Isolation and characterization of LH5, a novel rodent Embecovirus from Rattus tanezumi with respiratory tropism in a mouse model

BACKGROUND: Coronaviruses (CoVs) have contributed substantially to recent global public health crises (e.g., SARS, SARS-CoV-2, and MERS-CoV). Wild animals are the primary natural reservoirs of CoVs prior to human transmission. RESULTS: In this study, we report the isolation and characterization of a novel β-CoV strain, designated Murine-CoV-LH5, from Rattus tanezumi in Dehong Prefecture, Yunnan Province. This represents, to our knowledge, the first reported isolation of a coronavirus from this specific rodent species. Genomic analysis confirmed its classification within the subgenus Embecovirus. Notably, the genome encodes a furin cleavage site in the spike protein, a feature uncommon among known rodent Embecovirus, whose functional significance warrants further investigation. Molecular docking analysis predicted strong binding affinities between the LH5 spike protein and human host factors TMPRSS2 and ACE2, suggesting a potential interaction that requires experimental validation. The virus was isolated using intracerebral inoculation in neonatal mice. In this mouse model, immunohistochemistry and indirect immunofluorescence revealed viral tropism for bronchial and alveolar epithelial cells in the lungs, as well as cortical neurons in the brain. Furthermore, the establishment of a mouse-adapted LH5 strain provides a valuable in vivo model system for studying Embecovirus pathogenesis and for antiviral drug screening, particularly in research settings where handling high-containment pathogens is constrained. CONCLUSIONS: This study provides the initial characterization of LH5, including its genomic features and tropism in a laboratory mouse model. These findings contribute to the understanding of rodent CoV diversity and evolution, demonstrate the utility of LH5 as a tractable research model, and highlight the importance of continued surveillance of wildlife CoVs for assessing zoonotic potential. IMPORTANCE: Our study contributes to the understanding of CoV diversity in wildlife by reporting the isolation and initial characterization of a novel β-CoV (LH5) from Rattus tanezumi. While rodents are known reservoirs for various CoVs, the successful isolation of a replicative strain from this specific host provides a crucial in vivo model for research. This is particularly significant as LH5 demonstrates clear pulmonary tropism in a standard laboratory mouse model, offering a tractable and accessible system to study Embecovirus pathogenesis and host interactions in the respiratory tract, which can be leveraged for antiviral screening. Furthermore, the identification of genomic features in LH5, such as a furin cleavage site uncommon in rodent Embecovirus and predicted human receptor-binding potential, highlights the need for experimental studies to assess its zoonotic risk. Our findings emphasize that continuous surveillance of CoVs in rodent populations is essential for early detection of viral variants with enhanced cross-species potential, thereby informing strategies for the prevention of future zoonotic outbreaks.