROS action. TGF-β2 stimulates MRTF-A and MRTF-B nuclear translocation and strongly regulates EndMT. In contrast, the Spike protein stimulates TGF-β1 secretion as a result of ACE2 downregulation. TGF-β1 induces only MRTF-B, which, in turn, weakly regulates EndMT. Furthermore, aspirin, a common nonsteroidal anti-inflammatory drug, might prevent and reverse SARS-CoV-2-dependent EndMT induction through TGF-β-MRTF pathway deregulation.

CONCLUSION

The reported study revealed that SARS-CoV-2 infection induces EndMT. Moreover, it was demonstrated for the first time at the molecular level that the intensity of the EndMT triggered by SARS-CoV-2 infection may vary and depend on the viral protein involved. The N protein acts through TLR4-ROS-TGF-β2-MRTF-A/B, whereas the S protein acts through ACE2-TGF-β1-MRTF-B. Furthermore, we identified aspirin as a potential anti-fibrotic drug for treating patients with SARS-CoV-2 infection.

COVID-19-associated encephalopathy: connection between neuroinflammation and microbiota-gut-brain axis

While neurological complications of COVID-19, such as encephalopathy, are relatively rare, their potential significant impact on long-term morbidity is substantial, especially given the large number of infected patients. Two proposed hypotheses for the pathogenesis of this condition are hypoxia and the uncontrolled release of proinflammatory cytokines. The gut microbiota plays an important role in regulating immune homeostasis and overall gut health, including its effects on brain health through various pathways collectively termed the gut-brain axis. Recent studies have shown that COVID-19 patients exhibit gut dysbiosis, but how this dysbiosis can affect inflammation in the central nervous system (CNS) remains unclear. In this context, we discuss how dysbiosis could contribute to neuroinflammation and provide recent data on the features of neuroinflammation in COVID-19 patients.

The role of interleukin-36 in health and disease states

The interleukin (IL)-1 superfamily upregulates immune responses and maintains homeostasis between the innate and adaptive immune systems. Within the IL-1 superfamily, IL-36 plays a pivotal role in both innate and adaptive immune responses. Of the four IL-36 isoforms, three have agonist activity (IL-36α, IL-36β, IL-36γ) and the fourth has antagonist activity (IL-36 receptor antagonist [IL-36Ra]). All IL-36 isoforms bind to the IL-36 receptor (IL-36R). Binding of IL-36α/β/γ to the IL-36R recruits the IL-1 receptor accessory protein (IL-1RAcP) and activates downstream signalling pathways mediated by nuclear transcription factor kappa B and mitogen-activated protein kinase signalling pathways. Antagonist binding of IL-36Ra to IL-36R inhibits recruitment of IL-1RAcP, blocking downstream signalling pathways. Changes in the balance within the IL-36 cytokine family can lead to uncontrolled inflammatory responses throughout the body. As such, IL-36 has been implicated in numerous inflammatory diseases, notably a type of pustular psoriasis called generalized pustular psoriasis (GPP), a chronic, rare, potentially life-threatening, multisystemic skin disease characterised by recurrent fever and extensive sterile pustules. In GPP, IL-36 is central to disease pathogenesis, and the prevention of IL-36-mediated signalling can improve clinical outcomes. In this review, we summarize the literature describing the biological functions of the IL-36 pathway. We also consider the evidence for uncontrolled activation of the IL-36 pathway in a wide range of skin (e.g., plaque psoriasis, pustular psoriasis, hidradenitis suppurativa, acne, Netherton syndrome, atopic dermatitis and pyoderma gangrenosum), lung (e.g., idiopathic pulmonary fibrosis), gut (e.g., intestinal fibrosis, inflammatory bowel disease and Hirschsprung's disease), kidney (e.g., renal tubulointerstitial lesions) and infectious diseases caused by a variety of pathogens (e.g., COVID-19; Mycobacterium tuberculosis, Pseudomonas aeruginosa, Streptococcus pneumoniae infections), as well as in cancer. We also consider how targeting the IL-36 signalling pathway could be used in treating inflammatory disease states.

Host factors of SARS-CoV-2 in infection, pathogenesis, and long-term effects

SARS-CoV-2 is the causative virus of the devastating COVID-19 pandemic that results in an unparalleled global health and economic crisis. Despite unprecedented scientific efforts and therapeutic interventions, the fight against COVID-19 continues as the rapid emergence of different SARS-CoV-2 variants of concern and the increasing challenge of long COVID-19, raising a vast demand to understand the pathomechanisms of COVID-19 and its long-term sequelae and develop therapeutic strategies beyond the virus per se. Notably, in addition to the virus itself, the replication cycle of SARS-CoV-2 and clinical severity of COVID-19 is also governed by host factors. In this review, we therefore comprehensively overview the replication cycle and pathogenesis of SARS-CoV-2 from the perspective of host factors and host-virus interactions. We sequentially outline the pathological implications of molecular interactions between host factors and SARS-CoV-2 in multi-organ and multi-system long COVID-19, and summarize current therapeutic strategies and agents targeting host factors for treating these diseases. This knowledge would be key for the identification of new pathophysiological aspects and mechanisms, and the development of actionable therapeutic targets and strategies for tackling COVID-19 and its sequelae.