Studies of a virus isolated from a wild house mouse, Mus musculus, and producing splenomegaly and lymph node enlargement in mice.

Abstract

SUMMARYA virus (WM1 strain) was isolated from a wild house mouse, Mus musculus. It was infective for suckling and weaned mice inoculated intraperitoneally, but not for laboratory Rattus norvegicus, guinea‐pigs, rabbits or chick embryos.A prolonged chronic infection resulted, with normal blood picture, persistent viraemia, moderate splenomegaly and general enlargement of lymph nodes, which were sometimes massive. Most infected mice died within 11½ months.Microscopically, the splenomegaly was seen to be due to hyperplasia of both red and white pulp, while enlargement of lymph nodes was essentially due to medullary hyperplasia, with plasma cells prominent. Four of 79 infected weaned mice examined at random within 11½ months had developed neoplasms of the lymph nodes, while none was seen in any of the 87 control mice examined in the same period. However, two of 17 control mice had neoplasms of lymph nodes at 18 months.The virus passed through Gradocol membranes with average pore diameter of 320 mμ. lt was sensitive to ether, formalin, and heating at 56° C. for 30 minutes, but remained viable at −60° C. and after lyophilization, and was resistant to 5 p.c. ethanol at 4° C. for 24 hours.