Hamish E.G. McWilliam

A molecular basis underpinning the T cell receptor heterogeneity of mucosal-associated invariant T cells.

A novel MAIT cell antagonist, Ac-6-FP, stabilizes MR1 and can inhibit MAIT cell activation with the flexible TCR β-chain serving to fine-tune the affinity of the TCR for antigen-MR1 complexes.

MR1 presentation of vitamin B-based metabolite ligands

The major histocompatibility complex class I-related molecule MR1 can bind a novel class of antigens, namely a family of related small organic vitamin B metabolites. When bound to MR1 these metabolites are presented to a population of innate-like T cells, mucosal-associated invariant T (MAIT) cells that express a semi-invariant T cell receptor (TCR). Several non-activating and activating MR1-restricted ligands have been described, which are the degradation products of, or intermediates of, vitamin B9 (folic acid) or vitamin B2 (riboflavin), respectively. The MAIT-activating intermediates of the riboflavin synthesis pathway are unique to a wide range of microbes, and accordingly represent a molecular signature of microbial infection. Recently insights into the binding of these vitamin B metabolites to MR1, and subsequent recognition by the MAIT TCR, have been gleaned, illustrating a novel antigen presentation system.

Novel immunomic technologies for schistosome vaccine development.

Schistosomiasis remains one of the most common human helminthiases, despite the availability of an effective drug against the causative parasites. Drug treatment programmes have several limitations, and it is likely that a vaccine is required for effective control. While decades of vaccine development have seen the discovery and testing of several candidate antigens, none have shown consistent and acceptable high levels of protection. The migrating larval stages are susceptible to immunity, however few larval‐specific antigens have been discovered. Therefore, there is a need to identify novel larval‐specific antigens, which may prove to be more efficacious than existing targets. Immunomics, a relatively new field developed to cope with the recent large influx of biological information, holds promise for the discovery of vaccine targets, and this review highlights some immunomic approaches to schistosome vaccine development. Firstly, a method to focus on the immune response elicited by the important and vulnerable larval stage is described, which allows a targeted study of the immunome at different tissue sites. Then, two high‐throughput arrays are discussed for the identification of protein and carbohydrate antigens. It is anticipated that these approaches will progress vaccine development against the schistosomes, as well as other parasites.

Identification and characterisation of an immunodiagnostic marker for cyathostomin developing stage larvae.

Parasitic nematodes of the group Cyathostominae are an important cause of disease in horses. This group consists of approximately 50 species, all of which have similar life cycles that involve encystment of larval stages in the large intestinal wall. Encysted larvae can persist for months to years and, occasionally, large numbers can accumulate and emerge synchronously to cause severe pathology, resulting in diarrhoea, weight loss, colic and/or oedema. This syndrome, known as larval cyathostominosis, can be fatal in up to 50% of cases, despite treatment. There is no diagnostic method that enables detection of the encysted larval burden. Previously, we identified two native antigen complexes that showed utility as diagnostic markers for the estimation of cyathostomin encysted larval burdens. This paper reports the identification of a likely protein component of one of these antigen complexes. The protein, designated cyathostomin gut-associated larval antigen-1 (Cy-GALA-1), was isolated by immunoscreening a cyathostomin mixed-species, larval complementary DNA library using sera from experimentally-infected horses. The resultant recombinant protein, rCy-GALA-1, was expressed in Escherichia coli and shown to be a target of serum IgG(T) responses in experimentally- and naturally-infected horse populations. Transcription of Cy-gala-1 was restricted to cyathostomin encysted larvae and the presence of native protein was limited to developing larval stages. Importantly, rCy-GALA-1 exhibited no reactivity to serum from horses mono-specifically infected with other helminth species, nor did antisera, raised to the recombinant protein, bind to adult stage extracts of heterologous species. Immunohistochemical experiments located Cy-GALA-1 to the nematode gut. A region of the gene encoding orthologous GALA sequences was isolated from 10 separate cyathostomin species, indicating the ubiquity of the protein in this nematode group.

Local Modulation of Antigen-Presenting Cell Development after Resolution of Pneumonia Induces Long-Term Susceptibility to Secondary Infections

Summary Lung infections cause prolonged immune alterations and elevated susceptibility to secondary pneumonia. We found that, after resolution of primary viral or bacterial pneumonia, dendritic cells (DC), and macrophages exhibited poor antigen‐presentation capacity and secretion of immunogenic cytokines. Development of these “paralyzed” DCs and macrophages depended on the immunosuppressive microenvironment established upon resolution of primary infection, which involved regulatory T (Treg) cells and the cytokine TGF‐&bgr;. Paralyzed DCs secreted TGF‐&bgr; and induced local Treg cell accumulation. They also expressed lower amounts of IRF4, a transcription factor associated with increased antigen‐presentation capacity, and higher amounts of Blimp1, a transcription factor associated with tolerogenic functions, than DCs present during primary infection. Blimp1 expression in DC of humans suffering sepsis or trauma correlated with severity and complicated outcomes. Our findings describe mechanisms underlying sepsis‐ and trauma‐induced immunosuppression, reveal prognostic markers of susceptibility to secondary infections and identify potential targets for therapeutic intervention. Graphical Abstract Figure. No Caption available. HighlightsMacrophages and DCs produced after severe primary pneumonia are functionally impairedTGF‐&bgr; and Treg cells induce a tolerogenic differentiation program in these DCsThese “paralyzed” DC express high amounts of Blimp 1 and low amounts of IRF4Expression of Blimp 1 in human DC correlates with outcome in ICU patients &NA; Following a severe primary infection, the risk of developing pneumonia increases due to acquired immune defects collectively known as sepsis‐induced immunosuppression. Roquilly et al. show that resolution of the primary infection changed the local environment, leading to the development of DCs and macrophages that are functionally impaired in terms of T cell activation, and instead exhibit tolerogenic properties that contribute to immune suppression.

Local Immune Responses of the Chinese Water Buffalo, Bubalus bubalis, against Schistosoma japonicum Larvae: Crucial Insights for Vaccine Design

Asian schistosomiasis is a zoonotic parasitic disease infecting up to a million people and threatening tens of millions more. Control of this disease is hindered by the animal reservoirs of the parasite, in particular the water buffalo (Bubalus bubalis), which is responsible for significant levels of human transmission. A transmission-blocking vaccine administered to buffaloes is a realistic option which would aid in the control of schistosomiasis. This will however require a better understanding of the immunobiology of schistosomiasis in naturally exposed buffaloes, particularly the immune response to migrating schistosome larvae, which are the likely targets of an anti-schistosome vaccine. To address this need we investigated the immune response at the major sites of larval migration, the skin and the lungs, in previously exposed and re-challenged water buffaloes. In the skin, a strong allergic-type inflammatory response occurred, characterised by leukocyte and eosinophil infiltration including the formation of granulocytic abscesses. Additionally at the local skin site, interleukin-5 transcript levels were elevated, while interleukin-10 levels decreased. In the skin-draining lymph node (LN) a predominant type-2 profile was seen in stimulated cells, while in contrast a type-1 profile was detected in the lung draining LN, and these responses occurred consecutively, reflecting the timing of parasite migration. The intense type-2 immune response at the site of cercarial penetration is significantly different to that seen in naive and permissive animal models such as mice, and suggests a possible mechanism for immunity. Preliminary data also suggest a reduced and delayed immune response occurred in buffaloes given high cercarial challenge doses compared with moderate infections, particularly in the skin. This study offers a deeper understanding into the immunobiology of schistosomiasis in a natural host, which may aid in the future design of more effective vaccines.

The developing schistosome worms elicit distinct immune responses in different tissue regions

Schistosome parasites follow a complex migration path through various tissues, changing their antigenic profile as they develop. A thorough understanding of the antibody response in each tissue region could help unravel the complex immunology of these developing parasites and aid vaccine design. Here we used a novel strategy for analysing the local antibody responses induced by Schistosoma japonicum infection at each site of infection. Cells from rat lymph nodes draining the sites of larval migration (the skin and lungs), the liver‐lymph nodes where adults reside and the spleens were cultured to allow the in vivo‐induced antibody‐secreting cells to release antibody into the media. The amount and isotype of antibodies secreted in the supernatants differed significantly in the different lymph nodes and spleen, corresponding with the migration path of the schistosome worms. In addition, there were significant differences in binding specificity, as determined by surface labelling, western blots and by screening a glycan array. Through capturing the local antibody response, this study has revealed dramatic differences in the quality and specificity of the immune response at different tissue sites, and highlighted the existence of stage‐specific protein and carbohydrate antigens. This will provide a valuable tool for the isolation of novel vaccine targets against the larval stages of schistosomes.

Discovery of novel Schistosoma japonicum antigens using a targeted protein microarray approach

BackgroundNovel vaccine candidates against Schistosoma japonicum are required, and antigens present in the vulnerable larval developmental stage are attractive targets. Post-genomic technologies are now available which can contribute to such antigen discovery.MethodsA schistosome-specific protein microarray was probed using the local antibody response against migrating larvae. Antigens were assessed for their novelty and predicted larval expression and host-exposed features. One antigen was further characterised and its sequence and structure were analysed in silico. Real-time polymerase chain reaction was used to analyse transcript expression throughout development, and immunoblotting and enzyme-linked immunosorbent assays employed to determine antigen recognition by antibody samples.ResultsSeveral known and novel antigens were discovered, two of which showed up-regulated transcription in schistosomula. One novel antigen, termed S. japonicum Ly-6-like protein 1 (Sj-L6L-1), was further characterised and shown to share structural and sequence features with the Ly-6 protein family. It was found to be present in the worm tegument and expressed in both the larval and adult worms, but was found to be antigenic only in the lungs that the larvae migrate to and traverse.ConclusionsThis study represents a novel approach to vaccine antigen discovery and may contribute to schistosome vaccine development against this important group of human and veterinary pathogens.

Galectin secretion and binding to adult Fasciola hepatica during chronic liver fluke infection of sheep

Galectins are increasingly recognised as important mediators of immune homeostasis and disease regulation, but comparatively little is known about their role in parasite infection. This study investigates the interaction between two ovine galectins, galectin-11 and galectin-14, and the parasitic liver fluke, F. hepatica. Galectin-14 was found in eosinophils infiltrating the tissue surrounding infected bile ducts and secreted in the connective tissue, while galectin-11 was specifically induced in epithelial cells of bile ducts from infected sheep. Strong nuclear staining was observed for galectin-11. Both galectins were found to be secreted into the bile fluid of parasite infected sheep, and were also detected in the excretory/secretory products of adult flukes, following their removal from the ovine host. Recombinant galectin-14, but not recombinant galectin-11, was found to bind specifically to the surface tegument of adult flukes in a carbohydrate dependent manner. This study shows for the first time that both galectin-14 and galectin-11 are produced in liver tissue after chronic liver fluke infection and that they can directly interact with the parasite in the bile ducts. Galectin-11 may also be involved in epithelial cell turnover and cancerogenesis.

Ovine IgA-reactive proteins from Teladorsagia circumcincta infective larvae

Infection of small ruminants with Teladorsagia circumcincta has, until now, been controlled using a combination of pasture management and frequent anthelmintic treatments. Resistance to the commonly used anthelmintics has driven research into the development of a subunit vaccine, encouraged by the demonstration of development of protective immunity in sheep following exposure to this parasite. Local immune effectors in the abomasum, in particular IgA, are thought to play important roles in naturally- and experimentally-acquired immunity. L3s represent the first contact of this pathogen with the host immune system and, herein, the presence of L3 antigen-specific IgA was demonstrated in abomasal mucus from immune sheep. This antibody source was used to immunoaffinity purify and identify IgA-reactive molecules present in L3s. We identified 155 different proteins in this way, including a number of activation-associated secretory proteins, venom allergen-like-type proteins, detoxifying enzymes, galectins and a suite of other potential vaccine candidate molecules. Levels of immunoaffinity-enriched L3 antigen-specific IgA in gastric lymph from previously-infected sheep were statistically significantly higher (P=0.004) than those measured in helminth-free sheep and a statistically significant negative correlation (P=0.005, rs=-0.565) was identified between immunoaffinity-enriched L3 antigen-specific IgA levels in efferent gastric lymph and total T. circumcincta burden measured at necropsy. In addition, a statistically significant positive correlation (P=0.007, rs=0.534) was measured between immunoaffinity-enriched L3 antigen-specific IgA levels in efferent gastric lymph and the percentage of inhibited L4s enumerated at necropsy. These results indicate that the purified antigens contain components that could be strongly considered as vaccine candidates.