Growth curves of molecularly cloned and wild-type MHV-A59. Cultures of 2.0 × 105 DBT, BHK, or BHK-MHVR cells were infected with various molecularly cloned viruses and wild-type MHV-A59 at an MOI of 10 for 1 h. In some instances prior to infection, the cells had been pretreated with a 1:2 dilution of monoclonal antibody CC1, directed against the MHVR. Virus samples were taken at the indicated times. The figure shows virus growth in DBT (A), BHK-MHVR (B), and BHK (C) cells, respectively.