C-type lectins with a sweet spot for Mycobacterium tuberculosis

Role of pattern recognition receptors in sensing Mycobacterium tuberculosis

Mycobacterium tuberculosis is one of the major invasive intracellular pathogens causing most deaths by a single infectious agent. The interaction between host immune cells and this pathogen is the focal point of the disease, Tuberculosis. Host immune cells not only mount the protective action against this pathogen but also serve as the primary niche for growth. Thus, recognition of this pathogen by host immune cells and following signaling cascades are key dictators of the disease state. Immune cells, mainly belonging to myeloid cell lineage, recognize a wide variety of Mycobacterium tuberculosis ligands ranging from carbohydrate and lipids to proteins to nucleic acids by different membrane-bound and soluble pattern recognition receptors. Simultaneous interaction between different host receptors and pathogen ligands leads to immune-inflammatory response as well as contributes to virulence. This review summarizes the contribution of pattern recognition receptors of host immune cells in recognizing Mycobacterium tuberculosis and subsequent initiation of signaling pathways to provide the molecular insight of the specific Mtb ligands interacting with specific PRR, key adaptor molecules of the downstream signaling pathways and the resultant effector functions which will aid in identifying novel drug targets, and developing novel drugs and adjuvants.

Nano-in-Microparticles for Aerosol Delivery of Antibiotic-Loaded, Fucose-Derivatized, and Macrophage-Targeted Liposomes to Combat Mycobacterial Infections: In Vitro Deposition, Pulmonary Barrier Interactions, and Targeted Delivery

Nontuberculous mycobacterial infections rapidly emerge and demand potent medications to cope with resistance. In this context, targeted loco-regional delivery of aerosol medicines to the lungs is an advantage. However, sufficient antibiotic delivery requires engineered aerosols for optimized deposition. Here, the effect of bedaquiline-encapsulating fucosylated versus nonfucosylated liposomes on cellular uptake and delivery is investigated. Notably, this comparison includes critical parameters for pulmonary delivery, i.e., aerosol deposition and the noncellular barriers of pulmonary surfactant (PS) and mucus. Targeting increases liposomal uptake into THP-1 cells as well as peripheral blood monocyte- and lung-tissue derived macrophages. Aerosol deposition in the presence of PS, however, masks the effect of active targeting. PS alters antibiotic release that depends on the drug's hydrophobicity, while mucus reduces the mobility of nontargeted more than fucosylated liposomes. Dry-powder microparticles of spray-dried bedaquiline-loaded liposomes display a high fine particle fraction of >70%, as well as preserved liposomal integrity and targeting function. The antibiotic effect is maintained when deposited as powder aerosol on cultured Mycobacterium abscessus. When treating M. abscessus infected THP-1 cells, the fucosylated variant enabled enhanced bacterial killing, thus opening up a clear perspective for the improved treatment of nontuberculous mycobacterial infections.

The mannose receptor ligands and the macrophage glycome

A unique glycan-binding protein expressed in macrophages and some types of other immune cells is the mannose receptor (MR, CD206). It is an endocytic, transmembrane protein with multiple glycan-binding domains and different specificities in binding glycans. The mannose receptor is important as it has major roles in diverse biological processes, including regulation of circulating levels of reproductive hormones, homeostasis, innate immunity, and infections. These different functions involve the recognition of a wide range of glycans, and their nature is currently under intense study. But the mannose receptor is just one of many glycan-binding proteins expressed in macrophages, leading to an interest in the potential relationship between the macrophage glycome and how it may regulate cognate glycan-binding protein activities. This review focuses primarily on the mannose receptor and its carbohydrate ligands, as well as macrophages and their glycomes.

Glycans as a key factor in self and non-self discrimination: Impact on the breach of immune tolerance

Glycans are carbohydrates that are made by all organisms and covalently conjugated to other biomolecules. Glycans cover the surface of both human cells and pathogens and are fundamental to defining the identity of a cell or an organism, thereby contributing to discriminating self from non-self. As such, glycans are a class of "Self-Associated Molecular Patterns" that can fine-tune host inflammatory processes. In fact, glycans can be sensed and recognized by a variety of glycan-binding proteins (GBP) expressed by immune cells, such as galectins, siglecs and C-type lectins, which recognize changes in the cellular glycosylation, instructing both pro-inflammatory or anti-inflammatory responses. In this review, we introduce glycans as cell-identification structures, discussing how glycans modulate host-pathogen interactions and how they can fine-tune inflammatory processes associated with infection, inflammation and autoimmunity. Finally, from the clinical standpoint, we discuss how glycoscience research can benefit life sciences and clinical medicine by providing a source of valuable biomarkers and therapeutic targets for immunity.

Fucosylated lipid nanocarriers loaded with antibiotics efficiently inhibit mycobacterial propagation in human myeloid cells

Antibiotic treatment of tuberculosis (TB) is complex, lengthy, and can be associated with various adverse effects. As a result, patient compliance often is poor, thus further enhancing the risk of selecting multi-drug resistant bacteria. Macrophage mannose receptor (MMR)-positive alveolar macrophages (AM) constitute a niche in which Mycobacterium tuberculosis replicates and survives. Therefore, we encapsulated levofloxacin in lipid nanocarriers functionalized with fucosyl residues that interact with the MMR. Indeed, such nanocarriers preferentially targeted MMR-positive myeloid cells, and in particular, AM. Intracellularly, fucosylated lipid nanocarriers favorably delivered their payload into endosomal compartments, where mycobacteria reside. In an in vitro setting using infected human primary macrophages as well as dendritic cells, the encapsulated antibiotic cleared the pathogen more efficiently than free levofloxacin. In conclusion, our results point towards carbohydrate-functionalized nanocarriers as a promising tool for improving TB treatment by targeted delivery of antibiotics.

Mycobacterium tuberculosis EsxL induces TNF-α secretion through activation of TLR2 dependent MAPK and NF-κB pathways

Mycobacterium tuberculosis (Mtb) employs distinct strategies to circumvent host immune responses during the infection process. Various Mtb cell-wall associated and secretory proteins are known to play a critical role in the orchestration of host innate immune responses through modulation of signaling pathways. Mtb genome encodes for 23 (EsxA-EsxW) proteins belonging to the ESAT-6 like family; however, most of them are functionally unknown. Here, we show that Mtb EsxL induces tumor necrosis factor-alpha (TNF-α) production by activating nuclear translocation of nuclear factor-κB (NF-κB) via interaction with Toll-like Receptor 2 (TLR2). Blocking or silencing of TLR2 abrogated nuclear translocation of NF-kB and TNF-α production. Treatment with recombinant purified EsxL (rEsxL) activated mitogen-activated protein kinase (MAPK) pathway by inducing the phosphorylation of extracellular signal-regulated kinase (ERK) and p38 kinase (p38) pathways. At the same time, inhibition of ERK and p38 down-regulated the expression of TNF-α in rEsxL exposed murine macrophages. Besides TNF-α, EsxL also induced the production of IL-6 proinflammatory cytokine. Taken together, these results suggest that EsxL is able to induce TNF-α secretion via TLR2 through activation of NF-κB and MAPK signaling. This study will help in deducing therapeutic strategies for better control of the disease.

Innate Immune Pattern Recognition Receptors of Mycobacterium tuberculosis: Nature and Consequences for Pathogenesis of Tuberculosis

Innate immunity against Mycobacterium tuberculosis is a critical early response to prevent the establishment of the infection. Despite recent advances in understanding the host-pathogen dialogue in the early stages of tuberculosis (TB), much has yet to be learnt. The nature and consequences of this dialogue ultimately determine the path of infection: namely, either early clearance of M. tuberculosis, or establishment of M. tuberculosis infection leading to active TB disease and/or latent TB infection. On the frontline in innate immunity are pattern recognition receptors (PRRs), with soluble factors (e.g. collectins and complement) and cell surface factors (e.g. Toll-like receptors and other C-type lectin receptors (Dectin 1/2, Nod-like receptors, DC-SIGN, Mincle, mannose receptor, and MCL) that play a central role in recognising M. tuberculosis and facilitating its clearance. However, in a 'double-edged sword' scenario, these factors can also be involved in enhancement of pathogenesis as well. Furthermore, innate immunity is also a critical bridge in establishing the subsequent adaptive immune response, which is also responsible for granuloma formation that cordons off M. tuberculosis infection, establishing latency and acting as a reservoir for bacterial persistence and dissemination of future disease. This chapter discusses the current understanding of pattern recognition of M. tuberculosis by innate immunity and the role this plays in the pathogenesis and protection against TB.

Various Facets of Pathogenic Lipids in Infectious Diseases: Exploring Virulent Lipid-Host Interactome and Their Druggability

Lipids form an integral, structural, and functional part of all life forms. They play a significant role in various cellular processes such as membrane fusion, fission, endocytosis, protein trafficking, and protein functions. Interestingly, recent studies have revealed their more impactful and critical involvement in infectious diseases, starting with the manipulation of the host membrane to facilitate pathogenic entry. Thereafter, pathogens recruit specific host lipids for the maintenance of favorable intracellular niche to augment their survival and proliferation. In this review, we showcase the lipid-mediated host pathogen interplay in context of life-threatening viral and bacterial diseases including the recent SARS-CoV-2 infection. We evaluate the emergent lipid-centric approaches adopted by these pathogens, while delineating the alterations in the composition and organization of the cell membrane within the host, as well as the pathogen. Lastly, crucial nexus points in their interaction landscape for therapeutic interventions are identified. Lipids act as critical determinants of bacterial and viral pathogenesis by altering the host cell membrane structure and functions.

Collectins: Innate Immune Pattern Recognition Molecules

Collectins are collagen-containing C-type (calcium-dependent) lectins which are important pathogen pattern recognising innate immune molecules. Their primary structure is characterised by an N-terminal, triple-helical collagenous region made up of Gly-X-Y repeats, an a-helical coiled-coil trimerising neck region, and a C-terminal C-type lectin or carbohydrate recognition domain (CRD). Further oligomerisation of this primary structure can give rise to more complex and multimeric structures that can be seen under electron microscope. Collectins can be found in serum as well as in a range of tissues at the mucosal surfaces. Mannanbinding lectin can activate the complement system while other members of the collectin family are extremely versatile in recognising a diverse range of pathogens via their CRDs and bring about effector functions designed at the clearance of invading pathogens. These mechanisms include opsonisation, enhancement of phagocytosis, triggering superoxidative burst and nitric oxide production. Collectins can also potentiate the adaptive immune response via antigen presenting cells such as macrophages and dendritic cells through modulation of cytokines and chemokines, thus they can act as a link between innate and adaptive immunity. This chapter describes the structure-function relationships of collectins, their diverse functions, and their interaction with viruses, bacteria, fungi and parasites.

C-type Lectins in Immunity to Lung Pathogens

The respiratory tract is tasked with responding to a constant and vast influx of foreign agents. It acts as an important first line of defense in the innate immune system and as such plays a crucial role in preventing the entry of invading pathogens. While physical barriers like the mucociliary escalator exert their effects through the clearance of these pathogens, diverse and dynamic cellular mechanisms exist for the activation of the innate immune response through the recognition of pathogen-associated molecular patterns (PAMPs). These PAMPs are recognized by pattern recognition receptors (PRRs) that are expressed on a number of myeloid cells such as dendritic cells, macrophages, and neutrophils found in the respiratory tract. C-type lectin receptors (CLRs) are PRRs that play a pivotal role in the innate immune response and its regulation to a variety of respiratory pathogens such as viruses, bacteria, and fungi. This chapter will describe the function of both activating and inhibiting myeloid CLRs in the recognition of a number of important respiratory pathogens as well as the signaling events initiated by these receptors.

The human lung mucosa drives differential Mycobacterium tuberculosis infection outcome in the alveolar epithelium

Mycobacterium tuberculosis (M.tb) is deposited into the alveolus where it first encounters the alveolar lining fluid (ALF) prior contacts host cells. We demonstrated that M.tb-exposure to human ALF alters its cell surface, driving better M.tb infection control by professional phagocytes. Contrary to these findings, our results with non-professional phagocytes alveolar epithelial cells (ATs) define two distinct subsets of human ALFs; where M.tb exposure to Low (L)-ALF or High(H)-ALF results in low or high intracellular bacterial growth rates in ATs, respectively. H-ALF exposed-M.tb growth within ATs was independent of M.tb-uptake, M.tb-trafficking, and M.tb-infection induced cytotoxicity; however, it was associated with enhanced bacterial replication within LAMP-1⁺/ABCA1⁺ compartments. H-ALF exposed-M.tb infection of ATs decreased AT immune mediator production, decreased AT surface adhesion expression, and downregulated macrophage inflammatory responses. Composition analysis of H-ALF vs. L-ALF showed H-ALF with higher protein tyrosine nitration and less functional ALF-innate proteins important in M.tb pathogenesis. Replenishment of H-ALF with functional ALF-innate proteins reversed the H-ALF-M.tb growth rate to the levels observed for L-ALF-M.tb. These results indicate that dysfunctionality of innate proteins in the H-ALF phenotype promotes M.tb replication within ATs, while limiting inflammation and phagocyte activation, thus potentiating ATs as a reservoir for M.tb replication and survival.

Lectins of Mycobacterium tuberculosis - rarely studied proteins

The importance of bacterial lectins for adhesion, pathogenicity, and biofilm formation is well established for many Gram-positive and Gram-negative bacteria. However, there is very little information available about lectins of the tuberculosis-causing bacterium, Mycobacterium tuberculosis (Mtb). In this paper we review previous studies on the carbohydrate-binding characteristics of mycobacteria and related Mtb proteins, discussing their potential relevance to Mtb infection and pathogenesis.

The C-Type Lectin Receptor DC-SIGN Has an Anti-Inflammatory Role in Human M(IL-4) Macrophages in Response to Mycobacterium tuberculosis

DC-SIGN (CD209/CLEC4L) is a C-type lectin receptor (CLR) that serves as a reliable cell-surface marker of interleukin 4 (IL-4)-activated human macrophages [M(IL-4)], which historically represent the most studied subset within the M2 spectrum of macrophage activation. Although DC-SIGN plays important roles in Mycobacterium tuberculosis (Mtb) interactions with dendritic cells, its contribution to the Mtb–macrophage interaction remains poorly understood. Since high levels of IL-4 are correlated with tuberculosis (TB) susceptibility and progression, we investigated the role of DC-SIGN in M(IL-4) macrophages in the TB context. First, we demonstrate that DC-SIGN expression is present both in CD68⁺ macrophages found in tuberculous pulmonary lesions of non-human primates, and in the CD14⁺ cell population isolated from pleural effusions obtained from TB patients (TB-PE). Likewise, we show that DC-SIGN expression is accentuated in M(IL-4) macrophages derived from peripheral blood CD14⁺ monocytes isolated from TB patients, or in macrophages stimulated with acellular TB-PE, arguing for the pertinence of DC-SIGN-expressing macrophages in TB. Second, using a siRNA-mediated gene silencing approach, we performed a transcriptomic analysis of DC-SIGN-depleted M(IL-4) macrophages and revealed the upregulation of pro-inflammatory signals in response to challenge with Mtb, as compared to control cells. This pro-inflammatory gene signature was confirmed by RT-qPCR, cytokine/chemokine-based protein array, and ELISA analyses. We also found that inactivation of DC-SIGN renders M(IL-4) macrophages less permissive to Mtb intracellular growth compared to control cells, despite the equal level of bacteria uptake. Last, at the molecular level, we show that DC-SIGN interferes negatively with the pro-inflammatory response and control of Mtb intracellular growth mediated by another CLR, Dectin-1 (CLEC7A). Collectively, this study highlights a dual role for DC-SIGN as, on the one hand, being a host factor granting advantage for Mtb to parasitize macrophages and, on the other hand, representing a molecular switch to turn off the pro-inflammatory response in these cells to prevent potential immunopathology associated to TB.

Mannose-capped lipoarabinomannan in Mycobacterium tuberculosis pathogenesis

Mannose-capped lipoarabinomannan (ManLAM), present in all members of the Mycobacterium tuberculosis complex and in other pathogenic Mycobacterium spp, is a high molecular mass amphipathic lipoglycan with a defined critical role in mycobacterial survival during infection. In particular, ManLAM is well-characterized for its importance in providing M. tuberculosis a safe portal of entry to phagocytes, regulating the intracellular trafficking network, as well as immune responses of infected host cells. These ManLAM immunological characteristics are thought to be linked to the subtle but unique and well-defined structural characteristics of this molecule, including but not limited to the degree of acylation, the length of the D-mannan and D-arabinan cores, the length of the mannose caps, as well as the presence of other acidic constituents such as succinates, lactates and/or malates, and also the presence of 5-methylthioxylosyl. The impact of all these structural features on ManLAM spatial conformation and biological functions during M. tuberculosis infection is still uncertain. In this review, we dissect the relationship between ManLAM structure and biological function addressing how this relationship determines M. tuberculosis interactions with host cells, and how it aids this exceptional pathogen during the course of infection.

The Macrophage: A Disputed Fortress in the Battle against Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb), the etiological agent of human tuberculosis (TB), has plagued humans for thousands of years. TB still remains a major public health problem in our era, causing more than 4,400 deaths worldwide every day and killing more people than HIV. After inhaling Mtb-contaminated aerosols, TB primo-infection starts in the terminal lung airways, where Mtb is taken up by alveolar macrophages. Although macrophages are known as professional killers for pathogens, Mtb has adopted remarkable strategies to circumvent host defenses, building suitable conditions to survive and proliferate. Within macrophages, Mtb initially resides inside phagosomes, where its survival mostly depends on its ability to take control of phagosomal processing, through inhibition of phagolysosome biogenesis and acidification processes, and by progressively getting access to the cytosol. Bacterial access to the cytosolic space is determinant for specific immune responses and cell death programs, both required for the replication and the dissemination of Mtb. Comprehension of the molecular events governing Mtb survival within macrophages is fundamental for the improvement of vaccine-based and therapeutic strategies in order to help the host to better defend itself in the battle against the fierce invader Mtb. In this mini-review, we discuss recent research exploring how Mtb conquers and transforms the macrophage into a strategic base for its survival and dissemination as well as the associated defense strategies mounted by host.

Pattern recognition receptors and coordinated cellular pathways involved in tuberculosis immunopathogenesis: Emerging concepts and perspectives

Pattern Recognition Receptors (PRRs) play a central role in the recognition of numerous pathogens, including Mycobacterium tuberculosis, resulting in activation of innate and adaptive immune responses. Besides Toll Like Receptors, C-type Lectin Receptors and Nod Like Receptors are now being recognized for their involvement in inducing immune response against M. tuberculosis infection. Although, a functional redundancy of the PRRs has also been reported in many studies, emerging evidences support the notion that a cooperative and coordinated response generated by these receptors is critical to sustain the full immune control of M. tuberculosis infection. Many of the PRRs are now found to be involved in various cellular host defenses, such as inflammasome activation, phagosome biogenesis, endosomal trafficking, and antigen processing pathways that are all very critical for an effective immune response against M. tuberculosis. In support, polymorphism in several of these receptors has also been found associated with increased susceptibility to tuberculosis in humans. Nonetheless, increasing evidences also show that in order to enhance its intracellular survival, M. tuberculosis has also evolved multiple strategies to subvert and reprogram PPR-mediated immune responses. In light of these findings, this review analyzes the interaction of bacterial and host factors at the intersections of PRR signaling pathways that could provide integrative insights for the development of better vaccines and therapeutics for tuberculosis.

Development and evaluation of a double antibody sandwich ELISA for the detection of human sDC-SIGN

sDC-SIGN is the soluble form of dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN, CD209), which is a molecule involved with pathogen recognition and immune regulation. However, there is no commercially available ELISA kit for detecting human sDC-SIGN, and the normal range of this molecule is unknown. Here, we describe an ELISA for detecting human sDC-SIGN with high specificity. First, sDC-SIGN protein was expressed and purified. Monoclonal and polyclonal antibodies were then raised against the purified protein and subsequently characterized. A sandwich ELISA was developed using polyclonal antibodies specific for sDC-SIGN for capture and a biotin-labeled monoclonal antibody specific for sDC-SIGN for detection of protein. This method has sensitivity up to 0.2 ng/ml. Using this ELISA, we found that the concentration of sDC-SIGN in sera of healthy volunteers ranges from 0-319 ng/ml with a mean concentration of 27.14 ng/ml. Interestingly, the concentration of sDC-SIGN in sera from patients with cancer or chronic hepatitis B virus (CHB) infection was lower than that of health controls. The mean concentrations of sDC-SIGN in cancer patients and chronic hepatitis B virus infection patients were 3.2 ng/ml and 3.8 ng/ml, respectively. We developed a sandwich ELISA for detecting human sDC-SIGN and demonstrated its use by assessing sera concentrations of sDC-SIGN in patients with cancer and chronic CHB infection compared to that of healthy controls.

Signalling through MyD88 drives surface expression of the mycobacterial receptors MCL (Clecsf8, Clec4d) and Mincle (Clec4e) following microbial stimulation

The heterodimeric mycobacterial receptors, macrophage C-type lectin (MCL) and macrophage inducible C-type lectin (Mincle), are upregulated at the cell surface following microbial challenge, but the mechanisms underlying this response are unclear. Here we report that microbial stimulation triggers Mincle expression through the myeloid differentiation primary response gene 88 (MyD88) pathway; a process that does not require MCL. Conversely, we show that MCL is constitutively expressed but retained intracellularly until Mincle is induced, whereupon the receptors form heterodimers which are translocated to the cell surface. Thus this "two-step" model for induction of these key receptors provides new insights into the underlying mechanisms of anti-mycobacterial immunity.

An efficient siRNA-mediated gene silencing in primary human monocytes, dendritic cells and macrophages

Mononuclear phagocytes (MP) comprise monocytes, macrophages (MΦ) and dendritic cells (DC), including their lineage-committed progenitors, which together have an eminent role in health and disease. Lipid-based siRNA-mediated gene inactivation is an established approach to investigate gene function in MP cells. However, although there are few protocols dedicated for siRNA-mediated gene inactivation in primary human DC and MΦ, there are none available for primary human monocytes. Moreover, there is no available method to perform comparative studies of a siRNA-mediated gene silencing in primary monocytes and other MP cells. Here, we describe a protocol optimized for the lipid-based delivery of siRNA to perform gene silencing in primary human blood monocytes, which is applicable to DCs, and differs from the classical route of siRNA delivery into MΦs. Along with this protocol, we provide a comparative analysis of how monocytes, DC and MΦ are efficiently transfected with the target siRNA without affecting cell viability, resulting in strong gene knockdown efficiency, including the simultaneous inactivation of two genes. Moreover, siRNA delivery does not affect classical functions in MP such as differentiation, phagocytosis and migration, demonstrating that this protocol does not induce non-specific major alterations in these cells. As a proof-of-principle, a functional analysis of hematopoietic cell kinase (Hck) shows for the first time that this kinase regulates the protease-dependent migration mode in human monocytes. Collectively, this protocol enables efficient gene inactivation in primary MP, suggesting a wide spectrum of applications such as siRNA-based high-throughput screening, which could ultimately improve our knowledge about MP biology.

A negative effect of Campylobacter capsule on bacterial interaction with an analogue of a host cell receptor

BACKGROUND

Campylobacter jejuni (C. jejuni) is the leading causative agent of bacterial gastrointestinal infections. The rise of antibiotic resistant forms of this pathogen necessitates the development of novel intervention strategies. One approach is the design of drugs preventing bacterial attachment to host cells. Although some putative C. jejuni adhesins have been identified, the molecular mechanisms of their interaction with host cells and their role in pathogenesis remain to be elucidated. C. jejuni adhesion may also be modulated by a bacterial capsule. However, the role of this structure in adhesion was not clear due to conflicting results published by different research groups. The aim of this study was to clarify the role of capsule in bacterial interaction with host cells by using an in vitro model of adhesion and an analogue of a host cell receptor.

RESULTS

In this study, we developed an in vitro bacterial adhesion assay, which was validated using various tests, including competitive inhibition studies, exoglycosydase treatment and site-directed mutagenesis. We demonstrate that PEB3 is one of the cell surface glycoproteins required for bacterial interaction with an analogue of a host cell receptor. In contrast, JlpA glycoprotein adhesin is not required for such interaction. We demonstrate that the production of capsule reduces bacterial attachment, and that the genes involved in capsule and PEB3 adhesin biosynthesis are differentially regulated.

CONCLUSIONS

In this study we report an in vitro model for the investigation of bacterial interaction with analogs of host cell receptors. The results suggest an interfering effect of capsule on bacterial attachment. In addition, using a liquid culture, we demonstrate differential expression of a gene involved in capsule production (kpsM) and a gene encoding a glycoprotein adhesin (peb3). Further studies are required in order to establish if these genes are also differentially regulated during the infection process. The results will assist in better understanding of the mechanism of pathogenesis of C. jejuni in general and the role of capsule in the process in particular.

Molecular mechanisms and biological role of Campylobacter jejuni attachment to host cells

Adhesion to host cells is an important step in pathogenesis of Campylobacter jejuni, which is the most prevalent bacterial cause of human gastroenteritis worldwide. In contrast to other bacteria such as E. coli and Salmonella, adherence of C. jejuni is not mediated by fimbria or pili. A number of C. jejuni adhesion-related factors have been described. However, the results obtained by different researchers in different laboratories are often contradictory and inconclusive, with only some of the factors described being confirmed as true adhesins. In this review, we present the current state of studies on the mechanisms of attachment of C. jejuni to host cells.