Since SARS-CoV-2 emerged in late 2019, it spread from China to the rest of the world. An initial concern was the potential for vaccine- or antibody-dependent enhancement (ADE) of disease as had been ...reported with other coronaviruses. To evaluate this, we first developed a ferret model by exposing ferrets to SARS-CoV-2 by either mucosal inoculation (intranasal/oral/ocular) or inhalation using a small particle aerosol. Mucosal inoculation caused a mild fever and weight loss that resolved quickly; inoculation via either route resulted in virus shedding detected in the nares, throat, and rectum for 7–10 days post-infection. To evaluate the potential for ADE, we then inoculated groups of ferrets intravenously with 0.1, 0.5, or 1 mg/kg doses of a human polyclonal anti-SARS-CoV-2 IgG from hyper-immunized transchromosomic bovines (SAB-185). Twelve hours later, ferrets were challenged by mucosal inoculation with SARS-CoV-2. We found no significant differences in fever, weight loss, or viral shedding after infection between the three antibody groups or the controls. Signs of pathology in the lungs were noted in infected ferrets but no differences were found between control and antibody groups. The results of this study indicate that healthy, young adult ferrets of both sexes are a suitable model of mild COVID-19 and that low doses of specific IgG in SAB-185 are unlikely to enhance the disease caused by SARS-CoV-2.
Morbilliviruses can cause severe disease in a wide range of terrestrial and marine mammals with measles still responsible for large numbers of fatalities in developing countries despite the ...availability of an efficacious vaccine. Identification of morbillivirus receptors, the major determinant of host range and tissue tropism, is of paramount importance in understanding the disease induced by these viruses. Identification and characterisation of receptors also facilitates the development of novel antiviral drugs which block viral attachment and entry. SLAM, also known as CD 150, is the entry receptor for wild-type strains of measles virus (MY). Whereas laboratory-adapted MY can use both SLAM and CD46. The susceptibility of SLAM negative oligodendroglioma, astrocytoma and microglioma derived cell-lines to infection with recombinant (r) CD46 "receptor blind" rM suggests the expression of an unknown virus entry receptor. While it is currently unknown whether wild-type MY uses the same receptor molecule to infect glial and epithelial cells, the absence of infected glial cells following infection with an epithelial "receptor blind" rMY suggests that MY may use the same cellular receptor to infect both cell types. This unknown receptor could be identified through the construction of a cDNA library from these cell lines and subsequent analysis using the novel bimolecular fluorescent complementation (BiFC) fusion assay developed in this study. This assay, which was developed to identify unknown viral fusion receptors, has been validated using expression plasmids encoding MY glycoproteins and known cellular receptors. A BiFC based MY receptor screen using a human spleen cDNA library produced fluorescent fusion events. These were isolated and PCR amplification was used to attempt to identify the unknown receptor Fusion assays using expression plasmids encoding canine distemper virus (CDY) heamagglutinin (H) and fusion (F) glycoproteins and BiFC fusion assay demonstrated that the H glycoprotein is the key determinant of cell tropism.
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