Listeria Infection In Mice Research Articles

Herpes virus entry mediator licenses Listeria infection induced immunopathology through control of type I interferon.

Apoptosis of the splenic lymphocytes is often induced during the acute phase of Listeria infection in mice. However, the underlying mechanism remains incompletely understood. Here, we found that herpes virus entry mediator (HVEM) plays an important role for Listeria infection induced lymphocyte apoptosis. Mechanistically, HVEM is not directly involved in listeriolysin O (LLO) induced lymphocyte apoptosis or interferon beta induced T cell activation per se. Interestingly, HVEM is partially required for Listeria induced interferon (IFN)-I production in the spleen, particularly in macrophages. Consequently, the bystander activation of lymphocytes is significantly lower in HVEM deficient mice than that in wild-type (WT) mice upon Listeria infection. Thus, our results have revealed a novel role of HVEM on the regulation of IFN-I and immunopathology during Listeria infection.

Dominant-Negative Inhibitors of Soluble TNF Attenuate Experimental Arthritis without Suppressing Innate Immunity to Infection

TNF is a pleiotropic cytokine required for normal development and function of the immune system; however, TNF overexpression also induces inflammation and is associated with autoimmune diseases. TNF exists as both a soluble and a transmembrane protein. Genetic studies in mice have suggested that inflammation in disease models involves soluble TNF (solTNF) and that maintenance of innate immune function involves transmembrane TNF (tmTNF). These findings imply that selective pharmacologic inhibition of solTNF may be anti-inflammatory and yet preserve innate immunity to infection. To address this hypothesis, we now describe dominant-negative inhibitors of TNF (DN-TNFs) as a new class of biologics that selectively inhibits solTNF. DN-TNFs blocked solTNF activity in human and mouse cells, a human blood cytokine release assay, and two mouse arthritis models. In contrast, DN-TNFs neither inhibited the activity of human or mouse tmTNF nor suppressed innate immunity to Listeria infection in mice. These results establish DN-TNFs as the first selective inhibitors of solTNF, demonstrate that inflammation in mouse arthritis models is primarily driven by solTNF, and suggest that the maintenance of tmTNF activity may improve the therapeutic index of future anti-inflammatory agents.

The effect of centaurein on interferon-γ expression and Listeria infection in mice

We previously found that centaurein enhanced IFN-gamma transcription in T cells. Here, we demonstrate that centaurein increased the IFN-gamma expression in T and NK cells and the serum IFN-gamma level in mice. Centaurein elevated the transcription of T-bet but not GATA-3, which is consistent with its effect on that of IFN-gamma but not IL-4. Additionally, centaurein effectively protected mice against Listeria infection. Moreover, centaurein per se or in combination with antibiotics could treat Listeria infection. Our mechanistic studies suggest that centaurein augments IFN-gamma expression via a transcriptional up-regulation of T-bet and that centaurein protects against or treats Listeria infection via a modulation of IFN-gamma expression.

Potential antimicrobial effects of human lactoferrin against oral infection with Listeria monocytogenes in mice

Listeria monocytogenes is a food-borne pathogen that causes serious listeriosis in humans. Antimicrobial effects of human lactoferrin (hLF) against L. monocytogenes have been clearly demonstrated in in vitro studies. However, in vivo studies have not been reported yet. This study investigated whether the oral administration of hLF could inhibit oral infection of listeria in BALB/c mice. The MICs for several strains of L. monocytogenes were determined, and the most sensitive strain was used for the animal work. hLF was administered to BALB/c mice for 7 days, commencing 4 days before oral infection. The effect of hLF was determined by bacterial enumeration and histopathological analysis of the liver and spleen, which are well-known as the major targets of oral listeria infection in mice. In bacterial enumeration, hLF decreased the number of L. monocytogenes cells in the liver. Histopathologically, the size and frequency of necrotic foci in the liver samples decreased with hLF administration. However, these changes were not observed in the spleen samples. The mRNA levels of inflammatory cytokines, such as interleukin (IL)-1beta, tumour necrosis factor (TNF)-alpha and interferon (IFN)-gamma, decreased in the liver of mice receiving hLF. This study has shown that hLF decreases the hepatic colonization of L. monocytogenes, hepatic necrosis and expression of inflammatory cytokines. It revealed that perorally given hLF could mediate antimicrobial and anti-inflammatory activities remote from the gut (i.e. in the liver) of mice challenged with L. monocytogenes.

Novel tumor necrosis factor‐knockout mice that lack Peyer's patches

We generated a novel tumor necrosis factor (TNF) null mutation using Cre-loxP technology. Mice homozygous for this mutation differ from their "conventional" counterparts; in particular, they completely lack Peyer's patches (PP) but retain all lymph nodes. Our analysis of these novel TNF-knockout mice supports the previously disputed notion of the involvement of TNF-TNFR1 signaling in PP organogenesis. Availability of TNF-knockout strains both with and without PP enables more definitive studies concerning the roles of TNF and PP in various immune functions and disease conditions. Here, we report that systemic ablation of TNF, but not the presence of PP per se, is critical for protection against intestinal Listeria infection in mice.

Roles of caspase-1 in Listeria infection in mice

Caspase-1 [IL-1beta-converting enzyme (ICE)] processes substrate precursor molecules to yield the biologically active form of IL-1beta and IL-18, both of which are considered to play important roles in the host defense by activation of both innate and adaptive immunity. We evaluated the immune response of caspase-1(-/-) mice to Listeria monocytogenes (LM) infection. LM eradication in the early phase of infection was impaired in the mutant mice with a prominent decrease in IL-18 and IFN-gamma production, but not in IL-12. Caspase-1(-/-) spleen cells including dendritic cells and NK cells produced less IFN-gamma in response to heat-killed LM than wild-type cells in vitro. IFN-gamma production and bactericidal activity in LM-infected caspase-1(-/-) mice was reconstituted to normal levels by adding back IL-18 at the initial phase of infection, suggesting that the lack of this cytokine is primarily responsible for the susceptibility of caspase-1(-/-) mice against LM infection. Moreover, IFN-gamma injection of caspase-1(-/-) mice corrected the deficiency in pathogen clearance. In contrast, LM-specific acquired immunity in caspase-1(-/-) mice was normal and they successfully cleared the pathogen following secondary infection, in spite of a moderate skewing of cytokine profile to T(h)2 when compared to wild-type mice. These data shed light on the importance of caspase-1-mediated IL-18 processing in innate immunity against facultative intracellular pathogens.

Persistent production of interferon-gamma (IFN-gamma) and IL-12 is essential for the generation of protective immunity against Listeria monocytogenes.

IFN-gamma and IL-12 are believed to be important in the host defence against Listeria infection in mice. However, the relationship between these two cytokines and generation of protective immunity remains poorly understood. In the present study, it was found that at least 4 days of immunizing infection were required for the generation of protective immunity against L. monocytogenes. Protective immunity was generated only by immunizing infection with virulent strain. Even repeated injections of avirulent strain failed to induce protective immunity. When the immunizing infection was terminated with antibiotics, generation of protective immunity and IFN-gamma-producing ability was impaired, while expression of IFN-gamma and IL-12 was also impaired. The mutual relationship between IFN-gamma and IL-12 in L. monocytogenes infection was analysed in vitro. After neutralization of IL-12, IFN-gamma production was completely blocked and IFN-gamma expression was also inhibited. In contrast, there was no change of IL-12 expression after neutralization of IFN-gamma. Taking all facts into consideration, it may be concluded that persistent production of IFN-gamma induced by persistent production of IL-12 during immunizing infection is essential for the generation of protective immunity against L. monocytogenes.

Immunoparameter Kinetics of Listeria Infection in Mice Pretreated with Prednisolone or Diethylstilbestrol.

Although both Prednisolone (PRE), a corticoid hormone, and diethylstilbestrol (DES), an estrogen-like hormone, are known to be immunosuppressive drugs, we found that mice pretreated with PRE showed enhanced resistance to Listeria infection, while mice pretreated with DES showed decreased resistance to Listeria infection. To establish useful immunoparameters of host resistance to Listeria infection, we examined the kinetics of immune cells in PRE- or DES-pretreated mice after non-lethal infection with Listeria monocytogenes. The number of CD4+CD8+, CD4+ and CD8+ T-cell subsets in the thymus and spleen and macrophage (Mac-1+ cells) in the spleen were decreased in mice pretreated with PRE, however the number of T-cell subsets in the thymus and macrophage in the spleen were remarkably increased to the level of non Listeria -infected control mice on Day 4 after Listeria infection. However, mice pretreated with DES showed a decrease in CD4+CD8+ T-cells in the thymus and a decrease in macrophages in the spleen. Furthermore, these cells continued to show decreased numbers even after Listeria infection. A remarkable increase of CD8:CD4 T-cell ratios was observed in PRE-pretreated mice but not in DES-pretreated mice. These data demonstrated that the recovery of CD4+CD8+, CD4+ and CD8+ T-cell subsets in the thymus, increased CD8:CD4 T-cell ratios in the thymus and increased macrophages in the spleen on Day 4 after the infection play important roles in increasing the resistance to Listeria infection in mice pretreated with PRE. These results also suggested that changes in immune cell kinetics could be good immunoparameters to demonstrate susceptibility to Listeria infection in mice pretreated with immunosuppressive drugs.

Endogenous interleukin-4 does not suppress the resistance against a primary or a secondary Listeria monocytogenes infection in mice.

Interleukin-4 (IL-4), a cytokine produced by T-helper 2 (Th2) cells, can inhibit the development of T-helper 1 (Th1) cells, which results in a decreased release of cytokines by the latter. As interferon-gamma (IFN-gamma), produced by Th1 cells, is involved in the resistance against a Listeria monocytogenes infection, the role of endogenously formed IL-4 during a Listeria infection in mice was investigated. Neutralization of endogenously formed cytokines by subcutaneously injected alginate-encapsulated monoclonal antibody (MoAb)-forming cells results in high antibody titres in the circulation over a long time period. The aim of the present study was to reevaluate the effect of neutralization of IL-4 during a primary Listeria infection and to investigate the role of IL-4 during a secondary infection in mice using encapsulated MoAb-forming cells. During the course of a primary infection in mice given anti-IL-4 antibody-forming cells (anti-IL-4-FC), the number of Listeria found in the liver and spleen was comparable to that found in control mice given anti-beta-galactosidase antibody-forming cells (anti-beta-gal-FC). Activation of macrophages measured by inhibition of Toxoplasma gondii proliferation and the release of reactive nitrogen intermediates (RNI) was not affected by anti-IL-4-FC treatment during infection. Furthermore, during a secondary L. monocytogenes infection the number of bacteria in the liver and spleen of anti-IL-4-treated immune mice was comparable to anti-beta-gal-FC-treated, control, immune mice. The concentration of IFN-gamma in plasma of anti-IL-4-treated immune mice was similar to that of control immune mice. Taken together, these findings demonstrate that neutralization of endogenously formed IL-4 does not affect resistance to a primary or a secondary L. monocytogenes infection in mice.

Nitric oxide produced during murine listeriosis is protective.

Nitric oxide (NO) has been shown to be important for intracellular microbiostasis in vitro. To determine the role of NO in immune function in vivo, groups of C57BL/6 mice were given a sublethal intravenous inoculum of Listeria monocytogenes EGD, and their urine was monitored daily for nitrate, the mammalian end product of NO metabolism. Urinary nitrate levels peaked at 5 to 10 times the basal level on days 5 to 6, when spleen and liver Listeria counts declined most steeply, and decreased thereafter, when spleens and livers were nearly sterile. Peritoneal macrophages explanted from Listeria-infected mice produced nitrite spontaneously, whereas macrophages from uninfected mice did not. The inducible NO synthase mRNA was detectable in the spleens of infected mice on days 1 to 4 of infection. When Listeria-infected mice were treated orally throughout the infection with NG-monomethyl-L-arginine (NMMA), a specific NO synthase inhibitor they showed no detectable rise in urinary nitrate excretion. Mean Listeria counts in the livers and spleens NMMA-treated mice were 1 to 3 orders of magnitude greater than counts in control mice on days 4 through 8 of infection. Compared with control mice, NMMA-treated mice also showed worse clinical signs of infection, namely, weight loss, hypothermia, decreased food and water intake, and decreased urine output. Histologically NMMA-treated mice had many more inflammatory foci in their livers and spleens than control mice. The histologic observation that mononuclear cells are present at sites of infection suggests that inhibiting NO production did not block the flux of macrophages into infected viscera. As controls for possible drug toxicity, a group of uninfected mice given NMMA orally showed no detrimental effects on weight, temperature, and food and water intake. These experiments demonstrate that inhibition of NO production in Listeria-infected mice results in an exacerbated infection and thus that NO synthesis is important for immune defense against Listeria infection in mice.

Human tumor necrosis factor increases the resistance against Listeria infection in mice

The resistance in mice against Listeria infection was augmented by treatment with recombinant human tumor necrosis factor (TNF). To elucidate this phenomenon, we examined the effect of TNF on macrophage activation. TNF-treated macrophages had listericidal activity in vitro and superoxide anion production. In addition, macrophage migration was inhibited in the presence of TNF. Therefore, activation of macrophages by TNF was similar to activation by macrophage-activating factor or macrophage-migration-inhibitory factor.

T cell subsets in DTH, protection and granuloma formation in primary and secondary listeria infection in mice: superior role of Lyt-2 + cells in acquired immunity

T cell subsets in DTH, protection and granuloma formation in primary and secondary listeria infection in mice: superior role of Lyt-2 + cells in acquired immunity

T-cell subsets in delayed-type hypersensitivity, protection, and granuloma formation in primary and secondary Listeria infection in mice: superior role of Lyt-2+ cells in acquired immunity.

Immunity to Listeria monocytogenes was studied in mice treated with rat monoclonal antibodies (MAbs) specific for the Thy-1.2, L3T4, and Lyt-2 T-cell markers. Three characteristic T-cell-mediated phenomena were investigated. Delayed-type hypersensitivity (DTH) to listerial antigen was totally abolished in mice treated with anti-Thy-1.2 or anti-L3T4 MAbs, whereas anti-Lyt-2 MAb treatment had no effect, regardless of whether the MAb was given during the induction or the expression of DTH. On the other hand, the elimination of bacteria from the spleens of infected animals was inhibited only by the application of either anti-Thy-1.2 MAb or anti-Lyt-2 MAb. This could be shown most impressively during the secondary infection of immune mice with a normally lethal dose of listeriae. In this situation, treatment with anti-Lyt-2 MAb sufficed to completely abolish immunologic memory, whereas anti-L3T4 MAb had only a marginal effect on antibacterial protection. However, the accelerated development of mononuclear cell foci in the livers of immune mice was inhibited by the application of both anti-L3T4 MAb and anti-Lyt-2 MAb. It is concluded that in murine listeriosis, DTH and acquired immunity to reinfection are dissociable phenomena. Although DTH is a function of L3T4+ T lymphocytes, Lyt-2+ T cells are necessary and sufficient for the expression of acquired resistance to L. monocytogenes. The roles of the different T-cell subsets in granuloma formation warrant further investigation.

Indomethacin in vivo increases the sensitivity to Listeria infection in mice. A possible role for macrophage thromboxane A2 synthesis.

This paper demonstrates that in the presence of indomethacin, a cyclooxygenase inhibitor, 100% of the mice died when infected with live Listeria, whereas none of the animals died in the absence of the drug. The death of the animals correlated with the numbers of bacteria found extraperitoneally in the spleen and not with the Ia expression of the peritoneal macrophages. Increases in the spleen bacterial numbers between mice treated with either indomethacin or a specific thromboxane synthase inhibitor, OKY1581, and those not receiving either drug, were found as early as 2-4 h after infection. The differences in the initial increased bacterial spleen counts in the presence of indomethacin were reversed by administration of a stable thromboxane A2 analog or another potent vasoconstrictor, phenylephrine. Because thromboxane A2 does not regulate macrophage or T cell functions directly (Tripp, C.S., A. Wyche, E.R. Unanue, and P. Needleman, 1986, J. Immunol., In press; and Ceuppens, J.S., S. Vertessen, H. Deckmyn, and J. Vermylen, 1985, Cell Immunol., 90:458-463), but is probably generated at the site of an infection (Tripp, C.S., K.M. Leahy, and P. Needleman, 1985, J. Clin. Invest., 76:898-901), these data suggest an important role for the vasoconstrictive properties of thromboxane A2 in the regulation of immunity to Listeria infection.

Low molecular weight immunosuppressive factors found in elevated amounts in cancer ascitic fluids of mice. 2. 1-Methyladenosine isolated from cancer ascitic fluids enhances Listeria infection in mice.

The low molecular weight fraction (mol wt less than 1,000) of Ehrlich cancer ascitic fluid has been known to enhance Listeria infection in mice. Chemical characterization of the entities in this fraction revealed four purine and pyrimidine analogues, i.e. uric acid, uracil, pseudouridine and 1-methyladenosine (m1Ado). When the effect of each of these components was studied on Listeria infection in mice, only m1Ado markedly enhanced the infection and killed the mice within a short period. The optimal enhancement was obtained when m1Ado was given intravenously to mice 3-6 days before the infection at a concentration of between 1 and 100 micrograms/mouse. On the other hand, uric acid, uracil and pseudouridine failed to show such an enhancing effect. m1Ado inhibited macrophage accumulation in the peritoneal cavity of mice after an intraperitoneal injection of phytohemagglutinin. Although m1Ado did not show any inhibitory effect on the phagocytic and bactericidal activities of macrophages in vitro, peritoneal macrophages obtained from mice which received m1Ado 3 days ahead revealed impaired bactericidal activity, suggesting the migration of different cell populations from the bone marrow of m1Ado-receiving mice. The results may suggest that m1Ado is a major factor in tumor ascites causing, in small doses, an impairment of macrophage functioning as can be detected in tumor-bearing hosts.

Listeria Cell Wall Fraction: A B Cell Adjuvant

A crude cell wall-rich fraction of Listeria monocytogenes (LCWF) has previously been shown to induce resistance to Listeria infection in mice, to be a murine B cell mitogen, and to be an immunologic adjuvant. Data reported here show that LCWF stimulates immune responses by three different murine B cell populations that respond poorly or not at all to thymus-dependent antigens when T cells are severely depleted or absent. These B cell populations include nude mouse spleen cells, anti-theta serum-treated spleen cells and bone marrow-derived spleen cells. In addition, sheep erythrocytes coated with LCWF are converted to thymus-independent antigens. The adjuvant effect of LCWF on B cell populations is not enhanced by the presence of T cells, nor does LCWF increase in vivo education of T cells to sheep erythrocyte antigens. Thus, a direct effect of LCWF on T cells could not be demonstrated, suggesting that LCWF does not act on T cells. Because of these LCWF effects on B cells, the possible role of B cells in resistance to infection by Liseria monocytogenes is discussed.

Effects of Bacterial Products on Lymphocytes and Macrophages: Their Possible Role in Natural Resistance to Listeria Infection in Mice

Abstract Fluids from Listeria monocytogenes cultures contain products that possess a number of biologic activities. The fluids contain a mitogenic substance for B lymphocytes. Thus, their injection into mice produces striking hyperplasia of the B cell zones of the spleen. Also, lymphocytes in vitro are stimulated to proliferate, regardless of whether they are first depleted of T lymphocytes by exposure to anti-θ serum plus complement. These fluids injected intraperitoneally activate macrophages as judged by morphologic criteria. Mice that receive the products develop a transitory state of nonspecific resistance to infection by live Listeria. The relationships between B cell mitogenicity and macrophage activation—and protection—were not established. This kind of reaction of lymphoid cells to Listeria products may represent an early nonspecific line of defense against bacterial invasion.

The effect of cytotoxic agents on the primary immune response to Listeria monocytogenes.

Four drugs, representing four different categories of cytotoxic agents, were studied for their effect on the immune response to Listeria infection in mice. The development of the host's immune response is revealed by a progressive change in the slope of the bacterial growth curve in spleen and liver. It has its onset at 24 hr in untreated mice, but in the presence of effective immunosuppression the organism multiples uninterruptedly until the animal dies from overwhelming infection. When administered as single injections at the time of infection, cyclophosphamide, vinblastine, and azathioprine all produced an effective immunosuppression, characterized by continuous bacterial multiplication. Methotrexate was also immunosuppressive, but unlike the others its effects were reversible. They could be sustained, however, by further treatment. Studies of the time-response relationship indicated that cyclophosphamide was highly active over a broad time-span ranging from 2 days before infection to 4 days after infection. Vinblastine on the other hand was maximally active when given on the day of infection, while methotrexate had its greatest effect when given 48 hr after infection. These differences indicate that these three drugs act on different cell populations involved in the host's immune response. The effects observed have been discussed in relation to what is known of the modes of action of the drugs tested. An observation of interest was the phenomenon of enhanced immunity in animals treated with cyclophosphamide or vinblastine 7-11 days before, and with methotrexate 4 days before infection; reactive hyperplasia of lymphoid tissue following withdrawal of drug was again advanced as an explanation for the occurrence of this paradoxical effect. The experimental model employed is simple, requiring only routine bacteriological facilities and minimal equipment. It seems to offer a useful means of assessing the immunosuppressive activity of drugs and of determining the time-course of their action; it could also be of value in the screening of anticancer agents.

Mechanisms of pathogenesis in Listeria monocytogenes infection. I. Influence of iron.

Sword, C. P. (The University of Kansas, Lawrence). Mechanisms of pathogenesis in Listeria monocytogenes infection. I. Influence of iron. J. Bacteriol. 92: 536-542. 1966.-The effects of ferric and ferrous iron as well as other cations on Listeria infection in mice were studied. Iron compounds caused a reduction in the ld(50) dose of Listeria, and, when added to a synthetic medium, proved stimulatory for in vitro growth of the organism. Bacterial counts on spleen and liver tissue from iron-treated mice showed that iron injections caused more rapid growth of bacteria and resulted in higher numbers of organisms in the tissue. The reticuloendothelial system did not appear to be impaired by this treatment. Immunized animals were not affected by iron treatment during challenge. Mice with experimentally induced hemolytic anemia showed increased susceptibility to listeriosis, whereas those treated with Desferal, a specific iron-chelating agent, appeared more resistant. Iron proved stimulatory for the avirulent strain, 9037-7, and resulted in an ld(50) of 1.3 x 10(4) organisms in iron-treated animals. Growth of L. monocytogenes and mortality from experimental infection appeared to be correlated with availability of iron to the bacteria. The results suggest that host iron metabolism may play a part in the onset and progress of Listeria infections.

Serum Protein Alterations Induced by Listeria Monocytogenes Infections

Summary During experimental Listeria infection in mice an increase in total serum protein, serum hexose and hexose: protein ratio was observed. Paper electrophoretic studies showed an increase in α- and β-glycoproteins. Immunoelectrophoretic studies on serum from infected animals revealed an increase in albumin mobility, increase in α2-macroglobulin, increase in haptoglobin, increase in transferrin and conversion of β1C-globulin to β1D-globulin. Relatively little change was noted in γ-globulin during infection. Hyperimmunized-challenged animals showed an increase in amount and complexity of γ-globulin.