Helminth antigens modulate TLR-initiated dendritic cell activation

Intestinal helminth infection impairs vaccine-induced T cell responses and protection against SARS-CoV-2 in mice

Although vaccines have reduced the burden of COVID-19, their efficacy in helminth infection-endemic areas is not well characterized. We evaluated the impact of infection by Heligmosomoides polygyrus bakeri (Hpb), a murine intestinal roundworm, on the efficacy of an mRNA vaccine targeting the Wuhan-1 spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in mice. Although immunization generated similar B cell responses in Hpb-infected and uninfected mice, polyfunctional CD4+ and CD8+ T cell responses were markedly reduced in Hpb-infected mice. Hpb-infected and mRNA-vaccinated mice were protected against the ancestral SARS-CoV-2 strain WA1/2020, but control of lung infection was diminished against an Omicron variant compared with animals immunized without Hpb infection. Helminth-mediated suppression of spike protein-specific CD8+ T cell responses occurred independently of signal transducer and activator of transcription 6 (STAT6) signaling, whereas blockade of interleukin-10 (IL-10) rescued vaccine-induced CD8+ T cell responses. Together, these data show that, in mice, intestinal helminth infection impaired vaccine-induced T cell responses through an IL-10 pathway, which compromised protection against antigenically drifted SARS-CoV-2 variants.

Helminth-derived metabolites induce tolerogenic functional, metabolic, and transcriptional signatures in dendritic cells that attenuate experimental colitis

Inflammatory bowel diseases (IBD) are chronic inflammatory diseases in which abdominal pain, bloody diarrhea, weight loss, and fatigue collectively result in diminished quality of patient life. The disappearance of intestinal helminth infections in Western societies is associated with an increased prevalence of IBD and other immune-mediated inflammatory diseases. Evidence indicates that helminths induce tolerogenic dendritic cells (tolDCs), which promote intestinal tolerance and attenuate intestinal inflammation characteristic of IBD, but the exact mechanism is unclear. Helminth-derived excretory-secretory (HES) products including macromolecules, proteins, and polysaccharides have been shown to modulate the antigen presenting function of DCs with down-stream effects on effector CD4 + T cells. Previous studies indicate that DCs in helminth-infected animals induce tolerance to unrelated antigens and DCs exposed to HES display phenotypic and functional features of tolDCs. Here, we identify that nonpolar metabolites (HnpM) produced by a helminth, the murine gastrointestinal nematode Heligmosomoides polygyrus bakeri (Hpb), induce tolDCs as evidenced by decreased LPS-induced TNF and increased IL-10 secretion and reduced expression of MHC-II, CD86, and CD40. Furthermore, these DCs inhibited OVA-specific CD4 + T cell proliferation and induced CD4 + Foxp3 + regulatory T cells. Adoptive transfer of HnpM-induced tolDCs attenuated DSS-induced intestinal inflammation characteristic of IBD. Mechanistically, HnpM induced metabolic and transcriptional signatures in BMDCs consistent with tolDCs. Collectively, our findings provide groundwork for further investigation into novel mechanisms regulating DC tolerance and the role of helminth secreted metabolites in attenuating intestinal inflammation associated with IBD. Summary Sentence: Metabolites produced by Heligmosomoides polygyrus induce metabolic and transcriptional changes in DCs consistent with tolDCs, and adoptive transfer of these DCs attenuated DSS-induced intestinal inflammation.

IFN-γ inhibitory molecules derived from Eimeria maxima inhibit IL-12 secretion by modulating MAPK pathways in chicken macrophages

IFN-γ plays a crucial role in resisting intracellular parasitic protozoa, such as Eimeria species. In our previous study, we identified 4 molecules derived from Eimeria maxima (E. maxima) that significantly inhibited IFN-γ production. However, the mechanism underlying this inhibitory effect remains unknown. In this study, we first investigated the effects of these 4 IFN-γ inhibitory molecules on the expression levels of chicken Toll-like receptors (chTLRs), IL-12, IL-10, TGF-β, and TNF-α in chicken macrophage HD11 and bone marrow-derived dendritic cells (BMDCs). The results demonstrated that these 4 inhibitory molecules significantly downregulated the mRNA levels of chTLR-2, chTLR-4, chTLR-21, and both mRNA and protein levels of IL-12. Subsequently, to clarify the effects of these 4 inhibitory molecules on the IL-12 secretion-related signaling pathways in chicken macrophages, qRT-PCR and Western blot were used to detect the changes of key molecules involved in the signaling pathways of IL-12 secretion (NF-κB, ERK1/2, p38, JNK, STAT3) following coincubation with these inhibitory molecules. Finally, RNAi was employed to verify the function of key molecules in the signaling pathway. The results revealed a significant upregulation in the expression of ERK1/2 phosphorylated protein induced by the 4 inhibitory molecules. Knockdown of the ERK1/2 gene significantly reduced the inhibitory effect of the 4 E. maxima inhibitory molecules on IL-12. These findings indicate that the 4 inhibitory molecules can inhibit the secretion of IL-12 by upregulating the expression of ERK1/2 phosphorylated protein, which is a key molecule in the ERK-MAPK pathway. Our study may contribute to elucidating the mechanisms underlying immune evasion during E. maxima infections, thereby providing new insights for the control of chicken coccidiosis.

Intestinal helminth infection impairs vaccine-induced T cell responses and protection against SARS-CoV-2

Although vaccines have reduced COVID-19 disease burden, their efficacy in helminth infection endemic areas is not well characterized. We evaluated the impact of infection by Heligmosomoides polygyrus bakeri (Hpb), a murine intestinal hookworm, on the efficacy of an mRNA vaccine targeting the Wuhan-1 spike protein of SARS-CoV-2. Although immunization generated similar B cell responses in Hpb-infected and uninfected mice, polyfunctional CD4+ and CD8+ T cell responses were markedly reduced in Hpb-infected mice. Hpb-infected and mRNA vaccinated mice were protected against the ancestral SARS-CoV-2 strain WA1/2020, but control of lung infection was diminished against an Omicron variant compared to animals immunized without Hpb infection. Helminth mediated suppression of spike-specific CD8+ T cell responses occurred independently of STAT6 signaling, whereas blockade of IL-10 rescued vaccine-induced CD8+ T cell responses. In mice, intestinal helminth infection impairs vaccine induced T cell responses via an IL-10 pathway and compromises protection against antigenically shifted SARS-CoV-2 variants.

The regulatory roles of Fasciola hepatica GSTO1 protein in inflammatory cytokine expression and apoptosis in murine macrophages

Fascioliasis, a global zoonotic parasitic disease, is mainly caused by Fasciola hepatica (F. hepatica) parasitizing in the livers of hosts, mainly humans and herbivores. Glutathione S-transferase (GST) is one of the important excretory- secretory products (ESPs) from F. hepatica, however, the regulatory roles of its Omega subtype in the immunomodulatory effects remain unknown. Here, we expressed F. hepatica recombinant GSTO1 protein (rGSTO1) in Pichia pastoris and analyzed its antioxidant properties. Then, the interaction between F. hepatica rGSTO1 and RAW264.7 macrophages and its effects on inflammatory responses and cell apoptosis were further explored. The results revealed that GSTO1 of F. hepatica owned the potent ability to resist oxidative stress. F. hepatica rGSTO1 could interact with RAW264.7 macrophages and inhibit its cell viability, furthermore, it may suppress the production of pro-inflammatory cytokines IL-1β, IL-6 and TNF-α, but promote the expression of anti-inflammatory cytokine IL-10. In addition, F. hepatica rGSTO1 may down-regulate the ratio of Bcl-2/Bax, and increase the expression of pro-apoptotic protein caspase-3, thereby eliciting the apoptosis of macrophages. Notably, F. hepatica rGSTO1 inhibited the activation of nuclear factor-κB (NF-κB) and mitogen‑activated protein kinases (MAPKs p38, ERK and JNK) pathways in LPS-activated RAW264.7 cells, exerting potent modulatory effects on macrophages. These findings suggested that F. hepatica GSTO1 can modulate the host immune response, which provided new insights into the immune evasion mechanism of F. hepatica infection in host.

Lymph node-resident dendritic cells drive TH2 cell development involving MARCH1

Type 2 T helper (TH2) cells are protective against parasitic worm infections but also aggravate allergic inflammation. Although the role of dendritic cells (DCs) in TH2 cell differentiation is well established, the underlying mechanisms are largely unknown. Here, we show that DC induction of TH2 cells depends on membrane-associated RING-CH-1 (MARCH1) ubiquitin ligase. The pro-TH2 effect of MARCH1 relied on lymph node (LN)–resident DCs, which triggered T cell receptor (TCR) signaling and induced GATA-3 expression from naïve CD4+ T cells independent of tissue-driven migratory DCs. Mice with mutations in the ubiquitin acceptor sites of MHCII and CD86, the two substrates of MARCH1, failed to develop TH2 cells. These findings suggest that TH2 cell development depends on ubiquitin-mediated clearance of antigen-presenting and costimulatory molecules by LN-resident DCs and consequent control of TCR signaling.

Opisthorchis viverrini antigens up-regulates the expression of CD80 and MHC class II in JAWSII mouse dendritic cells and promotes IL-10 and TGF-β secretions

Dendritic cells (DCs) are antigen-presenting cells (APC) involved in the initiation of immune responses. Maturation of DCs is characterized by the high expression of major histocompatibility complex (MHC) class II and co-stimulatory clusters of differentiation (CD) 40, CD80, and CD86 molecules. Matured DCs are required for T cell differentiation and proliferation. However, the response of DCs to Opisthorchis viverrini antigens has not yet been understood. Therefore, this study sought to determine the expression of surface molecules of JAWSII mouse DCs stimulated by crude somatic (CS) and excretory-secretory (ES) antigens of O. viverrini. ES antigen significantly induced only mRNA expression of CD80 and MHC class II in JAWSII mouse DCs, while CS antigen promoted up-regulation of both mRNA and protein levels of CD80 and MHC class II, indicating relative maturation of JAWII mouse DCs. Moreover, the secreted cytokines from the co-cultures of O. viverrini antigens stimulated JAWSII DC with naïve CD4⁺ T cells was determined. Significantly increased levels of immunosuppressive cytokines interleukin (IL)-10 and transforming growth factor beta (TGF-β) were found. The up-regulation of these cytokines may indicate the response of regulatory T cells (Treg) to CS antigen-stimulated JAWSII DC. These findings may lead to a better understanding of the role that DCs play in O. viverrini infection.

Immunohistological detection of small particles of Echinococcus multilocularis and Echinococcus granulosus in lymph nodes is associated with enlarged lymph nodes in alveolar and cystic echinococcosis

BACKGROUND

Alveolar (AE) and cystic echinococcosis (CE) in humans are caused by the metacestode of the tapeworms Echinococcus multilocularis and Echinococcus granulosus sensu lato (s.l.). Immunohistochemistry with the monoclonal antibodies (mAb) Em2G11, specific for AE, and the mAb EmG3, specific for AE and CE, is an important pillar of the histological diagnosis of these two infections. Our aim was to further evaluate mAb EmG3 in a diagnostic setting and to analyze in detail the localization, distribution, and impact of small particles of Echinococcus multilocularis (spems) and small particles of Echinococcus granulosus s.l. (spegs) on lymph nodes.

METHODOLOGY/PRINCIPAL FINDINGS

We evaluated the mAb EmG3 in a cohort of formalin-fixed, paraffin embedded (FFPE) specimens of AE (n = 360) and CE (n = 178). These samples originated from 156 AE-patients and 77 CE-patients. mAb EmG3 showed a specific staining of the metacestode stadium of E. multilocularis and E. granulosus s.l. and had a higher sensitivity for spems than mAb Em2G11. Furthermore, we detected spegs in the surrounding host tissue and in almost all tested lymph nodes (39/41) of infected patients. 38/47 lymph nodes of AE showed a positive reaction for spems with mAb EmG3, whereas 29/47 tested positive when stained with mAb Em2G11. Spegs were detected in the germinal centers, co-located with CD23-positive follicular dendritic cells, and were present in the sinuses. Likewise, lymph nodes with spems and spegs in AE and CE were significantly enlarged in size in comparison to the control group.

CONCLUSIONS/SIGNIFICANCE

mAb EmG3 is specific for AE and CE and is a valuable tool in the histological diagnosis of echinococcosis. Based on the observed staining patterns, we hypothesize that the interaction between parasite and host is not restricted to the main lesion since spegs are detected in lymph nodes. Moreover, in AE the number of spems-affected lymph nodes is higher than previously assumed. The enlargement of lymph nodes with spems and spegs points to an immunological interaction with the small immunogenic particles (spems and spegs) of Echinococcus spp.

DC-SIGN signalling induced by Trichinella spiralis products contributes to the tolerogenic signatures of human dendritic cells

Tolerogenic dendritic cells (tolDCs) are central players in the maintenance of immune tolerance and thereby have been identified as the most favourable candidates for cell therapy of autoimmune diseases. We have recently shown that excretory-secretory products (ES L1) released by Trichinella spiralis larvae induce stable human tolDCs in vitro via Toll-like receptor 2 (TLR2) and TLR4. However, engagement of these receptors did not fully explain the tolerogenic profile of DCs. Here, we observed for the first time that dendritic cell-specific ICAM-3 grabbing non-integrin (DC-SIGN) interacts with highly glycosylated ES L1 and contributes to the generation of ES L1-induced tolDCs. Blocking DC-SIGN interfered with the ES L1-induced higher expression of CD40 and CCR7 and the production of IL-10 and TGF-β by DCs. The cooperation of TLR2, TLR4 and DC-SIGN receptors is of importance for the capacity of DCs to prime T cell response toward Th2 and to induce expansion of CD4+CD25+Foxp3+ T cells, as well as for the production of IL-10 and TGF-β by these cells. Overall, these results indicate that induction of tolDCs by ES L1 involves engagement of multiple pattern recognition receptors namely, TLR2, TLR4 and DC-SIGN.

Defined Intestinal Regions Are Drained by Specific Lymph Nodes That Mount Distinct Th1 and Th2 Responses Against Schistosoma mansoni Eggs

The balance of type 1 and type 2 immune responses plays a crucial role in anti-helminth immunity and can either support chronic infection or drive type 2 mediated expulsion of the parasite. Helminth antigens and secreted molecules directly influence this balance and induce a favorable immunological environment for the parasite’s survival. However, less is known if the site of infection also influences the balance of type 1 and type 2 immunity. Here, we report that tissue-specific immune responses are mounted against helminth antigens, which elicited strong IL-4 responses when injected into the skin, while the same antigen, delivered into the intestinal subserosa, induced increased IFN-γ and reduced Th2 responses. Immune responses in individual mesenteric lymph nodes that drain defined regions of the intestine furthermore displayed a site-specific pattern of type 1 and type 2 immunity after Schistosoma mansoni or Heligmosomoides polygyrus infection. S. mansoni egg-specific Th2 responses were detectable in all mesenteric lymph nodes but Th1 responses were only present in those draining the colon, while H. polygyrus infection elicited mixed Th1 and Th2 responses in the lymph nodes associated with the site of infection. Similar site-specific type 1 and type 2 immune responses were observed in the draining lymph nodes after the controlled delivery of S. mansoni eggs into different segments of the small and large intestine using microsurgical techniques. Different subsets of intestinal dendritic cells were hereby responsible for the uptake and priming of Th1 and Th2 responses against helminth antigens. Migratory CD11b⁺CD103⁻ and especially CD11b⁺CD103⁺ DC2s transported S. mansoni egg antigens to the draining lymph nodes to induce Th1 and Th2 responses, while CD103⁺ DC1s induced only IFN-γ responses. In contrast, H. polygyrus antigens were predominantly transported by CD11b⁺CD103⁻ DC2s and CD103⁺ DC1s and all DC subsets induced similar Th1 but weaker Th2 responses, compared to S. mansoni egg antigens. The development of adaptive anti-helminth immune responses is therefore influenced by the antigen itself, the uptake and priming characteristics of antigen-positive dendritic cell subsets and the site of infection, which shape the level of Th1 and Th2 responses in order to create a favorable immunological environment for the parasite.

Parasite-bacteria interrelationship

Parasites and bacteria have co-evolved with humankind, and they interact all the time in a myriad of ways. For example, some bacterial infections result from parasite-dwelling bacteria as in the case of Salmonella infection during schistosomiasis. Other bacteria synergize with parasites in the evolution of human disease as in the case of the interplay between Wolbachia endosymbiont bacteria and filarial nematodes as well as the interaction between Gram-negative bacteria and Schistosoma haematobium in the pathogenesis of urinary bladder cancer. Moreover, secondary bacterial infections may complicate several parasitic diseases such as visceral leishmaniasis and malaria, due to immunosuppression of the host during parasitic infections. Also, bacteria may colonize the parasitic lesions; for example, hydatid cysts and skin lesions of ectoparasites. Remarkably, some parasitic helminths and arthropods exhibit antibacterial activity usually by the release of specific antimicrobial products. Lastly, some parasite-bacteria interactions are induced as when using probiotic bacteria to modulate the outcome of a variety of parasitic infections. In sum, parasite-bacteria interactions involve intricate processes that never cease to intrigue the researchers. However, understanding and exploiting these interactions could have prophylactic and curative potential for infections by both types of pathogens.

Schistosoma egg antigens suppress LPS-induced inflammation in human IMR-90 cells by modulation of JAK/STAT1 signaling

BACKGROUND

The regulation of the balance between inflammatory and anti-inflammatory events during the treatment of pulmonary infection is very important. Soluble Schistosoma egg antigens (SEA) can effectively inhibit the expression of cytokines during hepatic acute inflammation. However, the mechanisms by which these proteins suppress the inflammatory responses in lung cells remain unclear. The purpose of this study was to investigate the ability of SEA to inhibit pulmonary inflammation.

METHODS

The effects of SEA were investigated in LPS-treated lung IMR-90 cells. The involvement of the JAK/STAT-1 signaling pathway in these effects was evaluated by employing CBA assays, quantitative polymerase chain reaction, and western blotting experiments.

RESULTS

Pretreatment of IMR-90 cells with appropriate concentrations of SEA protected cells against the cytotoxic effects of LPS-induced inflammation in a time-dependent manner. SEA pretreatment significantly attenuated the LPS-induced activation of the JAK/STAT1 signaling pathway, including the upregulation of JAK1/2 and STAT1, as well as the production of inflammatory cytokines. The level of phosphorylated STAT1 gradually declined in response to increasing concentrations of SEA. Based on these findings, we hypothesize that SEA-induced anti-inflammatory effects initiate with the downregulation of the IFN-γ-JAK-STAT1 signaling pathway, resulting in the attenuation of LPS-induced inflammation in IMR-90 cells.

CONCLUSION

Our study is the first to demonstrate the anti-inflammatory activity of SEA in an in vitro model of pulmonary inflammation, involving the modulation of JAK/STAT1 signaling. We propose SEA as potential therapeutic or preventive agents for the selective suppression of STAT1 and the control of inflammatory response in lung IMR-90 cells.

Schistosoma mansoni soluble egg antigen (SEA) and recombinant Omega-1 modulate induced CD4+ T-lymphocyte responses and HIV-1 infection in vitro

Parasitic helminths evade, skew and dampen human immune responses through numerous mechanisms. Such effects will likely have consequences for HIV-1 transmission and disease progression. Here we analyzed the effects that soluble egg antigen (SEA) from Schistosoma mansoni had on modulating HIV-1 infection and cytokine/chemokine production in vitro. We determined that SEA, specifically through kappa-5, can potently bind to DC-SIGN and thereby blocks DC-SIGN mediated HIV-1 trans-infection (p<0.05) whilst not interfering with cis-infection. DCs exposed to SEA whilst maturing under Th2 promoting conditions, will upon co-culture with naïve T-cells induce a T-cell population that was less susceptible to HIV-1 R5 infection (p<0.05) compared to DCs unexposed to SEA, whereas HIV-1 X4 virus infection was unaffected. This was not observed for DCs exposed to SEA while maturing under Th1 or Th1/Th2 (T_mix) promoting conditions. All T-cell populations induced by SEA exposed DCs demonstrate a reduced capacity to produce IFN-γ and MIP-1β. The infection profile of T-cells infected with HIV-1 R5 was not associated with down-modulation of CCR5 cell surface expression. We further show that DCs maturing under T_mix conditions exposed to plant recombinant omega-1 protein (rω-1), which demonstrates similar functions to natural ω-1, induced T-cell populations that were less sensitive for HIV-1 R5 infection (p<0.05), but not for X4 virus infection. This inhibition associated again with a reduction in IFN-γ and MIP-1β expression, but additionally correlated with reduced CCR5 expression. We have shown that SEA parasite antigens and more specifically rω-1 can modulate HIV-1 infectivity with the potential to influence disease course in co-infected individuals.

Parasitic helminths have developed a number of strategies to evade, skew and dampen human immune responses. Such effects will likely have consequences for HIV-1 transmission and disease progression. Here we analyzed the effect that soluble egg antigen (SEA) from Schistosoma mansoni had on HIV-1 infection in vitro. We determined that SEA, through kappa-5, can potently block DC-SIGN mediated HIV-1 trans-infection of CD4⁺ T-lymphocytes, but not block cis-infection. Dendritic cells (DC) exposed to SEA during maturation under Th2 skewing conditions, induce T-cell populations that are less susceptible to HIV-1 R5 infection compared to cells induced by unexposed DCs. HIV-1 X4 infection was unaffected. This restricted infection profile was not associated with down-modulation of CCR5 surface expression or observed differences in cytokine/chemokine production. Using recombinant omega-1, an abundant component of SEA, HIV-1 R5 infection was similarly inhibited with no effect on HIV-1 X4 infection levels. Hence SEA possesses antigens, namely omega-1, that can modulate HIV-1 infection and potentially influence disease course in co-infected individuals.

Tuftsin-phosphorylcholine (TPC) equally effective to methylprednisolone in ameliorating lupus nephritis in a mice model

The role of helminth treatment in autoimmune diseases is growing constantly. Systemic lupus erythematosus (SLE) is a multi-system autoimmune disease with challenging treatment options. Tuftsin-phosphorylcholine (TPC) is a novel helminth-based compound that modulates the host immune network. This study was conducted to evaluate the potential value of TPC in ameliorating lupus nephritis in a murine model and specifically to compare the efficacy of TPC to the existing first-line therapy for SLE: corticosteroids (methylprednisolone). Lupus-prone NZBxW/F₁ mice were treated with TPC (5 µg/mouse), methylprednisolone (MP; 5 mg/body weight) or phosphate-buffered saline (PBS) (control) three times per week once glomerulonephritis, defined as proteinuria of grade > 100 mg/dl, was established. Levels of anti-dsDNA autoantibodies were evaluated by enzyme-linked immunosorbent assay (ELISA), splenic cytokines were measured in vitro and the kidney microscopy was analysed following staining. TPC and MP treatments improved lupus nephritis significantly and prolonged survival in NZBxW/F₁ mice. TPC-treated mice showed a significantly decreased level of proteinuria (P < 0·001) and anti-dsDNA antibodies (P < 0·001) compared to PBS-treated mice. Moreover, TPC and MP inhibited the production of the proinflammatory cytokines interferon IFN-γ, interleukin IL-1β and IL-6 (P < 0·001) and enhanced expression of the anti-inflammatory cytokine IL-10 (P < 0·001). Finally, microscopy analysis of the kidneys demonstrated that TPC-treated mice maintained normal structure equally to MP-treated mice. These data indicate that the small molecule named TPC hinders lupus development in genetically lupus-prone mice equally to methylprednisolone in most of the cases. Hence, TCP may be employed as a therapeutic potential for lupus nephritis.

Glycans in the roles of parasitological diagnosis and host-parasite interplay

The investigation of the glycan repertoire of several organisms has revealed a wide variation in terms of structures and abundance of glycan moieties. Among the parasites, it is possible to observe different sets of glycoconjugates across taxa and developmental stages within a species. The presence of distinct glycoconjugates throughout the life cycle of a parasite could relate to the ability of that organism to adapt and survive in different hosts and environments. Carbohydrates on the surface, and in excretory-secretory products of parasites, play essential roles in host-parasite interactions. Carbohydrate portions of complex molecules of parasites stimulate and modulate host immune responses, mainly through interactions with specific receptors on the surface of dendritic cells, leading to the generation of a pattern of response that may benefit parasite survival. Available data reviewed here also show the frequent aspect of parasite immunomodulation of mammalian responses through specific glycan interactions, which ultimately makes these molecules promising in the fields of diagnostics and vaccinology.

Effect of Schistosoma mansoni infection and its treatment on antibody responses to measles catch-up immunisation in pre-school children: A randomised trial

BACKGROUND

Schistosoma infection is associated with immune modulation that can influence responses to non-schistosome antigens. Vaccine responses may be impaired in S. mansoni-infected individuals. We investigated effects of S. mansoni infection on responses to childhood measles catch-up immunisation and of praziquantel treatment on this outcome in a randomised trial.

METHODOLOGY

The Immune Modulation and Childhood Immunisation (IMoChI) study was based in Entebbe, Uganda. Children aged 3-5 years (193 S. mansoni-infected and 61 uninfected) were enrolled. Infected children were randomised in a 1:1:1 ratio to receive praziquantel 2 weeks before, at time of, or 1 week after, measles catch-up immunisation. Plasma anti-measles IgG was measured at enrolment, 1 week and 24 weeks after measles immunisation. Primary outcomes were IgG levels and percentage of participants with levels considered protective against measles.

RESULTS

Anti-measles IgG levels increased following immunisation, but at 1 week post-immunisation S. mansoni-infected, compared to uninfected, children had lower levels of anti-measles IgG (adjusted geometric mean ratio (aGMR) 0.4 [95% CI 0.2-0.7]) and the percentage with protective antibody levels was also lower (adjusted odds ratio 0.1 [0-0.9]). Among S. mansoni-infected children, anti-measles IgG one week post-immunisation was higher among those treated with praziquantel than among those who were not yet treated (treatment before immunisation, aGMR 2.3 [1.5-4.8]; treatment at immunisation aGMR 1.8 [1.1-3.5]). At 24 weeks post-immunisation, IgG levels did not differ between the trial groups, but tended to be lower among previously-infected children who were still S mansoni stool-positive than among those who became stool-negative.

CONCLUSIONS AND SIGNIFICANCE

Our findings suggest that S. mansoni infection among pre-school children is associated with a reduced antibody response to catch-up measles immunisation, and that praziquantel treatment improves the response. S. mansoni infection may contribute to impaired vaccine responses in endemic populations; effective schistosomiasis control may be beneficial for vaccine efficacy. This should be further explored.

TRIAL REGISTRATION

ISRCTN87107592.

Hepatoprotective immune response during Trichinella spiralis infection in mice

Infections with gastrointestinal nematodes provoke immune and inflammatory responses mediated by cytokines released from T-helper type-2 (Th2) cells. Infections with Trichinella species have been reported to differ by the host species. Previously, in rats, we observed acute liver inflammation in response to infection with Trichinella spiralis, and the rat hosts showed a series of biochemical changes characterized by a decrease in serum paraoxonase (PON) 1 activity associated with the down-regulation of hepatic PON1 synthesis. In the present study, we investigated the effect(s) of species differences on the immune response against T. spiralis infection by analyzing serum PON1 activity and the associated inflammatory/anti-inflammatory mediators in mice. There were inconsistent changes in the serum PON1 activity of mice infected with T. spiralis, and these changes were associated with significant increases in the serum levels of interleukin (IL)-2, IL-4, IL-10, IL-12 (p70), granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor α during the enteric phase of the infection, while the levels of IL-5 and interferon γ were significantly increased throughout the entire experimental period. Moreover, T. spiralis infection in mice was associated with little inflammatory cell infiltration in hepatic tissues. Given the zoonotic prevalence of T. spiralis, further mechanistic research in this area is warranted.

Maternal helminth infections and the shaping of offspring immunity

Helminth infections leave a long-lasting immunological footprint on their hosts. Clinical studies have provided first evidence that maternal helminth infections can result in an altered immune profile in their offspring which can potentially shape how they respond to conditions throughout life. This can relate to changes in offspring induction of immune responses against other diseases. However, whether these changes result in actual changes in offspring ability to control disease is unclear. Our understanding of which immune mechanisms are altered and how they are changed is limited. In this review, we highlight what we know from human and mouse studies about this important context of helminth exposure. Moreover, we discuss how mechanisms such as antibody transfer, antigen exposure, maternal cell uptake, chimerism and epigenetics are all likely to be functional contributors to the striking changes that are seen in offspring born or nursed by helminth exposed mothers.

Immunomodulation by Helminths: Intracellular Pathways and Extracellular Vesicles

Helminth parasites are masters at manipulating host immune responses, using an array of sophisticated mechanisms. One of the major mechanisms enabling helminths to establish chronic infections is the targeting of pattern recognition receptors (PRRs) including toll-like receptors, C-type lectin receptors, and the inflammasome. Given the critical role of these receptors and their intracellular pathways in regulating innate inflammatory responses, and also directing adaptive immunity toward Th1 and Th2 responses, recognition of the pathways triggered and/or modulated by helminths and their products will provide detailed insights about how helminths are able to establish an immunoregulatory environment. However, helminths also target PRRs-independent mechanisms (and most likely other yet unknown mechanisms and pathways) underpinning the battery of different molecules helminths produce. Herein, the current knowledge on intracellular pathways in antigen presenting cells activated by helminth-derived biomolecules is reviewed. Furthermore, we discuss the importance of helminth-derived vesicles as a less-appreciated components released during infection, their role in activating these host intracellular pathways, and their implication in the development of new therapeutic approaches for inflammatory diseases and the possibility of designing a new generation of vaccines.

Silent Witness: Dual-Species Transcriptomics Reveals Epithelial Immunological Quiescence to Helminth Larval Encounter and Fostered Larval Development

Gastrointestinal nematodes are among the most prevalent parasites infecting humans and livestock worldwide. Infective larvae of the soil-transmitted nematode Ascaris spp. enter the host and start tissue migration by crossing the intestinal epithelial barrier. The initial interaction of the intestinal epithelium with the parasite, however, has received little attention. In a time-resolved interaction model of porcine intestinal epithelial cells (IPEC-J2) and infective Ascaris suum larvae, we addressed the early transcriptional changes occurring simultaneously in both organisms using dual-species RNA-Seq. Functional analysis of the host response revealed an overall induction of metabolic activity, without induction of immune responsive genes or immune signaling pathways and showing suppression of chemotactic genes like CXCL8/IL-8 or CHI3L1. Ascaris larvae, when getting in contact with the epithelium, showed induction of genes that orchestrate motor activity and larval development, such as myosin, troponin, myoglobin, and protein disulfide isomerase 2 (PDI-2). In addition, excretory-secretory products that likely facilitate parasite invasion were increased, among them, aspartic protease 6 or hyaluronidase. Integration of host and pathogen data in an interspecies gene co-expression network indicated links between nematode fatty acid biosynthesis and host ribosome assembly/protein synthesis. In summary, our study provides new molecular insights into the early factors of parasite invasion, while at the same time revealing host immunological unresponsiveness. Reproducible software for dual RNA-Seq analysis of non-model organisms is available at https://gitlab.com/mkuhring/project_asuum and can be applied to similar studies.

Modulation of dendritic cell by pathogen antigens: Where do we stand?

Dendritic cells (DCs) are essential players in the activation of T cells and in the development of adaptive immune response towards invading pathogens. Upon antigen (Ag) recognition of Pathogen Associated Molecular Patterns (PAMPs) by their receptors (PRRs), DCs are activated and acquire an inflammatory profile. DCs have the ability to direct the profile of helper T (Th) cells towards Th1, Th2, Th17, Th9 and regulatory (Treg) cells. Each subset of Th cells presents a unique gene expression signature and is endowed with the ability to conduct or suppress effector cells in inflammation. Pathogens target DCs during infection. Many studies demonstrated that antigens and molecules derived from pathogens have the ability to dampen DC maturation and activation, leading these cells to a permissive state or tolerogenic profile (tolDCs). Although tolDCs may represent a hindrance in infection control, they could be positively used to modulate inflammatory disorders, such as autoimmune diseases. In this review, we focus on discussing findings that use pathogen-antigen modulated DCs and tolDCs in prophylactics and therapeutics approaches for vaccination against infectious diseases or inflammatory disorders.

TLR Specific Immune Responses against Helminth Infections

Despite marked improvement in the quality of lives across the globe, more than 2 million individuals in socioeconomically disadvantaged environments remain infected by helminth (worm) parasites. Owing to the longevity of the worms and paucity of immunologic controls, these parasites survive for long periods within the bloodstream, lymphatics, and gastrointestinal tract resulting in pathologic conditions such as anemia, cirrhosis, and lymphatic filariasis. Despite infection, an asymptomatic state may be maintained by the host immunoregulatory environment, which involves multiple levels of regulatory cells and cytokines; a breakdown of this regulation is observed in pathological disease. The role of TLR expression and function in relation to intracellular parasites has been documented but limited studies are available for multicellular helminth parasites. In this review, we discuss the unique and shared host effector mechanisms elicited by systemic helminth parasites and their derived products, including the role of TLRs and sphingolipids. Understanding and exploiting the interactions between these parasites and the host regulatory network are likely to highlight new strategies to control both infectious and immunological diseases.

Composition of the Schistosoma mansoni worm secretome: Identification of immune modulatory Cyclophilin A

The helminth Schistosoma mansoni modulates the infected host's immune system to facilitate its own survival, by producing excretory/secretory molecules that interact with a variety of the host's cell types including those of the immune system. Herein, we characterise the S. mansoni adult male worm secretome and identify 111 proteins, including 7 vaccine candidates and several molecules with potential immunomodulatory activity. Amongst the molecules present in the secretome, a 17-19kDa protein analogous to human cyclophilin A was identified. Given the ability of cyclophilin A to modulate the immune system by regulating antigen presenting cell activity, we sought to determine whether recombinant S. mansoni Cyclophilin A (rSmCypA) is capable of modulating bone-marrow derived dendritic cell (BMDC) and T cell responses under in vitro conditions. rSmCypA was enzymatically active and able to alter the pro-inflammatory cytokine profile of LPS-activated dendritic cells. rSmCypA also modulated DC function in the induction of CD4+ T cell proliferation with a preferential expansion of Treg cells. This work demonstrates the unique protein composition of the S. mansoni male worm secretome and immunomodulatory activity of S. mansoni Cyclophilin A.

Lipopolysaccharide-induced acute lung injury in mice chronically infected by Schistosoma mansoni

We used a murine model of Schistosoma mansoni (SM) infection and lipopolysaccharide (LPS)-induced endotoxicity to investigate if these conditions can interact to modify the pathological manifestations typically observed in each condition. Swiss mice were randomized into four groups: SAL, uninfected; SM, infected; LPS, uninfected + LPS; and SM + LPS, infected + LPS. S. mansoni infection developed over 120 days, after which blood samples and lungs were collected, peritoneal leukocytes were isolated and cultivated for 6 and 24 h after LPS inoculation (1 mL/kg). Infected animals presented marked granulomatous inflammation. LPS exposure transiently modified the profile of leucocyte migration into the lung tissue and increased NO production by isolated leukocytes, without inducing any acute effect on the structure of schistosomiasis granulomas. Beyond modifying lung morphology, S. mansoni and LPS interacted to modulate the circulating levels of cytokines. S. mansoni infection restricted INF-γ upregulation 6 and 24 h after LPS administration. Conversely, 24 h after inoculation, LPS increased IL-2 and IL-5 levels. Our findings indicate that LPS impaired the lung microenvironment by acutely disrupting inflammatory homeostatic mechanisms that control lung schistosomiasis. As schistosomiasis develops as a chronic condition, long-term exposure to endotoxins could aggravate the granulomatous process, an issue that requires further investigation.

The impact of environmental infections (parasites) on MS activity

MS incidence has significantly increased during the second half of the 20th century, generating considerable interest in analyzing the basis for this rise in the developed world. Particular emphasis is being placed on the role infections might play in exacerbating or preventing disease onset. Epidemiological data suggest that improvement in sanitation conditions and reduced exposure to infection might explain, at least in part, these changes. The hygiene hypothesis is not new and is currently used to explain the increasing incidence of allergies and other autoimmune diseases. Because helminths are powerful modulators of host immunity, some authors hypothesize that reduced parasite exposure due to improved hygiene conditions may favor MS development. We discuss epidemiological, experimental, clinical and molecular data supporting the protective role of helminthes against MS. Better understanding of host–parasite interactions caused by specific parasite molecules with immunomodulatory effects will help combat allergies and autoimmune disease without the price of untoward infection as a side-effect.

Immune responses to fungal aeroallergen in Heligmosomoides polygyrus-infected mice vary by age

Parasite infections in the developing world have been considered to promote resistance to immune-mediated diseases such as asthma. Mouse studies have shown that helminths and their products reduce the development of allergic asthma. Since epidemiologic studies that show similar protection are in relation to geohelminth infections that occur in early life, we hypothesized that the parasite-mediated protection against asthma may differ by age. Mice infected with Heligmosomoides polygyrus at 3-weeks of age had similar asthma phenotype compared to mice infected at 28-weeks of age wherein airway eosinophilia was unaltered but tissue inflammation and GC metaplasia were reduced. In contrast, mice infected at 18-weeks of age had elevated macrophagic airway inflammation with accompanying tissue pathology. The presence of γδ T cells and T_reg cells in the airways was also regulated by age at worm infection. Our findings demonstrate the importance of age in immune responses that may regulate gut and lung diseases.

Fasciola hepatica glycoconjugates immuneregulate dendritic cells through the Dendritic Cell-Specific Intercellular adhesion molecule-3-Grabbing Non-integrin inducing T cell anergy

Dendritic cell-specific ICAM-3 grabbing non-integrin (DC-SIGN) expressed on a variety of DCs, is a C-type lectin receptor that recognizes glycans on a diverse range of pathogens, including parasites. The interaction of DC-SIGN with pathogens triggers specific signaling events that modulate DC-maturation and activity and regulate T-cell activation by DCs. In this work we evaluate whether F. hepatica glycans can immune modulate DCs via DC-SIGN. We demonstrate that DC-SIGN interacts with F. hepatica glycoconjugates through mannose and fucose residues. We also show that mannose is present in high-mannose structures, hybrid and trimannosyl N-glycans with terminal GlcNAc. Furthermore, we demonstrate that F. hepatica glycans induce DC-SIGN triggering leading to a strong production of TLR-induced IL-10 and IL-27p28. In addition, parasite glycans induced regulatory DCs via DC-SIGN that decrease allogeneic T cell proliferation, via the induction of anergic/regulatory T cells, highlighting the role of DC-SIGN in the regulation of innate and adaptive immune responses by F. hepatica. Our data confirm the immunomodulatory properties of DC-SIGN triggered by pathogen-derived glycans and contribute to the identification of immunomodulatory glyans of helminths that might eventually be useful for the design of vaccines against fasciolosis.

Characterization of Schistosoma japonicum CP1412 protein as a novel member of the ribonuclease T2 molecule family with immune regulatory function

Background

Schistosome infection typically induces a polarized Th2 type host immune response. As egg antigen molecules play key roles in this immunoregulatory process, clarifying their functions in schistosomiasis would facilitate the development of vaccine and immunotherapeutic methods. Schistosoma japonicum (Sj) CP1412 (GenBank: AY57074.1) has been identified as a new member of the RNase T2 family with immune regulatory functions.

Methods

The expression plasmid Sj CP1412-pET28a was constructed and transformed into bacteria for production of recombinant Sj CP1412 protein (rSj CP1412) via IPTG induction. The RNase activity of Sj CP1412 was predicted by bioinformatic analysis and confirmed by digesting the yeast tRNA with rSj CP1412.C57BL/6j mice were immunized with rSj CP1412, and its immune regulatory effects in vivo and in vitro were investigated. Meanwhile, the relationship between the RNase activity of Sj CP1412 and its immune regulation was observed.

Results

Sj CP1412 was confirmed as a novel RNase T2 family protein with RNase activity. Immunoblotting and RT-PCR analyses demonstrated Sj CP1412 as a protein exclusively secreted/excreted from eggs, but not cercariae and adult worms. Stimulating RAW264.7 macrophages with rSj CP1412 raised the expression of CD206, Arg-1 and IL-10, which are related to M2 type macrophage differentiation. Stimulating dendritic cells (DCs) with rSjCP1412 failed to induce their maturation, and the recombinant protein also inhibited LPS-stimulated DC maturation. Depletion of Sj CP1412 from soluble egg antigen (SEA) impaired the ability of SEA to induce M2 type polarization of RAW264.7 macrophages. Immunizing mice with rSj CP1412 induced high antibody titers, increased serum IL-4 and TGF-β levels and splenic CD4 + CD25 + Foxp3 + T cells, downregulated serum IFN-γ levels and alleviated the egg granuloma pathology of schistosome infection. In vitro stimulation by rSj CP1412 significantly increased CD4 + CD25 + Foxp3 + T cell numbers in splenocytes of healthy mice. The rSj CP1412 protein with RNase activity inactivated by DEPC failed to induce M2 surface marker CD206 expression in RAW264.7 macrophages.

Conclusions

The Sj CP1412 protein expressed specifically in S. japonicum eggs is a novel member of the RNase T2 family. Similar to Omega-1 of Schistosoma mansoni, the Sj CP1412 protein drives polarization of the host Th2 immune response, which is dependent on its RNase activity. These data provide new evidence towards understanding the immune regulatory role of RNase T2 family proteins during schistosome infection.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1962-y) contains supplementary material, which is available to authorized users.

A mucin-like peptide from Fasciola hepatica instructs dendritic cells with parasite specific Th1-polarizing activity

Fasciolosis is a trematode zoonosis of interest in public health and cattle production. We report here the immunostimulatory effect of a 66 mer mucin-like peptide from Fasciola hepatica (Fhmuc), which synergizes with lipopolysaccharide (LPS) to promote dendritic cell (DC) maturation, endowing these cells with Th1-polarizing capacity. Exposure of DCs to Fhmuc in presence of LPS induced enhanced secretion of pro-inflammatory cytokines and expression of co-stimulatory molecules by DCs, promoting their T cell stimulatory capacity and selectively augmenting IFN-γ secretion by allogeneic T cells. Furthermore, exposure of DCs to Fhmuc augmented LPS-induced Toll-like receptor (TLR) 4 expression on the cell surface. Finally, Fhmuc-conditioned DCs induced parasite specific-adaptive immunity with increased levels of IFN-γ secreted by splenocytes from vaccinated animals, and higher parasite-specific IgG antibodies. However, Fhmuc-treated DC conferred modest protection against F. hepatica infection highlighting the potent immuno-regulatory capacity of the parasite. In summary, this work highlights the capacity of a mucin-derived peptide from F. hepatica to enhance LPS-maturation of DCs and induce parasite-specific immune responses with potential implications in vaccination and therapeutic strategies.

Functional Impairment of Murine Dendritic Cell Subsets following Infection with Infective Larval Stage 3 of Brugia malayi

Filarial parasites cause functional impairment of host dendritic cells (DCs). However, the effects of early infection on individual DC subsets are not known. In this study, we infected BALB/c mice with infective stage 3 larvae of the lymphatic filarial parasite Brugia malayi (Bm-L3) and studied the effect on fluorescence-activated cell sorter (FACS)-sorted DC subsets. While myeloid DCs (mDCs) accumulated by day 3 postinfection (p.i.), lymphoid DCs (LDCs) and CD8⁺ plasmacytoid DCs (pDCs) peaked at day 7 p.i. in the spleens and mesenteric lymph nodes (mLNs) of infected mice. Increased tumor necrosis factor alpha (TNF-α) but reduced interleukin 12 (IL-12) and Toll-like receptor 4 (TLR4), -6, and -9 and reciprocal secretion of IL-4 and IL-10 were also observed across all DC subsets. Interestingly, Bm-L3 increased the expression of CD80 and CD86 across all DC subsets but decreased that of major histocompatibility complex class II (MHC-II) on mDCs and pDCs, resulting in their impaired antigen uptake and presentation capacities, but maximally attenuated the T-cell proliferation capacity of only mDCs. Furthermore, Bm-L3 increased phosphorylated p38 (p-p38), but not p-ERK, in mDCs and LDCs but downregulated them in pDCs, along with differential modulation of protein tyrosine phosphatases SHP-1, TCPTP, PTEN, and PTP1B across all DC subsets. Taken together, we report hitherto undocumented effects of early Bm-L3 infection on purified host DC subsets that lead to their functional impairment and attenuated host T-cell response.

Inhibition of cytokine response to TLR stimulation and alleviation of collagen-induced arthritis in mice by Schistosoma japonicum peptide SJMHE1

Helminth‐derived products have recently been shown to prevent the development of inflammatory diseases in mouse models. However, most identified immunomodulators from helminthes are mixtures or macromolecules with potentially immunogenic side effects. We previously identified an immunomodulatory peptide called SJMHE1 from the HSP60 protein of Schistosoma japonicum. In this study, we assessed the ability of SJMHE1 to affect murine splenocytes and human peripheral blood mononuclear cells (PBMCs) stimulated by toll‐like receptor (TLR) ligands in vitro and its treatment effect on mice with collagen‐induced arthritis (CIA). We show that SJMHE1 not only modulates the cytokine production of murine macrophage (MΦ) and dendritic cell but also affects cytokine production upon coculturing with allogeneic CD4⁺ T cell. SJMHE1 potently inhibits the cytokine response to TLR ligands lipopolysaccharide (LPS), CpG oligodeoxynucleotides (CpG) or resiquimod (R848) from mouse splenocytes, and human PBMCs stimulated by LPS. Furthermore, SJMHE1 suppressed clinical signs of CIA in mice and blocked joint erosion progression. This effect was mediated by downregulation of key cytokines involved in the pathogenesis of CIA, such as interferon‐γ (IFN‐γ), tumour necrosis factor‐α (TNF‐α), interleukin (IL)‐6, IL‐17, and IL‐22 and up‐regulation of the inhibitory cytokine IL‐10, Tgf‐β1 mRNA, and CD4⁺CD25⁺Foxp3⁺ Tregs. This study provides new evidence that the peptide from S. japonicum, which is the ‘safe’ selective generation of small molecule peptide that has evolved during host–parasite interactions, is of great value in the search for novel anti‐inflammatory agents and therapeutic targets for autoimmune diseases.

Mast cells: new therapeutic target in helminth immune modulation

Helminth infection and their secreted antigens have a protective role in many immune-mediated inflammatory disorders such as inflammatory bowel disease, rheumatoid arthritis and multiple sclerosis. However, studies have focused primarily on identifying immune protective mechanisms of helminth infection and their secreted molecules on dendritic cells and macrophages. Given that mast cells have been shown to be implicated in the pathogenesis and progression of many inflammatory disorders, their role should also be examined and considered as cellular target for helminth-based therapies. As there is a dearth of studies examining the interaction of helminth-derived antigens and mast cells, this review will focus on the role of mast cells during helminth infection and examine our current understanding of the involvement of mast cells in TH 1/TH 17-mediated immune disorders. In this context, potential mechanisms by which helminths could target the TH 1/TH 17 promoting properties of mast cells can be identified to unveil novel therapeutic mast cell driven targets in combating these inflammatory disorders.

Regulatory T Cell Numbers in Inflamed Skin Are Controlled by Local Inflammatory Cues That Upregulate CD25 and Facilitate Antigen-Driven Local Proliferation

CD4(+)Foxp3(+) regulatory T cells (Tregs) are key immune suppressors that regulate immunity in diverse tissues. The tissue and/or inflammatory signals that influence the magnitude of the Treg response remain unclear. To define signals that promote Treg accumulation, we developed a simple system of skin inflammation using defined Ags and adjuvants that induce distinct cytokine milieus: OVA protein in CFA, aluminum salts (Alum), and Schistosoma mansoni eggs (Sm Egg). Polyclonal and Ag-specific Treg accumulation in the skin differed significantly between adjuvants. CFA and Alum led to robust Treg accumulation, with >50% of all skin CD4(+) T cells being Foxp3(+) In contrast, Tregs accumulated poorly in the Sm Egg-inflamed skin. Surprisingly, we found no evidence of inflammation-specific changes to the Treg gene program between adjuvant-inflamed skin types, suggesting a lack of selective recruitment or adaptation to the inflammatory milieu. Instead, Treg accumulation patterns were linked to differences in CD80/CD86 expression by APC and the regulation of CD25 expression, specifically in the inflamed skin. Inflammatory cues alone, without cognate Ag, differentially supported CD25 upregulation (CFA and Alum > Sm Egg). Only in inflammatory milieus that upregulated CD25 did the provision of Ag enhance local Treg proliferation. Reduced IL-33 in the Sm Egg-inflamed environment was shown to contribute to the failure to upregulate CD25. Thus, the magnitude of the Treg response in inflamed tissues is controlled at two interdependent levels: inflammatory signals that support the upregulation of the important Treg survival factor CD25 and Ag signals that drive local expansion.

Patency of Litomosoides sigmodontis infection depends on Toll-like receptor 4 whereas Toll-like receptor 2 signalling influences filarial-specific CD4(+) T-cell responses

BALB/c mice develop a patent state [release of microfilariae (Mf), the transmission life-stage, into the periphery] when exposed to the rodent filariae Litomosoides sigmodontis. Interestingly, only a portion of the infected mice become patent, which reflects the situation in human individuals infected with Wuchereria bancrofti. Since those individuals had differing filarial-specific profiles, this study compared differences in immune responses between Mf(+) and Mf(-) infected BALB/c mice. We demonstrate that cultures of total spleen or mediastinal lymph node cells from Mf(+) mice produce significantly more interleukin-5 (IL-5) to filarial antigens but equal levels of IL-10 when compared with Mf(-) mice. However, isolated CD4(+) T cells from Mf(+) mice produced significantly higher amounts of all measured cytokines, including IL-10, when compared with CD4(+) T-cell responses from Mf(-) mice. Since adaptive immune responses are influenced by triggering the innate immune system we further studied the immune profiles and parasitology in infected Toll-like receptor-2-deficient (TLR2(-/-)) and TLR4(-/-) BALB/c mice. Ninety-three per cent of L. sigmodontis-exposed TLR4(-/-) BALB/c mice became patent (Mf(+)) although worm numbers remained comparable to those in Mf(+) wild-type controls. Lack of TLR2 had no influence on patency outcome or worm burden but infected Mf(+) mice had significantly lower numbers of Foxp3(+) regulatory T cells and dampened peripheral immune responses. Interestingly, in vitro culturing of CD4(+) T cells from infected wild-type mice with granulocyte-macrophage colony-stimulating factor-derived TLR2(-/-) dendritic cells resulted in an overall diminished cytokine profile to filarial antigens. Hence, triggering TLR4 or TLR2 during chronic filarial infection has a significant impact on patency and efficient CD4(+) T-cell responses, respectively.

The Transcriptional Repressor Polycomb Group Factor 6, PCGF6, Negatively Regulates Dendritic Cell Activation and Promotes Quiescence

Pro-inflammatory signals provided by the microenvironment are critical to activate dendritic cells (DCs), components of the innate immune system that shape both innate and adaptive immunity. However, to prevent inappropriate immune activation, mechanisms must be in place to restrain DC activation to ensure DCs are activated only once sufficient stimuli have been received. Here, we report that DC activation and immunogenicity are regulated by the transcriptional repressor Polycomb group factor 6 (PCGF6). Pcgf6 is rapidly downregulated upon stimulation, and this downregulation is necessary to permit full DC activation. Silencing PCGF6 expression enhanced both spontaneous and stimulated DC activation. We show that PCGF6 associates with the H3K4me3 demethylase JARID1c, and together, they negatively regulate H3K4me3 levels in DCs. Our results identify two key regulators, PCGF6 and JARID1c that temper DC activation and implicate active transcriptional silencing via histone demethylation as a previously unappreciated mechanism for regulating DC activation and quiescence.

Myrrh and artesunate modulate some Th1 and Th2 cytokines secretion in Schistosoma mansoni infected mice

The effects of artesunate and myrrh on S. mansoni infection and the levels of some Th1 and Th2 cytokines were evaluated in the present study. Six weeks after infection, a group of mice was treated with 4 mg/kg of artesunate and other group was treated with 10 mg/kg of myrrh for 3 successive days. Worm burden was reduced with a percentage of 53.7% and 58.78% after treatment with myrrh and artesunate respectively as well as the levels of IgG antibodies were significantly reduced compared with infected group. No obvious changes were observed in the level of interferon γ after treatment. After treatment with artesunate, interleukin 2 (IL-2) level was significantly decreased, while no significant difference was observed in myrrh-treated group compared with the infected group. On the other hand, the level of IL-10 was not significantly decreased after treatment with artesunate, but it was significantly increased after treatment with myrrh. However, IL-12 levels were significantly decreased after treatment with artesunate. The results demonstrated that, artesunate or myrrh treatment could give a level of protection against S. mansoni infection and modulate the levels of some Th1 and Th2 cytokines in mice infected with S. mansoni.

Kelch-like Protein 21 (KLHL21) Targets IκB Kinase-β to Regulate Nuclear Factor κ-Light Chain Enhancer of Activated B Cells (NF-κB) Signaling Negatively

Activation of IKKβ is the key step in canonical activation of NF-κB signaling. Extensive work has provided insight into the mechanisms underlying IKKβ activation through the identification of context-specific regulators. However, the molecular processes responsible for its negative regulation are not completely understood. Here, we identified KLHL21, a member of the Kelch-like gene family, as a novel negative regulator of IKKβ. The expression of KLHL21 was rapidly down-regulated in macrophages upon treatment with proinflammatory stimuli. Overexpression of KLHL21 inhibited the activation of IKKβ and degradation of IκBα, whereas KLHL21 depletion via siRNA showed the opposite results. Coimmunoprecipitation assays revealed that KLHL21 specifically bound to the kinase domain of IKKβ via its Kelch domains and that this interaction was gradually attenuated upon TNFα treatment. Furthermore, KLHL21 did not disrupt the interaction between IKKβ and TAK1, TRAF2, or IκBα. Also, KLHL21 did not require its E3 ubiquitin ligase activity for IKKβ inhibition. Our findings suggest that KLHL21 may exert its inhibitory function by binding to the kinase domain and sequestering the region from potential IKKβ inducers. Taken together, our data clearly demonstrate that KLHL21 negatively regulates TNFα-activated NF-κB signaling via targeting IKKβ, providing new insight into the mechanisms underlying NF-κB regulation in cells.

Interaction Between Helminths and Toll-Like Receptors: Possibilities and Potentials for Asthma Therapy

Toll-like receptors (TLRs) are essential components of the innate immune system. They play an important role in the pathogenesis of allergic diseases, especially asthma. Since TLRs significantly orchestrate innate and adaptive immune response, their manipulation has widely been considered as a potential approach to control asthma symptoms. It is well established that helminths have immunoregulatory effects on host immune responses, especially innate immunity. They release bioactive molecules such as excretory-secretory (ES) products manipulating TLRs expression and signaling. Thus, given the promising results derived from preclinical studies, harnessing helminth-derived molecules affecting TLRs can be considered as a potential biological therapy for allergic diseases. Prospectively, the data that are available at present suggest that, in the near future, it is possible that helminth antigens will offer new therapeutic strategies and druggable targets for fighting allergic diseases. This review describes the interactions between helminths and TLRs and discusses the potential possibilities for asthma therapy. In this opinion paper, the authors aimed to review the updated literatures on the interplay between helminths, TLRs, and asthma with a view to proposing helminth-based asthma therapy.

Cohabitation in the Intestine: Interactions among Helminth Parasites, Bacterial Microbiota, and Host Immunity

Both intestinal helminth parasites and certain bacterial microbiota species have been credited with strong immunomodulatory effects. Recent studies reported that the presence of helminth infection alters the composition of the bacterial intestinal microbiota and, conversely, that the presence and composition of the bacterial microbiota affect helminth colonization and persistence within mammalian hosts. This article reviews recent findings on these reciprocal relationships, in both human populations and mouse models, at the level of potential mechanistic pathways and the implications these bear for immunomodulatory effects on allergic and autoimmune disorders. Understanding the multidirectional complex interactions among intestinal microbes, helminth parasites, and the host immune system allows for a more holistic approach when using probiotics, prebiotics, synbiotics, antibiotics, and anthelmintics, as well as when designing treatments for autoimmune and allergic conditions.

MGL Receptor and Immunity: When the Ligand Can Make the Difference

C-type lectin receptors (CLRs) on antigen-presenting cells (APCs) facilitate uptake of carbohydrate antigens for antigen presentation, modulating the immune response in infection, homeostasis, autoimmunity, allergy, and cancer. In this review, we focus on the role of the macrophage galactose type C-type lectin (MGL) in the immune response against self-antigens, pathogens, and tumor associated antigens (TAA). MGL is a CLR exclusively expressed by dendritic cells (DCs) and activated macrophages (MØs), able to recognize terminal GalNAc residues, including the sialylated and nonsialylated Tn antigens. We discuss the effects on DC function induced throughout the engagement of MGL, highlighting the importance of the antigen structure in the modulation of immune response. Indeed modifying Tn-density, the length, and steric structure of the Tn-antigens can result in generating immunogens that can efficiently bind to MGL, strongly activate DCs, mimic the effects of a danger signal, and achieve an efficient presentation in HLA classes I and II compartments.

IL-10 Production in Macrophages Is Regulated by a TLR-Driven CREB-Mediated Mechanism That Is Linked to Genes Involved in Cell Metabolism

IL-10 is produced by macrophages in diverse immune settings and is critical in limiting immune-mediated pathology. In helminth infections, macrophages are an important source of IL-10; however, the molecular mechanism underpinning production of IL-10 by these cells is poorly characterized. In this study, bone marrow-derived macrophages exposed to excretory/secretory products released by Schistosoma mansoni cercariae rapidly produce IL-10 as a result of MyD88-mediated activation of MEK/ERK/RSK and p38. The phosphorylation of these kinases was triggered by TLR2 and TLR4 and converged on activation of the transcription factor CREB. Following phosphorylation, CREB is recruited to a novel regulatory element in the Il10 promoter and is also responsible for regulating a network of genes involved in metabolic processes, such as glycolysis, the tricarboxylic acid cycle, and oxidative phosphorylation. Moreover, skin-resident tissue macrophages, which encounter S. mansoni excretory/secretory products during infection, are the first monocytes to produce IL-10 in vivo early postinfection with S. mansoni cercariae. The early and rapid release of IL-10 by these cells has the potential to condition the dermal microenvironment encountered by immune cells recruited to this infection site, and we propose a mechanism by which CREB regulates the production of IL-10 by macrophages in the skin, but also has a major effect on their metabolic state.

Treatment with Recombinant Trichinella spiralis Cathepsin B-like Protein Ameliorates Intestinal Ischemia/Reperfusion Injury in Mice by Promoting a Switch from M1 to M2 Macrophages

Intestinal ischemia/reperfusion (I/R) injury, in which macrophages play a key role, can cause high morbidity and mortality. The switch from classically (M1) to alternatively (M2) activated macrophages, which is dependent on the activation of STAT6 signaling, has been shown to protect organs from I/R injuries. In the current study, the effects of recombinant Trichinella spiralis cathepsin B-like protein (rTsCPB) on intestinal I/R injury and the potential mechanism related to macrophage phenotypes switch were investigated. In a mouse I/R model undergoing 60-min intestinal ischemia followed by 2-h or 7-d reperfusion, we demonstrated that intestinal I/R caused significant intestinal injury and induced a switch from M2 to M1 macrophages, evidenced by a decrease in levels of M2 markers (arginase-1 and found in inflammatory zone protein), an increase in levels of M1 markers (inducible NO synthase and CCR7), and a decrease in the ratio of M2/M1 macrophages. RTsCPB reversed intestinal I/R-induced M2-M1 transition and promoted M1-M2 phenotype switch evidenced by a significant decrease in M1 markers, an increase in M2 markers, and the ratio of M2/M1 macrophages. Meanwhile, rTsCPB significantly ameliorated intestinal injury and improved intestinal function and survival rate of animals, accompanied by a decrease in neutrophil infiltration and an increase in cell proliferation in the intestine. However, a selective STAT6 inhibitor, AS1517499, reversed the protective effects of rTsCPB by inhibiting M1 to M2 transition. These findings suggest that intestinal I/R injury causes a switch from M2 to M1 macrophages and that rTsCPB ameliorates intestinal injury by promoting STAT6-dependent M1 to M2 transition.

Potent Functional Immunogenicity of Plasmodium falciparum Transmission-Blocking Antigen (Pfs25) Delivered with Nanoemulsion and Porous Polymeric Nanoparticles

PURPOSE

To evaluate functional immunogenicity of CHrPfs25. a malaria transmission blocking vaccine antigen, using nanoemulsion and porous polymeric PLGA nanoparticles.

METHODS

CHrPfs25 was formulated with nanoemulsions (NE) and poly(D,L-lactide-co-glycolide) nanoparticles (PLGA-NP) and evaluated via IM route in mice. Transmission blocking efficacy of antibodies was evaluated by standard mosquito membrane feeding assay using purified IgG from immune sera. Physicochemical properties and stability of various formulations were evaluated by measuring poly-dispersity index, particle size and zeta potential.

RESULTS

Mice immunized with CHrPfs25 using alum via IP and IM routes induced comparable immune responses. The highest antibody response was obtained with CHrPfs25 formulated in 4% NE as compared to 8% NE and PLGA-NP. No further increases were observed by combining NE with MPL-A and chitosan. One hundred percent transmission blocking activity was demonstrated at 400 μg/ml of IgG for alum groups (both routes IP and IM), 4% NE and NE-MPL-A. Purified IgG from various adjuvant groups at lower doses (100 μg/mL) still exhibited >90% transmission blocking activity, while 52-81% blocking was seen at 50 μg/mL.

CONCLUSION

Results suggest that CHrPfs25 delivered in various adjuvants/nanoparticles elicited strong functional immunogenicity in pre-clinical studies in mice. We are now continuing these studies to develop effective vaccine formulations for further evaluation of immune correlates of relative immunogenicity of CHrPfs25 in various adjuvants and clinical trials.