Coronaviruses

SARS-CoV-2 is the causative agent of COVID-19 and human infections have resulted in a global health emergency. Small animal models that reproduce key elements of SARS-CoV-2 human infections are needed to rigorously screen candidate drugs to mitigate severe disease and prevent the spread of SARS-CoV-2. We and others have reported that transgenic mice expressing the human angiotensin-converting enzyme 2 (hACE2) viral receptor under the control of the Keratin 18 (K18) promoter develop severe and lethal respiratory disease subsequent to SARS-CoV-2 intranasal challenge. Here we report that some infected mice that survive challenge have residual pulmonary damages and persistent brain infection on day 28 post-infection despite the presence of anti-SARS-COV-2 neutralizing antibodies. Because of the hypersensitivity of K18-hACE2 mice to SARS-CoV-2 and the propensity of virus to infect the brain, we sought to determine if anti-infective biologics could protect against disease in this model system. We demonstrate that anti-SARS-CoV-2 human convalescent plasma protects K18-hACE2 against severe disease. All control mice succumbed to disease by day 7; however, all treated mice survived infection without observable signs of disease. In marked contrast to control mice, viral antigen and lesions were reduced or absent from lungs and absent in brains of antibody-treated mice. Our findings support the use of K18-hACE2 mice for protective efficacy studies of anti-SARS-CoV-2 medical countermeasures (MCMs). They also support the use of this system to study SARS-CoV-2 persistence and host recovery.

Bats host a broad diversity of coronaviruses (CoVs), including close relatives of human pathogens. There is only limited data on neotropical bat CoVs. We analysed faecal, blood and intestine specimens from 1562 bats sampled in Costa Rica, Panama, Ecuador and Brazil for CoVs by broad-range PCR. CoV RNA was detected in 50 bats representing nine different species, both frugivorous and insectivorous. These bat CoVs were unrelated to known human or animal pathogens, indicating an absence of recent zoonotic spill-over events. Based on RNA-dependent RNA polymerase (RdRp)-based grouping units (RGUs) as a surrogate for CoV species identification, the 50 viruses represented five different alphacoronavirus RGUs and two betacoronavirus RGUs. Closely related alphacoronaviruses were detected in Carollia perspicillata and C. brevicauda across a geographical distance exceeding 5600 km. Our study expands the knowledge on CoV diversity in neotropical bats and emphasizes the association of distinct CoVs and bat host genera.

A panel of hybridoma antibodies that react with the surface peplomer glycoprotein (E2) of the murine coronavirus JHM were produced to characterize major antigenic domains associated with functions related to virulence. Three groups of hybridoma antibodies were differentiated by immunoprecipitation of lysates from JHM-infected cells. One group precipitated the virion structural proteins gp170 and gp98 together with the intracellular form of E2, gp150. A second group reacted with gp98 and gp150, and a third group precipitated gp150 only. Competition assays with biotinylated hybridoma antibodies allowed the definition of at least six different epitope groups. Only those antibodies which immunoprecipitated both gp170 and gp98 neutralized infectivity, inhibited cell fusion and protected infected rats against acute disease. Another class of antibodies binding to gp170 and gp98 also neutralized JHM virus, but did not inhibit fusion and did not protect against disease. Antibodies that immunoprecipitated gp150 and gp98 revealed only weak neutralization and did not inhibit cell fusion or protect animals. Four epitopes were defined by antibodies that immunoprecipitated gp150, but revealed no biological activity. These data indicate that the site responsible for cell fusion is associated with an epitope group carried by gp170 and gp98. Neutralizing antibodies bind to this and another epitope. Furthermore, protection of JHM-infected rats against acute disease requires both inhibition of cell fusion and neutralization of virus.