Characteristics of a Plaque Method for the Murine Salivary Gland Virus.

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Abstract
Summary Using a double agar overlay, MSGV produced discrete spherical plaques in mouse embryonic fibroblasts, but not in chick embryo, HeLa or L cells. Plaques appeared about 36 hours after seeding as single large rounded inclusion-laden cells, surrounded by wide clear zones. Centrifugal expansion by progressive involvement of adjacent cells resulted in plaque diameters of 0.2 to 0.8 mm by the 6th day. Fluid medium from infected bottle cultures commonly contained 1 × 107 PFU/ml. A linear relationship was found between plaque counts and virus dilution. The virus was markedly stable when stored for 5 hours in PBS with 2% calf serum, but rapid loss of titer occurred if serum was omitted. Virus titer and CPE production in vitro were not significantly altered during 120 passages, but pathogenicity for mice was lost after about 36 passages.