Susceptibility of lipopolysaccharide-responsive and -hyporesponsive ItyS Mice to infection with rough mutants of Salmonella typhimurium

Abstract

The R5 (chemotype Rb) but not the R10 (chemotype Rd) mutant of murine pathogen Salmonella typhimurium 395MS was extremely virulent in intraperitoneal infections of C57BL/10ScCr mice carrying the ity s and lps d alleles. C57BL/6J (ity s lps n) and C3H/HeJ (ity r lps d) mice showed a much higher resistance to the R5 mutant. Further studies were performed with peritoneal macrophages in vitro in order to elucidate susceptibility in lipopolysaccharide (LPS)-hyporesponsive mice carrying Ity s. The intracellular killing capacity of the Ity s Lps d macrophages was lower than that of the Ity s Lps n macrophages for the R5 mutant and may partly explain the increased susceptibility of the Ity s Lps d mice. The deep rough mutant, R10, was rapidly killed intracellularly by the Ity s Lps d macrophages. Processing of the bacteria in macrophages that had phagocytosed R5 or R10 bacteria was followed for up to 18 days by endotoxin measurements (Limulus assay) and immunostaining, with monoclonal antibodies to various parts of the LPS molecule being used. Only 0.1% or less of the macrophageassociated bacteria remained alive after 48 h of incubation, and none were alive on day 7. Although immunostaining showed that LPS was present in both the Lps d and Lps n macrophages during the whole incubation period of 18 days, endotoxin activity in the Lps d macrophages on day 7 was lower than that in the Lps n macrophages, indicating that qualitative modifications of the chemical composition or physical state of the LPS molecule occurred. The interleukin-6 response in the Ity s Lps d macrophages was delayed and of shorter duration compared with that in the Ity s Lps n macrophages. The results suggest that the difference between the LPS-hyporesponsive and-responsive Ity s mice in susceptibility to infection with the R5 mutant was due to the lower activation state of the Lps d macrophages during infection, leading to a lower intracellular killing rate and a lower interleukin-6 response. Deep rough mutant R10 was highly sensitive to the intracellular bactericidal systems of the macrophages. A rapid killing of the bacterium should restrict the infection and may partly compensate for a diminished inflammatory response. The persistence of LPS within the cells is discussed.

Yersinia pestis Interacts With SIGNR1 (CD209b) for Promoting Host Dissemination and Infection

“…In addition, deep rough mutants of Gram-negative bacteria in general are more sensitive to biological killing (39, 40). This fact should be taken into consideration in interpreting the data from the gentamicin survival assay of KIM10-Δ ail -Core − and CS2429 (Figure 3A).…”

The role of the Lps gene in experimental ulcerative colitis in mice

“…The C3H/HeJ (Lpsd) mice showed endotoxin levels close to those of the other Lpsd group, suggesting that LPS clearance by the mononuclear phagocytic system was less effective, i.e., not having been activated. The capacity of Gram-negative bacteria to activate monocytic cells is diminished in Lpsd mice, which may partly reduce the clearance capacity (17,30,39). Therefore the endotoxin levels found in serum may be associated with the LPS susceptibility and the effectiveness with which invading bacteria are phagocytosed and killed in the presence of a ruptured mucosal barrier.…”

“…A single gene, Lps, on mouse chromosome 4 regulates the responsiveness of the host to the lipid A part of the LPS molecule (5,23,40). The Lps gene locus profoundly influences the natural resistance of mice to a number of pathogenic organisms (17,24,35,41). Svanborg-Ed& et al showed that the Lps gene was important for the host resistance at mucosal sites (35).…”

The Polysaccharide Portion of Lipopolysaccharide Regulates Antigen-Specific T-Cell Activation via Effects on Macrophage-Mediated Antigen Processing

“…Both rough and smooth strains could block phagosome-lysosome fusion to enhance intracellular survival (5,25). However, during intracellular infection, rough strains were ultimately more susceptible to killing (41,51). When used in vaccination studies, smooth and rough strains can both induce protective cell-mediated immunity (45).…”