Biologic Characteristics of Some Mouse Mammary Tumor Viruses 2

Abstract

The mammary tumor virus (MuMTV) in the milks of 7 mouse strains and substrains was titrated for infectivity in 4 strains. The data indicated that: 1) Each strain shed a different MuMTV and some genetic strains carried two MuMTV's, each discernible by its mouse strain preference in infectivity tests. 2) Less than 5% of RIIIf and about 10% of Af mice shed detectable MuMTV antigen in their milks after the third parturition. After the sixth parturition, 33% of RIIIf and 50% of Af, and after the ninth parturition, 60% of RIIIf and 90% of Af mice shed viral antigen in their milks. The MuMTV's in milks of high-parity mothers were most infectious in mouse strains different from those most susceptible to MuMTV in RIII and A milks of low-parity mothers. Therefore, RIII and A mice each harbored two viruses, one that was removed by foster-nursing and the other that was not. 3) The susceptibility incidence of RIIIfC57BL mice to RIII virus changed gradually from about 10% in 1970 to about 70% in 1975. Susceptibility of C57BL mice to RIII virus did not change appreciably over this period, and the natural tumor incidence in RIIIfC57BL remained unchanged (about 10%). In addition to their susceptibility to RIII virus, C57BL mice were also susceptible to GR virus; they were relatively resistant to other strains tested. They were especially resistant to RIIIf virus, to which Af and BALB/c mice were very susceptible. 4) Approximately 90% of C3HfC57BL and C3HfBALB/c mice shed antigen in their milks after the third parturition, although the tumor incidence was less and occurred later than in C3H mice. No clear-cut differences could be detected in infectivities between low-parity C3H milk and high-parity C3Hf milks tested in several assay strains.

Idiopathic mammary tumors in BALB/c mice

“…It is the purpose of this paper to report an appreciable mammary tumor incidence in a colony of BALB/c mice derived from the BALB/c/Crgl line, with additional data on whether or not an MuMTV is involved. tumors, the incidence of one subline reaching about 35% and of the other about 18% (in previous reports, Moore et al, 1974Moore et al, , 1976, a combined average incidence was given). Milk samples of both sublines were continuously monitored for the presence of MuMTV antigen by microimmunodiffusion tests (Charney et al, 1969) and for the presence of B particles by electron microscopy.…”

“…tumors, the incidence of one subline reaching about 35% and of the other about 18% (in previous reports, Moore et al, 1974Moore et al, , 1976, a combined average incidence was given). Milk samples of both sublines were continuously monitored for the presence of MuMTV antigen by microimmunodiffusion tests (Charney et al, 1969) and for the presence of B particles by electron microscopy.…”

MuMTV Antigen Expression and Mammary Tumor Incidence in Non-inbred dd Mice

“…Since MTV, discovered by Bittner in 1936, is generally considered to be a primary factor for mammary tumorigenesis in mice, several attempts have been made to detect the presence of MTV in the milk [15,16]. The ID test developed by Blair [5] demonstrated MTV antigen immunologically in the milk, and later it was postulated that the rate of MTV antigen expression is well correlated with the mammary tumor incidence in most inbred strains of mice [6,11,17].…”

Bioactivities and the effect of dilution on various milk‐borne murine mammary tumor viruses

“…In most reports, however, inoculations of milk at low dilutions have resulted in a lower incidence of infection than inoculations at higher dilutions (Bittner, 1945(Bittner, , 1962Moore et al, 1974Moore et al, , 1976; e.g., in attempts to reinfect RIIIfC57BL mice with RIlI virus, RIII milk dilutions of lo-' or gave no evidence of infection, whereas dilutions of did (Moore et al, 1974). In a recent study of the infectivity of various MuMTVs in several mouse strains and their F, hybrids, the slopes of inoculum dilution curves depended on the genetics of both the virus and the recipient mouse (Moore etal., 1978).…”