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Listeria monocytogenes cell walls induce decreased resistance to infection
Abstract:
A significant decrease in murine resistance to Listeria monocytogenes was induced by using crude Listeria cell wall fraction (LCWF) and purified Listeria cell walls (PF). When equal amounts of these materials were injected, PF was more effective than LCWF in decreasing resistance. The PF effect was dose dependent when measured either as a decrease in 50% lethal dose of the Listeria challenge or as a decrease in survival time of the infected mice. PF apparently does not act directly on the Listeria since it (i) did not cause a change in in vitro growth of Listeria and (ii) did not increase the virulence of Listeria passaged in vivo or in vitro. The greatest decrease in resistance was observed when both PF and the Listeria challenge were injected intraperitoneally, which may suggest a localized effect. A decrease in resistance was seen when PF was given as early as 3 days before challenge. There was little or no decrease in resistance when PF was given 2 days after the Listeria challenge. Mice previously immunized with live Listeria were immune to Listeria challenge. However, after PF injection the immune mice showed a decreased resistance which was of the same order of magnitude as that seen in unimmunized mice. The effect of PF seems to be at least partially nonspecific, since a decrease in resistance to Salmonella typhimurium could also be demonstrated in PF-treated mice. Phagocytosis of Listeria both in vivo and in vitro did not appear to be inhibited by PF, although the ability of PF-treated mice to kill Listeria in the peritoneal cavity was inhibited.
Insights
Purified Listeria cell walls (PF) significantly reduce mouse resistance to Listeria monocytogenes infection. This effect is dose-dependent and appears nonspecific, impacting even previously immunized mice and resistance to other bacteria.
Area of Science:
- Immunology
- Microbiology
- Bacterial Pathogenesis
Background:
- Listeria monocytogenes is a significant human pathogen.
- Understanding factors that modulate host resistance is crucial for developing effective treatments.
- Bacterial cell wall components can influence host immune responses.
Purpose of the Study:
- To investigate the effect of Listeria cell wall components on murine resistance to Listeria monocytogenes.
- To determine if purified Listeria cell walls (PF) alter host susceptibility to Listeria infection.
- To elucidate the mechanism by which PF affects host defense.
Main Methods:
- Mice were injected with crude Listeria cell wall fraction (LCWF) or purified Listeria cell walls (PF).
- Murine resistance was assessed by measuring the 50% lethal dose (LD50) and survival time after Listeria challenge.
- In vitro and in vivo growth of Listeria, as well as phagocytosis and bacterial killing, were evaluated in PF-treated and control groups.
Main Results:
- PF significantly decreased murine resistance to Listeria monocytogenes in a dose-dependent manner.
- PF did not directly affect Listeria growth or virulence.
- PF administration prior to challenge, particularly intraperitoneally, most effectively reduced resistance.
- PF treatment also decreased resistance to Salmonella typhimurium, suggesting a nonspecific effect.
- While phagocytosis was not inhibited, the ability of PF-treated mice to kill Listeria in the peritoneal cavity was impaired.
Conclusions:
- Purified Listeria cell walls (PF) induce a significant, dose-dependent decrease in murine resistance to Listeria monocytogenes.
- The mechanism appears to involve impaired bacterial killing rather than direct effects on the pathogen or phagocytosis inhibition.
- The observed nonspecificity suggests PF may broadly impact innate immune responses, offering insights into host-pathogen interactions.