Pathogenesis of Rift Valley Fever Virus in a BALB/c Mouse Model Is Affected by Virus Culture Conditions and Sex of the Animals

Rift Valley fever virus (RVFV) is a mosquito-borne zoonotic pathogen causing disease in livestock and humans. Whilst initially restricted to the African continent, recent spread to the Arabian Peninsula has highlighted the likelihood of entry into new regions. Due to the absence of a regulatory-approved human vaccine, work is ongoing to develop and assess countermeasures. As such, small animal models play a pivotal role in providing information on disease pathogenesis and elucidating which intervention strategies confer protection. To develop and establish the BALB/c mouse model, we challenged mice with RVFV grown from two separate cell lines: one derived from mosquitoes (C6/36) and the other mammalian derived (Vero E6). Following infection, we assessed the clinical course of disease progression at days 1 and 3 post-challenge and evaluated viral tropism and immune analytes. The results demonstrated that RVFV infection was affected by the cell line used to propagate the challenge virus, with those grown in insect cells resulting in a more rapid disease progression. The lowest dose that caused uniform severe disease remained the same across both virus preparations. In addition, to demonstrate reproducibility, the lowest dose was used for a subsequent infection study using male and female animals. The results further demonstrated that male mice succumbed to infection more rapidly than their female counterparts. Our results establish an RVFV mouse model and key parameters that affect the course of disease progression in BALB/c mice.

Mucosal Responses to Zika Virus Infection in Cynomolgus Macaques

Zika virus (ZIKV) cases continue to be reported, and no vaccine or specific antiviral agent has been approved for the prevention or treatment of infection. Though ZIKV is primarily transmitted by mosquitos, cases of sexual transmission and prolonged viral RNA presence in semen have been reported. In this observational study, we report the mucosal responses to sub-cutaneous and mucosal ZIKV exposure in cynomolgus macaques during acute and late chronic infection. Subcutaneous challenge induced a decrease in the growth factor VEGF in colorectal and cervicovaginal tissues 100 days post-challenge, in contrast to the observed increase in these tissues following vaginal infection. This different pattern was not observed in the uterus, where VEGF was upregulated independently of the challenge route. Vaginal challenge induced a pro-inflammatory profile in all mucosal tissues during late chronic infection. Similar responses were already observed during acute infection in a vaginal tissue explant model of ex vivo challenge. Non-productive and productive infection 100 days post-in vivo vaginal challenge induced distinct proteomic profiles which were characterized by further VEGF increase and IL-10 decrease in non-infected animals. Ex vivo challenge of mucosal explants revealed tissue-specific modulation of cytokine levels during the acute phase of infection. Mucosal cytokine profiles could represent biosignatures of persistent ZIKV infection.

Early Isolates of SARS-CoV-2 Result in Different Pathogenesis in the Transduced Mouse Model of COVID-19

A transduced mouse model of SARS-CoV-2 infection was established using Balb/c mice. This was achieved through the adenovirus-vectored delivery of the hACE2 gene, to render the mice transiently susceptible to the virus. The model was characterised in terms of the dissemination of hACE2 receptor expression, the dissemination of three SARS-CoV-2 virus variants in vivo up to 10 days following challenge, the resulting histopathology and the clinical signs induced in the mice. In transduced mice, the infection was short-term, with a rapid loss in body weight starting at day 2 with maximum weight loss at day 4, followed by subsequent recovery until day 10. The induced expression of the hACE2 receptor was evident in the lungs, but, upon challenge, the SARS-CoV-2 virus disseminated beyond the lungs to spleen, liver and kidney, peaking at day 2 post infection. However, by day 10 post infection, the virus was undetectable. The lung histopathology was characterised by bronchial and alveolar inflammation, which was still present at day 10 post infection. Transduced mice had differential responses to viral variants ranking CVR-Glasgow 1 > Victoria-1 > England-2 isolates in terms of body weight loss. The transduced mouse model provides a consistent and manipulatable model of SARS-CoV-2 infection to screen viral variants for their relative virulence and possible interventions.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Time of transforming growth factor beta 1 inoculation alters the incubation of BSE in mice

Groups of 20 C57BL/6J mice (10 males and 10 females) were given BSE strain 301C i.p. and subsequently given 2 microg recombinant human TGFbeta1 s.c. at single or multiple times. There was a significant positive correlation between the day of TGFbeta1 administration and incubation time; the later TGFbeta1 was administered after BSE inoculation the longer the incubation time became. The administration of TGFbeta1 at any time point did not significantly alter the distribution or severity of pathology. The effects of TGFbeta1 on BSE pathogenesis appears to be dependent upon its time of administration; early administration shortens the incubation time and late administration lengthens the incubation time.

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.

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.