Biologic characteristics of some mouse mammary tumor viruses
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.
Insights
Mammary tumor virus (MuMTV) strains vary by mouse genetics and parity. High-parity mothers shed more infectious MuMTV, with distinct viral strains identified by mouse susceptibility.
Area of Science:
- Virology
- Immunology
- Genetics
Background:
- The mammary tumor virus (MuMTV) is a key etiological agent in mouse mammary tumorigenesis.
- Understanding MuMTV strain diversity and transmission is crucial for studying viral oncogenesis.
- Previous studies have suggested genetic and environmental factors influence MuMTV shedding and infectivity.
Purpose of the Study:
- To characterize the infectivity and genetic diversity of MuMTV across different mouse strains and parities.
- To investigate the influence of maternal parity on MuMTV shedding and viral antigen presence in milk.
- To determine the susceptibility patterns of various mouse strains to different MuMTV isolates.
Main Methods:
- Titration of MuMTV infectivity in milk from 7 mouse strains/substrains across 4 different strains.
- Assessment of MuMTV antigen shedding in milk samples from mice of varying parity (3rd, 6th, and 9th parturition).
- Comparative analysis of mouse strain susceptibility to MuMTV isolates from different maternal parities and genetic backgrounds.
Main Results:
- Distinct MuMTV strains were identified, with some mouse strains harboring multiple viruses.
- MuMTV shedding increased significantly with parity, particularly in RIIIf and Af mice.
- Viral infectivity varied, with high-parity milk viruses showing altered host preferences compared to low-parity milk viruses.
- Specific mouse strains exhibited differential susceptibility to various MuMTV isolates, indicating genetic resistance/susceptibility.
- C57BL mice showed changing susceptibility to RIII virus over time, while natural tumor incidence remained stable.
Conclusions:
- Mouse strain genetics and maternal parity are critical determinants of MuMTV shedding and infectivity.
- The study identified distinct MuMTV strains with unique host tropisms, some of which were not cleared by foster-nursing.
- Long-term monitoring revealed evolving host-virus interactions, impacting susceptibility to MuMTV infection.
