Monocytogenes Infection In Mice Research Articles

Intestinal linoleic acid contributes to the protective effects of Akkermansia muciniphila against Listeria monocytogenes infection in mice.

Akkermansia muciniphila pretreatment mitigated Listeria monocytogenes infection in mice. A. muciniphila improved gut microbiota disturbed by L. monocytogenes infection and significantly increased the level of intestinal linoleic acid in mice. Linoleic acid strengthened the intestinal epithelial barrier and reduced pathogen translocation partly by regulating NF-κB/MLCK pathway in a GPR40-dependent manner.

Titanium dioxide E171 consumption exacerbates Listeria monocytogenes infection in mice

Abstract The food additive titanium dioxide is commonly utilized to enhance the appearance and flavor of food products. However, this substance has been linked to gastrointestinal disorders. The aim of this study was to investigate the impact of dietary exposure of titanium dioxide E171 on Listeria monocytogenes infection in mice. Mice were mainly divided into the control, LM group (L. monocytogenes infection), and E171+LM groups (E171 supplementation before L. monocytogenes infection). Pre-exposure to E171 resulted in increased bacterial counts in the liver, spleen, ileum, colon, mesenteric lymph nodes, and feces of mice after L. monocytogenes infection. Moreover, E171 exposure increased the levels of pro-inflammatory cytokines while attenuating the levels of anti-inflammatory cytokines in mice infected with L. monocytogenes. Meanwhile, mice in the E171+LM group exhibited considerably more severe colonic inflammation and worse intestinal barrier function than mice in the LM group. The 16S rRNA gene sequencing revealed a shift in the composition of the gut microbiota of mice in the E171+LM group, characterized by a decrease in the relative abundance of Firmicutes and a decrease in the Firmicutes-to-Bacteroidetes ratio. The levels of acetate, butyrate, and isobutyrate were markedly decreased within the cecum of mice in the E171+LM group in comparison to mice in the LM group. In conclusion, these results suggest that E171 exposure could exacerbate L. monocytogenes infection in mice, which may provide useful information for future risk assessment of this commonly used food additive.

Immunotherapeutic effect of chitosan and listeriolysin O on Listeria monocytogenes infection in mice

This study aimed to evaluate the effect of dietary chitosan and listeriolysin O (LLO) on the immune response against Listeria monocytogenes infection in mice. L. monocytogenes isolate was obtained from the unit of Zoonotic Disease, College of Veterinary Medicine, University of Baghdad. It was reactivated and cultured on PALCAM agar and exposed to a confirmatory diagnostic test. listeriolysin O (LLO) was extracted and purified. Sixty mice were used and divided into four groups each one involving 15 mice; the first group was fed on diet supplemented with a chitosan for 4 weeks. At the end of the 2nd week, normal saline was injected S/C; the second group was fed on a normal diet without any addition. At the end of 2nd week, 0.3 ml of LLO was injected S/C, then the booster dose of LLO was given after 14 days of 1st injection; the third group was fed on a diet supplemented with chitosan as in G1, and treated as in G2 and the fourth group fed on a normal diet without any addition and treated as in G1. A skin test was performed on 5 mice of each group while a Challenge test by injection of 0.2ml of 1x109 CFU/ml of viable L. monocytogenes intraperitoneally was performed on other mice. The concentration of IgG titer and IL6 were measured. The results revealed that the third group recorded significantly higher values in the skin thickness, IgG, and IL6 concentrations when compared with other groups at different times which indicate that LLO and chitosan may support each other to provide the most beneficial effect by eliciting of good cellular and humeral immunity against listeriosis.

Zearalenone and deoxynivalenol reduced Th1-mediated cellular immune response after Listeria monocytogenes infection by inhibiting CD4+ T cell activation and differentiation

Based on the fact that mycotoxins and the food-borne bacteria coexist in the natural environment and pose a significant health hazard to humans and animals, it is important to investigate the immunosuppressive mechanism of ZEA (zearalenone), DON (deoxynivalenol), and their combination in bacterial infections. In this study, we established a mouse model of mycotoxin low-dose exposure combined with Listeria monocytogenes infection and investigated the effects of ZEA, DON and their combination on Th1-mediated anti-intracellular bacterial infection based on CD4+ T cell activation and differentiation using both in vitro and in vivo analyses. The present study showed that both ZEA and DON aggravated Listeria monocytogenes infection in mice and affected the activation of CD4+ T cells and Th1 differentiation, including the effects on costimulatory molecules CD28 and CD152 and on cross-linking of IL-12 and IL-12R, by inhibiting T cell receptor (TCR) signaling. When compared with ZEA, DON was found to have a greater impact on many related indicators. Surprisingly, the combined effects of ZEA and DON did not appear to enhance toxicity compared to treatment with the individual mycotoxins. Our findings more clearly revealed that exposure to low-dose ZEA and DON caused immunosuppression in the body by mechanisms including inhibition of CD4+ T cells activation and reduction of Th1 cell differentiation, thus exacerbating infection of animals by Listeria monocytogenes.

Cutting Edge: NOX2 NADPH Oxidase Controls Infection by an Intracellular Bacterial Pathogen through Limiting the Type 1 IFN Response.

The NOX2 NADPH oxidase (NOX2) produces reactive oxygen species to kill phagosome-confined bacteria. However, we previously showed that Listeria monocytogenes is able to avoid the NOX2 activity in phagosomes and escape to the cytosol. Thus, despite the established role of NOX2 limiting L. monocytogenes infection in mice, the underlying mechanisms of this antibacterial activity remain unclear. In this article, we report that NOX2 controls systemic L. monocytogenes spread through modulation of the type I IFN response, which is known to be exploited by L. monocytogenes during infection. NOX2 deficiency results in increased expression of IFN-stimulated genes in response to type I IFN and leads to 1) promotion of cell-to-cell spread by L. monocytogenes, 2) defective leukocyte recruitment to infection foci, and 3) production of anti-inflammatory effectors IL-10 and thioredoxin 1. Our findings report a novel antimicrobial role for NOX2 through modulation of type I IFN responses to control bacterial dissemination.

Efficacy of Chitosan Immune Response Against Listeria Monocytogenes Infection in Mice

The present research aimed to study the effect of dietary chitosan supplementation against murineexperimentally infection by Listeria monocytogenes.forty mice were divided equally into 4 groups. The 1st and 2nd groups fed on diet supplement with chitosan(1mg/kg diet) and (1.5mg /kg diet) for (4) weeks respectively, While 3rd and 4th groups considered as controlpositive and negative groups. At (4) weeks the first three groups were inoculated intraperitoneally i/P with(0.2) ml (1×109) CFU/ml, while the 4th group (control negative) inoculated with (0.2) sterile normal saline.At (7) days post infection, the result revealed diet one of mice in each control positive and treated group at(24hrs.) post infection with heavy bacterial isolation from brain, spleen and liver of infected positive groupand mild to absent bacterial isolation in the 1st and 2nd group respectively.Grossly presence of severe congestion in the internal organs with necrotic foci seen on the splenic surface ofinfected positive control while the characteristic feature in the treated infected group was hepatosplenomegaly.Sever pathological changes were noticed in the infected positive control group characterized by suppurativeinflammation with necrosis accompanied with lymphoid depletion and amyloid like substance depositionwhile the main lesion in treated infected groups showed granulomatous lesion, lymphoid hyperplasia andmononuclear cells infiltration with heavy bacterial isolation from brain, spleen and liver of infected positivegroup and mild to absent bacterial isolation in the first and second group respectively, We concluded thatchitosan stimulated and improve the immune responses in mice against Listeria monocytogenes infection.

ADAP Promotes Degranulation and Migration of NK Cells Primed During in vivo Listeria monocytogenes Infection in Mice.

The adhesion and degranulation-promoting adaptor protein (ADAP) serves as a multifunctional scaffold and is involved in the formation of immune signaling complexes. To date only limited and moreover conflicting data exist regarding the role of ADAP in NK cells. To extend existing knowledge we investigated ADAP-dependency of NK cells in the context of in vivo infection with the intracellular pathogen Listeria monocytogenes (Lm). Ex vivo analysis of infection-primed NK cells revealed impaired cytotoxic capacity in NK cells lacking ADAP as indicated by reduced CD107a surface expression and inefficient perforin production. However, ADAP-deficiency had no global effect on NK cell morphology or intracellular distribution of CD107a-containing vesicles. Proteomic definition of ADAPko and wild type NK cells did not uncover obvious differences in protein composition during the steady state and moreover, similar early response patterns were induced in NK cells upon infection independent of the genotype. In line with protein network analyses that suggested an altered migration phenotype in naïve ADAPko NK cells, in vitro migration assays uncovered significantly reduced migration of both naïve as well as infection-primed ADAPko NK cells compared to wild type NK cells. Notably, this migration defect was associated with a significantly reduced expression of the integrin CD11a on the surface of splenic ADAP-deficient NK cells 1 day post-Lm infection. We propose that ADAP-dependent alterations in integrin expression might account at least in part for the fact that during in vivo infection significantly lower numbers of ADAPko NK cells accumulate in the spleen i.e., the site of infection. In conclusion, we show here that during systemic Lm infection in mice ADAP is essential for efficient cytotoxic capacity and migration of NK cells.

Short-term consumption of a high-fat diet increases host susceptibility to Listeria monocytogenes infection

A Westernized-diet comprising a high caloric intake from animal fats is known to influence the development of pathological inflammatory conditions. However, there has been relatively little focus upon the implications of such diets for the progression of infectious disease. Here we investigated the influence of a high-fat (HF) diet upon parameters that influence Listeria monocytogenes infection in mice. We determined that short-term administration of a HF diet increases the number of goblet cells, a known binding site for the pathogen in the gut, and also induces profound changes to the microbiota and promotes a pro-inflammatory gene expression profile in the host. Host physiological changes were concordant with significantly increased susceptibility to oral L. monocytogenes infection in mice fed a HF diet relative to low-fat (LF) or chow-fed animals. Prior to Listeria infection short-term consumption of HF diet elevated faecal levels of Firmicutes. During active infection with L. monocytogenes microbiota changes were further exacerbated but host inflammatory responses were significantly down-regulated relative to Listeria-infected LF or chow-fed groups, suggestive of a profound tampering of the host response influenced by infection in the context of a HF diet. Overall the results indicate that short-term consumption of a Westernized-diet has the capacity to significantly alter host susceptibility to L. monocytogenes infection concomitant with changes to the host physiological landscape. The findings suggest that diet should be a consideration when developing models that reflect human infectious disease.

Essential role of IκBNS for in vivo CD4+ T-cell activation, proliferation, and Th1-cell differentiation during Listeria monocytogenes infection in mice.

Acquisition of effector functions in T cells is guided by transcription factors, including NF‐κB, that itself is tightly controlled by inhibitory proteins. The atypical NF‐κB inhibitor, IκBNS, is involved in the development of Th1, Th17, and regulatory T (Treg) cells. However, it remained unclear to which extend IκBNS contributed to the acquisition of effector function in T cells specifically responding to a pathogen during in vivo infection. Tracking of adoptively transferred T cells in Listeria monocytogenes infected mice antigen‐specific activation of CD4+ T cells following in vivo pathogen encounter to strongly rely on IκBNS. While IκBNS was largely dispensable for the acquisition of cytotoxic effector function in CD8+ T cells, IκBNS‐deficient Th1 effector cells exhibited significantly reduced proliferation, marked changes in the pattern of activation marker expression, and reduced production of the Th1‐cell cytokines IFN‐γ, IL‐2, and TNF‐α. Complementary in vitro analyses using cells from novel reporter and inducible knockout mice revealed that IκBNS predominantly affects the early phase of Th1‐cell differentiation while its function in terminally differentiated cells appears to be negligible. Our data suggest IκBNS as a potential target to modulate specifically CD4+ T‐cell responses.

Short-term consumption of a high-fat diet increases host susceptibility to Listeria monocytogenes infection

BackgroundA westernized diet comprising a high caloric intake from animal fats is known to influence the development of pathological inflammatory conditions. However, there has been relatively little focus upon the implications of such diets for the progression of infectious disease. Here, we investigated the influence of a high-fat (HF) diet upon parameters that influence Listeria monocytogenes infection in mice.ResultsWe determined that short-term administration of a HF diet increases the number of goblet cells, a known binding site for the pathogen, in the gut and also induces profound changes to the microbiota and promotes a pro-inflammatory gene expression profile in the host. Host physiological changes were concordant with significantly increased susceptibility to oral L. monocytogenes infection in mice fed a HF diet relative to low fat (LF)- or chow-fed animals. Prior to Listeria infection, short-term consumption of HF diet elevated levels of Firmicutes including Coprococcus, Butyricicoccus, Turicibacter and Clostridium XIVa species. During active infection with L. monocytogenes, microbiota changes were further exaggerated but host inflammatory responses were significantly downregulated relative to Listeria-infected LF- or chow-fed groups, suggestive of a profound tempering of the host response influenced by infection in the context of a HF diet. The effects of diet were seen beyond the gut, as a HF diet also increased the sensitivity of mice to systemic infection and altered gene expression profiles in the liver.ConclusionsWe adopted a systems approach to identify the effects of HF diet upon L. monocytogenes infection through analysis of host responses and microbiota changes (both pre- and post-infection). Overall, the results indicate that short-term consumption of a westernized diet has the capacity to significantly alter host susceptibility to L. monocytogenes infection concomitant with changes to the host physiological landscape. The findings suggest that diet should be a consideration when developing models that reflect human infectious disease.

Immunomodulatory effects of mixed Weissella cibaria JW15 with water extract of black soybean and burdock on Listeria monocytogenes infection in mice.

The objective of this study is to assess immunomodulatory effects of mixed Weissella (W.) cibaria JW15 strain with water extract of black soybean (Glycine max) and burdock (Arctium lappa) on Listeria (L.) monocytogenes infection in mice. Female 7-9 week old BALB/c mice were given a daily dose of 1 × 109 CFU of viable JW15 and JW15 mixed with black soybean (BS) and burdock (BD) in 200 μL PBS for 2 weeks. The nomal control group (NC) and positive control group (PC) were given 200 μL PBS. After 2 weeks, mice were infected with L. monocytogenes (1.0 × 105 CFU/mouse) via the tail vein. The NC was injected with 100 μL PBS without L. monocytogenes. After 2 days, mice were euthanized and their body weights were determined. In addition, their livers and spleens were weighed, and serum were analyzed for cytokine (Interleukin-1β (IL-1β) and Tumor necrosis factor-α (TNF-α)) production. The survival rate was monitored using 5 mice in each group in the same way above until the mice died. Two days after infection with L. monocytogenes, mean spleen weight per body weight (g/kg) of JW15 (5.4 ± 0.88 g/kg), JW15 + BS (6.0 ± 0.64 g/kg), and JW15 + BD (5.3 ± 0.38 g/kg) group were significantly lower than that of the PC (6.8 ± 0.57 g/kg). The level of IL-1β in the serum of JW15 + BD (113.6 ± 31.03 pg/mL) was significantly higher than that of the JW15 (67.9 ± 15.15 pg/mL). Collectively, combination W. cibaria JW15 and water extract of BD and BD have ability to induce synergistic immunomodulative effects and are suitable for consideration as a functional food for humans and functional feed additives for companion animals.

Route of Injection Affects the Impact of InlB Internalin Domain Variants on Severity of Listeria monocytogenes Infection in Mice.

The facultative intracellular pathogen Listeria monocytogenes causes a severe food-borne infection in humans and animals. L. monocytogenes invasion factor InlB interacts with the tyrosine kinase c-Met via the N-terminal internalin domain. Previously, distinct variants of the InlB internalin domain (idInlB) have been described in L. monocytogenes field isolates. Three variants were used to restore full-length InlB expression in the L. monocytogenes strain EGDeΔinlB. Obtained isogenic L. monocytogenes strains were tested in the invasion assay and intravenous, intraperitoneal, and intragastric models of infection in mice. All idInlBs were functional, restored InlB activity as an invasion factor, and improved invasion of the parental strain EGDeΔinlB into human kidney HEK23 cells. Meanwhile, distinct idInlBs provided different mortality rates and bacterial loads in internal organs. When recombinant strains were compared, the variant designated idInlB14 decreased severity of disease caused by intravenous and intraperitoneal bacterial administration, whereas this variant improved intestine colonization and stimulated intragastric infection. Obtained results demonstrated that naturally occurring idInlBs differed in their impact on severity of L. monocytogenes infection in mice in dependence on the infection route.

Passive immunization with anti-ActA and anti-listeriolysin O antibodies protects against Listeria monocytogenes infection in mice.

Listeria monocytogenes is an intracellular pathogen that causes listeriosis. Due to its intracellular niche, L. monocytogenes has evolved to limit immune recognition and response to infection. Antibodies that are slightly induced by listerial infection are completely unable to protect re-infection of L. monocytogenes. Thus, a role of antibody on the protective effect against L. monocytogenes infection has been neglected for a long time. In the present study, we reported that passive immunization with an excessive amount of antibodies against ActA and listeriolysin O (LLO) attenuates severity of L. monocytogenes infection. Combination of these antibodies improved survival of L. monocytogenes infected mice. Bacterial load in spleen and liver of listerial infected mice and infected RAW264.7 cells were significantly reduced by administration of anti-ActA and anti-LLO antibodies. In addition, anti-LLO antibody neutralized LLO activity and inhibited the bacterial escape from the lysosomal compartments. Moreover, anti-ActA antibody neutralized ActA activity and suppressed actin tail formation and cell-to-cell spread. Thus, our studies reveal that passive immunization with the excessive amount of anti-ActA and -LLO antibodies has potential to provide the protective effect against listerial infection.

Data on the effect of Cytopiloyne against Listeria monocytogenes infection in mice.

Cytopiloyne (CP), a novel polyacetylene compound extracted from B. pilosa, shows a multi-bioactivity, including immunomodulatory and antidiabetes. Here, we investigated the anti-Listeria effect of cytopiloyne in mice by assessing mortality, clearance of L. monocytogenes, and pathology examination. The data presented herein are supplemental to our research article entitled “Cytopiloyne, a polyacetylenic glucoside from Bidens pilosa, acts as a novel anticandidial agent via regulation of macrophages” [1].

Splenic Leukocytes Traffic to the Thyroid and Produce a Novel TSHβ Isoform during Acute Listeria monocytogenes Infection in Mice.

The thyroid stimulating hormone beta-subunit (TSHβ) with TSHα form a glycoprotein hormone that is produced by the anterior pituitary in the hypothalamus-pituitary-thyroid (HPT) axis. Although TSHβ has been known for many years to be made by cells of the immune system, the role of immune system TSH has remained unclear. Recent studies demonstrated that cells of the immune system produce a novel splice variant isoform of TSHβ (TSHβv), but little if any native TSHβ. Here, we show that within three days of systemic infection of mice with Listeria monocytogenes, splenic leukocytes synthesized elevated levels of TSHβv. This was accompanied by an influx of CD14+, Ly6C+, Ly6G+ cells into the thyroid of infected mice, and increased levels of intrathyroidal TSHβv gene expression. Adoptive transfer of carboxyfluorescein succinimidyl ester (CFSE)-labeled splenic leukocytes from infected mice into non-infected mice migrated into the thyroid as early as forty-eight hours post-cell transfer, whereas CFSE-labeled cells from non-infected mice failed to traffic to the thyroid. These findings demonstrate for the first time that during bacterial infection peripheral leukocytes produce elevated levels of TSHβv, and that spleen cells traffic to the thyroid where they produce TSHβv intrathyroidally.

Interleukin-22-Induced Antimicrobial Phospholipase A2 Group IIA Mediates Protective Innate Immunity of Nonhematopoietic Cells against Listeria monocytogenes.

Listeria monocytogenes is a bacterial pathogen which establishes intracellular parasitism in various cells, including macrophages and nonhematopoietic cells, such as hepatocytes. It has been reported that several proinflammatory cytokines have pivotal roles in innate protection against L. monocytogenes infection. We found that a proinflammatory cytokine, interleukin 22 (IL-22), was expressed by CD3(+) CD4(+) T cells at an early stage of L. monocytogenes infection in mice. To assess the influence of IL-22 on L. monocytogenes infection in hepatocytes, cells of a human hepatocellular carcinoma line, HepG2, were treated with IL-22 before L. monocytogenes infection in vitro. Gene expression analysis of the IL-22-treated HepG2 cells identified phospholipase A2 group IIA (PLA2G2A) as an upregulated antimicrobial molecule. Addition of recombinant PLA2G2A to the HepG2 culture significantly suppressed L. monocytogenes infection. Culture supernatant of the IL-22-treated HepG2 cells contained bactericidal activity against L. monocytogenes, and the activity was abrogated by a specific PLA2G2A inhibitor, demonstrating that HepG2 cells secreted PLA2G2A, which killed extracellular L. monocytogenes. Furthermore, colocalization of PLA2G2A and L. monocytogenes was detected in the IL-22-treated infected HepG2 cells, which suggests involvement of PLA2G2A in the mechanism of intracellular killing of L. monocytogenes by HepG2 cells. These results suggest that IL-22 induced at an early stage of L. monocytogenes infection enhances innate immunity against L. monocytogenes in the liver by stimulating hepatocytes to produce an antimicrobial molecule, PLA2G2A.

Combination of Zinc and All-Trans Retinoic Acid Promotes Protection against Listeria monocytogenes Infection

Zinc (Zn) is the second most abundant transition metal after iron. It plays a vital role in living organisms and affects multiple aspects of the immune system. All-trans retinoic acid (atRA) is an isomeric form of the vitamin A or retinol. It possesses the greatest biological activity of Vitamin A. Vitamin A and related retinoids influence many aspects of immunity. In this study, we demonstrated that treatment with a combination of Zn and atRA contributes to host resistance against infection by Listeria monocytogenes. Pretreatment with Zn and atRA enhanced resistance against L. monocytogenes infection in mice and treatment with both Zn and atRA showed a higher protective effect than treatment with either alone. Supplementation with Zn, atRA or their combination decreased the number of L. monocytogenes present in target organs. In vitro, supplementation increased the bacterial uptake by macrophage cells and reduced the replication of L. monocytogenes. Our results suggest that the combination of Zn and atRA has a great bacteriostatic impact on L. monocytogenes and its infection.

3,4-methylenedioxymethamphetamine (MDMA--Ecstasy) decreases neutrophil activity through the glucocorticoid pathway and impairs host resistance to Listeria monocytogenes infection in mice.

Ecstasy is the popular name of the abuse drug 3,4-methylenedioxymethamphetamine (MDMA) that decreases immunity in animals. The mechanisms that generate such alterations are still controversial. Seven independent pharmacological approaches were performed in mice to identify the possible mechanisms underlying the decrease of neutrophil activity induced by MDMA and the possible effects of MDMA on host resistance to Listeria monocytogenes. Our data showed that MDMA (10 mg kg(-1)) administration decreases NFκB expression in circulating neutrophils. Metyrapone or RU-486 administration prior to MDMA treatment abrogated MDMA effects on neutrophil activity and NFκB expression, while 6-OHDA or ICI-118,551 administration did not. As MDMA treatment increased the plasmatic levels of adrenaline and noradrenaline, propranolol pre-treatment effects were also evaluated. Propranolol suppressed both MDMA-induced increase in corticosterone serum levels and its effects on neutrophil activity. In a L. monocytogenes experimental infection context, we showed that MDMA: induced myelosuppression by decreasing granulocyte-macrophage hematopoietic progenitors (CFU-GM) in the bone marrow but increased CFU-GM in the spleen; decreased circulating leukocytes and bone marrow cellularity and increased spleen cellularity; decreased pro-inflammatory cytokine (IL-12p70, TNF, IFN-γ, IL-6) and chemokine (MCP-1) production 24 h after the infection; increased the production of pro-inflammatory cytokines and chemokines 72 h after infection and decreased IL-10 levels at all time points analyzed. It was proposed that MDMA immunosuppressive effects on neutrophil activity and host resistance to L monocytogenes rely on NFκB signaling, being mediated by HPA axis activity and corticosterone.

Simvastatin Enhances Protection against Listeria monocytogenes Infection in Mice by Counteracting Listeria-Induced Phagosomal Escape

Statins are well-known cholesterol lowering drugs targeting HMG-CoA-reductase, reducing the risk of coronary disorders and hypercholesterolemia. Statins are also involved in immunomodulation, which might influence the outcome of bacterial infection. Hence, a possible effect of statin treatment on Listeriosis was explored in mice. Statin treatment prior to subsequent L. monocytogenes infection strikingly reduced bacterial burden in liver and spleen (up to 100-fold) and reduced histopathological lesions. Statin-treatment in infected macrophages resulted in increased IL-12p40 and TNF-α and up to 4-fold reduced bacterial burden within 6 hours post infection, demonstrating a direct effect of statins on limiting bacterial growth in macrophages. Bacterial uptake was normal investigated in microbeads and GFP-expressing Listeria experiments by confocal microscopy. However, intracellular membrane-bound cholesterol level was decreased, as analyzed by cholesterol-dependent filipin staining and cellular lipid extraction. Mevalonate supplementation restored statin-inhibited cholesterol biosynthesis and reverted bacterial growth in Listeria monocytogenes but not in listeriolysin O (LLO)-deficient Listeria. Together, these results suggest that statin pretreatment increases protection against L. monocytogenes infection by reducing membrane cholesterol in macrophages and thereby preventing effectivity of the cholesterol-dependent LLO-mediated phagosomal escape of bacteria.

128 : Truncated form of transforming growth factor-β receptor II, but not its absence, induces memory CD8+ T cell expansion and lymphoproliferative disorder in mice

Inflammatory and anti-inflammatory cytokines play an important role in the generation of effector and memory CD8 + T cells. We used two different models, transgenic expression of truncated (dominant negative) form of transforming growth factor- β receptor II (dnTGF β RII) and Cre-mediated deletion of the floxed TGF β RII to examine the role of TGF- β signaling in the formation, function, and homeostatic proliferation of memory CD8 + T cells. Blocking TGF- β signaling in effector CD8 + T cells using both of these models demonstrated a role for TGF- β in regulating the number of short-lived effector cells, but did not alter memory CD8 + T cell formation and their function upon Listeria monocytogenes infection in mice. Interestingly however, a massive lymphoproliferative disorder and cellular transformation were observed in antigen-experienced and homeostatically generated memory CD8 + T cells only in cells that express the dnTGF β RII, but not in cells with a complete deletion of TGF β RII. Furthermore, the development of transformed memory CD8 + T cells expressing dnTGF β RII was IL-7- and IL-15-independent, and MHC class I was not required for their proliferation. We show that transgenic expression of the dnTGF β RII, rather than the absence of TGF β RII-mediated signaling, is responsible for dysregulated expansion of memory CD8 + T cells. This study uncovers a previously unrecognized dominant function of the dnTGF β RII in CD8 + T cell proliferation and cellular transformation, which is caused by a mechanism that is different than the absence of TGF- β signaling. These results should be considered during both basic and translational studies where there is a desire to block TGF- β signaling in CD8 + T cells.