Lipocalin 2 Protects from Inflammation and Tumorigenesis Associated with Gut Microbiota Alterations

High mucosal and fecal concentrations of the antimicrobial siderophore-binding peptide Lipocalin-2 (Lcn2) are observed in inflammatory bowel disease. However, Lcn2 function in chronic intestinal inflammation remains unclear. Here, we demonstrate that Lcn2 protects from early-onset colitis and spontaneous emergence of right-sided colonic tumors resulting from IL-10 deficiency. Exacerbated inflammation in Lcn2(-/-)/Il10(-/-) mice is driven by IL-6, which also controls tumorigenesis. Lcn2(-/-)/Il10(-/-) mice exhibit profound alterations in gut microbial composition, which contributes to inflammation and tumorigenesis, as demonstrated by the transmissibility of the phenotype and protection conferred by antibiotics. Specifically, facultative pathogenic Alistipes spp. utilize enterobactin as iron source, bloom in Lcn2(-/-)/Il10(-/-) mice, and are sufficient to induce colitis and right-sided tumors when transferred into Il10(-/-) mice. Our results demonstrate that Lcn2 protects against intestinal inflammation and tumorigenesis associated with alterations in the microbiota.

ER stress transcription factor Xbp1 suppresses intestinal tumorigenesis and directs intestinal stem cells

X-box–binding protein 1 suppresses tumor formation in the gut by regulating Ire1α and Stat3-mediated regenerative responses in the epithelium as a consequence of ER stress.

Unresolved endoplasmic reticulum (ER) stress in the epithelium can provoke intestinal inflammation. Hypomorphic variants of ER stress response mediators, such as X-box–binding protein 1 (XBP1), confer genetic risk for inflammatory bowel disease. We report here that hypomorphic Xbp1 function instructs a multilayered regenerative response in the intestinal epithelium. This is characterized by intestinal stem cell (ISC) expansion as shown by an inositol-requiring enzyme 1α (Ire1α)–mediated increase in Lgr5⁺ and Olfm4⁺ ISCs and a Stat3-dependent increase in the proliferative output of transit-amplifying cells. These consequences of hypomorphic Xbp1 function are associated with an increased propensity to develop colitis-associated and spontaneous adenomatous polyposis coli (APC)–related tumors of the intestinal epithelium, which in the latter case is shown to be dependent on Ire1α. This study reveals an unexpected role for Xbp1 in suppressing tumor formation through restraint of a pathway that involves an Ire1α- and Stat3-mediated regenerative response of the epithelium as a consequence of ER stress. As such, Xbp1 in the intestinal epithelium not only regulates local inflammation but at the same time also determines the propensity of the epithelium to develop tumors.

Epithelial IL-23R Signaling Licenses Protective IL-22 Responses in Intestinal Inflammation

A plethora of functional and genetic studies have suggested a key role for the IL-23 pathway in chronic intestinal inflammation. Currently, pathogenic actions of IL-23 have been ascribed to specific effects on immune cells. Herein, we unveil a protective role of IL-23R signaling. Mice deficient in IL-23R expression in intestinal epithelial cells (Il23R(ΔIEC)) have reduced Reg3b expression, show a disturbed colonic microflora with an expansion of flagellated bacteria, and succumb to DSS colitis. Surprisingly, Il23R(ΔIEC) mice show impaired mucosal IL-22 induction in response to IL-23. αThy-1 treatment significantly deteriorates colitis in Il23R(ΔIEC) animals, which can be rescued by IL-22 application. Importantly, exogenous Reg3b administration rescues DSS-treated Il23R(ΔIEC) mice by recruiting neutrophils as IL-22-producing cells, thereby restoring mucosal IL-22 levels. The study identifies a critical barrier-protective immune pathway that originates from, and is orchestrated by, IL-23R signaling in intestinal epithelial cells.

Developmental control of the Nlrp6 inflammasome and a substrate, IL-18, in mammalian intestine

The inflammasome is a multiprotein complex whose formation is triggered when a NOD-like receptor binds a pathogen ligand, resulting in activated caspase-1, which converts certain interleukins (IL-1β, IL-18, and IL-33) to their active forms. There is currently no information on regulation of this system around the time of birth. We employed transcript profiling of fetal rat intestinal and lung RNA at embryonic days 16 (E16) and 20 (E20) with out-of-sample validation using quantitative RT-PCR. Transcript profiling and quantitative RT-PCR demonstrated that transcripts of core components of the NOD-like receptor Nlrp6 inflammasome (Nlrp6, Pycard, Caspase-1) and one of its substrates, IL-18, were increased at E20 compared with E16 in fetal intestine and not lung. Immunohistochemistry demonstrated increased Pycard in intestinal epithelium. Western blotting demonstrated that IL-18 was undetectable at E16, clearly detectable at E20 in its inactive form, and detectable postnatally in both its inactive and active form. Dramatic upregulation of IL-18 was also observed in the fetal sheep jejunum in late gestation (P = 0.006). Transcription factor binding analysis of the rat array data revealed an overrepresentation of nuclear transcription factor binding sites peroxisome proliferator-activated receptor γ (PPAR-γ) and retinoid X receptor-α and chicken ovalbumin upstream promoter transcription factor 1 in the region 1,000 bp upstream of the transcription start site. Rosiglitazone, a PPAR-γ agonist, more than doubled levels of NLRP6 mRNA in human intestinal epithelial (Caco2) cells. These observations provide the first evidence, to our knowledge, linking activity of PPAR-γ to expression of a NOD-like receptor and adds to a growing body of evidence linking pattern recognition receptors of the innate immune system and intestinal colonization.

Interferon-gamma increases neuronal death in response to amyloid-beta1-42

Background

Alzheimer's disease is a neurodegenerative disorder characterized by a progressive cognitive impairment, the consequence of neuronal dysfunction and ultimately the death of neurons. The amyloid hypothesis proposes that neuronal damage results from the accumulation of insoluble, hydrophobic, fibrillar peptides such as amyloid-β_1-42. These peptides activate enzymes resulting in a cascade of second messengers including prostaglandins and platelet-activating factor. Apoptosis of neurons is thought to follow as a consequence of the uncontrolled release of second messengers. Biochemical, histopathological and genetic studies suggest that pro-inflammatory cytokines play a role in neurodegeneration during Alzheimer's disease. In the current study we examined the effects of interferon (IFN)-γ, tumour necrosis factor (TNF)α, interleukin (IL)-1β and IL-6 on neurons.

Methods

Primary murine cortical or cerebellar neurons, or human SH-SY5Y neuroblastoma cells, were grown in vitro. Neurons were treated with cytokines prior to incubation with different neuronal insults. Cell survival, caspase-3 activity (a measure of apoptosis) and prostaglandin production were measured. Immunoblots were used to determine the effects of cytokines on the levels of cytoplasmic phospholipase A₂ or phospholipase C γ-1.

Results

While none of the cytokines tested were directly neurotoxic, pre-treatment with IFN-γ sensitised neurons to the toxic effects of amyloid-β_1-42 or HuPrP82-146 (a neurotoxic peptide found in prion diseases). The effects of IFN-γ were seen on cortical and cerebellar neurons, and on SH-SY5Y neuroblastoma cells. However, pre-treatment with IFN-γ did not affect the sensitivity to neurons treated with staurosporine or hydrogen peroxide. Pre-treatment with IFN-γ increased the levels of cytoplasmic phospholipase A₂ in SH-SY5Y cells and increased prostaglandin E₂ production in response to amyloid-β_1-42.

Conclusion

Treatment of neuronal cells with IFN-γ increased neuronal death in response to amyloid-β_1-42 or HuPrP82-146. IFN-γ increased the levels of cytoplasmic phospholipase A₂ in cultured neuronal cells and increased expression of cytoplasmic phospholipase A₂ was associated with increased production of prostaglandin E₂ in response to amyloid-β_1-42 or HuPrP82-146. Such observations suggest that IFN-γ produced within the brain may increase neuronal loss in Alzheimer's disease.

Simvastatin treatment prolongs the survival of scrapie-infected mice

Statins, drugs that decrease cholesterol biosynthesis, are known to reduce the formation of the disease-associated isoform of the prion protein (PrP) in neuroblastoma cells in vitro. In this study, we report the effects of simvastatin, a clinically approved statin that penetrates the brain, on mice infected with the ME7 strain of scrapie. The decline in motor functions associated with scrapie infection was delayed in mice receiving (1 mg/kg) simvastatin, a dosage used to treat hypercholesterolemia in humans. Simvastatin treatment also significantly prolonged the survival times of infected mice (193 vs. 183 days). These results indicate that low-dosage simvastatin treatment affects the progression of experimental scrapie, and supports the concept that statin treatment may influence the prion pathogenesis.

Prostaglandin D2 mediates neuronal damage by amyloid-β or prions which activates microglial cells

Microglial cells killed neurons damaged following incubation with sub-lethal concentrations of peptides derived from either the human prion protein (HuPrP82-146) or amyloid-beta1-42 (a peptide found in Alzheimer's disease). HuPrP82-146 or amyloid-beta1-42 induced phenotypic changes in neurons that caused them to bind a CD14-IgG chimera. In co-cultures microglial cells produced interleukin (IL)-6 in response to HuPrP82-146 or amyloid-beta1-42 damaged neurons. The binding of the CD14-IgG chimera to HuPrP82-146 or amyloid-beta1-42 damaged neurons was reduced by pre-treatment with cyclo-oxygenase (COX)-1 inhibitors and in co-cultures, COX-1 inhibitors significantly increased neuronal survival. Studies with individual prostaglandins demonstrated that the addition of prostaglandin D2, or prostaglandin E2, but not other prostaglandins (F2alpha, H2, I2 or 15-dJ2), mimicked the effects of amyloid-beta1-42 on neurons. Thus, prostaglandin D2 or E2 damaged neurons bound the CD14-IgG chimera, and in co-cultures prostaglandin D2 damaged neurons activated microglial cells. These effects were mediated via the DP prostanoid receptor; DP receptor agonists BW245C or SQ27986 induced neuronal damage, while the DP receptor antagonist BWA868C was neuroprotective in co-cultures. These results indicate that prostaglandin D2, produced following activation of COX-1 by sub-lethal concentrations of HuPrP82-146 or amyloid-beta1-42, causes phenotypic changes in neurons that activates microglial cells and leads to neuronal loss.

Platelet-activating factor antagonists protect amyloid-β damaged neurons from microglia-mediated death

Neurons treated with sub-lethal concentrations of amyloid-beta1-42 developed phenotypic changes and selectively bound a CD14-IgG chimera; in co-cultures, microglia recognised and killed these amyloid-beta1-42 -damaged neurons. Pre-treatment with the platelet-activating factor (PAF) antagonists (Hexa-PAF, CV6209 or ginkgolide B) reduced CD14-IgG binding to amyloid-beta1-42 -damaged neurons, and the presence of PAF antagonists in co-cultures increased neuronal survival in a dose-dependant manner. PAF antagonists also protected neurons treated with HuPrP82-146, a peptide found in prion diseases. Second messenger studies demonstrated that the addition of PAF mimicked some of the effects of amyloid-beta1-42 on neurons. PAF-damaged neurons bound CD14-IgG, and PAF-damaged neurons were killed by microglia in a CD14-dependent process. Neuronal death was inversely related to both the concentration of PAF, and the number of microglia added. The effects of PAF were reduced by an antagonist of the prostanoid D receptor (BWA868C) indicating that neuronal damage induced by PAF is partly mediated by prostaglandins. These observations are compatible with the hypothesis that sub-lethal concentrations of amyloid-beta1-42 stimulate a cascade of second messengers including PAF and the prostaglandins. At nanomolar concentrations PAF induces a change in neuronal phenotype that activates microglia via the CD14 molecule, these activated microglia then kill the amyloid-beta1-42 damaged neurons.

Leptin Matures Aspects of Lung Structure and Function in the Ovine Fetus

In human and ovine fetuses, glucocorticoids stimulate leptin secretion, although the extent to which leptin mediates the maturational effects of glucocorticoids on pulmonary development is unclear. This study investigated the effects of leptin administration on indices of lung structure and function before birth. Chronically catheterized singleton sheep fetuses were infused iv for 5 days with either saline or recombinant ovine leptin (0.5 mg/kg · d leptin (LEP), 0.5 LEP or 1.0 mg/kg · d, 1.0 LEP) from 125 days of gestation (term ∼145 d). Over the infusion, leptin administration increased plasma leptin, but not cortisol, concentrations. On the fifth day of infusion, 0.5 LEP reduced alveolar wall thickness and increased the volume at closing pressure of the pressure-volume deflation curve, interalveolar septal elastin content, secondary septal crest density, and the mRNA abundance of the leptin receptor (Ob-R) and surfactant protein (SP) B. Neither treatment influenced static lung compliance, maximal lung volume at 40 cmH2O, lung compartment volumes, alveolar surface area, pulmonary glycogen, protein content of the long form signaling Ob-Rb or phosphorylated signal transducers and activators of transcription-3, or mRNA levels of SP-A, C, or D, elastin, vascular endothelial growth factor-A, the vascular endothelial growth factor receptor 2, angiotensin-converting enzyme, peroxisome proliferator-activated receptor γ, or parathyroid hormone-related peptide. Leptin administration in the ovine fetus during late gestation promotes aspects of lung maturation, including up-regulation of SP-B.

Analysis of Serological Biomarkers of SARS-CoV-2 Infection in Convalescent Samples From Severe, Moderate and Mild COVID-19 Cases

Precision monitoring of antibody responses during the COVID-19 pandemic is increasingly important during large scale vaccine rollout and rise in prevalence of Severe Acute Respiratory Syndrome-related Coronavirus-2 (SARS-CoV-2) variants of concern (VOC). Equally important is defining Correlates of Protection (CoP) for SARS-CoV-2 infection and COVID-19 disease. Data from epidemiological studies and vaccine trials identified virus neutralising antibodies (Nab) and SARS-CoV-2 antigen-specific (notably RBD and S) binding antibodies as candidate CoP. In this study, we used the World Health Organisation (WHO) international standard to benchmark neutralising antibody responses and a large panel of binding antibody assays to compare convalescent sera obtained from: a) COVID-19 patients; b) SARS-CoV-2 seropositive healthcare workers (HCW) and c) seronegative HCW. The ultimate aim of this study is to identify biomarkers of humoral immunity that could be used to differentiate severe from mild or asymptomatic SARS-CoV-2 infections. Some of these biomarkers could be used to define CoP in further serological studies using samples from vaccination breakthrough and/or re-infection cases. Whenever suitable, the antibody levels of the samples studied were expressed in International Units (IU) for virus neutralisation assays or in Binding Antibody Units (BAU) for ELISA tests. In this work we used commercial and non-commercial antibody binding assays; a lateral flow test for detection of SARS-CoV-2-specific IgG/IgM; a high throughput multiplexed particle flow cytometry assay for SARS-CoV-2 Spike (S), Nucleocapsid (N) and Receptor Binding Domain (RBD) proteins); a multiplex antigen semi-automated immuno-blotting assay measuring IgM, IgA and IgG; a pseudotyped microneutralisation test (pMN) and an electroporation-dependent neutralisation assay (EDNA). Our results indicate that overall, severe COVID-19 patients showed statistically significantly higher levels of SARS-CoV-2-specific neutralising antibodies (average 1029 IU/ml) than those observed in seropositive HCW with mild or asymptomatic infections (379 IU/ml) and that clinical severity scoring, based on WHO guidelines was tightly correlated with neutralisation and RBD/S antibodies. In addition, there was a positive correlation between severity, N-antibody assays and intracellular virus neutralisation.

Localization and control of expression of VEGF-A and the VEGFR-2 receptor in fetal sheep intestines

We studied expression of vascular endothelial growth factor A (VEGF-A) and its main receptor, VEGFR-2, in the small intestine from five groups of fetal sheep (each n = 5): 1) preterm controls, 2) term controls, 3) preterm animals where the fetus was infused with cortisol, or 4) saline, and 5) term animals where adrenalectomy had been performed preterm. The main transcript expressed in fetal small intestine was VEGF-A165. Comparing term with preterm animals, there were significantly higher levels of expression of VEGF-A protein (p = 0.005). Levels of VEGF-A protein expression were lower in term adrenalectomized animals (p = 0.01) and were higher in preterm animals infused with cortisol (p = 0.01), compared with their respective control groups. Immunohistochemistry demonstrated strongest expression of VEGF-A protein in the epithelial cells and lamina propria of the villi. Intestinal expression of mRNA encoding the VEGFR-2 receptor did not significantly vary with gestational age. In situ hybridization localized VEGFR-2 to the lamina propria of the villous core and receptor autoradiography using 125I VEGF-A demonstrated binding in the same site. These data show that intestinal VEGF-A is up-regulated with advancing gestation in a glucocorticoid-dependent manner--novel findings consistent with a role for VEGF-A stimulated angiogenesis in preparing the fetal gut for birth.

Clusterin shortens the incubation and alters the histopathology of bovine spongiform encephalopathy in mice

Clusterin accumulates in significant quantity in prion protein lesions associated with bovine spongiform encephalopathy (BSE) and we therefore sought to elucidate its ability to alter BSE pathogenesis and incubation time by comparison of wild type C57BL/6J mice and clusterin knock out (ko) mice. The ko mice had a 40 day increase in mean incubation time compared to wild type mice. PrP deposition in the medulla was less aggregated in clusterin knock out mice when compared to wild type BSE infected mice and a more marked astrocytosis, as determined by GFAP staining, was evident. The vacuolation profiles did not differ between the two strains of mice. Taken together these results suggest that clusterin alters the extracellular deposition of PrP(BSE) and accelerates BSE pathogenesis.

Paraoxonase-3, a putative circulating antioxidant, is systemically up-regulated in late gestation in the fetal rat, sheep, and human

CONTEXT

Surfactant is a successful therapeutic based on supplementing preterm infants with a substance that would normally have been up-regulated in late gestation. Although prematurity is associated with oxidative stress, no effective antioxidant therapy has yet been identified.

OBJECTIVE

Our objective was to identify endogenous antioxidants involved in fetal preparation for birth.

DESIGN

We performed transcript profiling of fetal rat lung and intestine at 16 d gestational age (dGA) and 20 dGA with out-of-sample validation. Gene expression was then measured in fetal sheep tissues, comparing 1) advancing GA, 2) exogenous maternal dexamethasone (compared with saline, at 130 dGA), and 3) fetal adrenalectomy at 115-118 d on levels at term. Protein levels were compared in human umbilical cord serum using Western blot.

RESULTS

Four transcripts were up-regulated more than 20-fold on the array in both rat lung and intestine. One of these, paraoxonase-3 (Pon3), had been identified as a putative circulating antioxidant. Up-regulation of Pon3 mRNA in rat lung, intestine, and liver was confirmed in siblings (all P<0.001). Pon3 mRNA levels in fetal sheep lung and intestine increased 5.1- and 5.3-fold, respectively (both P<0.001) between 100 and 145 dGA and were strongly correlated with plasma cortisol (both P<0.001). Fetal sheep pulmonary Pon3 transcript level was increased 55% (P=0.01) by dexamethasone and reduced 74% (P<0.001) by adrenalectomy. Term human infants had more than 6-fold higher umbilical cord serum levels of Pon3 than preterm (24-28 wk GA) infants (P<0.001).

CONCLUSIONS

Pon3, a putative circulating antioxidant, was systemically up-regulated in late-gestation rat, sheep, and human fetuses and is a candidate therapeutic in preterm human infants.

Methylation of exon 2 of p16 is associated with late stage oesophageal cancer

Methylation of the p16 gene was studied in 16 oesophageal tumours. Five (31%) of the tumours were found to be methylated in exon 1 and eight (50%) were methylated in exon 2. The loss of p16 protein correlated with methylation of exon 1 (P = 0.005). However, methylation of exon 2, but not exon 1, was found to be associated with late stage tumours (P = 0.01). We conclude that the methylation of exon 2 of p16 may have effects on the progression of oesophageal tumours that are independent of the expression of the p16 protein.

Disruption of paraoxonase 3 impairs proliferation and antioxidant defenses in human A549 cells and causes embryonic lethality in mice

We had shown previously that paraoxonase 3 (PON3), a putative circulating antioxidant, was systemically upregulated in late-gestation rat, sheep, and human fetuses. Our overarching hypothesis is that preterm human infants are delivered with low levels of PON3 and that this contributes to a state of oxidative stress. We sought to determine whether absence of Pon3 was associated with reduced neonatal viability in mice and studied the offspring from crosses between Pon3(+/-) mice. The number of Pon3(-/-) animals at E10.5 and E17.5 was significantly lower than the expected 25% (9.3 and 7.9% respectively, P < 0.001). On the first day of postnatal life, this was reduced further (2.4%, significantly less than the proportion in fetal life, P = 0.04). Pon3(+/-) animals had lower body and placental weights than wild-type littermates at E17.5, an effect that was independent of the parent of origin of the mutant allele. We then studied the effect of PON3 knockdown in a human cell line, A549. Stable knockdown of PON3 using short-hairpin RNA reduced cell proliferation in 21% oxygen. We then studied the effect of transient knockdown of PON3 using short interfering RNA (siRNA) in the same cell line in low (2%) or ambient (21%) oxygen. Knockdown of PON3 using siRNA reduced total antioxidant capacity in 21% (P = 0.008) but not 2% oxygen. We conclude that the absence of Pon3 in mice resulted in increased rates of early fetal and neonatal death. Knockdown of PON3 in human cells reduced cell proliferation and total antioxidant capacity.

Developmental Expression and Glucocorticoid Control of the Leptin Receptor in Fetal Ovine Lung

The effects of endogenous and synthetic glucocorticoids on fetal lung maturation are well-established, although the role of leptin in lung development before birth is unclear. This study examined mRNA and protein levels of the signalling long-form leptin receptor (Ob-Rb) in fetal ovine lungs towards term, and after experimental manipulation of glucocorticoid levels in utero by fetal cortisol infusion or maternal dexamethasone treatment. In fetal ovine lungs, Ob-Rb protein was localised to bronchiolar epithelium, bronchial cartilage, vascular endothelium, alveolar macrophages and type II pneumocytes. Pulmonary Ob-Rb mRNA abundance increased between 100 (0.69 fractional gestational age) and 144 days (0.99) of gestation, and by 2-4-fold in response to fetal cortisol infusion and maternal dexamethasone treatment. In contrast, pulmonary Ob-Rb protein levels decreased near term and were halved by glucocorticoid treatment, without any significant change in phosphorylated signal transducer and activator of transcription-3 (pSTAT3) at Ser727, total STAT3 or the pulmonary pSTAT3:STAT3 ratio. Leptin mRNA was undetectable in fetal ovine lungs at the gestational ages studied. These findings demonstrate differential control of pulmonary Ob-Rb transcript abundance and protein translation, and/or post-translational processing, by glucocorticoids in utero. Localisation of Ob-Rb in the fetal ovine lungs, including alveolar type II pneumocytes, suggests a role for leptin signalling in the control of lung growth and maturation before birth.

Impaired motor coordination on static rods in BSE-infected mice

Scrapie and bovine spongiform encephalopathy (BSE) are both progressive neurodegenerative diseases that are transmissible to mice. The onset of clinical symptoms is more subtle and variable in murine BSE than in murine scrapie. Assessment of behavioural changes that occur throughout disease would aid early diagnosis of disease so that more consistent end points could be made and potential therapies could be investigated. C57BL/6J mice inoculated via the intraperitoneal route with 301C BSE or control inoculum were monitored on a fortnightly basis. The end point was when a mouse showed clinical signs as opposed to behavioural signs of BSE for two consecutive observations. Significant loss of motor function, as assessed by mice balancing on a static rod, was observed consistently from approximately 40 days prior to death. No significant differences in home cage activity (locomotion, rearing) or cognitive function (T-maze alternation) were observed. However, there was an increase in digging by BSE-infected mice from an early stage. This data will aid the standardisation of behavioural tests to characterise and assess the onset of BSE.

Tat protein expression in MDBK cells does not confer susceptibility to bovine immunodeficiency virus

The ability of BIV strain R29 to infect bovine cell lines in the presence or absence of a functional lentiviral Tat protein is described. Jembrana disease virus (JDV) Tat protein was stably expressed in MDBK cells. No viral replication could be detected in this cell line after infection with BIV R29. Transfection of MDBK cells and MDBK Tat expressing cells with BIV R29 proviral DNA established that BIV R29 could not replicate in MDBK cells. Whether viral entry into MDBK cells is also a block to BIV R29 infection of MDBK cells has yet to be established.

Intrinsic host susceptibility among multiple species to intranasal SARS-CoV-2 identifies diverse virological, biodistribution and pathological outcomes

SARS-CoV-2 exhibits a diverse host species range with variable outcomes, enabling differential host susceptibility studies to assess suitability for pre-clinical countermeasure and pathogenesis studies. Baseline virological, molecular and pathological outcomes were determined among multiple species-one Old World non-human primate (NHP) species (cynomolgus macaques), two New World NHP species (red-bellied tamarins; common marmosets) and Syrian hamsters-following single-dose, atraumatic intranasal administration of SARS-CoV-2/Victoria-01. After serial sacrifice 2, 10 and 28-days post-infection (dpi), hamsters and cynomolgus macaques displayed differential virus biodistribution across respiratory, gastrointestinal and cardiovascular systems. Uniquely, New World tamarins, unlike marmosets, exhibited high levels of acute upper airway infection, infectious virus recovery associated with mild lung pathology representing a host previously unrecognized as susceptible to SARS-CoV-2. Across all species, lung pathology was identified post-clearance of virus shedding (antigen/RNA), with an association of virus particles within replication organelles in lung sections analysed by electron microscopy. Disrupted cell ultrastructure and lung architecture, including abnormal morphology of mitochondria 10-28 dpi, represented on-going pathophysiological consequences of SARS-CoV-2 in predominantly asymptomatic hosts. Infection kinetics and host pathology comparators using standardized methodologies enables model selection to bridge differential outcomes within upper and lower respiratory tracts and elucidate longer-term consequences of asymptomatic SARS-CoV-2 infection.

SARS-CoV-2 Virus-like Particles Produced by a Single Recombinant Baculovirus Generate Anti-S Antibody and Protect against Variant Challenge

Coronavirus Disease 2019 (COVID-19), caused by infection with Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), has highlighted the need for the rapid generation of efficient vaccines for emerging disease. Virus-like particles, VLPs, are an established vaccine technology that produces virus-like mimics, based on expression of the structural proteins of a target virus. SARS-CoV-2 is a coronavirus where the basis of VLP formation has been shown to be the co-expression of the spike, membrane and envelope structural proteins. Here we describe the generation of SARS-CoV-2 VLPs by the co-expression of the salient structural proteins in insect cells using the established baculovirus expression system. VLPs were heterologous ~100 nm diameter enveloped particles with a distinct fringe that reacted strongly with SARS-CoV-2 convalescent sera. In a Syrian hamster challenge model, non-adjuvanted VLPs induced neutralizing antibodies to the VLP-associated Wuhan S protein and reduced virus shedding and protected against disease associated weight loss following a virulent challenge with SARS-CoV-2 (B.1.1.7 variant). Immunized animals showed reduced lung pathology and lower challenge virus replication than the non-immunized controls. Our data suggest SARS-CoV-2 VLPs offer an efficient vaccine that mitigates against virus load and prevents severe disease.

Potential human immunotherapeutics for plague

Two monoclonal antibodies directed to the V antigen of Yersinia pestis have been tested for protective efficacy in a murine model of bubonic plague. Mice were infected with a current clinical isolate from Madagascar, designated Y. pestis 10-21/S. Mab7.3, delivered to mice intra-periteoneally at either 24 h prior to, or 24 h post-infection, was fully protective, building on many studies which have demonstrated the protective efficacy of this Mab against a number of different clinical isolates of Y. pestis. Mab 29.3, delivered intra-peritoneally at either -24 h or +24 h, protected 4/5 mice in either condition; this has demonstrated the protective efficacy of this Mab in vivo for the first time. These results add to the cumulative data about Mab7.3, which is currently being humanized and highlight its potential as a human immunotherapeutic for plague, which is an enduring endemic disease in Madagascar and other regions of Africa, Asia, and South America.

Towards quantification of protective antibody responses by passive transfer of the 1st WHO International Standard for Ebola virus antibody in a guinea pig model

Ebola virus (EBOV) represents a major concern to global health due to the unpredictable nature of outbreaks. Infection with EBOV can cause a severe viral haemorrhagic fever with no licensed vaccine or treatment, restricting work with live EBOV to Containment/Biosafety Level 4 facilities. Whilst the magnitude of recent outbreaks has provided an impetus for vaccine and antiviral development, establishing the efficacy of candidate vaccine materials relies on EBOV challenge models and advanced human trials should outbreaks occur and where logistics and funding allow. To address these hurdles in vaccine development, we investigated whether a recently established serological reference standard, the 1st WHO International Standard for Ebola virus antibody, could be used to provide a quantifiable correlate of immune protection in vivo. Dilutions of the International Standard were inoculated into naïve guinea pigs 24 h before challenge with a lethal dose of Ebola virus. Only subjects receiving the highest dose of the International Standard exhibited evidence of delayed progression. Due to it being a WHO established reagent and available globally upon request, this standard allows for effective comparisons of data between laboratories and may prove valuable to select the candidate vaccines that are most likely to confer humoral immune protection ensuring the most promising candidates progress into efficacy studies.