Neither interleukin-4 receptor alpha expression on CD4+ T cells, or macrophages and neutrophils is required for protective immunity to Trichinella spiralis

Integrative biology defines novel biomarkers of resistance to strongylid infection in horses

The widespread failure of anthelmintic drugs against nematodes of veterinary interest requires novel control strategies. Selective treatment of the most susceptible individuals could reduce drug selection pressure but requires appropriate biomarkers of the intrinsic susceptibility potential. To date, this has been missing in livestock species. Here, we selected Welsh ponies with divergent intrinsic susceptibility (measured by their egg excretion levels) to cyathostomin infection and found that their divergence was sustained across a 10-year time window. Using this unique set of individuals, we monitored variations in their blood cell populations, plasma metabolites and faecal microbiota over a grazing season to isolate core differences between their respective responses under worm-free or natural infection conditions. Our analyses identified the concomitant rise in plasma phenylalanine level and faecal Prevotella abundance and the reduction in circulating monocyte counts as biomarkers of the need for drug treatment (egg excretion above 200 eggs/g). This biological signal was replicated in other independent populations. We also unravelled an immunometabolic network encompassing plasma beta-hydroxybutyrate level, short-chain fatty acid producing bacteria and circulating neutrophils that forms the discriminant baseline between susceptible and resistant individuals. Altogether our observations open new perspectives on the susceptibility of equids to strongylid infection and leave scope for both new biomarkers of infection and nutritional intervention.

Immunity to gastrointestinal nematode infections

Numerous species of nematodes have evolved to inhabit the gastrointestinal tract of animals and humans, with over a billion of the world's population infected with at least one species. These large multicellular pathogens present a considerable and complex challenge to the host immune system given that individuals are continually exposed to infective stages, as well as the high prevalence in endemic areas. This review summarizes our current understanding of host-parasite interactions, detailing induction of protective immunity, mechanisms of resistance, and resolution of the response. It is clear from studies of well-defined laboratory model systems that these responses are dominated by innate and adaptive type 2 cytokine responses, regulating cellular and soluble effectors that serve to disrupt the niche in which the parasites live by strengthening the physical mucosal barrier and ultimately promoting tissue repair.

Interleukin-13 Receptor α1-Dependent Responses in the Intestine Are Critical to Parasite Clearance

Nematode infection upregulates interleukin-4 (IL-4) and IL-13 and induces STAT6-dependent changes in gut function that promote worm clearance. IL-4 and IL-13 activate the type 2 IL-4 receptor (IL-4R), which contains the IL-13Rα1 and IL-4Rα chains. We used mice deficient in IL-13Rα1 (IL-13Rα1(-/-)) to examine the contribution of IL-13 acting at the type 2 IL-4R to immune and functional responses to primary (Hb1) and secondary (Hb2) infections with the gastrointestinal nematode parasite Heligmosomoides bakeri There were differences between strains in the IL-4 and IL-13 expression responses to Hb1 but not Hb2 infection. Following Hb2 infection, deficient mice had impaired worm expulsion and higher worm fecundity despite normal production of Th2-derived cytokines. The upregulation of IL-25 and IL-13Rα2 in Hb1- and Hb2-infected wild-type (WT) mice was absent in IL-13Rα1(-/-)mice. Goblet cell numbers and resistin-like molecule beta (RELM-β) expression were attenuated significantly in IL-13Rα1(-/-)mice following Hb2 infections. IL-13Rα1 contributes to the development of alternatively activated macrophages, but the type 1 IL-4R is also important. Hb1 infection had no effects on smooth muscle function or epithelial permeability in either strain, while the enhanced mucosal permeability and changes in smooth muscle function and morphology observed in response to Hb2 infection in WT mice were absent in IL-13Rα1(-/-)mice. Notably, the contribution of claudin-2, which has been linked to IL-13, does not mediate the increased mucosal permeability following Hb2 infection. These results show that activation of IL-13Rα1 is critical for key aspects of the immune and functional responses to Hb2 infection that facilitate expulsion.

Macrophage proliferation, provenance, and plasticity in macroparasite infection

Macrophages have long been center stage in the host response to microbial infection, but only in the past 10–15 years has there been a growing appreciation for their role in helminth infection and the associated type 2 response. Through the actions of the IL-4 receptor α (IL-4Rα), type 2 cytokines result in the accumulation of macrophages with a distinctive activation phenotype. Although our knowledge of IL-4Rα-induced genes is growing rapidly, the specific functions of these macrophages have yet to be established in most disease settings. Understanding the interplay between IL-4Rα-activated macrophages and the other cellular players is confounded by the enormous transcriptional heterogeneity within the macrophage population and by their highly plastic nature. Another level of complexity is added by the new knowledge that tissue macrophages can be derived either from a resident prenatal population or from blood monocyte recruitment and that IL-4 can increase macrophage numbers through proliferative expansion. Here, we review current knowledge on the contribution of macrophages to helminth killing and wound repair, with specific attention paid to distinct cellular origins and plasticity potential.

Coinfection with Clonorchis sinensis modulates murine host response against Trichinella spiralis infection

Concomitant infections of different species of parasites are common in the field. Infection with one parasite species likely triggers host responses that may influence the subsequent infection of another species and alter disease outcomes. So far, the majority of studies have focused on single species parasite infection, and the mechanisms of protection induced by the first parasite infection against the secondary infection remain poorly defined. In this study, we assess the impact of trematode Clonorchis sinensis infection on the course of another tissue nematode Trichinella spiralis challenge. We observed that mice with preexisting C. sinensis infection had lower worm burden of intestinal T. spiralis than those infected with T. spiralis alone; mice with preexisting C. sinensis also had severe enteric histopathological changes and higher counts of intestinal Paneth cells in responses to T. spiralis challenge. The mRNA levels of interleukin (IL)-4, IL-10, IL-13, and tumor necrosis factor (TNF)-α from the small intestine and spleen of the different groups were analyzed using quantitative real-time polymerase chain reaction. Compared with that in mice infected with T. spiralis alone, the mRNA expression of IL-13 was significantly increased in the small intestine tissues and IL-4, IL-13, and TNF-α were significantly increased in the spleen tissues in the dually infected mice. Our findings suggest that a "preexisting" trematode infection of C. sinensis is a factor which contributes to reducing the establishment of T. spiralis adult worms in the small intestine.

Cancer-related inflammation

Solid tumors consist of neoplastic cells, non-malignant stromal cells, and migratory hematopoietic cells. Complex interactions between the cell types in this microenvironment regulate tumor growth, progression, metastasis, and angiogenesis. The cells and mediators of inflammation form a major part of the epithelial tumor microenvironment. In some cancers, inflammatory conditions precede development of malignancy; in others, oncogenic change drives a tumor-promoting inflammatory milieu. Whatever its origin, this "smoldering" inflammation aids proliferation and survival of malignant cells, stimulates angiogenesis and metastasis, subverts adaptive immunity, and alters response to hormones and chemotherapy. Cytokines are major mediators of communication between cells in the inflammatory tumor microenvironment. It is known that neoplastic cells often over-express proinflammatory mediators including proteases, eicosanoids, cytokines, and chemokines. Several cytokines such as macrophage migratory inhibitory factor (MIF), TNF-α, IL-6, IL-17, IL-12, IL-23, IL-10, and TGF-β have been linked with both experimental and human cancers and can either promote or inhibit tumor development. MIF is a major cytokine in many cancers and there is evidence that the cytokine is produced by both malignant cells and infiltrating leukocytes. In this article we will discuss the role of cancer-associated inflammation and the particular role of MIF in malignant disease.

Cancer-related inflammation

Solid tumors consist of neoplastic cells, non-malignant stromal cells, and migratory hematopoietic cells. Complex interactions between the cell types in this microenvironment regulate tumor growth, progression, metastasis, and angiogenesis. The cells and mediators of inflammation form a major part of the epithelial tumor microenvironment. In some cancers, inflammatory conditions precede development of malignancy; in others, oncogenic change drives a tumor-promoting inflammatory milieu. Whatever its origin, this "smoldering" inflammation aids proliferation and survival of malignant cells, stimulates angiogenesis and metastasis, subverts adaptive immunity, and alters response to hormones and chemotherapy. Cytokines are major mediators of communication between cells in the inflammatory tumor microenvironment. It is known that neoplastic cells often over-express proinflammatory mediators including proteases, eicosanoids, cytokines, and chemokines. Several cytokines such as macrophage migratory inhibitory factor (MIF), TNF-α, IL-6, IL-17, IL-12, IL-23, IL-10, and TGF-β have been linked with both experimental and human cancers and can either promote or inhibit tumor development. MIF is a major cytokine in many cancers and there is evidence that the cytokine is produced by both malignant cells and infiltrating leukocytes. In this article we will discuss the role of cancer-associated inflammation and the particular role of MIF in malignant disease.

Myeloid cell-specific expression of Ship1 regulates IL-12 production and immunity to helminth infection

Helminth infection leads to the local proliferation and accumulation of macrophages in tissues. However, the function of macrophages during helminth infection remains unclear. SH2-containing inositol 5'-phosphatase 1 (Ship1, Inpp5d) is a lipid phosphatase that has been shown to play a critical role in macrophage function. Here, we identify a critical role for Ship1 in the negative regulation of interleukin (IL)-12/23p40 production by macrophages during infection with the intestinal helminth parasite Trichuris muris. Mice with myeloid cell-specific deletion of Ship1 (Ship1(ΔLysM) mice) develop a non-protective T-helper type 1 cell response and fail to expel parasites. Ship1-deficient macrophages produce heightened levels of IL-12/23p40 in vitro and in vivo and antibody blockade of IL-12/23p40 renders Ship1(ΔLysM) mice resistant to Trichuris infection. Our results identify a critical role for the negative regulation of IL-12/23p40 production by macrophages in the development of a protective T(H)2 cell response.

A DNA vaccine co-expressingTrichinella spiralisMIF and MCD-1 with murine ubiquitin induces partial protective immunity in mice

Co-expression ofTrichinella spiralismacrophage migration inhibitory factor (TsMIF) withT. spiraliscystatin-like domain protein (TsMCD-1) in a DNA vaccine induces a Th1 immune response and partial protection againstT. spiralisinfection. The present study evaluated whether co-expression of mouse ubiquitin (Ub) withTsMIF andTsMCD-1 might improve the immune response againstT. spiralisinfection. Groups of BALB/c mice were immunized twice at 2-week intervals with 100 μg of plasmid DNA encoding either aTsMIF–TsMCD-1 fusion protein (pVAX1-Tsmif-Tsmcd-1) or an Ub-co-expressing triple fusion protein Ub–TsMIF–TsMCD-1 (pVAX1-Ub-Tsmif-Tsmcd-1). Control animals were immunized with pVAX1-Ubor blank vector plasmid. Specific antibody levels (IgG, IgG1, IgG2a, IgG2b, IgM, IgA, IgE) against the recombinant proteinTsMIF–TsMCD-1, serum cytokines (interferon (IFN)-γ, interleukin (IL)-4, IL-5, transforming growth factor (TGF)-β1 and IL-17), CD4+/CD8+T cells and cytotoxic T lymphocyte (CTL) responses were monitored. Challenge infection was performed 2 weeks after the second immunization and worm burden was assayed at 35 days post-challenge. Antibody responses induced by pVAX1-Ub-Tsmif-Tsmcd-1were significantly lower than forTsMIF-TsMCD-1, but the vaccine induced increased levels of Th1 cytokine (IFN-γ) and increased T-cell cytotoxicity. The reduction of worm burden (37.95%) following immunization with pVAX1-Ub-Tsmif-Tsmcd-1was significantly greater than that induced by the pVAX1-Tsmif-Tsmcd-1vaccine (23.17%;P< 0.05).

The vitamin D receptor and inducible nitric oxide synthase associated pathways in acquired resistance to Cooperia oncophora infection in cattle

Cooperia oncophora is an economically important gastrointestinal nematode in ruminants. Acquired resistance to Cooperia oncophora infection in cattle develops rapidly as a result of prior infections. Naïve cattle, when given a primary infection of high-dose infective L3 larvae, develop a strong immunity to subsequent reinfection. Compared to primary infection, reinfection resulted in a marked reduction in worm establishment. In order to understand molecular mechanisms underlying the development of acquired resistance, we characterized the transcriptomic responses of the bovine small intestine to a primary infection and reinfection. A total of 23 pathways were significantly impacted during infection. The vitamin D receptor activation was strongly induced only during reinfection, suggesting that this pathway may play an important role in the development of acquired resistance via its potential roles in immune regulation and intestinal mucosal integrity maintenance. The expression of inducible nitric oxide synthase (NOS2) was strongly induced during reinfection but not during primary infection. As a result, several canonical pathways associated with NOS2 were impacted. The genes involved in eicosanoid synthesis, including prostaglandin synthase 2 (PTGS2 or COX2), remained largely unchanged during infection. The rapid development of acquired resistance may help explain the lack of relative pathogenicity by Cooperia oncophora infection in cattle. Our findings facilitate the understanding of molecular mechanisms underlying the development of acquired resistance, which could have an important implication in vaccine design.

Similarity and diversity in macrophage activation by nematodes, trematodes, and cestodes

This review summarizes current knowledge of macrophages in helminth infections, with a focus not only on delineating the striking similarities in macrophage phenotype between diverse infections but also on highlighting the differences. Findings from many different labs illustrate that macrophages in helminth infection can act as anti-parasite effectors but can also act as powerful immune suppressors. The specific role for their alternative (Th2-mediated) activation in helminth killing or expulsion versus immune regulation remains to be determined. Meanwhile, the rapid growth in knowledge of alternatively activated macrophages will require an even more expansive view of their potential functions to include repair of host tissue and regulation of host metabolism.