Vr 764

L2 cells (ATCC CCL-149TM) were used for the MHV plaque assay. In addition, the mouse asterocytoma-derived cell line (DBT), was used to propagate MHV (generously provided by Julian Leibowitz, Texas A&M Health Science Center, College Station, TX). All cells used in this study were cultured at 37°C in 5% CO₂ in Dulbecco’s modified Eagle’s medium (DMEM; Cellgro) supplemented with 10% fetal bovine serum (FBS), penicillin (50 IU/mL), and streptomycin (50 μg/mL). MHV strain A59 (ATCC VR-764) was used for all the experiments in this study. The virus stocks used for this study were produced as previously described (59 (link)). The MHV viral titer used for all experiments was ~1.0 × 10⁴ PFU/mL. We chose 100 μL (1.0 × 10³ virus particles) to inoculate on each of our samples because 1.0 × 10² – 2.0 × 10³ virus particles is the predicted minimal amount of virus particles needed in order to infect someone (60 (link), 61 (link)). In addition, we chose 1.0 × 10³ virus particles because according to a recent publication modeling the SARS-CoV-2 viral titer when sneezing or coughing on a surface, the range of virus particles for a cough or sneeze was ~1.0 × 10³ – 1.0 × 10⁵, which is in this range (62 (link)).

L2 cells (ATCC CCL-149TM) were used for the MHV plaque assay. In addition, the mouse asterocytoma-derived cell line (DBT), was used to propagate MHV (generously provided by Julian Leibowitz, Texas A&M Health Science Center, College Station, TX). All cells used in this study were cultured at 37°C in 5% CO₂ in Dulbecco’s modified Eagle’s medium (DMEM; Cellgro) supplemented with 10% fetal bovine serum (FBS), penicillin (50 IU/mL), and streptomycin (50 μg/mL). MHV strain A59 (ATCC VR-764) was used for all the experiments in this study. The virus stocks used for this study were produced as previously described (59 (link)). The MHV viral titer used for all experiments was ~1.0 × 10⁴ PFU/mL. We chose 100 μL (1.0 × 10³ virus particles) to inoculate on each of our samples because 1.0 × 10² – 2.0 × 10³ virus particles is the predicted minimal amount of virus particles needed in order to infect someone (60 (link), 61 (link)). In addition, we chose 1.0 × 10³ virus particles because according to a recent publication modeling the SARS-CoV-2 viral titer when sneezing or coughing on a surface, the range of virus particles for a cough or sneeze was ~1.0 × 10³ – 1.0 × 10⁵, which is in this range (62 (link)).

Each cell line used in the study was maintained in the author’s laboratory. Mouse L929 fibroblast cells were purchased from ATCC and cultured in Dulbecco’s Modified Eagle’s Medium (DMEM) supplemented with 10% fetal bovine serum (FBS) and 1% penicillin–streptomycin. Mouse RAW 264.7-Lucia and RAW 264.7-Lucia-KO-IRF3 macrophages, purchased from InvivoGen (San Diego, CA, USA), were cultured in DMEM containing 10% FBS, 1% penicillin-streptomycin, and 0.1% Normocin.
Mouse hepatitis virus strain A59 (MHV) was obtained from ATCC (VR-764). Viral stocks were maintained by propagating MHV in our mouse L929 fibroblasts. Virus titers were quantified by performing a plaque assay in L929 cells overlayed with 1% carboxy-methyl cellulose (CMC).