Developing a mouse model of human coronavirus NL63 infection: comparison with rhinovirus-A1B and effects of prior rhinovirus infection.

ABSTRACT

Human coronavirus (HCoV)-NL63 causes respiratory tract infections in humans and employs angiotensin-converting enzyme 2 (ACE2) as a receptor. We sought to establish a mouse model of HCoV-NL63 and determine if prior RV-A1B infection affected HCoV-NL63 replication. HCoV-NL63 was propagated in LLC-MK2 cells expressing human ACE2. RV-A1B was grown in HeLa-H1 cells. C57BL6/J or transgenic mice expressing human ACE2 were infected intranasally with sham LLC-MK2 cell supernatant or 1 x 105 TCID50 units HCoV-NL63. Wild-type mice were infected with 1 x 106 PFU RV-A1B. Lungs were assessed for vRNA, bronchoalveolar lavage (BAL) cells, histology, HCoV-NL63 non-structural protein 3 (nsp3), and host gene expression by next generation sequencing and qPCR. To evaluate sequential infections, mice were infected with RV-A1B followed by HCoV-NL63 infection four days later. We report that hACE2 mice infected with HCoV-NL63 showed evidence of replicative infection with increased levels of vRNA, BAL neutrophils and lymphocytes, peribronchial and perivascular infiltrates, and expression of nsp3. Viral replication peaked three days after infection and inflammation persisted six days after infection. HCoV-NL63-infected hACE2 mice showed increased mRNA expression of IFNs, IFN-stimulated proteins and pro-inflammatory cytokines. Infection with RV-A1B four days before HCoV-NL63 significantly decreased both HCoV-NL63 vRNA levels and airway inflammation. Mice infected with RV-A1B prior to HCoV-NL63 showed increased expression of antiviral proteins compared to sham-treated mice. In conclusion, we established a mouse model of HCoV-NL63 replicative infection characterized by relatively persistent viral replication and inflammation. Prior infection with RV-A1B reduced HCoV-NL63 replication and airway inflammation, indicative of viral interference.