IL-37 impairs host resistance to Listeria infection by suppressing macrophage function.

Listeria monocytogenes is a Gram-positive intracellular bacterium that was transmitted through contaminated food and causes sepsis and even death. IL-37 has been described as an important anti-inflammatory factor, but little is known about the function of IL-37 in host defense against Liseria monocytogenes (Lm) infection. In mice model of systemic infection, we found that mice treated with IL-37 were more sensitive to Lm infection compared with PBS-treated mice. This reduced resistance to Lm in IL-37-treated mice is accompanied with increased bacterial burden and liver damage. Serum levels of colony-stimulating factors were decreased in IL-37-treated mice. IL-37 treatment reduced bactericidal ability of bone marrow derived macrophages (BMDMs) in vitro, which contribute to the inability of IL-37-treated mice to combat Lm infection. Furthermore, increased apoptosis was observed in Lm-infected macrophages treated with IL-37. Increased macrophage apoptosis reduced percentage in liver macrophages was observed in IL-37-treated mice following Lm infection. These results indicate the negative regulatory effect of IL-37 on host resistance during immune defense against Lm.

Two novel roles of buffalo milk lactoperoxidase, antibiofilm agent and immunomodulator against multidrug resistant Salmonella enterica serovar Typhi and Listeria monocytogenes.

The increasing occurrence of multidrug resistant bacteria causing bacteremia infection, constitutes a major health problem, difficult-to-treat bacteremia due to its ability to form biofilm. Buffalo milk lactoperoxidase (BMLpo) is effective and safe to use as bacteriostatic agent. The MIC of BMLpo and amikacin were used to evaluate the antibiofilm activity against resistant L. monocytogenes and S. typhi. Prophylactic effects of BMLpo against L. monocytogenes and S. typhi bacteremia in vivo have been tested and ELISA test used to evaluate serum cytokines. Significant antibiofilm activity of BMLpo observed against the highest biofilm producer isolates. Our results showed that the prophylactic effect of BMLpo in BALB/c mice bacteremic model. A significant clearance of L. monocytogenes and S. typhi, investigated in blood and different organs tissues in BMLpo-treated infected groups when compared to the non-treated groups. Further, analysis of serum cytokines levels revealed that BMLpo prophylaxis modulates their release in different way when it compared to the control. This study showed, BMLpo effects as an alternative antibiofilm agent to compact gram negative pathogens, and protects the host against bacteremia infection. Moreover, the BMLpo role as an immunomodulatory. These investigations indicated the BMLpo crucial role in the practical clinical applications.

Brain abscess due to Listeria monocytogenes after HELLP syndrome in a patient with antiphospholipid syndrome.

Objective To illustrate an unusual case of Listeria cerebral abscess. Material and methods A 32-year-old pregnant woman with thrombotic antiphospholipid syndrome (APS) received corticotherapy for two weeks due to hemolysis, elevated liver enzymes, low platelet (HELLP) syndrome. After delivery she presented with neurological symptoms and fever. Results The MRI scan confirmed the presence of a brain abscess, and Listeria monocytogenes was isolated in blood cultures. After eight weeks of antibiotic treatment, the patient presented no sequelae. Conclusion L. monocytogenes should be included in the differential diagnosis of patients with fever and neurological dysfunction, especially in those with a recent history of corticotherapy.

Invasive listeriosis in a patient with several episodes of antibiotic associated colitis presumably due to Clostridium difficile.

A 62-year-old man developed a blood stream infection and meningitis due to Listeria monocytogenes, 20 days after an episode of pseudo-membranous colitis. The patient, hospitalized for the first time for transurethral prostatectomy, was readmitted 20 days later with watery diarrhea. Pseudo-membranous colitis was diagnosed and treated successfully, without testing for Clostridium difficile infection (CDI). After 15 more days, the patient developed again diarrhea, fever and confusion. Hospitalized again, blood and cerebrospinal fluid cultures resulted positive for L. monocytogenes. The patient was treated successfully and a diagnosis of recurrent CDI was confirmed following culture and nucleic acid amplification assays both positive for C. difficile. This is the first report of an invasive listeriosis after CDI underlines the importance of taking greater awareness in complicated blood stream infections that may arise after CDI.

[Clinical analysis of 19 pregnancies complicated listeriosis].

Objective: To analyze the clinical characteristics and perinatal outcomes of listeriosis during pregnancy. Methods: From July 2010 to April 2017, 70 131 women delivered in West China Second University Hospital. Nineteen cases were confirmed as listeriosis. The clinical symptoms, laboratory results, pathogens, placenta pathology and perinatal outcomes were analyzed retrospectively. Results: The median age of the 19 cases was 29.7 (19.0-42.0) years old. The median time before diagnosis was 4.8(0.5-19.0) days. The main clinical symptoms at first visits were high fever (17/19), increased white blood cells (18/19), abdominal pain (12/19). Listeria was found in samples of mother's blood (11/19), vaginal secretions (15/19), placenta (1/19), neonatal blood (4/19), neonatal phlegm (5/19) and neonatal ear secretions (1/19), respectively. Inflammation of placenta was identified in all 19 cases. Among the 19 cases, 1 was grade Ⅰ chorioamnionitis, 4 was grade Ⅱ, 5 was grade Ⅲ and 9 was grade Ⅵ. Only 4 newborn survived after therapy, and others suffered perinatal death, including 8 cases of intrauterine death, 3 cases of miscarriage and 6 cases of treatment failure. Conclusions: Listeriosis has characteristics of acute onset, quick development and high morbidity during pregnancy. The empiric use of antibiotics might not cover listeria. The understanding of listeriosis should be improved.

Assessment of the Incubation Period for Invasive Listeriosis.

We characterized incubation periods among outbreak-associated listeriosis cases, using a simulation model to account for patients with multiple exposure dates. The median was 11 days; 90% of cases occurred within 28 days, and incubation periods varied by clinical manifestation.

Temporal requirements for B cells in the establishment of CD4 T cell memory.

CD4 T cell memory generation is shaped by a number of factors, including the strength and duration of TCR signaling, as well as the priming environment, all of which can be modified by B cells. Studies using B cell-deficient mice indicate B cells play a critical role in generating effector and memory CD4 T cells; however, when and how B cells are acting to promote these responses has not yet been ascertained. In this study, we use anti-CD20 Ab depletion of B cells at different times following Listeria monocytogenes infection to show that B cells are necessary for the induction of optimal CD4 T cell memory, but not for the transition and maintenance of this population. Importantly, the prerequisite of B cells early postinfection is partially dependent on their expression of MHC class II. B cells are not only required during the priming phase, but also necessary for the initiation of robust secondary responses by memory CD4 T cells. Interestingly, the requirement during the recall response is independent of B cell Ag presentation. Overall, these studies demonstrate the temporally and functionally distinct roles for B cells in regulating CD4 T cell responses.

Intrinsic role of FoxO3a in the development of CD8+ T cell memory.

CD8(+) T cells undergo rapid expansion during infection with intracellular pathogens, which is followed by swift and massive culling of primed CD8(+) T cells. The mechanisms that govern the massive contraction and maintenance of primed CD8(+) T cells are not clear. We show in this study that the transcription factor, FoxO3a, does not influence Ag presentation and the consequent expansion of CD8(+) T cell response during Listeria monocytogenes infection, but plays a key role in the maintenance of memory CD8(+) T cells. The effector function of primed CD8(+) T cells as revealed by cytokine secretion and CD107a degranulation was not influenced by inactivation of FoxO3a. Interestingly, FoxO3a-deficient CD8(+) T cells displayed reduced expression of proapoptotic molecules BIM and PUMA during the various phases of response, and underwent reduced apoptosis in comparison with wild-type cells. A higher number of memory precursor effector cells and memory subsets was detectable in FoxO3a-deficient mice compared with wild-type mice. Furthermore, FoxO3a-deficient memory CD8(+) T cells upon transfer into normal or RAG1-deficient mice displayed enhanced survival. These results suggest that FoxO3a acts in a cell-intrinsic manner to regulate the survival of primed CD8(+) T cells.

Deficits in serum amyloid A contribute to increased neonatal mortality during murine listeriosis.

BACKGROUND: To understand the increased susceptibility of preterm neonates to infection. METHODS: A murine listeriosis model using immunohistochemistry, microarray technology, and real-time polymerase chain reaction (PCR). RESULTS: We report that recombinant serum amyloid A (SAA) administered prophylactically 18 h before intraperitoneal (i.p.) inoculation with Listeria monocytogenes conferred a dramatic survival benefit compared with administration of only vehicle in neonatal mice. Neonates that received the recombinant SAA protein had significantly fewer Listeria colony counts on plating of infected liver and showed significantly more activated macrophages, but SAA did not affect postnatal growth. Real-time PCR was used to confirm the microarray findings that gene expression levels for the SAA proteins 1 (Saa1) and 2 (Saa2), in addition to that for orosomucoid-2 (Orm2), were strikingly elevated in the adult compared with those in the neonate. Real-time PCR analysis showed that of the acute phase cytokines, tumor necrosis factor (TNF) gene expression increased exponentially with time in the infected adult, whereas neonates did not show similar increases. CONCLUSION: The increased susceptibility of neonatal mice to listeriosis is in part mediated by a deficiency in the acute phase response, specifically expression of SAA, and that prophylactic SAA protein before neonatal murine listeriosis results in more macrophage activation, lower Listeria counts, and greater survival.

Role of p47phox in antigen-presenting cell-mediated regulation of humoral immunity in mice.

Microbial-induced inflammation is important for eliciting humoral immunity. Genetic defects of NADPH oxidase 2-based proteins interrupt phagocyte superoxide generation and are the basis for the human immunodeficiency chronic granulomatous disease (CGD). Hyperinflammation is also a significant clinical manifestation of CGD. Herein, we evaluated humoral immunity in the phagocyte oxidase p47(phox)-deficient model of CGD and found that UV-inactivated Streptococcus pneumoniae and Listeria monocytogenes (Lm) elicited higher specific antibody (Ab) titers in p47(phox-/-) mice than wild-type (WT) mice. Both organisms elicited robust and distinct antigen-presenting cell maturation phenotypes, including IL-12 hypersecretion, and higher major histocompatibility complex II and costimulatory protein expression in Lm-stimulated p47(phox-/-) dendritic cells (DCs) relative to WT DCs. Furthermore, p47(phox-/-) DCs pulsed with Lm and adoptively transferred into naïve WT mice elicited Ab titers, whereas Lm-pulsed WT DCs did not elicit these titers. The observed robust p47(phox-/-) mouse humoral response was recapitulated with live Lm and sustained in vivo in p47(phox-/-) mice. Notably, anti-serum samples from p47(phox-/-) mice that survived secondary Lm infection were protective in WT and p47(phox-/-) mice that were rechallenged with secondary lethal Lm infection. These findings demonstrate a novel benefit of NADPH oxidase 2 deficiency (ie, dependent inflammation in antigen-presenting cell-mediated humoral immunity) and that anti-Lm Ab can be protective in an immunodeficient CGD host.

Discriminating experimental Listeria monocytogenes infections in mice using serum profiling.

Serum profiling was used to distinguish mice infected with wild-type or mutant Listeria monocytogenes from noninfected control mice. Identifications of significant electrospray ionization mass spectrometry (ESI-MS) sera peak areas between Listeria-infected- and control mice were performed using t tests. ESI-MS cohort peak distributions differed from mice infected with wild-type or ∆actA Listeria versus control mice with p values of 0.00012 and 0.015, respectively. A "% wild-type Listeria peaks identified" assessment tool yielded values of 64 % for wild-type infection, 51 % for ∆actA infection, and 47 % for no infection. Receiver operator characteristic area discriminatory values were 0.97 (wild-type) and 0.82 (∆actA) versus controls. Predictive value measurements revealed overall test sensitivities of 88 % for wild-type infection and 63 % for ∆actA infection. These studies indicate that ESI-MS serum profiling holds promise for diagnosis of infection with intracellular pathogens such as Listeria and indicate that the technology could be useful in understanding the L. monocytogenes infection process.

High level of heterogeneity among Listeria monocytogenes isolates from clinical and food origin specimens in Greece.

In order to examine the genetic variation of clinical and food isolates of Listeria monocytogenes in Greece, a total of 61 L. monocytogenes non-duplicate isolates, recovered from clinical specimens (n=19) and food (n=42), were serotyped and genotyped using two different Random Amplification of Polymorphic DNA (RAPD) protocols and Multiple Locus Variable Number Tandem Repeat Analysis (MLVA). Serotype group 4b, 4d, 4e prevailed (39.4%), among both clinical and food isolates, followed by serotype group 1/2a, 3a (23.0%), which nevertheless was detected only among food isolates. The most discriminatory typing protocol was MLVA, which grouped four isolates into two pairs, while the remaining isolates produced unique fingerprints. Similar results were obtained when taking into account the combination of the two RAPD protocols (Simpson index 0.999); six isolates were grouped into three pairs, two of which were the pairs that were identified also by MLVA. Single use of each RAPD protocol resulted in inferior discrimination (Simpson index 0.978 and 0.997, respectively). In conclusion, the two molecular procedures, MLVA, and the combined RAPD protocols, produced similar results, showing that L. monocytogenes isolates from clinical and food specimens were highly heterogenous and that clustering was very uncommon.

[Listeria monocytogenes in human infections]. / Paleczki Listeria monocytogenes w zakazeniach ludzi.

The Listeria genus is distinguished into six species from which just one--Listeria monocytogenes is pathogenic for humans. The main route of acquisition of Listeria is through the ingestion of contaminated food products. An important element of the L. monocytogenes pathogenesis infection is affiliation with high-risk group of immunocompromised patients, infants or pregnant women, who infected by this microorganism can lead to miscarriage. Listeriosis can appear in the form of sepsis, infection of the nervous system or local abscesses. Another form of listeriosis is gastrointestinal tract infection--noticed in case of food poisoning outbreak.

Genomic characteristics of listeria monocytogenes causing invasive listeriosis in Japan.

We reviewed 18 listeriosis cases in Japan and performed molecular analysis of causative Listeria monocytogenes (LM) isolates. Strains genetically related to those from other countries caused various types of listeriosis, including vascular listeriosis in immunocompetent elderly people. Our results highlight the importance of integrated clinical and genomic analysis of LM.

Comparison of recombinant and synthetic listeriolysin- O peptide- based indirect ELISA vis-à-vis cultural isolation for detection of listeriosis in caprine and ovine species.

The present study evaluated the comparative serodiagnostic efficacy of recombinant listeriolysin-O (rLLO) and synthetic LLO- 2 peptide-based indirect ELISA vis-à-vis cultural isolation using samples (n = 1326; blood, sera, vaginal swabs, and rectal swabs) collected from caprines (n = 350) and ovines (n = 50) having reproductive and/or nervous system disorders and/or healthy animals. On screening the test sera by rLLO- based ELISA, the antibodies against LLO (ALLO) were observed in 17.71% of the caprines and 2% of the ovines, respectively, while synthetic LLO-2- based ELISA revealed ALLO in 6.86% of caprines and not in ovines. Moreover, the adsorption of positive test sera with streptolysin-O (SLO) resulted in a significant reduction (7.43%; p < 0.05) in the seropositivity with rLLO- based ELISA, whereas LLO-2- based ELISA revealed marginal reduction (4.29%; p > 0.05) in the seropositivity. Overall, the seropositivity with LLO-2 synthetic peptide revealed comparatively less cross-reactivity in comparison to rLLO. The cultural isolation yielded five pathogenic L. monocytogenes isolates and three non-pathogenic Listeria spp. from caprine samples; however, Listeria spp. could not be recovered from any of the ovine samples. Further, on comparing seropositivity with the isolation study results, it was found that two out of the five animals from which pathogenic L. monocytogenes isolated were also found seropositive in both the ELISAs even after adsorption with SLO. Interestingly, rLLO- based ELISA detected antibodies against unadsorbed caprine sera even in those samples from which non-pathogenic Listeria spp. were isolated, whereas antibodies were not detected in LLO-2 peptide-based ELISA. In conclusion, it could be inferred that the synthetic LLO-2 peptide serves as a non- cross-reactive, ideal diagnostic antigen in serodiagnosis of capro-ovine listeriosis.

Characteristics and Outcomes of Neonates With Blood Stream Infection Due to Listeria monocytogenes.

BACKGROUND: Infection due to Listeria monocytogenes (LM) is rare in neonates; thus, its clinical presentation and outcomes are not commonly reported, especially in low- and middle-income countries. In 2017, South Africa had an outbreak due to LM. OBJECTIVE: To determine demographic characteristics, clinical and laboratory findings and outcomes of all neonates infected with LM during the outbreak period. METHODS: This is a retrospective analytic study. Clinical and laboratory records of neonates admitted at Chris Hani Baragwanath Academic Hospital from January 2017 to May 2018 with positive blood and cerebrospinal fluid culture with LM were reviewed for demographic characteristics, clinical presentation, ancillary laboratory test results and outcomes at hospital discharge. RESULTS: There were 42 neonates with positive cultures due to LM. Thirty-four (81%) were born preterm. Mode of delivery was vaginal in 78.6% and 31.0% were HIV exposed. All patients presented within the first 6 days of life as an early-onset disease. Common clinical presentation was respiratory depression (52.4%) and respiratory distress (38.1%) with 69% requiring invasive or noninvasive respiratory support. Common abnormal laboratory findings were high C-reactive protein (77.1%) followed by leukopenia (23.8%). Fourteen patients (40%) had features of meningitis based on blood and cerebrospinal fluid findings (4 culture proven). There were 11 deaths at hospital discharge, giving a mortality rate of 26.2%. CONCLUSIONS: The majority of neonates infected with LM were born preterm, raising the possibility that LM itself may have been responsible for preterm labor. All presented in the first 6 days of life and most presented with respiratory distress or depression. A high proportion had meningitis, and there was a high-mortality overall.

Expeditious recruitment of circulating memory CD8 T cells to the liver facilitates control of malaria.

Circulating memory CD8 T cell trafficking and protective capacity during liver-stage malaria infection remains undefined. We find that effector memory CD8 T cells (Tem) infiltrate the liver within 6 hours after malarial or bacterial infections and mediate pathogen clearance. Tem recruitment coincides with rapid transcriptional upregulation of inflammatory genes in Plasmodium-infected livers. Recruitment requires CD8 T cell-intrinsic LFA-1 expression and the presence of liver phagocytes. Rapid Tem liver infiltration is distinct from recruitment to other non-lymphoid tissues in that it occurs both in the absence of liver tissue resident memory "sensing-and-alarm" function and ∼42 hours earlier than in lung infection by influenza virus. These data demonstrate relevance for Tem in protection against malaria and provide generalizable mechanistic insights germane to control of liver infections.

Elevated non-specific immunity and normal Listeria clearance in young and old vitamin D receptor knockout mice.

1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] and the vitamin D receptor (VDR) are important regulators of autoimmunity. The effect of the VDR on the ability of mice to fight a primary or secondary infection has not been determined. Young and old VDR knockout (KO) mice were able to clear both primary and secondary infections with Listeria monocytogenes. However, the kinetics of clearance was somewhat delayed in the absence of the VDR. Memory T cell development was not different in young VDR KO and wild-type (WT) mice; however, old VDR KO mice had significantly less memory T cells than their WT counterparts but still mounted an adequate immune response as determined by the complete clearance of L. monocytogenes. Although the primary and secondary immune responses were largely intact in the VDR KO mice, the old VDR KO mice had increased cytokines and antibody responses compared with the old WT mice. In particular, old VDR KO mice had elevated antigen non-specific antibodies; however, these magnified immune responses did not correspond to more effective Listeria clearance. The increased antibody and cytokine responses in the old VDR KO mice are consistent with the increased susceptibility of these mice to autoimmunity.

Neurotropic Lineage III Strains of Listeria monocytogenes Disseminate to the Brain without Reaching High Titer in the Blood.

Listeria monocytogenes is thought to colonize the brain using one of three mechanisms: direct invasion of the blood-brain barrier, transportation across the barrier by infected monocytes, and axonal migration to the brain stem. The first two pathways seem to occur following unrestricted bacterial growth in the blood and thus have been linked to immunocompromise. In contrast, cell-to-cell spread within nerves is thought to be mediated by a particular subset of neurotropic L. monocytogenes strains. In this study, we used a mouse model of foodborne transmission to evaluate the neurotropism of several L. monocytogenes isolates. Two strains preferentially colonized the brain stems of BALB/cByJ mice 5 days postinfection and were not detectable in blood at that time point. In contrast, infection with other strains resulted in robust systemic infection of the viscera but no dissemination to the brain. Both neurotropic strains (L2010-2198, a human rhombencephalitis isolate, and UKVDL9, a sheep brain isolate) typed as phylogenetic lineage III, the least characterized group of L. monocytogenes Neither of these strains encodes InlF, an internalin-like protein that was recently shown to promote invasion of the blood-brain barrier. Acute neurologic deficits were observed in mice infected with the neurotropic strains, and milder symptoms persisted for up to 16 days in some animals. These results demonstrate that neurotropic L. monocytogenes strains are not restricted to any one particular lineage and suggest that the foodborne mouse model of listeriosis can be used to investigate the pathogenic mechanisms that allow L. monocytogenes to invade the brain stem.IMPORTANCE Progress in understanding the two naturally occurring central nervous system (CNS) manifestations of listeriosis (meningitis/meningoencephalitis and rhombencephalitis) has been limited by the lack of small animal models that can readily distinguish between these distinct infections. We report here that certain neurotropic strains of Listeria monocytogenes can spread to the brains of young otherwise healthy mice and cause neurological deficits without causing a fatal bacteremia. The novel strains described here fall within phylogenetic lineage III, a small collection of L. monocytogenes isolates that have not been well characterized to date. The animal model reported here mimics many features of human rhombencephalitis and will be useful for studying the mechanisms that allow L. monocytogenes to disseminate to the brain stem following natural foodborne transmission.

Selenium deficiency impairs host innate immune response and induces susceptibility to Listeria monocytogenes infection.

BACKGROUND: Susceptibility or resistance to infection with Listeria monocytogenes correlates with Selenium (Se) deficiency in response to infection. RESULTS: Se-deficient mouse models of listeriosis were used to study the innate immune response during the course of L. monocytogenes infection. Blood samples from mouse models were used for Se status. The concentration of MDA, SOD, GPx and CAT in blood has revealed that lower Se level exist in Se-deficient mice. Intestine, mesenteric lymph node, liver, spleen and brain from each mouse were to study the bacterial burden in organs. The analysis of cell types of spleen from Se-deficient mice revealed that the ability of the host to elicit a rapid recruitment and activation of systemic innate immune response to infection was to a certain extent compromised under conditions of Se deficiency. The cytokine levels in the serum and cytokine expression levels in the livers from Se-deficient mice revealed that the innate immune response of Se-deficient mice was impaired throughout the course of infection. These results suggest that innate immune response is altered by Se deficiency after infection with L. monocytogenes. CONCLUSION: In conclusion, induced susceptibility of host resistance is associated with an impaired innate immune response following infection with L. monocytogenes in C57BL/6 Se-deficient mice.