SARS Coronavirus 2 (SARS-CoV-2) emerged in late 2019, leading to the Coronavirus Disease 2019 (COVID-19) pandemic that continues to cause significant global mortality in human populations. Given its sequence similarity to SARS-CoV, as well as related coronaviruses circulating in bats, SARS-CoV-2 is thought to have originated in Chiroptera species in China. However, whether the virus spread directly to humans or through an intermediate host is currently unclear, as is the potential for this virus to infect companion animals, livestock, and wildlife that could act as viral reservoirs. Using a combination of surrogate entry assays and live virus, we demonstrate that, in addition to human angiotensin-converting enzyme 2 (ACE2), the Spike glycoprotein of SARS-CoV-2 has a broad host tropism for mammalian ACE2 receptors, despite divergence in the amino acids at the Spike receptor binding site on these proteins. Of the 22 different hosts we investigated, ACE2 proteins from dog, cat, and cattle were the most permissive to SARS-CoV-2, while bat and bird ACE2 proteins were the least efficiently used receptors. The absence of a significant tropism for any of the 3 genetically distinct bat ACE2 proteins we examined indicates that SARS-CoV-2 receptor usage likely shifted during zoonotic transmission from bats into people, possibly in an intermediate reservoir. Comparison of SARS-CoV-2 receptor usage to the related coronaviruses SARS-CoV and RaTG13 identified distinct tropisms, with the 2 human viruses being more closely aligned. Finally, using bioinformatics, structural data, and targeted mutagenesis, we identified amino acid residues within the Spike–ACE2 interface, which may have played a pivotal role in the emergence of SARS-CoV-2 in humans. The apparently broad tropism of SARS-CoV-2 at the point of viral entry confirms the potential risk of infection to a wide range of companion animals, livestock, and wildlife.

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.

18SARS-CoV-2 emerged in late 2019, leading to the COVID-19 pandemic that continues to 19 cause significant global mortality in human populations. Given its sequence similarity to CoV, as well as related coronaviruses circulating in bats, SARS-CoV-2 is thought to have 21 originated in Chiroptera species in China. However, whether the virus spread directly to 22 humans or through an intermediate host is currently unclear, as is the potential for this virus 23to infect companion animals, livestock and wildlife that could act as viral reservoirs. Using a 24 combination of surrogate entry assays and live virus we demonstrate that, in addition to human 25 ACE2, the Spike glycoprotein of SARS-CoV-2 has a broad host tropism for mammalian ACE2 26 receptors, despite divergence in the amino acids at the Spike receptor binding site on these 27proteins. Of the twenty-two different hosts we investigated, ACE2 proteins from dog, cat and 28 rabbit were the most permissive to SARS-CoV-2, while bat and bird ACE2 proteins were the 29 least efficiently used receptors. The absence of a significant tropism for any of the three 30 genetically distinct bat ACE2 proteins we examined indicates that SARS-CoV-2 receptor 31 usage likely shifted during zoonotic transmission from bats into people, possibly in an 32 intermediate reservoir. Interestingly, while SARS-CoV-2 pseudoparticle entry was inefficient 33in cells bearing the ACE2 receptor from bats or birds the live virus was still able to enter these 34 cells, albeit with markedly lower efficiency. The apparently broad tropism of SARS-CoV-2 at 35 the point of viral entry confirms the potential risk of infection to a wide range of companion 36 animals, livestock and wildlife. 37 38Introduction 39 40The β-coronavirus SARS-CoV-2 emerged in late 2019, causing a large epidemic of respiratory 41 disease in the Hubei province of China, centred in the city of Wuhan [1]. Subsequent 42 international spread has led to an ongoing global pandemic, currently responsible for 8 million 43 infections and over 435,000 deaths (as of 11 th June 2020, John Hopkins University statistics; 44 https://coronavirus.jhu.edu/map.html). As for SARS-CoV, which emerged in China in late 45 2002, and MERS-CoV, which emerged in Saudi Arabia in 2012, the original animal reservoir 46 of zoonotic coronaviruses is thought to be bats [2]. Spill-over into humans is suspected or 47 proven to be facilitated through an intermediate host, e.g. civets for SARS-CoV [2] or camels 48 for MERS-CoV [3]. For SARS-CoV-2, a bat origin is supported by the 2013 identification of a 49 related coronavirus RaTG13 from Rhinolophus affinis (intermediate horseshoe bat), which is 50 96% identical at the genome level to SARS-CoV-2 [1]. Identifying the animal reservoir of 51 SARS-CoV-2, and any intermediate hosts via which the virus ultimately spread to humans, 52 may help to understand how, where and when this virus spilled over into people. This 53information could be vital in identifying future risk and preventing subsequent outbreaks of 54 both re...

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.