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Extensive cytocidal replication of lactate dehydrogenase-elevating virus in cultured peritoneal macrophages from
C O Onyekaba1, J T Harty, P G Plagemann
1Department of Microbiology, Medical School, University of Minnesota, Minneapolis 55455.
Abstract:
Indirect fluorescent antibody staining was used to examine the replication of lactate dehydrogenase-elevating virus (LDV) in primary cultures of peritoneal macrophages from BALB/c mice of different ages. Up to 80% of the total peritoneal macrophages from 1-2-week-old mice were susceptible to productive infection by LDV, though only 1-2% of the cells expressed detectable levels of IA antigen. The proportion of LDV-permissive peritoneal macrophages progressively decreased to 5-15% between 2 and 5 weeks of age of the mice. Macrophages from 9-day-old mice, when cultured in the presence of L cell conditioned medium, retained undiminished LDV permissiveness for at least 10 days in culture. The maximum proportion of LDV antigen-positive cells was detected between 8-10 h post infection of macrophages cultured from both 1-2-week-old and adult mice, concomitant with maximum LDV RNA synthesis. The LDV antigen positive macrophages disappeared between 12 and 48 h post infection. In cultures of macrophages from 9-10-day-old mice, the loss of infected cells was clearly due to cell killing, proving unequivocally that LDV replication is cytocidal. Disintegration of LDV-infected macrophages or phagocytosis of killed macrophages by surviving macrophages must be very sudden and complete since infected cells disappeared without the appearance of trypan blue-stainable cells in the culture. Ten cell lines established from macrophages of 2, 9, and 10-day-old mice all contained a small proportion of LDV-permissive cells (1-4%). Individual clones of one of the lines contained a similar small proportion of LDV-permissive cells.
Insights
Lactate dehydrogenase-elevating virus (LDV) productively infects young mouse macrophages, but permissiveness declines with age. LDV replication is cytocidal, causing rapid macrophage death without trypan blue staining.
Area of Science:
- Virology
- Immunology
- Cell Biology
Background:
- Lactate dehydrogenase-elevating virus (LDV) is a significant pathogen in mice.
- Peritoneal macrophages play a crucial role in the innate immune response.
- Understanding LDV-macrophage interactions is key to controlling viral pathogenesis.
Purpose of the Study:
- To investigate the age-dependent susceptibility of mouse peritoneal macrophages to LDV infection.
- To determine the cytopathic effects of LDV replication in macrophages.
- To characterize LDV permissiveness in long-term macrophage cultures and cell lines.
Main Methods:
- Indirect fluorescent antibody staining to detect LDV antigen.
- Primary culture of peritoneal macrophages from BALB/c mice of varying ages.
- Macrophage culture with L cell conditioned medium.
- Assessment of cell viability using trypan blue staining.
- Establishment and analysis of macrophage-derived cell lines.
Main Results:
- Macrophages from 1-2-week-old mice showed high LDV permissiveness (up to 80%), decreasing with age.
- LDV antigen expression peaked at 8-10 hours post-infection, coinciding with RNA synthesis.
- LDV-infected macrophages exhibited rapid cell death (cytocidal effect) within 12-48 hours post-infection.
- Established cell lines contained a small proportion of LDV-permissive cells.
Conclusions:
- Macrophage permissiveness to LDV is age-dependent, with younger mice being more susceptible.
- LDV replication is unequivocally cytocidal to macrophages, leading to rapid cell death.
- The study provides insights into LDV pathogenesis and host-pathogen interactions in macrophages.