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Quantitative comparison of milk-released C3H and RIII mammary tumor viruses in infected BALB/c hosts
Abstract:
The C3H and RIII mammary tumor viruses (MTV) carried by BALB/cfC3H and BALB/cfRIII breeding females have been quantified and compared in milk samples, after partial purification with a sucrose density gradient. The samples were collected at identical times during the first 3 lactation periods from individual mice (6 per strain), standardized for age at delivery and size of litter. Milk samples from 6 MTV negative BALB/c controls have also been analyzed. Data for comparison are expressed in optical density units (ODU) and refer to the protein content of the whole milk using MTV-negative Balb/c milk as blank. The results have shown 1) an increase of MTV released through milk in each MTV-carrying female from the first (average ODU, 0.542) to the second (1,351) and third (2.105) lactation, 2) individual variations, and 3) a significant difference in release between C3H and RIII MTV, the latter being more than double (average ODU, 1.801) in respect to the former (0.847). The apparent discrepancy between these results and the bioactivity in BALB/c mice of C3H and RIII MTV, significantly lower for the latter, is discussed.
Insights
Mammary tumor viruses (MTV) levels in milk increase with each lactation period in mice. RIII MTV strains show significantly higher milk release than C3H MTV strains, despite differing bioactivity.
Area of Science:
- Virology
- Oncology
- Mammalian Genetics
Background:
- Mammary tumor viruses (MTV) are oncogenic retroviruses associated with mammary cancer in mice.
- Quantifying MTV in milk is crucial for understanding transmission and disease pathogenesis.
Purpose of the Study:
- To quantify and compare the release of C3H and RIII MTV in the milk of BALB/cf mice during lactation.
- To investigate the relationship between MTV milk levels and viral bioactivity.
Main Methods:
- Milk samples from BALB/cfC3H and BALB/cfRIII breeding females were collected across three lactation periods.
- Mammary tumor viruses (MTV) were partially purified using sucrose density gradients.
- Viral quantification was performed using optical density units (ODU), normalized to milk protein content.
Main Results:
- MTV levels in milk significantly increased from the first to the third lactation period.
- Individual variations in MTV milk release were observed among mice.
- RIII MTV strains exhibited more than double the milk release compared to C3H MTV strains.
Conclusions:
- MTV shedding in milk is a dynamic process that increases with successive lactations.
- Significant differences exist in the milk shedding patterns of C3H and RIII MTV strains.
- The study highlights a potential discrepancy between MTV milk levels and their observed bioactivity, warranting further investigation.