A virus (WM1 strain) was isolated from a wild mouse, Mus musculus. During the course of the studies the following three strains of virus were recognized.
1) WM1(-) strain, causing lymphoid hyperplasia in mice.
(2) WM1-B strain, a typical strain of Friend virus causing reticulum-cell neoplasia.
(3) avirulent WM1-B strain, a previously unknown avirulent strain of Friend virus.
The general properties of the WM1 virus were studied before it was known that an avirulent strain of Friend virus was also present. In Q.I.M.R. mice the WM.1 strain produced a chronic infection characterized by splenomegaly and lymphadenopathy. Greatly enlarged lymph nodes occurred in 20 p.c. of infected weaned mice and in 34 p.c. of infected suckling mice. Such enlargement was first observed three months after inoculation.
In mice examined at random, the splenomegaly and most of the lymphadenopathy was due to hyperplasia...
...An apparent relationship between WM1 and WM1-B virus was detected and WM1 virus protected mice against challenge with WM1-B virus. Also, the serum of C3H mice inoculated with WM1 virus neutralized WM1-B virus. This relationship was found to be due to the presence of an avirulent strain of Friend virus in the WM1 line, and the concentration of the two viruses was found to be similar. By treatment with antiserum the WM1 virus was freed of the avirulent Friend virus component.
A series of 17 wild mice was examined. Five strains of virus resembling WM1 virus and four strains of avirulent Friend virus were isolated. Two of the strains of WM1-type virus were not related to Friend virus and one strain of Friend virus did not produce splenomegaly. This was further evidence that WM1 virus was distinct from avirulent Friend virus. Antibodies to Friend virus were detected in the serum of wild mice showing that avirulent Friend virus commonly infects wild mice in Brisbane.