There is need for effective and affordable vaccines against SARS-CoV-2 to tackle the ongoing pandemic. In this study, we describe a protein nanoparticle vaccine against SARS-CoV-2. The vaccine is based on the display of coronavirus spike glycoprotein receptor-binding domain (RBD) on a synthetic virus-like particle (VLP) platform, SpyCatcher003-mi3, using SpyTag/SpyCatcher technology. Low doses of RBD-SpyVLP in a prime-boost regimen induce a strong neutralising antibody response in mice and pigs that is superior to convalescent human sera. We evaluate antibody quality using ACE2 blocking and neutralisation of cell infection by pseudovirus or wild-type SARS-CoV-2. Using competition assays with a monoclonal antibody panel, we show that RBD-SpyVLP induces a polyclonal antibody response that recognises key epitopes on the RBD, reducing the likelihood of selecting neutralisation-escape mutants. Moreover, RBD-SpyVLP is thermostable and can be lyophilised without losing immunogenicity, to facilitate global distribution and reduce cold-chain dependence. The data suggests that RBD-SpyVLP provides strong potential to address clinical and logistic challenges of the COVID-19 pandemic.

Clinical development of the COVID-19 vaccine candidate ChAdOx1 nCoV-19, a replication-deficient simian adenoviral vector expressing the full-length SARS-CoV-2 spike (S) protein was initiated in April 2020 following non-human primate studies using a single immunisation. Here, we compared the immunogenicity of one or two doses of ChAdOx1 nCoV-19 in both mice and pigs. Whilst a single dose induced antigen-specific antibody and T cells responses, a booster immunisation enhanced antibody responses, particularly in pigs, with a significant increase in SARS-CoV-2 neutralising titres.

Scrapie of sheep and goats is the most common prion disease (or transmissible spongiform encephalopathy, TSE) of mammals and aggregates of abnormal, proteinase-resistant prion protein (PrP Sc) are found in all naturally occurring prion diseases. During active surveillance of British sheep for TSEs, 29 201 sheep brain stem samples were collected from abattoirs and analysed for the presence of PrP Sc. Of these samples, 54 were found to be positive by using an ELISA screening test, but 28 of these could not be confirmed initially by immunohistochemistry. These unconfirmed or atypical cases were generally found in PrP genotypes normally associated with relative resistance to clinical scrapie and further biochemical analysis revealed that they contained forms of PrP Sc with a relatively protease-sensitive amyloid core, some resembling those of Nor98 scrapie. The presence of these atypical forms of protease-resistant PrP raises concerns that some TSE disorders of PrP metabolism previously may have escaped identification in the British sheep population.

There is dire need for an effective and affordable vaccine against SARS-CoV-2 to tackle the ongoing pandemic. In this study, we describe a modular virus-like particle vaccine candidate displaying the SARS-CoV-2 spike glycoprotein receptor-binding domain (RBD) using SpyTag/SpyCatcher technology (RBD-SpyVLP). Low doses of RBD-SpyVLP in a prime-boost regimen induced a strong neutralising antibody response in mice and pigs that was superior to convalescent human sera. We evaluated antibody quality using ACE2 blocking and neutralisation of cell infection by pseudovirus or wild-type SARS-CoV-2. Using competition assays with a monoclonal antibody panel, we showed that RBD-SpyVLP induced a polyclonal antibody response that recognised all key epitopes on the RBD, reducing the likelihood of selecting neutralisation-escape mutants. The induction of potent and polyclonal antibody responses by RBD-SpyVLP provides strong potential to address clinical and logistic challenges of the COVID-19 pandemic. Moreover, RBD-SpyVLP is highly resilient, thermostable and can be lyophilised without losing immunogenicity, to facilitate global distribution and reduce cold-chain dependence.

Conventional dendritic cells (cDC) are professional antigen-presenting cells that induce immune activation or tolerance. Two functionally specialised populations, termed cDC1 and cDC2, have been described in humans, mice, ruminants and recently in pigs. Pigs are an important biomedical model species and a key source of animal protein; therefore further understanding of their immune system will help underpin the development of disease prevention strategies. To characterise cDC populations in porcine blood, DC were enriched from PBMC by CD14 depletion and CD172a enrichment then stained with lineage mAbs (Lin; CD3, CD8α, CD14 and CD21) and mAbs specific for CD172a, CD1 and CD4. Two distinct porcine cDC subpopulations were FACSorted CD1− cDC (Lin−CD172+ CD1−CD4−) and CD1+ cDC (Lin−CD172a+ CD1+ CD4−), and characterised by phenotypic and functional analyses. CD1+ cDC were distinct from CD1− cDC, expressing higher levels of CD172a, MHC class II and CD11b. Following TLR stimulation, CD1+ cDC produced IL-8 and IL-10 while CD1− cDC secreted IFN-α, IL-12 and TNF-α. CD1− cDC were superior in stimulating allogeneic T cell responses and in cross-presenting viral antigens to CD8 T cells. Comparison of transcriptional profiles further suggested that the CD1− and CD1+ populations were enriched for the orthologues of cDC1 and cDC2 subsets respectively.

The role of blood in the iatrogenic transmission of transmissible spongiform encephalopathy (TSE) or prion disease has become an increasing concern since the reports of variant Creutzfeldt-Jakob disease (vCJD) transmission through blood transfusion from humans with subclinical infection. The development of highly sensitive rapid assays to screen for prion infection in blood is of high priority in order to facilitate the prevention of transmission via blood and blood products. In the present study we show that PrP sc , a surrogate marker for TSE infection, can be detected in cells isolated from the blood from naturally and experimentally infected sheep by using a rapid ligand-based immunoassay. In sheep with clinical disease, PrP sc was detected in the blood of 55% of scrapie agent-infected animals (n ‫؍‬ 80) and 71% of animals with bovine spongiform encephalopathy (n ‫؍‬ 7). PrP sc was also detected several months before the onset of clinical signs in a subset of scrapie agent-infected sheep, followed from 3 months of age to clinical disease. This study confirms that PrP sc is associated with the cellular component of blood and can be detected in preclinical sheep by an immunoassay in the absence of in vitro or in vivo amplification.

African swine fever virus (ASFV) causes a lethal, haemorrhagic disease in domestic swine that threatens pig production across the globe. Unlike domestic pigs, warthogs, which are wildlife hosts of the virus, do not succumb to the lethal effects of infection. There are three amino acid differences between the sequence of the warthog and domestic pig ReLA protein; a subunit of the nf-κB transcription factor that plays a key role in regulating the immune response to infections. Domestic pigs with all 3 or 2 of the amino acids from the warthog RELA orthologue have been generated by gene editing. To assess if these variations confer resilience to ASF we established an intranasal challenge model with a moderately virulent ASFV. No difference in clinical, virological or pathological parameters were observed in domestic pigs with the 2 amino acid substitution. Domestic pigs with all 3 amino acids found in warthog RELA were not resilient to ASF but a delay in onset of clinical signs and less viral DNA in blood samples and nasal secretions was observed in some animals. Inclusion of these and additional warthog genetic traits into domestic pigs may be one way to assist in combating the devastating impact of ASFV. African swine fever virus (ASFV) is a large DNA virus and sole member of the family Asfarviridae that causes a mostly lethal haemorrhagic disease, African swine fever (ASF), in domestic pigs and Eurasian wild boar. ASFV can genetically be separated into 24 genotypes that cause the same disease, but immunological cross-protection is limited and poorly understood 1. The introduction of ASF into a country results in trade restrictions and pig losses, thus the disease has a high socioeconomic consequence for both commercial and backyard farmers 2. Accordingly, the spread of this disease is a serious concern for the global pig industry. Following the incursion of a genotype II ASFV into the Caucasus in 2007 the virus has spread through Russia, entered the European Union in 2014 and, in 2018, was detected for the first time in China. Since then the Chinese pig population has declined by at least 20% and ASFV has further spread across many countries in South East Asia 3,4. Combating this global threat is hampered by the lack of a vaccine and is particularly difficult in production systems with poor biosecurity which are more vulnerable to virus introduction and contact with wild suids 1. ASFV infects all members of the family Suidae, which as well as domestic pigs (Sus scrofa domesticus), wild boar (Sus scrofa spp) and others also includes bushpigs (Potamochoerus spp.) and warthogs (Phacochoerus spp.), which are considered natural reservoir hosts 5. In domestic pigs and wild boar acute and subacute forms dominate,

Mouse bioassay remains the gold standard for determining proof of infectivity, strain type, and infectious titer estimation in prion disease research. The development of an approach using ex vivo cell-based assays remains an attractive alternative, both in order to reduce the use of mice and to hasten results. The main limitation of a cell-based approach is the scarcity of cell lines permissive to infection with natural transmissible spongiform encephalopathy strains. This study combines two advances in this area, namely, the standard scrapie cell assay (SSCA) and the Rov9 and MovS6 cell lines, which both express the ovine PrP VRQ allele, to assess to what extent natural and experimental ovine scrapie can be detected ex vivo. Despite the Rov9 and MovS6 cell lines being of different biological origin, they were both permissive and resistant to infection with the same isolates of natural sheep scrapie as detected by SSCA. Rov9 subclones that are 20 times more sensitive than Rov9 to SSBP/1-like scrapie infection were isolated, but all the subclones maintained their resistance to isolates that failed to transmit to the parental line. The most sensitive subclone of the Rov9 cell line was used to estimate the infectious titer of a scrapie brain pool (RBP1) and proved to be more sensitive than the mouse bioassay using wild-type mice. Increasing the sensitivity of the Rov9 cell line to SSBP/1 infection did not correlate with broadening susceptibility, as the specificity of permissiveness and resistance to other scrapie isolates was maintained.