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The interaction of Naegleria fowleri amoebae with murine macrophage cell lines
K Fischer-Stenger1, G A Cabral, F Marciano-Cabral
1Department of Microbiology and Immunology, Virginia Commonwealth University, Medical College of Virginia, Richmond 23298-0678.
Abstract:
The present study was undertaken to determine whether murine macrophage cell lines exhibited in vitro amoebicidal activity comparable to that elicited by activated murine peritoneal macrophages. Peritoneal macrophages activated in vivo by bacillus Calmette-Guérin or Propionibacterium acnes demonstrated significant cytolysis of Naegleria fowleri amoebae. The macrophage cell line RAW264.7 also effected cytolysis of amoebae, but to a lesser extent than that elicited by activated peritoneal macrophages. However, the macrophage cell lines, J774A.1 and P388D1, did not exhibit amoebicidal activity. Macrophage conditioned medium prepared from RAW264.7 macrophages mediated cytolysis of L929 tumor cells but had no effect on N. fowleri amoebae. In addition, neither recombinant tumor necrosis factor nor recombinant interleukin-1 exhibited amoebicidal activity. Scanning electron microscopy of co-cultures revealed that N. fowleri bound to activated peritoneal macrophages and RAW264.7 macrophages. These results suggest that RAW264.7 macrophages treated in vitro with lipopolysaccharide are similar to macrophages activated in vivo in that they effect contact-dependent cytolysis of Naegleria fowleri amoebae. The RAW264.7 macrophages are unlike primary macrophage cultures in that they either do not release soluble amoebicidal factors into the conditioned medium or they release insufficient quantities.
Insights
Murine macrophage cell lines were tested for amoebicidal activity against Naegleria fowleri. RAW264.7 cells showed contact-dependent cytolysis, unlike other cell lines or soluble factors.
Area of Science:
- Immunology
- Cell Biology
- Parasitology
Background:
- Macrophages are key immune cells involved in host defense.
- Naegleria fowleri is an opportunistic parasitic amoeba causing primary amoebic meningoencephalitis.
- Understanding macrophage-mediated immunity against N. fowleri is crucial for developing therapeutic strategies.
Purpose of the Study:
- To investigate the in vitro amoebicidal activity of murine macrophage cell lines against Naegleria fowleri.
- To compare the efficacy of macrophage cell lines with activated primary murine peritoneal macrophages.
- To determine the role of soluble factors and cell contact in macrophage-induced amoebic cell lysis.
Main Methods:
- Co-culturing of Naegleria fowleri with activated murine peritoneal macrophages and various macrophage cell lines (RAW264.7, J774A.1, P388D1).
- Assessment of amoebicidal activity through cytolysis assays.
- Preparation and testing of conditioned medium from RAW264.7 macrophages.
- Use of scanning electron microscopy to visualize cell interactions.
Main Results:
- Activated peritoneal macrophages demonstrated significant cytolysis of N. fowleri.
- RAW264.7 macrophage cell line exhibited contact-dependent cytolysis of N. fowleri, though less potent than activated peritoneal macrophages.
- J774A.1 and P388D1 macrophage cell lines showed no amoebicidal activity.
- Conditioned medium from RAW264.7 macrophages did not lyse N. fowleri, indicating a lack of soluble amoebicidal factors.
Conclusions:
- RAW264.7 macrophages, particularly when stimulated with lipopolysaccharide, possess contact-dependent amoebicidal activity against Naegleria fowleri.
- Unlike primary macrophages, RAW264.7 cells do not appear to release significant soluble amoebicidal factors.
- This study highlights the potential of specific macrophage cell lines in studying host-pathogen interactions with N. fowleri.