Immunological factors linked to geographical variation in vaccine responses

Vaccination is one of medicine's greatest achievements; however, its full potential is hampered by considerable variation in efficacy across populations and geographical regions. For example, attenuated malaria vaccines in high-income countries confer almost 100% protection, whereas in low-income regions these same vaccines achieve only 20-50% protection. This trend is also observed for other vaccines, such as bacillus Calmette-Guérin (BCG), rotavirus and yellow fever vaccines, in terms of either immunogenicity or efficacy. Multiple environmental factors affect vaccine responses, including pathogen exposure, microbiota composition and dietary nutrients. However, there has been variable success with interventions that target these individual factors, highlighting the need for a better understanding of their downstream immunological mechanisms to develop new ways of modulating vaccine responses. Here, we review the immunological factors that underlie geographical variation in vaccine responses. Through the identification of causal pathways that link environmental influences to vaccine responsiveness, it might become possible to devise modulatory compounds that can complement vaccines for better outcomes in regions where they are needed most.

Safety and infectivity of female cercariae in Schistosoma-naïve, healthy participants: a controlled human Schistosoma mansoni infection study

BACKGROUND

A controlled human infection model for schistosomiasis (CHI-S) can speed up vaccine development and provides insight into early immune responses following schistosome exposure. Recently, we established CHI-S model using single-sex male-only Schistosoma mansoni (Sm) cercariae in Schistosoma-naïve individuals. Given important differences in antigenic profile and human immune responses to schistosomes of different sex, we pioneered a single-sex female-only CHI-S model for future use in vaccine development.

METHODS

We exposed 13 healthy, Schistosoma-naïve adult participants to 10 (n = 3) or 20 (n = 10) female cercariae and followed for 20 weeks, receiving treatment with praziquantel (PZQ) 60 mg/kg at week 8 and 12 after exposure.

FINDINGS

The majority (11/13) participants reported rash and/or itch at the site of exposure, 5/13 had transient symptoms of acute schistosomiasis. Exposure to 20 cercariae led to detectable infection, defined as serum circulating anodic antigen levels >1.0 pg/mL, in 6/10 participants. Despite two rounds of PZQ treatment, 4/13 participants showed signs of persistent infection. Additional one- or three-day PZQ treatment (1 × 60 mg/kg and 3 × 60 mg/kg) or artemether did not result in cure, but over time three participants self-cured. Antibody, cellular, and cytokine responses peaked at week 4 post infection, with a mixed Th1, Th2, and regulatory profile. Cellular responses were (most) discriminative for symptoms.

INTERPRETATION

Female-only infections exhibit similar clinical and immunological profiles as male-only infections but are more resistant to PZQ treatment. This limits future use of this model and may have important implications for disease control programs.

FUNDING

European Union's Horizon 2020 (grant no. 81564).

Inflammatory and tolerogenic myeloid cells determine outcome following human allergen challenge

Innate mononuclear phagocytic system (MPS) cells preserve mucosal immune homeostasis. We investigated their role at nasal mucosa following allergen challenge with house dust mite. We combined single-cell proteome and transcriptome profiling on nasal immune cells from nasal biopsies cells from 30 allergic rhinitis and 27 non-allergic subjects before and after repeated nasal allergen challenge. Biopsies of patients showed infiltrating inflammatory HLA-DRhi/CD14+ and CD16+ monocytes and proallergic transcriptional changes in resident CD1C+/CD1A+ conventional dendritic cells (cDC)2 following challenge. In contrast, non-allergic individuals displayed distinct innate MPS responses to allergen challenge: predominant infiltration of myeloid-derived suppressor cells (MDSC: HLA-DRlow/CD14+ monocytes) and cDC2 expressing inhibitory/tolerogenic transcripts. These divergent patterns were confirmed in ex vivo stimulated MPS nasal biopsy cells. Thus, we identified not only MPS cell clusters involved in airway allergic inflammation but also highlight novel roles for non-inflammatory innate MPS responses by MDSC to allergens in non-allergic individuals. Future therapies should address MDSC activity as treatment for inflammatory airway diseases.

Corrigendum: Dynamics of host immune response development during Schistosoma mansoni infection

[This corrects the article DOI: 10.3389/fimmu.2022.906338.].

Schistosoma mansoni egg-derived thioredoxin and Sm14 drive the development of IL-10 producing regulatory B cells

During chronic schistosome infections, a complex regulatory network is induced to regulate the host immune system, in which IL-10-producing regulatory B (Breg) cells play a significant role. Schistosoma mansoni soluble egg antigens (SEA) are bound and internalized by B cells and induce both human and mouse IL-10 producing Breg cells. To identify Breg-inducing proteins in SEA, we fractionated SEA by size exclusion chromatography and found 6 fractions able to induce IL-10 production by B cells (out of 18) in the high, medium and low molecular weight (MW) range. The high MW fractions were rich in heavily glycosylated molecules, including multi-fucosylated proteins. Using SEA glycoproteins purified by affinity chromatography and synthetic glycans coupled to gold nanoparticles, we investigated the role of these glycan structures in inducing IL-10 production by B cells. Then, we performed proteomics analysis on active low MW fractions and identified a number of proteins with putative immunomodulatory properties, notably thioredoxin (SmTrx1) and the fatty acid binding protein Sm14. Subsequent splenic murine B cell stimulations and hock immunizations with recombinant SmTrx1 and Sm14 showed their ability to dose-dependently induce IL-10 production by B cells both in vitro and in vivo. Identification of unique Breg cells-inducing molecules may pave the way to innovative therapeutic strategies for inflammatory and auto-immune diseases.

Life stage-specific glycosylation of extracellular vesicles from Schistosoma mansoni schistosomula and adult worms drives differential interaction with C-type lectin receptors DC-SIGN and MGL

Schistosomes can survive in mammalian hosts for many years, and this is facilitated by released parasite products that modulate the host’s immune system. Many of these products are glycosylated and interact with host cells via C-type lectin receptors (CLRs). We previously reported on specific fucose-containing glycans present on extracellular vesicles (EVs) released by schistosomula, the early juvenile life stage of the schistosome, and the interaction of these EVs with the C-type lectin receptor Dendritic Cell-Specific Intercellular adhesion molecule-3-Grabbing Non-integrin (DC-SIGN or CD209). EVs are membrane vesicles with a size range between 30–1,000 nm that play a role in intercellular and interspecies communication. Here, we studied the glycosylation of EVs released by the adult schistosome worms. Mass spectrometric analysis showed that GalNAcβ1–4GlcNAc (LacDiNAc or LDN) containing N-glycans were the dominant glycan type present on adult worm EVs. Using glycan-specific antibodies, we confirmed that EVs from adult worms were predominantly associated with LDN, while schistosomula EVs displayed a highly fucosylated glycan profile. In contrast to schistosomula EV that bind to DC-SIGN, adult worm EVs are recognized by macrophage galactose-type lectin (MGL or CD301), and not by DC-SIGN, on CLR expressing cell lines. The different glycosylation profiles of adult worm- and schistosomula-derived EVs match with the characteristic glycan profiles of the corresponding life stages and support their distinct roles in schistosome life-stage specific interactions with the host.

Special considerations for studies of extracellular vesicles from parasitic helminths: A community-led roadmap to increase rigour and reproducibility

Over the last decade, research interest in defining how extracellular vesicles (EVs) shape cross-species communication has grown rapidly. Parasitic helminths, worm species found in the phyla Nematoda and Platyhelminthes, are well-recognised manipulators of host immune function and physiology. Emerging evidence supports a role for helminth-derived EVs in these processes and highlights EVs as an important participant in cross-phylum communication. While the mammalian EV field is guided by a community-agreed framework for studying EVs derived from model organisms or cell systems [e.g., Minimal Information for Studies of Extracellular Vesicles (MISEV)], the helminth community requires a supplementary set of principles due to the additional challenges that accompany working with such divergent organisms. These challenges include, but are not limited to, generating sufficient quantities of EVs for descriptive or functional studies, defining pan-helminth EV markers, genetically modifying these organisms, and identifying rigorous methodologies for in vitro and in vivo studies. Here, we outline best practices for those investigating the biology of helminth-derived EVs to complement the MISEV guidelines. We summarise community-agreed standards for studying EVs derived from this broad set of non-model organisms, raise awareness of issues associated with helminth EVs and provide future perspectives for how progress in the field will be achieved.

Dynamics of Host Immune Response Development During Schistosoma mansoni Infection

Schistosomiasis is a disease of global significance, with severity and pathology directly related to how the host responds to infection. The immunological narrative of schistosomiasis has been constructed through decades of study, with researchers often focussing on isolated time points, cell types and tissue sites of interest. However, the field currently lacks a comprehensive and up-to-date understanding of the immune trajectory of schistosomiasis over infection and across multiple tissue sites. We have defined schistosome-elicited immune responses at several distinct stages of the parasite lifecycle, in three tissue sites affected by infection: the liver, spleen, and mesenteric lymph nodes. Additionally, by performing RNA-seq on the livers of schistosome infected mice, we have generated novel transcriptomic insight into the development of schistosome-associated liver pathology and fibrosis across the breadth of infection. Through depletion of CD11c+ cells during peak stages of schistosome-driven inflammation, we have revealed a critical role for CD11c+ cells in the co-ordination and regulation of Th2 inflammation during infection. Our data provide an updated and high-resolution account of how host immune responses evolve over the course of murine schistosomiasis, underscoring the significance of CD11c+ cells in dictating host immunopathology against this important helminth infection.

Fasciola hepatica Fatty Acid Binding Protein 1 Modulates T cell Polarization by Promoting Dendritic Cell Thrombospondin-1 Secretion Without Affecting Metabolic Homeostasis in Obese Mice

Background

The parasitic trematode Fasciola hepatica evades host immune defenses through secretion of various immunomodulatory molecules. Fatty Acid Binding Proteins (fhFABPs) are among the main excreted/secreted proteins and have been shown to display anti-inflammatory properties. However, little is currently known regarding their impact on dendritic cells (DCs) and their subsequent capacity to prime specific CD4+ T cell subsets.

Methodology/Principal Findings

The immunomodulatory effects of both native F. hepatica extracts and recombinant fhFABPs were assessed on monocyte-derived human DCs (moDCs) and the underlying mechanism was next investigated using various approaches, including DC-allogenic T cell co-culture and DC phenotyping through transcriptomic, proteomic and FACS analyses. We mainly showed that fhFABP1 induced a tolerogenic-like phenotype in LPS-stimulated moDCs characterized by a dose-dependent increase in the cell-surface tolerogenic marker CD103 and IL-10 secretion, while DC co-stimulatory markers were not affected. A significant decrease in secretion of the pro-inflammatory cytokines IL-12p70 and IL-6 was also observed. In addition, these effects were associated with an increase in both Th2-on-Th1 ratio and IL-10 secretion by CD4+ T cells following DC-T cell co-culture. RNA sequencing and targeted proteomic analyses identified thrombospondin-1 (TSP-1) as a non-canonical factor highly expressed and secreted by fhFABP1-primed moDCs. The effect of fhFABP1 on T cell skewing was abolished when using a TSP-1 blocking antibody during DC-T cell co-culture. Immunomodulation by helminth molecules has been linked to improved metabolic homeostasis during obesity. Although fhFABP1 injection in high-fat diet-fed obese mice induced a potent Th2 immune response in adipose tissue, it did not improved insulin sensitivity or glucose homeostasis.

Conclusions/Significance

We show that fhFABP1 modulates T cell polarization, notably by promoting DC TSP-1 secretion in vitro, without affecting metabolic homeostasis in a mouse model of type 2 diabetes.

Plasmacytoid Dendritic Cells Facilitate Th Cell Cytokine Responses throughout Schistosoma mansoni Infection

Plasmacytoid dendritic cells (pDCs) are potent producers of type I IFN (IFN-I) during viral infection and respond to IFN-I in a positive feedback loop that promotes their function. IFN-I shapes dendritic cell responses during helminth infection, impacting their ability to support Th2 responses. However, the role of pDCs in type 2 inflammation is unclear. Previous studies have shown that pDCs are dispensable for hepatic or splenic Th2 responses during the early stages of murine infection with the trematode Schistosoma mansoni at the onset of parasite egg laying. However, during S. mansoni infection, an ongoing Th2 response against mature parasite eggs is required to protect the liver and intestine from acute damage and how pDCs participate in immune responses to eggs and adult worms in various tissues beyond acute infection remains unclear. We now show that pDCs are required for optimal Th2 cytokine production in response to S. mansoni eggs in the intestinal-draining mesenteric lymph nodes throughout infection and for egg-specific IFN-γ at later time points of infection. Further, pDC depletion at chronic stages of infection led to increased hepatic and splenic pathology as well as abrogated Th2 cell cytokine production and activation in the liver. In vitro, mesenteric lymph node pDCs supported Th2 cell responses from infection-experienced CD4+ T cells, a process dependent on pDC IFN-I responsiveness, yet independent of Ag. Together, these data highlight a previously unappreciated role for pDCs and IFN-I in maintaining and reinforcing type 2 immunity in the lymph nodes and inflamed tissue during helminth infection.

A Praziquantel Treatment Study of Immune and Transcriptome Profiles in Schistosoma haematobium-Infected Gabonese Schoolchildren

Background

Although Schistosoma haematobium infection has been reported to be associated with alterations in immune function, in particular immune hyporesponsiveness, there have been only few studies that have used the approach of removing infection by drug treatment to establish this and to understand the underlying molecular mechanisms.

Methods

Schistosoma haematobium-infected schoolchildren were studied before and after praziquantel treatment and compared with uninfected controls. Cellular responses were characterized by cytokine production and flow cytometry, and in a subset of children RNA sequencing (RNA-Seq) transcriptome profiling was performed.

Results

Removal of S haematobium infection resulted in increased schistosome-specific cytokine responses that were negatively associated with CD4+CD25+FOXP3+ T-cells and accompanied by increased frequency of effector memory T-cells. Innate responses to Toll like receptor (TLR) ligation decreased with treatment and showed positive association with CD4⁺CD25⁺FOXP3⁺ T-cells. At the transcriptome level, schistosome infection was associated with enrichment in cell adhesion, whereas parasite removal was associated with a more quiescent profile. Further analysis indicated that alteration in cellular energy metabolism was associated with S haematobium infection and that the early growth response genes 2 and 3 (EGR 2 and EGR3), transcription factors that negatively regulate T-cell activation, may play a role in adaptive immune hyporesponsiveness.

Conclusions

Using a longitudinal study design, we found contrasting effects of schistosome infection on innate and adaptive immune responses. Whereas the innate immune system appears more activated, the adaptive immunity is in a hyporesponsive state reflected in alterations in CD4⁺CD25⁺FOXP3⁺ T-cells, cellular metabolism, and transcription factors involved in anergy.

Preschool wheezing and asthma in children: A systematic review of guidelines and quality appraisal with the AGREE II instrument

BACKGROUND

Asthma-like symptoms in preschool children, such as wheezing and dyspnea, are common time- and resource-consuming diagnostic and management challenges. Quality of wheezing and asthma recommendations varies. The purpose of this study, carried out by the European Academy of Allergy and Clinical Immunology (EAACI) Task Force for Preschool Wheeze, was to systematically review and assess the quality of guidelines for diagnosis and treatment of preschool wheezing and/or asthma.

METHODS

The Cochrane Library, MEDLINE, and EMBASE were searched until June 2018. The methodological rigor, quality, and transparency of relevant guidelines were assessed with the use of the Appraisal of Guidelines for Research and Evaluation (AGREE II) tool.

RESULTS

We identified 26 guidelines. The quality scores for each domain varied. Of all domains, clarity and presentation had the highest mean score, whereas applicability and stakeholder involvement had the lowest. The scores (median) for individual domains were as follows: score and purpose 86%; stakeholder involvement 49%; rigor of development 54%; clarity of presentation 85%; applicability 51%; and editorial independence 63%.

CONCLUSION

Although several guidelines on asthma management in children are available, however, their quality varies. Additionally, there is a considerable gap in reliable recommendations on the management and treatment of non-asthmatic preschool wheeze.

Early origins of lung disease: towards an interdisciplinary approach

The prenatal and perinatal environments can have profound effects on the development of chronic inflammatory diseases. However, mechanistic insight into how the early-life microenvironment can impact upon development of the lung and immune system and consequent initiation and progression of respiratory diseases is still emerging. Recent studies investigating the developmental origins of lung diseases have started to delineate the effects of early-life changes in the lung, environmental exposures and immune maturation on the development of childhood and adult lung diseases. While the influencing factors have been described and studied in mostly animal models, it remains challenging to pinpoint exactly which factors and at which time point are detrimental in lung development leading to respiratory disease later in life. To advance our understanding of early origins of chronic lung disease and to allow for proper dissemination and application of this knowledge, we propose four major focus areas: 1) policy and education; 2) clinical assessment; 3) basic and translational research; and 4) infrastructure and tools, and discuss future directions for advancement. This review is a follow-up of the discussions at the European Respiratory Society Research Seminar "Early origins of lung disease: towards an interdisciplinary approach" (Lisbon, Portugal, November 2019).

Primary prevention of asthma: from risk and protective factors to targeted strategies for prevention

Asthma is a complex disease that often starts in childhood. Genomic and environmental factors as well as aberrant immune maturation early in life can contribute to the onset of disease, with great disparity over time and geographical regions. Epidemiological studies have scrutinised environmental exposures and attempted to translate these exposures into prevention strategies. Some approaches for patients with asthma have been successful (eg, smoking ban, the Finnish Asthma Programme), and primary prevention of wheeze in pre-school children (age 0-5 years) by the supplementation of vitamin D or fish oil, or both, to pregnant women seems promising. Several recent prevention initiatives are based on strong asthma-protective environmental microbial exposures associated with traditional rural lifestyles. Preclinical studies with various bacterial lysates, bacterial and dietary metabolites, or helminthic compounds have yielded promising results that await translation into clinical practice. Given the immense societal and individual burden of asthma, there is an urgent need to further develop novel strategies to eradicate the disease.

Host-microbe cross-talk in the lung microenvironment: implications for understanding and treating chronic lung disease

Chronic respiratory diseases are highly prevalent worldwide and will continue to rise in the foreseeable future. Despite intensive efforts over recent decades, the development of novel and effective therapeutic approaches has been slow. However, there is new and increasing evidence that communities of micro-organisms in our body, the human microbiome, are crucially involved in the development and progression of chronic respiratory diseases. Understanding the detailed mechanisms underlying this cross-talk between host and microbiota is critical for development of microbiome- or host-targeted therapeutics and prevention strategies. Here we review and discuss the most recent knowledge on the continuous reciprocal interaction between the host and microbes in health and respiratory disease. Furthermore, we highlight promising developments in microbiome-based therapies and discuss the need to employ more holistic approaches of restoring both the pulmonary niche and the microbial community.

The reciprocal interaction between microbes and host in the lung is increasingly recognised as an important determinant of health. The complexity of this cross-talk needs to be taken into account when studying diseases and developing future new therapies.https://bit.ly/2VKYUfT

Akkermansia muciniphila Exerts Lipid-Lowering and Immunomodulatory Effects without Affecting Neointima Formation in Hyperlipidemic APOE*3-Leiden.CETP Mice

SCOPE

Akkermansia muciniphila (A. muciniphila) is an intestinal commensal with anti-inflammatory properties both in the intestine and other organs. The aim is to investigate the effects of oral administration of A. muciniphila on lipid metabolism, immunity, and cuff-induced neointima formation in hyperlipidemic APOE*3-Leiden (E3L).CETP mice.

METHODS AND RESULTS

Hyperlipidemic male E3L.CETP mice are daily treated with 2 × 108 CFU A. muciniphila by oral gavage for 4 weeks and the effects are determined on plasma lipid levels, immune parameters, and cuff-induced neointima formation and composition. A. muciniphila administration lowers body weight and plasma total cholesterol and triglycerides levels. A. muciniphila influences the immune cell composition in mesenteric lymph nodes, as evident from an increased total B cell population, while reducing the total T cell and neutrophil populations. Importantly, A. muciniphila reduces the expression of the activation markers MHCII on dendritic cells and CD86 on B cells. A. muciniphila also increases whole blood ex vivo lipopolysaccharide-stimulated IL-10 release. Finally, although treatment with A. muciniphila improves lipid metabolism and immunity, it does not affect neointima formation or composition.

CONCLUSIONS

Four weeks of treatment with A. muciniphila exerts lipid-lowering and immunomodulatory effects, which are insufficient to inhibit neointima formation in hyperlipidemic E3L.CETP mice.

DC-SIGN mediated internalisation of glycosylated extracellular vesicles from Schistosoma mansoni increases activation of monocyte-derived dendritic cells

Helminths like Schistosoma mansoni release excretory/secretory (E/S) products that modulate host immunity to enable infection. Extracellular vesicles (EVs) are among these E/S products, yet molecular mechanisms and functionality of S. mansoni EV interaction with host immune cells is unknown. Here we demonstrate that EVs released by S. mansoni schistosomula are internalised by human monocyte-derived dendritic cells (moDCs). Importantly, we show that this uptake was mainly mediated via DC-SIGN (CD209). Blocking DC-SIGN almost completely abrogated EV uptake, while blocking mannose receptor (MR, CD206) or dendritic cell immunoreceptor (DCIR, CLEC4A) had no effect on EV uptake. Mass spectrometric analysis of EV glycans revealed the presence of surface N-glycans with terminal Galβ1-4(Fucα1-3)GlcNAc (LewisX) motifs, and a wide array of fucosylated lipid-linked glycans, including LewisX, a known ligand for DC-SIGN. Stimulation of moDCs with schistosomula EVs led to increased expression of costimulatory molecules CD86 and CD80 and regulatory surface marker PD-L1. Furthermore, schistosomula EVs increased expression of IL-12 and IL-10 by moDCs, which was partly dependent on the interaction with DC-SIGN. These results provide the first evidence that glycosylation of S. mansoni EVs facilitates the interaction with host immune cells and reveals a role for DC-SIGN and EV-associated glycoconjugates in parasite-induced immune modulation.

Modulating local airway immune responses to treat allergic asthma: lessons from experimental models and human studies

With asthma affecting over 300 million individuals world-wide and estimated to affect 400 million by 2025, developing effective, long-lasting therapeutics is essential. Allergic asthma, where Th2-type immunity plays a central role, represents 90% of child and 50% of adult asthma cases. Research based largely on animal models of allergic disease have led to the generation of a novel class of drugs, so-called biologicals, that target essential components of Th2-type inflammation. Although highly efficient in subclasses of patients, these biologicals and other existing medication only target the symptomatic stage of asthma and when therapy is ceased, a flare-up of the disease is often observed. Therefore, it is suggested to target earlier stages in the inflammatory cascade underlying allergic airway inflammation and to focus on changing and redirecting the initiation of type 2 inflammatory responses against allergens and certain viral agents. This focus on upstream aspects of innate immunity that drive development of Th2-type immunity is expected to have longer-lasting and disease-modifying effects, and may potentially lead to a cure for asthma. This review highlights the current understanding of the contribution of local innate immune elements in the development and maintenance of inflammatory airway responses and discusses available leads for successful targeting of those pathways for future therapeutics.

Establishing the Production of Male Schistosoma mansoni Cercariae for a Controlled Human Infection Model

To accelerate the development of novel vaccines for schistosomiasis, we set out to develop a human model for Schistosoma mansoni infection in healthy volunteers. During natural infections, female schistosomes produce eggs that give rise to morbidity. Therefore, we produced single-sex, male Schistosoma mansoni cercariae for human infection without egg production and associated pathology. Cercariae were produced in their intermediate snail hosts in accordance with the principles of good manufacturing practice (GMP). The application of GMP principles to an unconventional production process is a showcase for the controlled production of complex live challenge material in the European Union or under Food and Drug Administration guidance.

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.

Type I interferons provide additive signals for murine regulatory B cell induction by Schistosoma mansoni eggs

The helminth Schistosoma mansoni (S. mansoni) induces a network of regulatory immune cells, including interleukin (IL)-10-producing regulatory B cells (Bregs). However, the signals required for the development and activation of Bregs are not well characterized. Recent reports suggest that helminths induce type I interferons (IFN-I), and that IFN-I drive the development of Bregs in humans. We therefore assessed the role of IFN-I in the induction of Bregs by S. mansoni. Mice chronically infected with S. mansoni or i.v. injected with S. mansoni soluble egg antigen (SEA) developed a systemic IFN-I signature. Recombinant IFN-α enhanced IL-10 production by Bregs stimulated with S. mansoni SEA in vitro, while not activating Bregs by itself. IFN-I signaling also supported ex vivo IL-10 production by SEA-primed Bregs but was dispensable for activation of S. mansoni egg-induced Bregs in vivo. These data indicate that although IFN-I can serve as a coactivator for Breg IL-10 production, they are unlikely to participate in the development of Bregs in response to S. mansoni eggs.

Innate and adaptive nasal mucosal immune responses following experimental human pneumococcal colonization

Streptococcus pneumoniae (Spn) is a common cause of respiratory infection, but also frequently colonizes the nasopharynx in the absence of disease. We used mass cytometry to study immune cells from nasal biopsy samples collected following experimental human pneumococcal challenge in order to identify immunological mechanisms of control of Spn colonization. Using 37 markers, we characterized 293 nasal immune cell clusters, of which 7 were associated with Spn colonization. B cell and CD161⁺CD8⁺ T cell clusters were significantly lower in colonized than in noncolonized subjects. By following a second cohort before and after pneumococcal challenge we observed that B cells were depleted from the nasal mucosa upon Spn colonization. This associated with an expansion of Spn polysaccharide–specific and total plasmablasts in blood. Moreover, increased responses of blood mucosa-associated invariant T (MAIT) cells against in vitro stimulation with pneumococcus prior to challenge associated with protection against establishment of Spn colonization and with increased mucosal MAIT cell populations. These results implicate MAIT cells in the protection against pneumococcal colonization and demonstrate that colonization affects mucosal and circulating B cell populations.

Extract of Helicobacter pylori Ameliorates Parameters of Airway Inflammation and Goblet Cell Hyperplasia following Repeated Allergen Exposure

BACKGROUND

An inverse relation between Helicobacter pylori infection and asthma has been shown in epidemiological studies. Infection with H. pylori, or application of an extract of it before or after sensitization, inhibits allergic airway disease in mice.

OBJECTIVES

The aim of this study was to investigate the effect of an extract of H. pylori on allergic airway disease induced by repeated allergen exposure in mice that were sensitized and challenged prior to extract application.

METHOD

C57BL/6 mice were intranasally (i.n.) sensitized and challenged with house dust mite (HDM). After a minimum of 4 weeks, mice received the H. pylori extract intraperitoneally and were rechallenged i.n. with HDM. Allergen-specific antibodies were measured by ELISA. Cells present in the bronchoalveolar lavage fluid and dendritic cell (DC) subsets in the lung tissue were analyzed by flow cytometry. Tissue inflammation and goblet cell hyperplasia were assessed by histology. Cells of the mediastinal lymph node (mLN) were isolated and in vitro restimulated with HDM or H. pylori extract.

RESULTS

Treatment with H. pylori extract before rechallenge reduced allergen-specific IgE, the DC numbers in the tissue, and goblet cell hyperplasia. Cells isolated from mLN of mice treated with the extract produced significantly more IL-10 and IL-17 after in vitro restimulation with HDM. mLN cells of H. pylori-treated mice that were re-exposed to the H. pylori extract produced significantly more interferon gamma.

CONCLUSIONS

An extract of H. pylori is effective in reducing mucus production and various features of inflammation in HDM rechallenged mice.

Bronchiolitis needs a revisit: Distinguishing between virus entities and their treatments

Current data indicate that the “bronchiolitis” diagnosis comprises more than one condition. Clinically, pathophysiologically, and even genetically three main clusters of patients can be identified among children suffering from severe bronchiolitis (or first wheezing episode): (a) respiratory syncytial virus (RSV)‐induced bronchiolitis, characterized by young age of the patient, mechanical obstruction of the airways due to mucus and cell debris, and increased risk of recurrent wheezing. For this illness, an effective prophylactic RSV‐specific monoclonal antibody is available; (b) rhinovirus‐induced wheezing, associated with atopic predisposition of the patient and high risk of subsequent asthma development, which may, however, be reversed with systemic corticosteroids in those with severe illness; and (c) wheeze due to other viruses, characteristically likely to be less frequent and severe. Clinically, it is important to distinguish between these partially overlapping patient groups as they are likely to respond to different treatments. It appears that the first episode of severe bronchiolitis in under 2‐year‐old children is a critical event and an important opportunity for designing secondary prevention strategies for asthma. As data have shown bronchiolitis cannot simply be diagnosed using a certain cutoff age, but instead, as we suggest, using the viral etiology as the differentiating factor.

Schistosome Egg Migration: Mechanisms, Pathogenesis and Host Immune Responses

Many parasitic worms possess complex and intriguing life cycles, and schistosomes are no exception. To exit the human body and progress to their successive snail host, Schistosoma mansoni eggs must migrate from the mesenteric vessels, across the intestinal wall and into the feces. This process is complex and not always successful. A vast proportion of eggs fail to leave their definite host, instead becoming lodged within intestinal or hepatic tissue, where they can evoke potentially life-threatening pathology. Thus, to maximize the likelihood of successful egg passage whilst minimizing host pathology, intriguing egg exit strategies have evolved. Notably, schistosomes actively exert counter-inflammatory influences on the host immune system, discreetly compromise endothelial and epithelial barriers, and modulate granuloma formation around transiting eggs, which is instrumental to their migration. In this review, we discuss new developments in our understanding of schistosome egg migration, with an emphasis on S. mansoni and the intestine, and outline the host-parasite interactions that are thought to make this process possible. In addition, we explore the potential immune implications of egg penetration and discuss the long-term consequences for the host of unsuccessful egg transit, such as fibrosis, co-infection and cancer development.

Modulation of Host Immunity by Helminths: The Expanding Repertoire of Parasite Effector Molecules

Helminths are extraordinarily successful parasites due to their ability to modulate the host immune response. They have evolved a spectrum of immunomodulatory molecules that are now beginning to be defined, heralding a molecular revolution in parasite immunology. These discoveries have the potential both to transform our understanding of parasite adaptation to the host and to develop possible therapies for immune-mediated disease. In this review we will summarize the current state of the art in parasite immunomodulation and discuss perspectives on future areas for research and discovery.

Isolated Schistosoma mansoni eggs prevent allergic airway inflammation

Chronic helminth infection with Schistosoma (S.) mansoni protects against allergic airway inflammation (AAI) in mice and is associated with reduced Th2 responses to inhaled allergens in humans, despite the presence of schistosome‐specific Th2 immunity. Schistosome eggs strongly induce type 2 immunity and allow to study the dynamics of Th2 versus regulatory responses in the absence of worms. Treatment with isolated S. mansoni eggs by i.p. injection prior to induction of AAI to ovalbumin (OVA)/alum led to significantly reduced AAI as assessed by less BAL and lung eosinophilia, less cellular influx into lung tissue, less OVA‐specific Th2 cytokines in lungs and lung‐draining mediastinal lymph nodes and less circulating allergen‐specific IgG1 and IgE antibodies. While OVA‐specific Th2 responses were inhibited, treatment induced a strong systemic Th2 response to the eggs. The protective effect of S. mansoni eggs was unaltered in μMT mice lacking mature (B2) B cells and unaffected by Treg cell depletion using anti‐CD25 blocking antibodies during egg treatment and allergic sensitization. Notably, prophylactic egg treatment resulted in a reduced influx of pro‐inflammatory, monocyte‐derived dendritic cells into lung tissue of allergic mice following challenge. Altogether, S. mansoni eggs can protect against the development of AAI, despite strong egg‐specific Th2 responses.

Pathogen-Derived Extracellular Vesicle-Associated Molecules That Affect the Host Immune System: An Overview

Recently, the interest in extracellular vesicles (EVs) released by pathogens like bacteria, fungi, and parasites has rapidly increased. Many of these pathogens actively modulate the immune responses of their host and there is accumulating evidence that pathogen-derived EV contribute to this process. The effects of pathogen-derived EV on the host immune system have been attributed to proteins, lipids, nucleic acids, and glycans contained in, or present on these EV. For example, toxins in bacterial EV can modulate pathogen clearance and antigen presentation, while EV-associated polysaccharides are potential vaccine targets because they induce protective immune responses. Furthermore, parasite EV-associated microRNA may increase parasite survival via host gene repression, and the lipid A moiety of LPS in bacteria-derived EV induces strong pro-inflammatory responses. Research on pathogen EV-associated molecules may pave new avenues to combat infectious diseases by immune intervention. This review provides an overview of the current knowledge of EV-associated molecules released by extracellular pathogens and their effects on the host immune system. The current focus and future hotspots of this rapidly expanding field will be highlighted and discussed.

Worms: Pernicious parasites or allies against allergies?

Type 2 immune responses are most commonly associated with allergy and helminth parasite infections. Since the discovery of Th1 and Th2 immune responses more than 30 years ago, models of both allergic disease and helminth infections have been useful in characterizing the development, effector mechanisms and pathological consequences of type 2 immune responses. The observation that some helminth infections negatively correlate with allergic and inflammatory disease led to a large field of research into parasite immunomodulation. However, it is worth noting that helminth parasites are not always benign infections, and that helminth immunomodulation can have stimulatory as well as suppressive effects on allergic responses. In this review, we will discuss how parasitic infections change host responses, the consequences for bystander immunity and how this interaction influences clinical symptoms of allergy.

Therapeutic Application of an Extract of Helicobacter pylori Ameliorates the Development of Allergic Airway Disease

Epidemiological and experimental studies have shown that exposure to the gastric bacterium Helicobacter pylori, especially in early life, prevents the development of asthma. Recent mouse studies have shown that this protective effect does not require live bacteria and that treatment with an extract of H. pylori in neonates prevents the development of airway inflammation and goblet cell metaplasia. In the current study, the effect of administration of an extract of H. pylori was assessed in a therapeutic study design with application of the extract just prior to allergen challenge. C57BL/6 mice were sensitized and challenged with OVA or house dust mite. Treatment with H. pylori extract just prior to the challenge significantly reduced airway inflammation, as assessed in bronchoalveolar lavage fluid and lung tissue, and reduced airway remodeling, as assessed by goblet cell quantification. These effects were apparent in the OVA model and in the house dust mite model. Injection of H. pylori extract reduced the processing of allergen by dendritic cells in the lungs and mediastinal lymph node. Bone marrow-derived dendritic cells exposed to H. pylori extract were affected with regard to their ability to process Ag. These data show that application of H. pylori extract after sensitization effectively inhibits allergic airway disease.

Protective immunity differs between routes of administration of attenuated malaria parasites independent of parasite liver load

In humans and murine models of malaria, intradermal immunization (ID-I) with genetically attenuated sporozoites that arrest in liver induces lower protective immunity than intravenous immunization (IV-I). It is unclear whether this difference is caused by fewer sporozoites migrating into the liver or by suboptimal hepatic and injection site-dependent immune responses. We therefore developed a Plasmodium yoelii immunization/boost/challenge model to examine parasite liver loads as well as hepatic and lymph node immune responses in protected and unprotected ID-I and IV-I animals. Despite introducing the same numbers of genetically attenuated parasites in the liver, ID-I resulted in lower sterile protection (53-68%) than IV-I (93-95%). Unprotected mice developed less sporozoite-specific CD8⁺ and CD4⁺ effector T-cell responses than protected mice. After immunization, ID-I mice showed more interleukin-10-producing B and T cells in livers and skin-draining lymph nodes, but fewer hepatic CD8 memory T cells and CD8⁺ dendritic cells compared to IV-I mice. Our results indicate that the lower protection efficacy obtained by intradermal sporozoite administration is not linked to low hepatic parasite numbers as presumed before, but correlates with a shift towards regulatory immune responses. Overcoming these immune suppressive responses is important not only for live-attenuated malaria vaccines but also for other live vaccines administered in the skin.

Schistosome egg antigens, including the glycoprotein IPSE/alpha-1, trigger the development of regulatory B cells

Infection with the helminth Schistosoma (S.) mansoni drives the development of interleukin (IL)-10-producing regulatory B (Breg) cells in mice and man, which have the capacity to reduce experimental allergic airway inflammation and are thus of high therapeutic interest. However, both the involved antigen and cellular mechanisms that drive Breg cell development remain to be elucidated. Therefore, we investigated whether S. mansoni soluble egg antigens (SEA) directly interact with B cells to enhance their regulatory potential, or act indirectly on B cells via SEA-modulated macrophage subsets. Intraperitoneal injections of S. mansoni eggs or SEA significantly upregulated IL-10 and CD86 expression by marginal zone B cells. Both B cells as well as macrophages of the splenic marginal zone efficiently bound SEA in vivo, but macrophages were dispensable for Breg cell induction as shown by macrophage depletion with clodronate liposomes. SEA was internalized into acidic cell compartments of B cells and induced a 3-fold increase of IL-10, which was dependent on endosomal acidification and was further enhanced by CD40 ligation. IPSE/alpha-1, one of the major antigens in SEA, was also capable of inducing IL-10 in naïve B cells, which was reproduced by tobacco plant-derived recombinant IPSE. Other major schistosomal antigens, omega-1 and kappa-5, had no effect. SEA depleted of IPSE/alpha-1 was still able to induce Breg cells indicating that SEA contains more Breg cell-inducing components. Importantly, SEA- and IPSE-induced Breg cells triggered regulatory T cell development in vitro. SEA and recombinant IPSE/alpha-1 also induced IL-10 production in human CD1d⁺ B cells. In conclusion, the mechanism of S. mansoni-induced Breg cell development involves a direct targeting of B cells by SEA components such as the secretory glycoprotein IPSE/alpha-1.

Infection with helminth parasites is known to be inversely associated with hyper-inflammatory disorders. While Schistosoma (S.) mansoni has been described to exert its down-modulatory effects on inflammation by inducing a network of regulatory immune cells such as regulatory B (Breg), the mechanisms of Breg cell induction remain unclear. Here, we use in vivo and in vitro approaches to show that antigens from S. mansoni eggs, among which the major glycoprotein IPSE/alpha-1, directly interact with splenic marginal zone B cells of mice which triggers them to produce the anti-inflammatory cytokine IL-10 and their capacity to induce regulatory T (Treg) cells. We also found that IPSE/alpha-1 induces IL-10 in human CD1d⁺ B cells, and that both natural and recombinant IPSE/alpha-1 are equally effective in driving murine and human Breg cells. Our study thus provides insight into the mechanisms of Breg cell induction by schistosomes, and an important step towards the development of helminth-based treatment strategies against hyper-inflammatory diseases.

Production and glyco-engineering of immunomodulatory helminth glycoproteins in plants

Helminth parasites control host-immune responses by secreting immunomodulatory glycoproteins. Clinical trials and mouse model studies have demonstrated the potential of helminth-derived glycoproteins for the treatment of immune-related diseases, like allergies and autoimmune diseases. Studies are however hampered by the limited availability of native parasite-derived proteins. Moreover, recombinant protein production systems have thus far been unable to reconstitute helminth-like glycosylation essential for the functionality of some helminth glycoproteins. Here we exploited the flexibility of the N-glycosylation machinery of plants to reconstruct the helminth glycoproteins omega-1 and kappa-5, two major constituents of immunomodulatory Schistosoma mansoni soluble egg antigens. Fine-tuning transient co-expression of specific glycosyltransferases in Nicotiana benthamiana enabled the synthesis of Lewis X (LeX) and LDN/LDN-F glycan motifs as found on natural omega-1 and kappa-5, respectively. In vitro and in vivo evaluation of the introduction of native LeX motifs on plant-produced omega-1 confirmed that LeX on omega-1 contributes to the glycoprotein's Th2-inducing properties. These data indicate that mimicking the complex carbohydrate structures of helminths in plants is a promising strategy to allow targeted evaluation of therapeutic glycoproteins for the treatment of inflammatory disorders. In addition, our results offer perspectives for the development of effective anti-helminthic vaccines by reconstructing native parasite glycoprotein antigens.

Microbes and asthma: Opportunities for intervention

The worldwide incidence and prevalence of asthma continues to increase. Asthma is now understood as an umbrella term for different phenotypes or endotypes, which arise through different pathophysiologic pathways. Understanding the many factors contributing to development of the disease is important for the identification of novel therapeutic targets for the treatment of certain asthma phenotypes. The hygiene hypothesis has been formulated to explain the increasing prevalence of allergic disease, including asthma. This hypothesis postulates that decreased exposure at a young age to certain infectious agents as a result of improved hygiene, increased antibiotic use and vaccination, and changes in lifestyle and dietary habits is associated with changes in the immune system, which predispose subjects to allergy. Many microbes, during their coevolution with human subjects, developed mechanisms to manipulate the human immune system and to increase their chances of survival. Improving models of asthma, as well as choosing adequate end points in clinical trials, will lead to a more complete understanding of the underlying mechanisms, thus providing an opportunity to devise primary and secondary interventions at the same time as identifying new molecular targets for treatment. This article reports the discussion and conclusion of a workshop under the auspices of the Netherlands Lung Foundation to extend our understanding of how modulation of the immune system by bacterial, parasitic, and viral infections might affect the development of asthma and to map out future lines of investigation.

Environmental 24-hr Cycles Are Essential for Health

Circadian rhythms are deeply rooted in the biology of virtually all organisms. The pervasive use of artificial lighting in modern society disrupts circadian rhythms and can be detrimental to our health. To investigate the relationship between disrupting circadian rhythmicity and disease, we exposed mice to continuous light (LL) for 24 weeks and measured several major health parameters. Long-term neuronal recordings revealed that 24 weeks of LL reduced rhythmicity in the central circadian pacemaker of the suprachiasmatic nucleus (SCN) by 70%. Strikingly, LL exposure also reduced skeletal muscle function (forelimb grip strength, wire hanging duration, and grid hanging duration), caused trabecular bone deterioration, and induced a transient pro-inflammatory state. After the mice were returned to a standard light-dark cycle, the SCN neurons rapidly recovered their normal high-amplitude rhythm, and the aforementioned health parameters returned to normal. These findings strongly suggest that a disrupted circadian rhythm reversibly induces detrimental effects on multiple biological processes.

Patients with Tuberculosis Have a Dysfunctional Circulating B-Cell Compartment, Which Normalizes following Successful Treatment

B-cells not only produce immunoglobulins and present antigens to T-cells, but also additional key roles in the immune system. Current knowledge on the role of B-cells in infections caused by intracellular bacteria is fragmentary and contradictory. We therefore analysed the phenotypical and functional properties of B-cells during infection and disease caused by Mycobacterium tuberculosis (Mtb), the bacillus causing tuberculosis (TB), and included individuals with latent TB infection (LTBI), active TB, individuals treated successfully for TB, and healthy controls. Patients with active or treated TB disease had an increased proportion of antibodies reactive with mycobacteria. Patients with active TB had reduced circulating B-cell frequencies, whereas only minor increases in B-cells were detected in the lungs of individuals deceased from TB. Both active TB patients and individuals with LTBI had increased relative fractions of B-cells with an atypical phenotype. Importantly, these B-cells displayed impaired proliferation, immunoglobulin- and cytokine- production. These defects disappeared upon successful treatment. Moreover, T-cell activity was strongest in individuals successfully treated for TB, compared to active TB patients and LTBI subjects, and was dependent on the presence of functionally competent B-cells as shown by cellular depletion experiments. Thus, our results reveal that general B-cell function is impaired during active TB and LTBI, and that this B-cell dysfunction compromises cellular host immunity during Mtb infection. These new insights may provide novel strategies for correcting Mtb infection-induced immune dysfunction towards restored protective immunity.

In infections with intracellular pathogens like Mycobacterium tuberculosis (Mtb), B-cells have long been ignored as their primary product, immunoglobulins, are unlikely to recognize intracellular bacteria. However, we have analysed here the frequency, phenotype and function of B-cells in tuberculosis (TB) infection and disease. Our data revealed that during active TB disease B-cell numbers are decreased and remaining B-cells are functionally impaired. Surprisingly, also individuals recently infected with Mtb suffered from poorly functional B-cells, but patients cured from the disease recovered with normal B-cell numbers and function. Thus, B-cell dysfunction contributes to impaired immune activation during Mtb infection.

Childhood allergies and asthma: New insights on environmental exposures and local immunity at the lung barrier

While certain bacteria and respiratory viruses promote local inflammation and disease onset, a more diverse colonization of the different species in the (gut) microbiome may be linked to more regulatory responses and protection against asthma and allergies. These processes are also influenced in part by food intake, both targeting the composition of the gut microbiome and influencing the immune system via metabolites. Early life environmental microbial exposure also contributes to protection against asthma and allergy and is linked with an early activation of the innate immune system and the development of regulatory immune responses. Although greater mechanistic insight is needed, it is tempting to speculate that part of the environmental effect can be explained by modulation of the microbiome composition at mucosal surfaces, epithelial barrier function and/or local immunity. A review of the latest studies is provided.

CD24(hi)CD27(+) B cells from patients with allergic asthma have impaired regulatory activity in response to lipopolysaccharide

BACKGROUND

Regulatory B cells have been identified that strongly reduce allergic and auto-immune inflammation in experimental models by producing IL-10. Recently, several human regulatory B-cell subsets with an impaired function in auto-immunity have been described, but there is no information on regulatory B cells in allergic asthma.

OBJECTIVE

In this study, the frequency and function of IL-10 producing B-cell subsets in allergic asthma were investigated.

METHODS

Isolated peripheral blood B cells from 13 patients with allergic asthma and matched healthy controls were analyzed for the expression of different regulatory B-cell markers. Next, the B cells were activated by lipopolysaccharide (LPS), CpG or through the B-cell receptor, followed by co-culture with endogenous memory CD4(+) T cells and house dust mite allergen DerP1.

RESULTS

Lower number of IL-10 producing B cells were found in patients in response to LPS, however, this was not the case when B cells were activated through the B-cell receptor or by CpG. Further dissection showed that only the CD24(hi)CD27(+) B-cell subset was reduced in number and IL-10 production to LPS. In response to DerP1, CD4(+) T cells from patients co-cultured with LPS-primed total B cells produced less IL-10 compared to similar cultures from controls. These results are in line with the finding that sorted CD24(hi)CD27(+) B cells are responsible for the induction of IL-10(+) CD4(+) T cells.

CONCLUSIONS

Taken together, these data indicate that CD24(hi)CD27(+) B cells from allergic asthma patients produce less IL-10 in response to LPS leading to a weaker IL-10 induction in T cells in response to DerP1, which may play a role in allergic asthma.