No abstract

Recent advances have shown that the abnormal inflammatory response observed in CD involves an interplay among intestinal microbiota, host genetics and environmental factors. The escalating consumption of fat and sugar in Western countries parallels an increased incidence of CD during the latter 20th century. The impact of a HF/HS diet in mice was evaluated for the gut micro-inflammation, intestinal microbiota composition, function and selection of an E. coli population. The HF/HS diet created a specific inflammatory environment in the gut, correlated with intestinal mucosa dysbiosis characterized by an overgrowth of pro-inflammatory Proteobacteria such as E. coli, a decrease in protective bacteria, and a significantly decreased of SCFA concentrations. The expression of GPR43, a SCFA receptor was reduced in mice treated with a HF/HS diet and reduced in CD patients compared with controls. Interestingly, mice treated with an agonist of GPR43 were protected against DSS-induced colitis. Finally, the transplantation of feces from HF/HS treated mice to GF mice increased susceptibility to AIEC infection. Together, our results demonstrate that a Western diet could aggravate the inflammatory process and that the activation of the GPR43 receptor pathway could be used as a new strategy to treat CD patients.

Brucella is a facultative intracellular pathogen and the etiological agent of brucellosis. In some cases, human brucellosis results in a persistent infection that may reactivate years after the initial exposure. The mechanisms by which the parasite evades clearance by the immune response to chronically infect its host are unknown. We recently demonstrated that dendritic cells (DCs), which are critical components of adaptive immunity, are highly susceptible to Brucella infection and are a preferential niche for the development of the bacteria. Here, we report that in contrast to several intracellular bacteria, Brucella prevented the infected DCs from engaging in their maturation process and impaired their capacities to present antigen to naïve T cells and to secrete interleukin-12. Moreover, Brucella-infected DCs failed to release tumor necrosis factor alpha (TNF-␣), a defect involving the bacterial protein Omp25. Exogenous TNF-␣ addition to Brucella-infected DCs restored cell maturation and allowed them to present antigens. Two avirulent mutants of B. suis, B. suis bvrR and B. suis omp25 mutants, which do not express the Omp25 protein, triggered TNF-␣ production upon DC invasion. Cells infected with these mutants subsequently matured and acquired the ability to present antigens, two properties which were dramatically impaired by addition of anti-TNF-␣ antibodies. In light of these data, we propose a model in which virulent Brucella alters the maturation and functions of DCs through Omp25-dependent control of TNF-␣ production. This model defines a specific evasion strategy of the bacteria by which they can escape the immune response to chronically infect their host.Brucella is a facultative intracellular ␣2-proteobacterium that induces chronic infections in a wide variety of mammals, including field ruminants, humans, and marine mammals. In addition to the attention received from its classification as a potential weapon for bioterrorism (41), this bacterium is principally known because of its ability to induce infectious abortion in domestic animals and because brucellosis is the most frequent anthropozoonosis (20). The three most infectious species in humans are B. melitensis, B. abortus, and B. suis. Infection occurs through inhalation of aerosols or ingestion of infected food. Following invasion of the lymphoid system, the bacteria develop within mononuclear phagocytes, and infected cells play a crucial role in the dissemination of the bacteria in specific locations of the body. Also known as Malta fever, human brucellosis consists of an acute infection, characterized by undulant fever and asthenia, which evolves in 30% of infected patients into a chronic phase with erratic recurrent fevers and localized infections, such as endocarditis, encephalitis, and spondylitis. Chronic brucellosis patients display a T helper 2 (Th2)-specific immune response (19,43). In mice, which are not natural hosts for Brucella and display a certain resistance to infection, the protection is conferred by a Th1-oriented immune respon...

Colorectal cancer (CRC) is the second leading cause of cancer worldwide. CRC is still associated with a poor prognosis among patients with advanced disease. On the contrary, due to its slow progression from detectable precancerous lesions, the prognosis for patients with early stages of CRC is encouraging. While most robust methods are invasive and costly, actual patient-friendly screening methods for CRC suffer of lack of sensitivity and specificity. Therefore, the development of sensitive, non-invasive and cost-effective methods for CRC detection and prognosis are necessary for increasing the chances of a cure. Beyond its beneficial functions for the host, increasing evidence suggests that the intestinal microbiota is a key factor associated with carcinogenesis. Many clinical studies have reported a disruption in the gut microbiota balance and an alteration in the faecal metabolome of CRC patients, suggesting the potential use of a microbial-based test as a non-invasive diagnostic and/or prognostic tool for CRC screening. This review aims to discuss the microbial signatures associated with CRC known to date, including dysbiosis and faecal metabolome alterations, and the potential use of microbial variation markers for non-invasive early diagnosis and/or prognostic assessment of CRC and advanced adenomas. We will finally discuss the possible use of these markers as predicators for treatment response and their limitations.

Bacteria from the Brucella genus are able to survive and proliferate within macrophages. Because they are phylogenetically closely related to macrophages, myeloid dendritic cells (DCs) constitute potential targets for Brucella bacteria. Here we report that DCs display a great susceptibility to Brucella infection. Therefore, DCs might serve as a reservoir and be important for the development of Brucella bacteria within their host.Brucella are facultative intracellular bacteria that induce chronic infections in a wide range of mammals, including domestic animals and humans. Brucella bacteria are responsible for brucellosis and Mediterranean fever, also known as Malta fever. After invasion of the lymphoid system, the bacteria develop within mononuclear phagocytes, and the infected cells play a crucial role in the dissemination of the bacteria in specific locations of the body (spleen, brain, heart, and bones). Of intramacrophagic pathogens, Brucella bacteria are among the most powerful and are able to multiply intracellularly up to several thousandfold. The common ontogeny of macrophages and myeloid dendritic cells (DCs) and the discovery of a primordial role for DCs in immunity have raised the question of a relationship between DCs and intramacrophagic pathogens. Therefore, we have investigated the possible interaction between Brucella bacteria and DCs.Macrophages and immature DCs were prepared from peripheral blood circulating monocytes obtained by centrifugation on Ficoll-Hypaque (Sigma, Lyon, France) of buffy coat from healthy donors. Monocytes were purified on a magnetic column using anti-CD14-antibody-conjugated microbeads (Miltenyi-Biotec, Paris, France) and differentiated for 5 days in complete medium (RPMI 1640-10% fetal calf serum) supplemented with 50 M ␤-mercaptoethanol, 500 U/ml of interleukin-4, and 1,000 U/ml of granulocyte-macrophage colony-stimulating factor (Immunotools, Friesoythe, Germany) for DCs or with 10 Ϫ7 M vitamin D3 (Hoffman-Laroche, Bale, Switzerland) for syngeneic macrophages. Immature DCs were CD14 null (100%), CD83 null (Ͼ95%), DC-SIGN positive (100%), and CD1a positive (100%) and CMH-II low (100%). Macrophages were 100% CD14 positive, CD54 low, CD80 low, and CD86 low. After their differentiation, the cells were infected for 1 h at a multiplicity of infection (MOI) of 50 with the green fluorescent protein (GFP)-expressing strains of three Brucella species, B. suis, B. abortus, and B. melitensis, or with different B. suis attenuated mutants (Table 1). They were then washed with phosphate-buffered saline (PBS) and reincubated in fresh medium supplemented with 30 g/ml gentamicin to kill remaining extracellular bacteria. Figure 1A shows the observation by fluorescence microscopy of cells infected with the GFPexpressing Brucella spp. (11) at 48 h postinfection (p.i.).As frequently described, whatever the species considered, Brucella bacteria have strongly proliferated inside macrophages. Strikingly, the cytoplasm of DCs was completely invaded, some cells containing several hundred Brucell...

Recently, preclinical and clinical studies targeting several types of cancer strongly supported the key role of the gut microbiota in the modulation of host response to anti-tumoral therapies such as chemotherapy, immunotherapy, radiotherapy and even surgery. Intestinal microbiome has been shown to participate in the resistance to a wide range of anticancer treatments by direct interaction with the treatment or by indirectly stimulating host response through immunomodulation. Interestingly, these effects were described on colorectal cancer but also in other types of malignancies. In addition to their role in therapy efficacy, gut microbiota could also impact side effects induced by anticancer treatments. In the first part of this review, we summarized the role of the gut microbiome on the efficacy and side effects of various anticancer treatments and underlying mechanisms. In the second part, we described the new microbiota-targeting strategies, such as probiotics and prebiotics, antibiotics, fecal microbiota transplantation and physical activity, which could be effective adjuvant therapies developed in order to improve anticancer therapeutic efficiency.

The molecular mechanisms involved in the assembly of newly synthesized Human Immunodeficiency Virus (HIV) particles are poorly understood. Most of the work on HIV-1 assembly has been performed in T cells in which viral particle budding and assembly take place at the plasma membrane. In contrast, few studies have been performed on macrophages, the other major target of HIV-1. Infected macrophages represent a viral reservoir and probably play a key role in HIV-1 physiopathology. Indeed macrophages retain infectious particles for long periods of time, keeping them protected from anti-viral immune response or drug treatments. Here, we present an overview of what is known about HIV-1 assembly in macrophages as compared to T lymphocytes or cell lines.Early electron microscopy studies suggested that viral assembly takes place at the limiting membrane of an intracellular compartment in macrophages and not at the plasma membrane as in T cells. This was first considered as a late endosomal compartment in which viral budding seems to be similar to the process of vesicle release into multi-vesicular bodies. This view was notably supported by a large body of evidence involving the ESCRT (Endosomal Sorting Complex Required for Transport) machinery in HIV-1 budding, the observation of viral budding profiles in such compartments by immuno-electron microscopy, and the presence of late endosomal markers associated with macrophage-derived virions. However, this model needs to be revisited as recent data indicate that the viral compartment has a neutral pH and can be connected to the plasma membrane via very thin micro-channels. To date, the exact nature and biogenesis of the HIV assembly compartment in macrophages remains elusive. Many cellular proteins potentially involved in the late phases of HIV-1 cycle have been identified; and, recently, the list has grown rapidly with the publication of four independent genome-wide screens. However, their respective roles in infected cells and especially in macrophages remain to be characterized. In summary, the complete process of HIV-1 assembly is still poorly understood and will undoubtedly benefit from the ongoing explosion of new imaging techniques allowing better time-lapse and quantitative studies.

Adherent and invasive Escherichia coli (AIEC) associated with Crohn's disease are able to survive and to replicate extensively in active phagolysosomes within macrophages. AIEC-infected macrophages release large amounts of tumour necrosis factor-alpha (TNF-a) and do not undergo cell death. The aim of the present study was to determine what benefit AIEC bacteria could gain from inducing the release of large amounts of TNF-a by infected macrophages and to what extent the neutralization of TNF-a could affect AIEC intramacrophagic replication. Our results showed that the amount of TNF-a released by infected macrophages is correlated with the load of intramacrophagic AIEC bacteria and their intracellular replication. TNF-a secretion was not related to the number of bacteria entering host cells because when the number of bacteria internalized in macrophage was decreased by blocking lipid raft-dependent and clathrin-coated pits-dependent endocytosis, the amount of TNF-a secreted by infected macrophages was not modified. Interestingly, dose-dependent increases in the number of intracellular AIEC LF82 bacteria were observed when infected macrophages were stimulated with exogenous TNF-a, and neutralization of TNF-a secreted by AIEC-infected macrophages using anti-TNF-a antibodies induced a significant decrease in the number of intramacrophagic bacteria. These results indicate that AIEC bacteria use TNF-a as a Trojan horse to ensure their intracellular replication because replication of AIEC bacteria within macrophages induces the release of TNF-a, which in turn increases the intramacrophagic replication of AIEC. Neutralizing TNF-a secreted by infected macrophages may represent an effective strategy to control AIEC intracellular replication.