CD4+CD25+ T Cells are Essential for Behavioral Effects of Lactobacillus rhamnosus JB-1 in Male BALB/c mice.

Over the past decade there has been increasing interest in the involvement of the microbiota-gut-brain axis in mental health. However, there are major gaps in our knowledge regarding the complex signaling systems through which gut microbes modulate the CNS. The immune system is a recognized mediator in the bidirectional communication continuously occurring between gut and brain. We previously demonstrated that Lactobacillus rhamnosus JB-1 (JB-1), a bacterial strain that has anxiolytic- and antidepressant-like effects in mice, modulates the immune system through induction of immunosuppressive T regulatory cells. Here we examined a potential causal relationship between JB-1 induced regulatory T cells and the observed effects on behaviour. We found that depletion of regulatory T cells, via treatment with monoclonal antibody against CD25, inhibited the antidepressant- and anxiolytic-like effects induced by 4-week oral administration of JB-1 in mice. Ly6Chi monocytes were found to be decreased in JB-1 fed mice with intact regulatory T cells, but not in JB-1 fed mice following depletion. Furthermore, adoptive transfer of CD4+CD25+ cells, from JB-1 treated donor mice, but not from controls, induced antidepressant- and anxiolytic-like effects in recipient mice. Ly6Chi monocytes were also significantly decreased in mice receiving CD4+CD25+ cells from JB1 fed donors. This study identifies cells within the CD4+CD25+ population, most likely regulatory T cells, as both necessary and sufficient in JB-1-induced antidepressant- and anxiolytic-like effects in mice, providing novel mechanistic insight into microbiota-gut-brain communication in addition to highlighting the potential for immunotherapy in psychiatric disorders.

Prenatal low-dose penicillin results in long-term sex-specific changes to murine behaviour, immune regulation, and gut microbiota.

Growing evidence suggests that environmental disruptors of maternal microbes may have significant detrimental consequences for the developing fetus. Antibiotic exposure during early life can have long-term effects on neurodevelopment in mice and humans. Here we explore whether exposure to low-dose penicillin during only the last week of gestation in mice has long-term effects on offspring behaviour, brain, immune function, and gut microbiota. We found that this treatment had sex-specific effects in the adult mouse offspring. Female, but not male, mice demonstrated decreased anxiety-like behaviours, while male, but not female, mice had abnormal social behaviours which correlated with altered brain expression of AVPR1A, AVPR1B, and OXTR, and decreases in the balance of splenic FOXP3+ regulatory T cells. Prenatal penicillin exposure also led to distinct microbiota compositions that clustered differently by sex. These data suggest that exposure of pregnant mice to even a low dose of penicillin through only the last week before birth is nonetheless sufficient to induce long-term sex-specific developmental changes in both male and female offspring.

Oral treatment with Lactobacillus rhamnosus attenuates behavioural deficits and immune changes in chronic social stress.

BACKGROUND: Stress-related disorders involve systemic alterations, including disruption of the intestinal microbial community. Given the putative connections between the microbiota, immunity, neural function, and behaviour, we investigated the potential for microbe-induced gut-to-brain signalling to modulate the impact of stress on host behaviour and immunoregulation. METHODS: Male C57BL/6 mice treated orally over 28 days with either Lactobacillus rhamnosus (JB-1) ™ or vehicle were subjected to chronic social defeat and assessed for alterations in behaviour and immune cell phenotype. 16S rRNA sequencing and mass spectrometry were employed to analyse the faecal microbial community and metabolite profile. RESULTS: Treatment with JB-1 decreased stress-induced anxiety-like behaviour and prevented deficits in social interaction with conspecifics. However, JB-1 did not alter development of aggressor avoidance following social defeat. Microbial treatment attenuated stress-related activation of dendritic cells while increasing IL-10+ regulatory T cells. Furthermore, JB-1 modulated the effect of stress on faecal metabolites with neuroactive and immunomodulatory properties. Exposure to social defeat altered faecal microbial community composition and reduced species richness and diversity, none of which was prevented by JB-1. Stress-related microbiota disruptions persisted in vehicle-treated mice for 3 weeks following stressor cessation. CONCLUSIONS: These data demonstrate that despite the complexity of the gut microbiota, exposure to a single microbial strain can protect against certain stress-induced behaviours and systemic immune alterations without preventing dysbiosis. This work supports microbe-based interventions for stress-related disorders.

Gut commensal microvesicles reproduce parent bacterial signals to host immune and enteric nervous systems.

Ingestion of a commensal bacteria, Lactobacillus rhamnosus JB-1, has potent immunoregulatory effects, and changes nerve-dependent colon migrating motor complexes (MMCs), enteric nerve function, and behavior. How these alterations occur is unknown. JB-1 microvesicles (MVs) are enriched for heat shock protein components such as chaperonin 60 heat-shock protein isolated from Escherichia coli (GroEL) and reproduce regulatory and neuronal effects in vitro and in vivo. Ingested labeled MVs were detected in murine Peyer's patch (PP) dendritic cells (DCs) within 18 h. After 3 d, PP and mesenteric lymph node DCs assumed a regulatory phenotype and increased functional regulatory CD4(+)25(+)Foxp3+ T cells. JB-1, MVs, and GroEL similarly induced phenotypic change in cocultured DCs via multiple pathways including C-type lectin receptors specific intercellular adhesion molecule-3 grabbing non-integrin-related 1 and Dectin-1, as well as TLR-2 and -9. JB-1 and MVs also decreased the amplitude of neuronally dependent MMCs in an ex vivo model of peristalsis. Gut epithelial, but not direct neuronal application of, MVs, replicated functional effects of JB-1 on in situ patch-clamped enteric neurons. GroEL and anti-TLR-2 were without effect in this system, suggesting the importance of epithelium neuron signaling and discrimination between pathways for bacteria-neuron and -immune communication. Together these results offer a mechanistic explanation of how Gram-positive commensals and probiotics may influence the host's immune and nervous systems.

HIV-1 gp120 induces TLR2- and TLR4-mediated innate immune activation in human female genital epithelium.

Although women constitute half of all HIV-1-infected people worldwide (UNAIDS World AIDS Day Report, 2011), the earliest events in the female reproductive tract (FRT) during heterosexual HIV-1 transmission are poorly understood. Recently, we demonstrated that HIV-1 could directly impair the mucosal epithelial barrier in the FRT. This suggested that the HIV-1 envelope glycoprotein gp120 was being recognized by a membrane receptor on genital epithelial cells, leading to innate immune activation. In this study, we report that pattern-recognition receptors TLR2 and -4 bind to HIV-1 gp120 and trigger proinflammatory cytokine production via activation of NF-κB. The gp120-TLR interaction also required the presence of heparan sulfate (HS). Bead-binding assays showed that gp120 can bind to HS, TLR2, and TLR4, and studies in transfected HEK293 cells demonstrated that HS and TLR2 and -4 were necessary to mediate downstream signaling. Exposure to seminal plasma from HIV-1-infected and uninfected men with gp120 added to it induced a significant proinflammatory cytokine response from genital epithelial cells and disruption of tight junctions, indicating a role for gp120 in mucosal barrier disruption during HIV-1 heterosexual transmission. These studies provide, for the first time to our knowledge, a possible mechanism by which HIV-1 gp120 could directly initiate innate immune activation in the FRT during heterosexual transmission.

IL-15 can signal via IL-15Rα, JNK, and NF-κB to drive RANTES production by myeloid cells.

IL-15 plays many important roles within the immune system. IL-15 signals in lymphocytes via trans presentation, where accessory cells such as macrophages and dendritic cells present IL-15 bound to IL-15Rα in trans to NK cells and CD8(+) memory T cells expressing IL-15/IL-2Rß and common γ chain (γ(c)). Previously, we showed that the prophylactic delivery of IL-15 to Rag2(-/-)γ(c)(-/-) mice (mature T, B, and NK cell negative) afforded protection against a lethal HSV-2 challenge and metastasis of B16/F10 melanoma cells. In this study, we demonstrated that in vivo delivery of an adenoviral construct optimized for the secretion of human IL-15 to Rag2(-/-)γ(c)(-/-) mice resulted in significant increases in spleen size and cell number, leading us to hypothesize that IL-15 signals differently in myeloid immune cells compared with lymphocytes, for which IL-15/IL-2Rß and γ(c) expression are essential. Furthermore, treatment with IL-15 induced RANTES production by Rag2(-/-)γ(c)(-/-) bone marrow cells, but the presence of γ(c) did not increase bone marrow cell sensitivity to IL-15. This IL-15-mediated RANTES production by Rag2(-/-)γ(c)(-/-) bone marrow cells occurred independently of the IL-15/IL-2Rß and Jak/STAT pathways and instead required IL-15Rα signaling as well as activation of JNK and NF-κB. Importantly, we also showed that the trans presentation of IL-15 by IL-15Rα boosts IL-15-mediated IFN-γ production by NK cells but reduces IL-15-mediated RANTES production by Rag2(-/-)γ(c)(-/-) myeloid bone marrow cells. Our data clearly show that IL-15 signaling in NK cells is different from that of myeloid immune cells. Additional insights into IL-15 biology may lead to novel therapies aimed at bolstering targeted immune responses against cancer and infectious disease.

Critical role of natural killer cells in lung immunopathology during influenza infection in mice.

Influenza viral infection results in excessive pulmonary inflammation that has been linked to the damage caused by immune responses and viral replication. The multifunctional cytokine interleukin (IL-15), influences the proliferation and maintenance of immune cells such as CD8(+) T cells and natural killer (NK) cells. Here we show that IL-15(-/-) mice are protected from lethal influenza infection. Irrespective of the mouse strains, the protection observed was linked to the lack of NK cells. Increased survival in the IL-15(-/-) or NK1.1(+) cell-depleted wild-type mice was associated with significantly lower lung lesions as well as decreased mononuclear cells and neutrophils in the airway lumen. Levels of interleukin 10 were significantly higher and levels of proinflammatory cytokines, including interleukin 6 and interleukin 12, were significantly lower in the bronchoalveolar lavage fluid from IL-15(-/-) and NK1.1(+) cell-depleted wild-type mice than in that from control mice. Our data suggest that NK cells significantly augment pulmonary inflammation, contributing to the pathogenesis of influenza infection.

Human vaginal microbiota colonization is regulated by female sex hormones in a mouse model.

Introduction: Clinically, a Lactobacillus rich vaginal microbiota (VMB) is considered optimal for reproductive outcomes, while a VMB populated by anaerobes is associated with dysbiosis and the clinical condition bacterial vaginosis (BV), which is linked to increased susceptibility to sexually transmitted infections and adverse reproductive outcomes. Mouse models that mimic eubiotic and dysbiotic VMB are currently lacking but could play a critical role in improving protective interventions. Methods: In this study, probiotic, eubiotic, and dysbiotic models were developed in C57BL/6 mice, using probiotic strains Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14, eubiotic Lactobacillus crispatus, or dysbiotic Gardnerella vaginalis strains. Endogenous sex hormones were manipulated by either ovariectomizing (OVX) mice or administering 17ß-estradiol or progesterone pellets in OVX mice. Hormone-altered mice were inoculated with probiotic Lactobacillus species, L. crispatus, or G. vaginalis, and colonization was tracked using quantitative plating assays. Glycogen and MUC-1 levels in hormone-treated mice were determined with ELISA and MUC-1 staining. Results: Following a single administration, L. rhamnosus and L. reuteri persisted in the mouse vaginal tract for up to eight days, L. crispatus persisted for up to three days, and G. vaginalis persisted for up to two days, as measured by quantitative plating assays and qPCR. Colonization of G. vaginalis was facilitated by the presence of mucin. The lack of endogenous hormones in OVX mice dramatically decreased VMB bacterial load compared to normal mice. None of the exogenous bacteria including Lactobacilli could colonize OVX mice for more than 24 hours. Treatment with 17ß-estradiol but not progesterone restored the endogenous VMB and colonization with Lactobacilli and G. vaginalis. Interestingly, 17ß-estradiol treated mice had significantly increased levels of glycogen compared to OVX and progesterone-treated mice. Discussion: Based on the results, we have shown that estrogen played a significant role in the ability for human VMB species to colonize in our mouse models, potentially through a glycogen mediated mechanism. These results suggest there is a dynamic interaction between sex hormones and the VMB, which can affect bacterial diversity and the ability for a VMB to colonize.

Endometrial epithelial cell responses to coinfecting viral and bacterial pathogens in the genital tract can activate the HIV-1 LTR in an NF{kappa}B-and AP-1-dependent manner.

BACKGROUND: Sexually transmitted infections (STIs) are associated with increased human immunodeficiency virus type 1 (HIV-1) susceptibility and viral shedding in the genital tract, but the mechanisms underlying this association are poorly understood. METHODS: Direct activation of HIV long terminal repeats (LTRs), a proxy measure for HIV-1 replication, was measured after treatment of 1G5 T cells with Toll-like receptor (TLR) ligands, herpes simplex virus type 1 or 2 (HSV-1/2), or Neisseria gonorrhoeae. For indirect activation, 1G5 T cells were incubated with supernatants from female primary genital epithelial cells (GECs) previously exposed to these agents. Proinflammatory cytokines and chemokines were measured in GEC supernatants. Proinflammatory pathways were blocked to determine the mechanisms of direct and indirect HIV-LTR activation. RESULTS: HSV-1/2, N. gonorrhoeae, and TLR ligands FimH (TLR-4), flagellin (TLR-5), and Poly (I:C) (TLR-3) directly induced HIV-LTR activation in 1G5 T cells. Supernatants collected from GECs incubated with these agents indirectly induced HIV-LTR activation. Production of tumor necrosis factor α, interleukin 6, interleukin 8, and monocyte chemoattractant protein-1 was elevated in GECs exposed to copathogens. Inhibition of nuclear factor κB and activator protein-1 (AP-1) signaling pathways in 1G5 T cells abrogated both direct and indirect HIV-LTR activation. CONCLUSIONS: STIs may increase HIV-1 replication in the female genital tract via proinflammatory signaling pathways directly and indirectly via their effects on GECs. This increased HIV-1 replication may enhance sexual and vertical HIV transmission.

Regulatory T Cell Modulation by Lactobacillus rhamnosus Improves Feather Damage in Chickens.

It is currently unclear whether potential probiotics such as lactic acid bacteria could affect behavioral problems in birds. To this end, we assessed whether a supplementation of Lactobacillus rhamnosus JB-1 can reduce stress-induced severe feather pecking (SFP), feather damage and fearfulness in adult birds kept for egg laying. In parallel, we assessed SFP genotypic and phenotypic-related immune responses and aromatic amino acid status linked to neurotransmitter production. Social stress aggravated plumage damage, while L. rhamnosus treatment improved the birds' feather cover in non-stressed birds, but did not impact fearfulness. Our data demonstrate the significant impact of L. rhamnosus supplementation on the immune system. L. rhamnosus supplementation induced immunosuppressive regulatory T cells and cytotoxic T cells in both the cecal tonsils and the spleen. Birds exhibiting the SFP phenotype possessed lower levels of cecal tonsils regulatory T cells, splenic T helper cells and a lower TRP:(PHE+TYR). Together, these results suggest that bacteria may have beneficial effects on the avian immune response and may be useful therapeutic adjuncts to counteract SFP and plumage damage, thus increasing animal health and welfare.

FimH can directly activate human and murine natural killer cells via TLR4.

Although the importance of natural killer (NK) cells in innate immune responses against tumors or viral infections are well documented, their ability to directly recognize pathogens is less well defined. We have recently reported FimH, a bacterial fimbrial protein, as a novel Toll-like receptor (TLR)4 ligand that potently induces antiviral responses. Here, we investigated whether FimH either directly or indirectly can activate human and murine NK cells. We demonstrate that FimH potently activates both human and murine NK cells in vitro to induce cytokines [interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha] and cytotoxicity. Importantly, NK cells directly recognize FimH-expressing pathogens as FimH(+), but not FimH(-), bacteria were able to activate human NK cells. FimH activation of NK cells required TLR4 and MyD88 signaling, as NK cells from both TLR4(-/-) and MyD88(-/-) mice as well as human NK-92 cells, which lack TLR4, were all unresponsive to FimH. In addition, TLR4 neutralization significantly abrogated the response of human NK cells to FimH. Activation of purified NK cells by FimH was independent of lipopolysaccharide (LPS) or other bacterial contaminations. These data demonstrate for the first time that highly purified NK cells directly recognize and respond to FimH via TLR4-MyD88 pathways to aid innate protection against cancer or microbial infections.

Membrane vesicles of Lacticaseibacillus rhamnosus JB-1 contain immunomodulatory lipoteichoic acid and are endocytosed by intestinal epithelial cells.

Intestinal bacteria have diverse and complex influence on their host. Evidence is accumulating that this may be mediated in part by bacterial extracellular membrane vesicles (MV), nanometer-sized particles important for intercellular communication. Little is known about the composition of MV from gram-positive beneficial bacteria nor how they interact with intestinal epithelial cells (IEC). Here we demonstrate that MV from Lacticaseibacillus rhamnosus JB-1 are endocytosed in a likely clathrin-dependent manner by both mouse and human IEC in vitro and by mouse IEC in vivo. We further show that JB-1 MV contain lipoteichoic acid (LTA) that activates Toll-like receptor 2 (TLR2) and induces immunoregulatory interleukin-10 expression by dendritic cells in an internalization-dependent manner. By contrast, neither LTA nor TLR2 appear to be required for JB-1 MV endocytosis by IEC. These results demonstrate a novel mechanism by which bacterial MV can influence host physiology and suggest one potential route for beneficial influence of certain bacteria and probiotics.

Loss of vagal integrity disrupts immune components of the microbiota-gut-brain axis and inhibits the effect of Lactobacillus rhamnosus on behavior and the corticosterone stress response.

The vagus nerve is one of the major signalling components between the gut microbiota and brain. However, the exact relationship between gut-brain signaling along the vagus and the effects of gut microbes on brain function and behaviour is unclear. In particular, the relationship between the vagus nerve and immune signaling, that also appears to play a critical role in microbiota-gut-brain communication, has not been delineated. The aim of the present study was to determine the effect of subdiaphragmatic vagotomy on peripheral and central immune changes associated with the anxiolytic actions of L.rhamnosus. Male mice underwent vagotomy or sham surgery, followed by administration of L.rhamnosus for 14 days. L.rhamnosus administration following sham surgery resulted in reduced anxiety-like behaviour, and an attenuation of the hypothalamic-pituitary-adrenal axis (HPA axis), as indicated by reduced plasma corticosterone after acute restraint stress. These effects were associated with an increase in splenic T regulatory cells and a decrease in activated microglia in the hippocampus. The anxiolytic effects, HPA modulation and increase in T regulatory cells were prevented by vagotomy, whereas vagotomy alone led to a significant increase in activated microglia in the hippocampus that was not altered with L.rhamnosus treatment. Thus, both microbe induced and constitutive vagal signaling influences critical immune components of the microbiota-gut-brain axis. These findings suggest that, rather than acting as a direct neural link to the central nervous system, the role of the vagus nerve in gut-microbe to brain signalling is as an integral component of a bi-directional neuroimmunoendocrine pathway.

Bacterial membrane vesicles and phages in blood after consumption of lacticaseibacillus rhamnosus JB-1.

Gut microbiota have myriad roles in host physiology, development, and immunity. Though confined to the intestinal lumen by the epithelia, microbes influence distal systems via poorly characterized mechanisms. Recent work has considered the role of extracellular vesicles in interspecies communication, but whether they are involved in systemic microbe-host interaction is unclear. Here, we show that distinctive nanoparticles can be isolated from mouse blood within 2.5 h of consuming Lacticaseibacillus rhamnosus JB-1. In contrast to blood nanoparticles from saline-fed mice, they reproduced lipoteichoic acid-mediated immune functions of the original bacteria, including activation of TLR2 and increased IL-10 expression by dendritic cells. Like the fed bacteria, they also reduced IL-8 induced by TNF in an intestinal epithelial cell line. Though enriched for host neuronal proteins, these isolated nanoparticles also contained proteins and viral (phage) DNA of fed bacterial origin. Our data strongly suggest that oral consumption of live bacteria rapidly leads to circulation of their membrane vesicles and phages and demonstrate a nanoparticulate pathway whereby beneficial bacteria and probiotics may systemically affect their hosts.

Differential effects of chronic immunosuppression on behavioral, epigenetic, and Alzheimer's disease-associated markers in 3xTg-AD mice.

BACKGROUND: Circulating autoantibodies and sex-dependent discrepancy in prevalence are unexplained phenomena of Alzheimer's disease (AD). Using the 3xTg-AD mouse model, we reported that adult males show early manifestations of systemic autoimmunity, increased emotional reactivity, enhanced expression of the histone variant macroH2A1 in the cerebral cortex, and loss of plaque/tangle pathology. Conversely, adult females display less severe autoimmunity and retain their AD-like phenotype. This study examines the link between immunity and other traits of the current 3xTg-AD model. METHODS: Young 3xTg-AD and wild-type mice drank a sucrose-laced 0.4 mg/ml solution of the immunosuppressant cyclophosphamide on weekends for 5 months. After behavioral phenotyping at 2 and 6 months of age, we assessed organ mass, serologic markers of autoimmunity, molecular markers of early AD pathology, and expression of genes associated with neurodegeneration. RESULTS: Chronic immunosuppression prevented hematocrit drop and reduced soluble Aß in 3xTg-AD males while normalizing the expression of histone variant macroH2A1 in 3xTg-AD females. This treatment also reduced hepatosplenomegaly, lowered autoantibody levels, and increased the effector T cell population while decreasing the proportion of regulatory T cells in both sexes. Exposure to cyclophosphamide, however, neither prevented reduced brain mass and BDNF expression nor normalized increased tau and anxiety-related behaviors. CONCLUSION: The results suggest that systemic autoimmunity increases soluble Aß production and affects transcriptional regulation of macroH2A1 in a sex-related manner. Despite the complexity of multisystem interactions, 3xTg-AD mice can be a useful in vivo model for exploring the regulatory role of autoimmunity in the etiology of AD-like neurodegenerative disorders.

L. rhamnosus improves the immune response and tryptophan catabolism in laying hen pullets.

In mammals, early-life probiotic supplementation is a promising tool for preventing unfavourable, gut microbiome-related behavioural, immunological, and aromatic amino acid alterations later in life. In laying hens, feather-pecking behaviour is proposed to be a consequence of gut-brain axis dysregulation. Lactobacillus rhamnosus decreases stress-induced severe feather pecking in adult hens, but whether its effect in pullets is more robust is unknown. Consequently, we investigated whether early-life, oral supplementation with a single Lactobacillus rhamnosus strain can prevent stress-induced feather-pecking behaviour in chickens. To this end, we monitored both the short- and long-term effects of the probiotic supplement on behaviour and related physiological parameters. We hypothesized that L. rhamnosus would reduce pecking behaviour by modulating the biological pathways associated with this detrimental behaviour, namely aromatic amino acid turnover linked to neurotransmitter production and stress-related immune responses. We report that stress decreased the proportion of cytotoxic T cells in the tonsils (P = 0.047). Counteracting this T cell depression, birds receiving the L. rhamnosus supplementation significantly increased all T lymphocyte subset proportions (P < 0.05). Both phenotypic and genotypic feather peckers had lower plasma tryptophan concentrations compared to their non-pecking counterparts. The probiotic supplement caused a short-term increase in plasma tryptophan (P < 0.001) and the TRP:(PHE + TYR) ratio (P < 0.001). The administration of stressors did not significantly increase feather pecking in pullets, an observation consistent with the age-dependent onset of pecking behaviour. Despite minimal changes to behaviour, our data demonstrate the impact of L. rhamnosus supplementation on the immune system and the turnover of the serotonin precursor tryptophan. Our findings indicate that L. rhamnosus exerts a transient, beneficial effect on the immune response and tryptophan catabolism in pullets.

Ingestion of Lactobacillus rhamnosus modulates chronic stress-induced feather pecking in chickens.

Feather pecking (FP) is a stress-induced neuropsychological disorder of birds. Intestinal dysbiosis and inflammation are common traits of these disorders. FP is, therefore, proposed to be a behavioral consequence of dysregulated communication between the gut and the brain. Probiotic bacteria are known to favorably modulate the gut microbiome and hence the neurochemical and immune components of the gut-brain axis. Consequently, probiotic supplementation represents a promising new therapeutic to mitigate widespread FP in domestic chickens. We monitored FP, gut microbiota composition, immune markers, and amino acids related to the production of neurochemicals in chickens supplemented with Lactobacillus rhamnosus or a placebo. Data demonstrate that, when stressed, the incidence of FP increased significantly; however, L. rhamnosus prevented this increase. L. rhamnosus supplementation showed a strong immunological effect by increasing the regulatory T cell population of the spleen and the cecal tonsils, in addition to limiting cecal microbiota dysbiosis. Despite minimal changes in aromatic amino acid levels, data suggest that catecholaminergic circuits may be an interesting target for further studies. Overall, our findings provide the first data supporting the use of a single-strain probiotic to reduce stress-induced FP in chickens and promise to improve domestic birds' welfare.

Cutting edge: FimH adhesin of type 1 fimbriae is a novel TLR4 ligand.

Several TLR ligands of bacterial origin induce innate immune responses. Although FimH, the adhesin portion of type 1 fimbria, plays an important role in the pathogenicity of some gram-negative bacteria, its ability to stimulate the innate immune system via TLR signaling remains unclear. In this study we report that FimH induces potent innate responses in a MyD88-dependent fashion. The FimH-induced innate activity was restricted to cells expressing TLR4. In addition, FimH was able to bind directly to TLR4. More importantly, cells unresponsive to LPS were responsive to FimH and the presence or absence of MD-2 and CD14 had no effect on FimH activity. Our data suggest that TLR4 is a functional receptor for the adhesin portion of bacterial type 1 fimbria.

Cigarette smoke attenuation of poly I:C-induced innate antiviral responses in human PBMC is mainly due to inhibition of IFN-beta production.

The cellular response to dsRNA or its synthetic analog polyinosinic-polycytidylic acid (poly I:C) results in IRF-3-, IRF-7- and NF-kB-mediated activation of type 1 IFNs and pro-inflammatory cytokines critical for innate antiviral immune responses. To investigate whether cigarette smoke compromises type 1 IFN signaling in humans, peripheral blood mononuclear cells (PBMCs) from non-smoking individuals were treated with smoke-conditioned media (SCM) and stimulated with poly I:C. We observed a marked attenuation of IRF-3 and NF-kB activation in PBMCs exposed to SCM compared to control PBMCs. Similarly, PBMCs from smokers or splenocytes from smoke-exposed mice also displayed marked reduction of poly I:C-induced antiviral responses compared with either non-smokers or sham-exposed mice. Cigarette smoke was found to block the production of type I IFNs following poly I:C treatment and inhibit subsequent STAT1 activation. Finally, we confirmed that inhibition of IFN-beta, but not IFN-alpha, predominantly contributes to the cigarette smoke-mediated suppression of innate antiviral responses. These findings provide novel mechanistic insights to the susceptibility of cigarette smokers to viral infections.

Increased persistence of avoidance behaviour and social deficits with L.rhamnosus JB-1 or selective serotonin reuptake inhibitor treatment following social defeat.

Chronic social defeat (CSD) in mice has been suggested as a model for studying post-traumatic stress disorder (PTSD). Our previous work indicated that exposure to Lactobacillus rhamnosus JB-1 (JB-1) during CSD can attenuate subsequent behavioural and immune disruption, suggesting a potential for microbe based therapeutic approaches in PTSD. In the current study, we assessed the ability of JB-1 to mitigate the behavioral consequences of CSD when treatment is instigated in the early post-stress period and compared the probiotic effects with those of the selective serotonin reuptake inhibitor (SSRI), sertraline. JB-1 or sertraline were administered orally 48 h following 10-days of CSD in male C57BL/6 mice. Contrary to our hypothesis of a beneficial effect, 30 days of treatment with either JB-1 or sertraline increased the persistence of both aggressor avoidance and reduced sociability in defeated mice. This was accompanied by lower hippocampal mRNA expression for genes related to fear memory. Defeated mice treated with either JB-1 or sertraline also exhibited systemic immune changes, with a decrease in Th1 cells, activated monocytes, and the monocyte chemoattractant CCL2. This study identifies potentially detrimental effects of both JB-1 and sertraline if administered in the early post-trauma period and suggests caution should be applied when considering psychobiotic or SSRI based approaches for early intervention in trauma related psychiatric disorders.