The ongoing COVID-19 pandemic has prioritized the development of small animal models for SARS-CoV-2. Herein, we adapted a clinical isolate of SARS-CoV-2 by serial passaging in the respiratory tract of aged BALB/c mice. The resulting mouse-adapted strain at passage 6 (termed MASCp6) showed increased infectivity in mouse lung, and led to interstitial pneumonia and inflammatory responses in both young and aged mice following intranasal inoculation. Deep sequencing revealed a panel of adaptive mutations potentially associated with the increased virulence. In particular, the N501Y mutation is located at the receptor binding domain (RBD) of the spike protein. The protective efficacy of a recombinant RBD vaccine candidate was validated using this model. Thus, this mouse-adapted strain and associated challenge model should be of value in evaluating vaccines and antivirals against SARS-CoV-2.

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Coronavirus disease 2019 (COVID-19) threatens global public health and economy. In order to develop safe and effective vaccines, suitable animal models must be established. Here we report the rapid adaption of SARS-CoV-2 in BALB/c mice, based on which a convenient, economical and effective animal model was developed. Specifically, we found that mouse-adapted SARS-CoV-2 at passage 6 (MACSp6) efficiently infected both aged and young wild-type BALB/c mice, resulting in moderate pneumonia as well as inflammatory responses. The elevated infectivity of MACSp6 in mice could be attributed to the substitution of a key residue (N501Y) in the receptorbinding domain (RBD). Using this novel animal model, we further evaluated the in vivo protective efficacy of an RBD-based SARS-CoV-2 subunit vaccine, which elicited highly potent neutralizing antibodies and conferred full protection against SARS-CoV-2 MACSp6 challenge. This novel mouse model is convenient and effective in evaluating the in vivo protective efficacy of SARS-CoV-2 vaccine. SummaryThis study describes a unique mouse model for SARS-CoV-2 infection and confirms protective efficacy of a SARS-CoV-2 RBD subunit vaccine.

Lung cancer is the leading cause of cancer related deaths worldwide. TGF-β-induced epithelial-mesenchymal transition (EMT) is a key cell-intrinsic identity for tumor cell migration, invasion, and stemness acquisition in cancer metastasis. Long noncoding RNAs (lncRNAs) have not been fully investigated for their involvement in regulating TGF-β-induced EMT and metastasis in lung cancer. Here, we demonstrated that the transcription of lncRNA in nonhomologous end joining (NHEJ) pathway 1 (LINP1) was inhibited by TGF-β1 in a SMAD4-dependent manner. LINP1 suppressed EMT of lung cancer cells, thereby controlling cancer cell migration, invasion, and stemless. Moreover, LINP1 inhibited TGF-β-induced EMT and cell invasion in lung cancer cells. Our study reveals the role of LINP1 in the regulation of TGF-β-induced EMT in human lung cancer.