Golden Syrian hamster as a model to study cardiovascular complications associated with SARS-CoV-2 infection

SARS-CoV-2 variants divergently infect and damage cardiomyocytes in vitro and in vivo

BACKGROUND

COVID-19 can cause cardiac complications and the latter are associated with poor prognosis and increased mortality. SARS-CoV-2 variants differ in their infectivity and pathogenicity, but how they affect cardiomyocytes (CMs) is unclear.

METHODS

The effects of SARS-CoV-2 variants were investigated using human induced pluripotent stem cell-derived (hiPSC-) CMs in vitro and Golden Syrian hamsters in vivo.

RESULTS

Different variants exhibited distinct tropism, mechanism of viral entry and pathology in the heart. Omicron BA.2 most efficiently infected and injured CMs in vitro and in vivo, and induced expression changes consistent with increased cardiac dysfunction, compared to other variants tested. Bioinformatics and upstream regulator analyses identified transcription factors and network predicted to control the unique transcriptome of Omicron BA.2 infected CMs. Increased infectivity of Omicron BA.2 is attributed to its ability to infect via endocytosis, independently of TMPRSS2, which is absent in CMs.

CONCLUSIONS

In this study, we reveal previously unknown differences in how different SARS-CoV-2 variants affect CMs. Omicron BA.2, which is generally thought to cause mild disease, can damage CMs in vitro and in vivo. Our study highlights the need for further investigations to define the pathogenesis of cardiac complications arising from different SARS-CoV-2 variants.

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.

Mycobacterium tuberculosis strain with deletions in menT3 and menT4 is attenuated and confers protection in mice and guinea pigs

The genome of Mycobacterium tuberculosis encodes for a large repertoire of toxin-antitoxin systems. In the present study, MenT3 and MenT4 toxins belonging to MenAT subfamily of TA systems have been functionally characterized. We demonstrate that ectopic expression of these toxins inhibits bacterial growth and this is rescued upon co-expression of their cognate antitoxins. Here, we show that simultaneous deletion of menT3 and menT4 results in enhanced susceptibility of M. tuberculosis upon exposure to oxidative stress and attenuated growth in guinea pigs and mice. We observed reduced expression of transcripts encoding for proteins that are essential or required for intracellular growth in mid-log phase cultures of ΔmenT4ΔT3 compared to parental strain. Further, the transcript levels of proteins involved in efficient bacterial clearance were increased in lung tissues of ΔmenT4ΔT3 infected mice relative to parental strain infected mice. We show that immunization of mice and guinea pigs with ΔmenT4ΔT3 confers significant protection against M. tuberculosis infection. Remarkably, immunization of mice with ΔmenT4ΔT3 results in increased antigen-specific TH1 bias and activated memory T cell response. We conclude that MenT3 and MenT4 are important for M. tuberculosis pathogenicity and strains lacking menT3 and menT4 have the potential to be explored further as vaccine candidates.

Challenges and opportunities in long COVID research

Long COVID (LC) is a condition in which patients do not fully recover from the initial SARS-CoV-2 infection but rather have persistent or new symptoms for months to years following the infection. Ongoing research efforts are investigating the pathophysiologic mechanisms of LC and exploring preventative and therapeutic treatment approaches for patients. As a burgeoning area of investigation, LC research can be structured to be more inclusive, innovative, and effective. In this perspective, we highlight opportunities for patient engagement and diverse research expertise, as well as the challenges of developing definitions and reproducible studies. Our intention is to provide a foundation for collaboration and progress in understanding the biomarkers and mechanisms driving LC.

COVID-19 and Comorbidities: What Has Been Unveiled by Metabolomics?

The COVID-19 pandemic has brought about diverse impacts on the global population. Individuals with comorbidities were more susceptible to the severe symptoms caused by the virus. Within the crisis scenario, metabolomics represents a potential area of science capable of providing relevant information for understanding the metabolic pathways associated with the intricate interaction between the viral disease and previous comorbidities. This work aims to provide a comprehensive description of the scientific production pertaining to metabolomics within the specific context of COVID-19 and comorbidities, while highlighting promising areas for exploration by those interested in the subject. In this review, we highlighted the studies of metabolomics that indicated a variety of metabolites associated with comorbidities and COVID-19. Furthermore, we observed that the understanding of the metabolic processes involved between comorbidities and COVID-19 is limited due to the urgent need to report disease outcomes in individuals with comorbidities. The overlap of two or more comorbidities associated with the severity of COVID-19 hinders the comprehension of the significance of each condition. Most identified studies are observational, with a restricted number of patients, due to challenges in sample collection amidst the emergent situation.

Safety, immunogenicity and efficacy of Relcovax®, a dual receptor binding domain (RBD) and nucleocapsid (N) subunit protein vaccine candidate against SARS-CoV-2 virus

SARS-CoV-2, severe acute respiratory syndrome coronavirus-2, causes coronavirus disease- 2019 (COVID-19). Mostly, COVID-19 causes respiratory symptoms that can resemble those of a cold, the flu, or pneumonia. COVID-19 may harm more than just lungs and respiratory systems. It may also have an impact on other parts of the body and debilitating effects on humans, necessitating the development of vaccines at an unprecedented rate in order to protect humans from infections. In response to SARS-CoV-2 infection, mRNA, viral vector-based carrier and inactivated virus-based vaccines, as well as subunit vaccines, have recently been developed. We developed Relcovax®, a dual antigen (Receptor binding domain (RBD) and Nucleocapsid (N) proteins) subunit protein vaccine candidate. Preliminary mouse preclinical studies revealed that Relcovax® stimulates cell-mediated immunity and provides broader protection against two SARS-CoV-2 variants, including the delta strain. Before conducting human studies, detailed preclinical safety assessments are required, so Relcovax® was tested for safety, and immunogenicity in 28-day repeated dose toxicity studies in rats and rabbits. In the toxicity studies, there were no mortality or morbidity, abnormal clinical signs, abnormalities in a battery of neurobehavioral observations, abnormalities in detailed clinical and ophthalmological examinations, or changes in body weights or feed consumption. In any of the studies, no abnormal changes in organ weights, haematology, clinical chemistry, urinalysis parameters, or pathological findings were observed. Immunogenicity tests on rats and rabbits revealed 100 % seroconversion. Relcovax® was therefore found to be safe in animals, with a No Observed Adverse Effect Level (NOAEL) of 20 µg/protein in rats and rabbits. In efficacy studies, Relcovax® immunised hamsters demonstrated dose-dependent protection against SARS-CoV-2 infection, with a high dose (20 µg/protein) being the most protective, while in cynomolgus macaque monkey study, lowest dose 5 µg/protein had the highest efficacy. In conclusion, Relcovax® was found to be safe, immunogenic, and efficacious in in vivo studies.

A highly susceptible hACE2-transgenic mouse model for SARS-CoV-2 research

Several animal models have been used to assist the development of vaccines and therapeutics since the COVID-19 outbreak. Due to the lack of binding affinity of mouse angiotensin-converting enzyme II (ACE2) to the S protein of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), increasing the susceptibility of mice to SARS-CoV-2 infection was considered in several ways. Here, we generated a COVID-19 mouse model expressing human ACE2 (hACE2) under the control of the CAG promoter. Overexpression of hACE2 did not pose a significant effect on weight growth. After SARS-CoV-2 inoculation, mice showed obvious viral replication and production of inflammation within 7 days, with a gradual decrease in body weight until death. Virological testing found that the virus can replicate in the respiratory system, small intestine, and brain. Additionally, this mouse model was applied to compare two antibody drug candidates, the anti-RBD antibody (MW06) and the mouse CD24-conjugated anti-RBD antibody (mCD24-MW06). Differences in antiviral effects between these two antibodies can be demonstrated in this mouse model when a challenge dose that invalidates the anti-RBD antibody treatment was used. This study provided a new mouse model for studying SARS-CoV-2 pathogenesis and evaluating potential interventions.

Comparative Pathogenesis of Severe Acute Respiratory Syndrome Coronaviruses

Over the last two decades the world has witnessed the global spread of two genetically related highly pathogenic coronaviruses, severe acute respiratory syndrome coronavirus (SARS-CoV) and SARS-CoV-2. However, the impact of these outbreaks differed significantly with respect to the hospitalizations and fatalities seen worldwide. While many studies have been performed recently on SARS-CoV-2, a comparative pathogenesis analysis with SARS-CoV may further provide critical insights into the mechanisms of disease that drive coronavirus-induced respiratory disease. In this review, we comprehensively describe clinical and experimental observations related to transmission and pathogenesis of SARS-CoV-2 in comparison with SARS-CoV, focusing on human, animal, and in vitro studies. By deciphering the similarities and disparities of SARS-CoV and SARS-CoV-2, in terms of transmission and pathogenesis mechanisms, we offer insights into the divergent characteristics of these two viruses. This information may also be relevant to assessing potential novel introductions of genetically related highly pathogenic coronaviruses.

Clinical and experimental evidence suggest omicron variant of SARS-CoV-2 is inherently less pathogenic than delta variant independent of previous immunity

OBJECTIVES

To study clinical disease outcomes in both human and animal models to understand the pathogenicity of omicron compared to the delta variant.

METHODS

In this cross-sectional observational study, clinical outcomes of adults who tested positive at 2 testing centres in Delhi National Capital Region between January 2022 and March 2022 (omicron-infected; N = 2998) were compared to a similar geographical cohort (delta-infected; N = 3292). In addition, disease course and outcomes were studied in SARS-CoV-2-infected golden Syrian hamsters and K-18 humanized ACE2 transgenic mice.

RESULTS

Omicron variant infection was associated with a milder clinical course [83% (95% CI 61, 94) reduced risk of severity compared against delta] adjusting for vaccination, age, sex, prior infection and occupational risk. This correlated with lower disease index and vir comparing omicron with other variants in animal models.

CONCLUSIONS

Infections caused by the omicron variant were milder compared to those caused by the delta variant independent of previous immunity.

Niclosamide as a chemical probe for analyzing SARS-CoV-2 modulation of host cell lipid metabolism

Introduction

SARS-CoV-2 subverts host cell processes to facilitate rapid replication and dissemination, and this leads to pathological inflammation.

Methods

We used niclosamide (NIC), a poorly soluble anti-helminth drug identified initially for repurposed treatment of COVID-19, which activates the cells' autophagic and lipophagic processes as a chemical probe to determine if it can modulate the host cell's total lipid profile that would otherwise be either amplified or reduced during SARS-CoV-2 infection.

Results

Through parallel lipidomic and transcriptomic analyses we observed massive reorganization of lipid profiles of SARS-CoV-2 infected Vero E6 cells, especially with triglycerides, which were elevated early during virus replication, but decreased thereafter, as well as plasmalogens, which were elevated at later timepoints during virus replication, but were also elevated under normal cell growth. These findings suggested a complex interplay of lipid profile reorganization involving plasmalogen metabolism. We also observed that NIC treatment of both low and high viral loads does not affect virus entry. Instead, NIC treatment reduced the abundance of plasmalogens, diacylglycerides, and ceramides, which we found elevated during virus infection in the absence of NIC, resulting in a significant reduction in the production of infectious virions. Unexpectedly, at higher viral loads, NIC treatment also resulted in elevated triglyceride levels, and induced significant changes in phospholipid metabolism.

Discussion

We posit that future screens of approved or new partner drugs should prioritize compounds that effectively counter SARS-CoV-2 subversion of lipid metabolism, thereby reducing virus replication, egress, and the subsequent regulation of key lipid mediators of pathological inflammation.

Evaluation of Ayush-64 (a Polyherbal Formulation) and Its Ingredients in the Syrian Hamster Model for SARS-CoV-2 Infection Reveals the Preventative Potential of Alstonia scholaris

In the current study, we evaluated the efficacy of Ayush-64 (A64), a polyherbal formulation containing Alstonia scholaris (L.) R. Br. (A. scholaris), Caesalpinia crista L. (C. crista), Picrorhiza kurroa Royle ex Benth (P. kurroa), and Swertia chirata (Roxb.) H. Karst. (S. chirata) against COVID-19 in a Syrian hamster infection model. Preventative use of A64 resulted in the late-phase recovery of body weight loss in severe acquired respiratory syndrome coronavirus-2 (SARS-CoV-2)-infected hamsters, suppression of pro-inflammatory cytokines, and blunted pulmonary pathology. In addition, we also investigated the efficacy of individual ingredients of A64, viz., A. scholaris, C. crista, P. kurroa, and S. chirata, in the hamster model. The hamster challenge data showed robust anti-viral and immunomodulatory potential in A. scholaris, followed by P. kurroa. However, C. crista and S. chirata of A64 showed prominent immunomodulatory potential without limiting the lung viral load. In order to better understand the immunomodulatory potential of these herbal extracts, we used an in vitro assay of helper T cell differentiation and found that A. scholaris mediated a more profound suppression of Th1, Th2, and Th17 cell differentiation as compared to A64 and other ingredients. Taken together, our animal study data identifies the ameliorative potential of A64 in mitigating coronavirus disease-19 (COVID-19) pulmonary pathology. A. scholaris, a constituent extract of A64, showed relatively higher anti-viral and immunomodulatory potential against COVID-19. The present study warrants further investigations to identify the active pharmaceutical ingredients of A. scholaris for further studies.

Omicron sub-lineage BA.5 infection results in attenuated pathology in hACE2 transgenic mice

A recently emerged sub-lineage of Omicron, BA.5, together with BA.4, caused a fifth wave of coronavirus disease (COVID-19) in South Africa and subsequently emerged as a predominant strain globally due to its high transmissibility. The lethality of BA.5 infection has not been studied in an acute hACE2 transgenic (hACE2.Tg) mouse model. Here, we investigated tissue-tropism and immuno-pathology induced by BA.5 infection in hACE2.Tg mice. Our data show that intranasal infection of BA.5 in hACE2.Tg mice resulted in attenuated pulmonary infection and pathology with diminished COVID-19-induced clinical and pathological manifestations. BA.5, similar to Omicron (B.1.1.529), infection led to attenuated production of inflammatory cytokines, anti-viral response and effector T cell response as compared to the ancestral strain of SARS-CoV-2, Wuhan-Hu-1. We show that mice recovered from B.1.1.529 infection showed robust protection against BA.5 infection associated with reduced lung viral load and pathology. Together, our data provide insights as to why BA.5 infection escapes previous SARS-CoV-2 exposure induced-T cell immunity but may result in milder immuno-pathology and alleviated chances of re-infectivity in Omicron-recovered individuals.

Evaluation of Nafamostat as Chemoprophylaxis for SARS-CoV-2 Infection in Hamsters

The successful development of a chemoprophylaxis against SARS-CoV-2 could provide a tool for infection prevention that is implementable alongside vaccination programmes. Nafamostat is a serine protease inhibitor that inhibits SARS-CoV-2 entry in vitro, but it has not been characterised for chemoprophylaxis in animal models. Clinically, nafamostat is limited to intravenous delivery and has an extremely short plasma half-life. This study sought to determine whether intranasal dosing of nafamostat at 5 mg/kg twice daily was able to prevent the airborne transmission of SARS-CoV-2 from infected to uninfected Syrian Golden hamsters. SARS-CoV-2 RNA was detectable in the throat swabs of the water-treated control group 4 days after cohabitation with a SARS-CoV-2 inoculated hamster. However, throat swabs from the intranasal nafamostat-treated hamsters remained SARS-CoV-2 RNA negative for the full 4 days of cohabitation. Significantly lower SARS-CoV-2 RNA concentrations were seen in the nasal turbinates of the nafamostat-treated group compared to the control (p = 0.001). A plaque assay quantified a significantly lower concentration of infectious SARS-CoV-2 in the lungs of the nafamostat-treated group compared to the control (p = 0.035). When taken collectively with the pathological changes observed in the lungs and nasal mucosa, these data are strongly supportive of the utility of intranasally delivered nafamostat for the prevention of SARS-CoV-2 infection.

Cytokine response and damages in the lungs of aging Syrian hamsters on a high-fat diet infected with the SARS-CoV-2 virus

Hypertriglyceridemia, obesity, and aging are among the key risk factors for severe COVID-19 with acute respiratory distress syndrome (ARDS). One of the main prognostic biomarkers of ARDS is the level of cytokines IL-6 and TNF-α in the blood. In our study, we modeled hyperglyceridemia and hypercholesterolemia on 18-month-old Syrian hamsters (Mesocricetus auratus). By 18 months, the animals showed such markers of aging as weight stabilization with a tendency to reduce it, polycystic liver disease, decreased motor activity, and foci of alopecia. The high-fat diet caused an increase in triglycerides and cholesterol, as well as fatty changes in the liver. On the third day after infection with the SARS-CoV-2 virus, animals showed a decrease in weight in the groups with a high-fat diet. In the lungs of males on both diets, there was an increase in the concentration of IFN-α, as well as IL-6 in both males and females, regardless of the type of diet. At the same time, the levels of TNF-α and IFN-γ did not change in infected animals. Morphological studies of the lungs of hamsters with SARS-CoV-2 showed the presence of a pathological process characteristic of ARDS. These included bronchointerstitial pneumonia and diffuse alveolar damages. These observations suggest that in aging hamsters, the immune response to pro-inflammatory cytokines may be delayed to a later period. Hypertriglyceridemia, age, and gender affect the severity of COVID-19. These results will help to understand the pathogenesis of COVID-19 associated with age, gender, and disorders of fat metabolism in humans.

IL-9 aggravates SARS-CoV-2 infection and exacerbates associated airway inflammation

SARS-CoV-2 infection is known for causing broncho-alveolar inflammation. Interleukin 9 (IL-9) induces airway inflammation and bronchial hyper responsiveness in respiratory viral illnesses and allergic inflammation, however, IL-9 has not been assigned a pathologic role in COVID-19. Here we show, in a K18-hACE2 transgenic (ACE2.Tg) mouse model, that IL-9 contributes to and exacerbates viral spread and airway inflammation caused by SARS-CoV-2 infection. ACE2.Tg mice with CD4⁺ T cell-specific deficiency of the transcription factor Forkhead Box Protein O1 (Foxo1) produce significantly less IL-9 upon SARS-CoV-2 infection than the wild type controls and they are resistant to the severe inflammatory disease that characterises the control mice. Exogenous IL-9 increases airway inflammation in Foxo1-deficient mice, while IL-9 blockade reduces and suppresses airway inflammation in SARS-CoV-2 infection, providing further evidence for a Foxo1-Il-9 mediated Th cell-specific pathway playing a role in COVID-19. Collectively, our study provides mechanistic insight into an important inflammatory pathway in SARS-CoV-2 infection, and thus represents proof of principle for the development of host-directed therapeutics to mitigate disease severity.

Renin-Angiotensin System and Sex Differences in COVID-19: A Critical Assessment

The current epidemic of corona virus disease (COVID-19) has resulted in an immense health burden that became the third leading cause of death and potentially contributed to a decline in life expectancy in the United States. The severe acute respiratory syndrome-related coronavirus-2 binds to the surface-bound peptidase angiotensin-converting enzyme 2 (ACE2, EC 3.4.17.23) leading to tissue infection and viral replication. ACE2 is an important enzymatic component of the renin-angiotensin system (RAS) expressed in the lung and other organs. The peptidase regulates the levels of the peptide hormones Ang II and Ang-(1-7), which have distinct and opposing actions to one another, as well as other cardiovascular peptides. A potential consequence of severe acute respiratory syndrome-related coronavirus-2 infection is reduced ACE2 activity by internalization of the viral-ACE2 complex and subsequent activation of the RAS (higher ratio of Ang II:Ang-[1-7]) that may exacerbate the acute inflammatory events in COVID-19 patients and possibly contribute to the effects of long COVID-19. Moreover, COVID-19 patients present with an array of autoantibodies to various components of the RAS including the peptide Ang II, the enzyme ACE2, and the AT1 AT2 and Mas receptors. Greater disease severity is also evident in male COVID-19 patients, which may reflect underlying sex differences in the regulation of the 2 distinct functional arms of the RAS. The current review provides a critical evaluation of the evidence for an activated RAS in COVID-19 subjects and whether this system contributes to the greater severity of severe acute respiratory syndrome-related coronavirus-2 infection in males as compared with females.

A tissue specific-infection mouse model of SARS-CoV-2

Animal models play crucial roles in the rapid development of vaccines/drugs for the prevention and therapy of COVID-19, but current models have some deficits when studying the pathogenesis of SARS-CoV-2 on some special tissues or organs. Here, we generated a human ACE2 and SARS-CoV-2 N^F/F knockin mouse line that constitutively expresses human ACE2 and specifically expresses SARS-CoV-2 N gene induced by Cre-recombinase. By crossing with Cre transgenic lines allowing for lung-specific and constitutive expression, we generated lung-specific (Sftpc-hACE2-N^F/F) and constitutive SARS-CoV-2 N (EIIa-hACE2-N^F/F) expressing mice. Upon intranasal infection with a SARS-CoV-2 GFP/ΔN strain which can only replicate in SARS-CoV-2 N expressed cells, we demonstrated that both the Sftpc-hACE2-N^F/F and EIIa-hACE2-N^F/F mice support viral replication. Consistent with our design, viral replication was limited to the lung tissues in Sftpc-hACE2-N^F/F mice, while the EIIa-hACE2-N^F/F mice developed infections in multiple tissues. Furthermore, our model supports different SARS-CoV-2 variants infection, and it can be successfully used to evaluate the effects of therapeutic monoclonal antibodies (Ab1F11) and antiviral drugs (Molnupiravir). Finally, to test the effect of SARS-CoV-2 infection on male reproduction, we generated Sertoli cell-specific SARS-CoV-2 N expressed mice by crossing with AMH-Cre transgenic line. We found that SARS-CoV-2 GFP/ΔN strain could infect Sertoli cells, led to spermatogenic defects due to the destruction of blood-testis barrier. Overall, combining with different tissue-specific Cre transgenic lines, the human ACE2 and SARS-CoV-2 N^F/F line enables us to evaluate antivirals in vivo and study the pathogenesis of SARS-CoV-2 on some special tissues or organs.

G4-binding drugs, chlorpromazine and prochlorperazine, repurposed against COVID-19 infection in hamsters

The COVID-19 pandemic caused by SARS-CoV-2 has caused millions of infections and deaths worldwide. Limited treatment options and the threat from emerging variants underline the need for novel and widely accessible therapeutics. G-quadruplexes (G4s) are nucleic acid secondary structures known to affect many cellular processes including viral replication and transcription. We identified heretofore not reported G4s with remarkably low mutation frequency across >5 million SARS-CoV-2 genomes. The G4 structure was targeted using FDA-approved drugs that can bind G4s - Chlorpromazine (CPZ) and Prochlorperazine (PCZ). We found significant inhibition in lung pathology and lung viral load of SARS-CoV-2 challenged hamsters when treated with CPZ or PCZ that was comparable to the widely used antiviral drug Remdesivir. In support, in vitro G4 binding, inhibition of reverse transcription from RNA isolated from COVID-infected humans, and attenuated viral replication and infectivity in Vero cell cultures were clear in case of both CPZ and PCZ. Apart from the wide accessibility of CPZ/PCZ, targeting relatively invariant nucleic acid structures poses an attractive strategy against viruses like SARS-CoV-2, which spread fast and accumulate mutations quickly.

Comparison of Cardiovascular Pathology In Animal Models of SARS-CoV-2 Infection: Recommendations Regarding Standardization of Research Methods

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged as the viral pathogen that led to the global COVID-19 pandemic that began in late 2019. Because SARS-CoV-2 primarily causes a respiratory disease, much research conducted to date has focused on the respiratory system. However, SARS-CoV-2 infection also affects other organ systems, including the cardiovascular system. In this critical analysis of published data, we evaluate the evidence of cardiovascular pathology in human patients and animals. Overall, we find that the presence or absence of cardiovascular pathology is reported infrequently in both human autopsy studies and animal models of SARS-CoV-2 infection. Moreover, in those studies that have reported cardiovascular pathology, we identified issues in their design and execution that reduce confidence in the conclusions regarding SARS-CoV-2 infection as a cause of significant cardiovascular pathology. Throughout this overview, we expand on these limitations and provide recommendations to ensure a high level of scientific rigor and reproducibility.

Fenbendazole treatment against Dentostomella translucida in Syrian golden hamsters

Dentostomella translucida is an oxyurid nematode that was first discovered in the Mongolian gerbil but has also been detected in other wild and housed rodents. In conventional laboratory animals, oxyurid nematode parasites are widespread infections. A proven treatment strategy for pinworm eradication is the oral application of benzimidazoles, such as fenbendazole. In general, this drug is regarded as safe with minimal side effects. Nevertheless, in Sprague Dawley rats, a significantly reduced litter size could be seen after longer treatment with fenbendazole. Even though Dentostomella translucida was already described in Syrian golden hamsters (Mesocricetus auratus), data on treatment with fenbendazole and its effects on reproduction is lacking. Therefore, the main purposes of the study were (1) the verification of the effectiveness of fenbendazole as medicated feed (150 ppm) against this parasite in naturally infected Syrian golden hamsters in conventional husbandry and (2) monitoring of possible effects on reproduction during the treatment. Results show that fenbendazole treatment was highly effective against Dentostomella translucida, as numbers of pinworm eggs in the faeces were significantly reduced already after the first week of treatment in all animals. After four weeks of treatment, eggs were eradicated entirely. Interestingly, the average weaning weight was significantly reduced during treatment, but the litters were in good health.

A role for Toll-like receptor 3 in lung vascular remodeling associated with SARS-CoV-2 infection

Cardiovascular sequelae of severe acute respiratory syndrome (SARS) coronavirus-2 (CoV-2) disease 2019 (COVID-19) contribute to the complications of the disease. One potential complication is lung vascular remodeling, but the exact cause is still unknown. We hypothesized that endothelial TLR3 insufficiency contributes to lung vascular remodeling induced by SARS-CoV-2. In the lungs of COVID-19 patients and SARS-CoV-2 infected Syrian hamsters, we discovered thickening of the pulmonary artery media and microvascular rarefaction, which were associated with decreased TLR3 expression in lung tissue and pulmonary artery endothelial cells (ECs). In vitro , SARS-CoV-2 infection reduced endothelial TLR3 expression. Following infection with mouse-adapted (MA) SARS-CoV-2, TLR3 knockout mice displayed heightened pulmonary artery remodeling and endothelial apoptosis. Treatment with the TLR3 agonist polyinosinic:polycytidylic acid reduced lung tissue damage, lung vascular remodeling, and endothelial apoptosis associated with MA SARS-CoV-2 infection. In conclusion, repression of endothelial TLR3 is a potential mechanism of SARS-CoV-2 infection associated lung vascular remodeling and enhancing TLR3 signaling is a potential strategy for treatment.

Development of a Syrian hamster anti-PD-L1 monoclonal antibody enables oncolytic adenoviral immunotherapy modelling in an immunocompetent virus replication permissive setting

Introduction

Immune checkpoint inhibitors (ICIs) have revolutionized the treatment of cancer, but preclinical testing of hypotheses such as combination therapies has been complicated, in part due to species incompatibility issues. For example, one of few known permissive animal models for oncolytic adenoviruses is the Syrian hamster, for which an ICI, mainly an anti-PD-L1 monoclonal antibody (mAb) was not previously available. In this study, we developed an anti-Syrian hamster PD-L1 mAb to enable the evaluation of safety and efficacy, when combining anti-PD-L1 with an oncolytic adenovirus encoding tumour necrosis factor alpha (TNFα) and interleukin-2 (IL-2) (Ad5/3-E2F-D24-hTNFα-IRES-hIL-2 or TILT-123).

Methods

Recombinant Syrian hamster PD-L1 was expressed and mice immunized for mAb formation using hybridoma technology. Clonal selection through binding and functional studies in vitro, in silico and in vivo identified anti-PD-L1 clone 11B12-1 as the primary mAb candidate for immunotherapy modelling. The oncolytic virus (OV) and ICI combination approach was then evaluated using 11B12-1 and TILT-123 in a Syrian hamster model of pancreatic ductal adenocarcinoma (PDAC).

Results

Supernatants from hybridoma parent subclone 11B12B4 provided the highest positive PD-L1 signal, on Syrian hamster PBMCs and three cancer cell lines (HT100, HapT1 and HCPC1). In vitro co-cultures revealed superior immune modulated profiles of cell line matched HT100 tumour infiltrating lymphocytes when using subclones of 7G2, 11B12 and 12F1. Epitope binning and epitope prediction using AlphaFold2 and ColabFold revealed two distinct functional epitopes for clone 11B12-1 and 12F1-1. Treatment of Syrian hamsters bearing HapT1 tumours, with 11B12-1 induced significantly better (p<0.05) tumour growth control than isotype control by day 12. 12F1-1 did not induce significant tumour growth control. The combination of 11B12-1 with oncolytic adenovirus TILT-123 improved tumour growth control further, when compared to monotherapy (p<0.05) by day 26.

Conclusions

Novel Syrian hamster anti-PD-L1 clone 11B12-1 induces tumour growth control in a hamster model of PDAC. Combining 11B12-1 with oncolytic adenovirus TILT-123 improves tumour growth control further and demonstrates good safety and toxicity profiles.

Pharmacological potential of Withania somnifera (L.) Dunal and Tinospora cordifolia (Willd.) Miers on the experimental models of COVID-19, T cell differentiation, and neutrophil functions

Cytokine release syndrome (CRS) due to severe acute respiratory coronavirus-2 (SARS-CoV-2) infection leads to life-threatening pneumonia which has been associated with coronavirus disease (COVID-19) pathologies. Centuries-old Asian traditional medicines such as Withania somnifera (L.) Dunal (WS) and Tinospora cordifolia (Willd.) Miers (TC) possess potent immunomodulatory effects and were used by the AYUSH ministry, in India during the COVID-19 pandemic. In the present study, we investigated WS and TC's anti-viral and immunomodulatory efficacy at the human equivalent doses using suitable in vitro and in vivo models. While both WS and TC showed immuno-modulatory potential, WS showed robust protection against loss in body weight, viral load, and pulmonary pathology in the hamster model of SARS-CoV2. In vitro pretreatment of mice and human neutrophils with WS and TC had no adverse effect on PMA, calcium ionophore, and TRLM-induced ROS generation, phagocytosis, bactericidal activity, and NETs formation. Interestingly, WS significantly suppressed the pro-inflammatory cytokines-induced Th1, Th2, and Th17 differentiation. We also used hACE2 transgenic mice to further investigate the efficacy of WS against acute SARS-CoV2 infection. Prophylactic treatment of WS in the hACE2 mice model showed significant protection against body weight loss, inflammation, and the lung viral load. The results obtained indicate that WS promoted the immunosuppressive environment in the hamster and hACE2 transgenic mice models and limited the worsening of the disease by reducing inflammation, suggesting that WS might be useful against other acute viral infections. The present study thus provides pre-clinical efficacy data to demonstrate a robust protective effect of WS against COVID-19 through its broader immunomodulatory activity.

A broadly neutralizing monoclonal antibody overcomes the mutational landscape of emerging SARS-CoV-2 variants of concern

The emergence of new variants of SARS-CoV-2 necessitates unremitting efforts to discover novel therapeutic monoclonal antibodies (mAbs). Here, we report an extremely potent mAb named P4A2 that can neutralize all the circulating variants of concern (VOCs) with high efficiency, including the highly transmissible Omicron. The crystal structure of the P4A2 Fab:RBD complex revealed that the residues of the RBD that interact with P4A2 are a part of the ACE2-receptor-binding motif and are not mutated in any of the VOCs. The pan coronavirus pseudotyped neutralization assay confirmed that the P4A2 mAb is specific for SARS-CoV-2 and its VOCs. Passive administration of P4A2 to K18-hACE2 transgenic mice conferred protection, both prophylactically and therapeutically, against challenge with VOCs. Overall, our data shows that, the P4A2 mAb has immense therapeutic potential to neutralize the current circulating VOCs. Due to the overlap between the P4A2 epitope and ACE2 binding site on spike-RBD, P4A2 may also be highly effective against a number of future variants.

Proinflammatory Innate Cytokines and Distinct Metabolomic Signatures Shape the T Cell Response in Active COVID-19

The underlying factors contributing to the evolution of SARS-CoV-2-specific T cell responses during COVID-19 infection remain unidentified. To address this, we characterized innate and adaptive immune responses with metabolomic profiling longitudinally at three different time points (0–3, 7–9, and 14–16 days post-COVID-19 positivity) from young, mildly symptomatic, active COVID-19 patients infected during the first wave in mid-2020. We observed that anti-RBD IgG and viral neutralization are significantly reduced against the delta variant, compared to the ancestral strain. In contrast, compared to the ancestral strain, T cell responses remain preserved against the delta and omicron variants. We determined innate immune responses during the early stage of active infection, in response to TLR 3/7/8-mediated activation in PBMCs and serum metabolomic profiling. Correlation analysis indicated PBMCs-derived proinflammatory cytokines, IL-18, IL-1β, and IL-23, and the abundance of plasma metabolites involved in arginine biosynthesis were predictive of a robust SARS-CoV-2-specific Th1 response at a later stage (two weeks after PCR positivity). These observations may contribute to designing effective vaccines and adjuvants that promote innate immune responses and metabolites to induce a long-lasting anti-SARS-CoV-2-specific T cell response.

Pathobiology and dysbiosis of the respiratory and intestinal microbiota in 14 months old Golden Syrian hamsters infected with SARS-CoV-2

The pandemic of severe acute respiratory syndrome coronavirus 2 (SARS2) affected the geriatric population. Among research models, Golden Syrian hamsters (GSH) are one of the most representative to study SARS2 pathogenesis and host responses. However, animal studies that recapitulate the effects of SARS2 in the human geriatric population are lacking. To address this gap, we inoculated 14 months old GSH with a prototypic ancestral strain of SARS2 and studied the effects on virus pathogenesis, virus shedding, and respiratory and gastrointestinal microbiome changes. SARS2 infection led to high vRNA loads in the nasal turbinates (NT), lungs, and trachea as well as higher pulmonary lesions scores later in infection. Dysbiosis throughout SARS2 disease progression was observed in the pulmonary microbial dynamics with the enrichment of opportunistic pathogens (Haemophilus, Fusobacterium, Streptococcus, Campylobacter, and Johnsonella) and microbes associated with inflammation (Prevotella). Changes in the gut microbial community also reflected an increase in multiple genera previously associated with intestinal inflammation and disease (Helicobacter, Mucispirillum, Streptococcus, unclassified Erysipelotrichaceae, and Spirochaetaceae). Influenza A virus (FLUAV) pre-exposure resulted in slightly more pronounced pathology in the NT and lungs early on (3 dpc), and more notable changes in lungs compared to the gut microbiome dynamics. Similarities among aged GSH and the microbiome in critically ill COVID-19 patients, particularly in the lower respiratory tract, suggest that GSHs are a representative model to investigate microbial changes during SARS2 infection. The relationship between the residential microbiome and other confounding factors, such as SARS2 infection, in a widely used animal model, contributes to a better understanding of the complexities associated with the host responses during viral infections.

Prophylactic treatment of Glycyrrhiza glabra mitigates COVID-19 pathology through inhibition of pro-inflammatory cytokines in the hamster model and NETosis

Severe coronavirus disease (COVID-19) is accompanied by acute respiratory distress syndrome and pulmonary pathology, and is presented mostly with an inflammatory cytokine release, a dysregulated immune response, a skewed neutrophil/lymphocyte ratio, and a hypercoagulable state. Though vaccinations have proved effective in reducing the COVID-19-related mortality, the limitation of the use of vaccine against immunocompromised individuals, those with comorbidity, and emerging variants remains a concern. In the current study, we investigate for the first time the efficacy of the Glycyrrhiza glabra (GG) extract, a potent immunomodulator, against SARS-CoV-2 infection in hamsters. Prophylactic treatment with GG showed protection against loss in body weight and a 35%–40% decrease in lung viral load along with reduced lung pathology in the hamster model. Remarkably, GG reduced the mRNA expression of pro-inflammatory cytokines and plasminogen activator inhibitor-1 (PAI-1). In vitro, GG acted as a potent immunomodulator by reducing Th2 and Th17 differentiation and IL-4 and IL-17A cytokine production. In addition, GG also showed robust potential to suppress ROS, mtROS, and NET generation in a concentration-dependent manner in both human polymorphonuclear neutrophils (PMNs) and murine bone marrow-derived neutrophils (BMDNs). Taken together, we provide evidence for the protective efficacy of GG against COVID-19 and its putative mechanistic insight through its immunomodulatory properties. Our study provides the proof of concept for GG efficacy against SARS-CoV-2 using a hamster model and opens the path for further studies aimed at identifying the active ingredients of GG and its efficacy in COVID-19 clinical cases.

After the virus has cleared-Can preclinical models be employed for Long COVID research?

Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2) can cause the life-threatening acute respiratory disease called COVID-19 (Coronavirus Disease 2019) as well as debilitating multiorgan dysfunction that persists after the initial viral phase has resolved. Long COVID or Post-Acute Sequelae of COVID-19 (PASC) is manifested by a variety of symptoms, including fatigue, dyspnea, arthralgia, myalgia, heart palpitations, and memory issues sometimes affecting between 30% and 75% of recovering COVID-19 patients. However, little is known about the mechanisms causing Long COVID and there are no widely accepted treatments or therapeutics. After introducing the clinical aspects of acute COVID-19 and Long COVID in humans, we summarize the work in animals (mice, Syrian hamsters, ferrets, and nonhuman primates (NHPs)) to model human COVID-19. The virology, pathology, immune responses, and multiorgan involvement are explored. Additionally, any studies investigating time points longer than 14 days post infection (pi) are highlighted for insight into possible long-term disease characteristics. Finally, we discuss how the models can be leveraged for treatment evaluation, including pharmacological agents that are currently in human clinical trials for treating Long COVID. The establishment of a recognized Long COVID preclinical model representing the human condition would allow the identification of mechanisms causing disease as well as serve as a vehicle for evaluating potential therapeutics.

Animal models for COVID-19: advances, gaps and perspectives

COVID-19, caused by SARS-CoV-2, is the most consequential pandemic of this century. Since the outbreak in late 2019, animal models have been playing crucial roles in aiding the rapid development of vaccines/drugs for prevention and therapy, as well as understanding the pathogenesis of SARS-CoV-2 infection and immune responses of hosts. However, the current animal models have some deficits and there is an urgent need for novel models to evaluate the virulence of variants of concerns (VOC), antibody-dependent enhancement (ADE), and various comorbidities of COVID-19. This review summarizes the clinical features of COVID-19 in different populations, and the characteristics of the major animal models of SARS-CoV-2, including those naturally susceptible animals, such as non-human primates, Syrian hamster, ferret, minks, poultry, livestock, and mouse models sensitized by genetically modified, AAV/adenoviral transduced, mouse-adapted strain of SARS-CoV-2, and by engraftment of human tissues or cells. Since understanding the host receptors and proteases is essential for designing advanced genetically modified animal models, successful studies on receptors and proteases are also reviewed. Several improved alternatives for future mouse models are proposed, including the reselection of alternative receptor genes or multiple gene combinations, the use of transgenic or knock-in method, and different strains for establishing the next generation of genetically modified mice.

Cardiopulmonary Injury in the Syrian Hamster Model of COVID-19

The Syrian hamster has proved useful in the evaluation of therapeutics and vaccines for severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2). To advance the model for preclinical studies, we conducted serial sacrifice of lungs, large pulmonary vessels, and hearts from male and female Syrian hamsters for days 1–4, and 8 post-infection (dpi) following infection with a high dose of SARS-CoV-2. Evaluation of microscopic lung histopathology scores suggests 4 and 8 dpi as prime indicators in the evaluation of moderate pathology with bronchial hyperplasia, alveolar involvement and bronchiolization being key assessments of lung disease and recovery, respectively. In addition, neutrophil levels, red blood cell count and hematocrit showed significant increases during early infection. We present histological evidence of severe damage to the pulmonary vasculature with extensive leukocyte transmigration and the loss of endothelial cells and tunica media. Our evidence of endothelial and inflammatory cell death in the pulmonary vessels suggests endothelialitis secondary to SARS-CoV-2 epithelial cell infection as a possible determinant of the pathological findings along with the host inflammatory response. Lastly, pathological examination of the heart revealed evidence for intracardiac platelet/fibrin aggregates in male and female hamsters on 8 dpi, which might be indicative of a hypercoagulative state in these animals.

Natural and genetically-modified animal models to investigate pulmonary and extrapulmonary manifestations of COVID-19

Coronavirus disease-19 (COVID-19), a pandemic caused by Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), is a primarily respiratory tract disease. Suitable animal models for COVID-19 are required to study various aspects of pathogenesis, drug discovery, effective and safe vaccine development. Several laboratory animals including, non-human primates, hamsters, ferrets, transgenic mice, and zebrafish, have been used and proven their significance experimentally. Currently available animal models of SARS-CoV-2 can be broadly classified into two categories 1) natural animal models 2) genetically-modified that exhibit different degrees of susceptibility of SARS-CoV-2, tissue damage in respiratory and other organ systems. Not all the available animal models mimic COVID-19-like phenotype completely. Therefore, understanding various aspects of COVID-19 requires different animal models. In this review article, we provide an update on the immune response and clinical manifestations observed in naturally occurring and genetically-modified animals of COVID-19. We then review the transmission, viral replication, lung pathology, immunological aspects, and extrapulmonary phenotypes observed in various animal models. In the end, we put forth our perspective on the anticipated uses, disadvantages, and limitations of each type of animal model.

Designing and characterization of a SARS-CoV-2 immunogen with receptor binding motif grafted on a protein scaffold: An epitope-focused vaccine approach

The COVID-19 pandemic caused by SARS-CoV-2 has a significant burden on the economy and healthcare around the world. Vaccines are the most effective tools to fight infectious diseases by containing the spread of the disease. The current vaccines against SARS-CoV-2 are mostly based on the spike protein of SARS-CoV-2, which is large and has many immune-dominant non-neutralizing epitopes that may effectively skew the antibody response towards non-neutralizing antibodies. Here, we have explored the possibility of immune-focusing the receptor binding motif (RBM) of the spike protein of SARS-CoV-2 that induces mostly neutralizing antibodies in natural infection or in vacinees. The result shows that the scaffolded RBM can bind to Angiotensin Converting Enzyme 2 (ACE2) although with low affinity and induces a strong antibody response in mice. The immunized sera can bind both, the receptor binding domain (RBD) and the spike protein, which holds the RBM in its natural context. Sera from the immunized mice showed robust interferon γ response but poor neutralization of SARS-CoV-2 suggesting presence of a predominant T cell epitope on scaffolded RBM. Together, we provide a strategy for inducing strong antigenic T cell response which could be exploited further for future vaccine designing and development against SARS-CoV-2 infection.

Construction of a new chromosome-scale, long-read reference genome assembly for the Syrian hamster, Mesocricetus auratus

BACKGROUND

The Syrian hamster (Mesocricetus auratus) has been suggested as a useful mammalian model for a variety of diseases and infections, including infection with respiratory viruses such as SARS-CoV-2. The MesAur1.0 genome assembly was generated in 2013 using whole-genome shotgun sequencing with short-read sequence data. Current more advanced sequencing technologies and assembly methods now permit the generation of near-complete genome assemblies with higher quality and greater continuity.

FINDINGS

Here, we report an improved assembly of the M. auratus genome (BCM_Maur_2.0) using Oxford Nanopore Technologies long-read sequencing to produce a chromosome-scale assembly. The total length of the new assembly is 2.46 Gb, similar to the 2.50-Gb length of a previous assembly of this genome, MesAur1.0. BCM_Maur_2.0 exhibits significantly improved continuity, with a scaffold N50 that is 6.7 times greater than MesAur1.0. Furthermore, 21,616 protein-coding genes and 10,459 noncoding genes are annotated in BCM_Maur_2.0 compared to 20,495 protein-coding genes and 4,168 noncoding genes in MesAur1.0. This new assembly also improves the unresolved regions as measured by nucleotide ambiguities, where ∼17.11% of bases in MesAur1.0 were unresolved compared to BCM_Maur_2.0, in which the number of unresolved bases is reduced to 3.00%.

CONCLUSIONS

Access to a more complete reference genome with improved accuracy and continuity will facilitate more detailed, comprehensive, and meaningful research results for a wide variety of future studies using Syrian hamsters as models.