Enhanced pro-inflammatory cytokine responses following Toll-like-receptor ligation in Schistosoma haematobium-infected schoolchildren from rural Gabon

Effects of toll-like receptor agonists and SARS-CoV-2 antigens on interferon (IFN) expression by peripheral blood CD3+ T cells from COVID-19 patients

BACKGROUND

Signaling by toll-like receptors (TLRs) initiates important immune responses against viral infection. The role of TLRs in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is not well elucidated. Thus, we investigated the interaction of TLRs agonists and SARS-COV-2 antigens with immune cells in vitro.

MATERIAL & METHODS

30 coronavirus disease 2019 (COVID-19) patients (15 severe and 15 moderate) and 10 age and sex-matched healthy control (HC) were enrolled. Peripheral blood mononuclear cells (PBMCs) were isolated and activated with TLR3, 7, 8, and 9 agonists, the spike protein (SP) of SARS-CoV-2, and the receptor binding domain (RBD) of SP. Frequencies of CD3+IFN-β+ T cells, and CD3+IFN-γ+ T cells were evaluated by flow cytometry. Interferon (IFN)-β gene expression was assessed by qRT-PCR.

RESULTS

The frequency of CD3+IFN-β+ T cells was higher in PBMCs from moderate (p < 0.0001) and severe (p = 0.009) patients at baseline in comparison with HCs. The highest increase in the frequency of CD3+IFN-β+ T cells in cell from moderate patients was induced by TLR8 agonist and SP (p < 0.0001 for both) when compared to HC, while, the highest increase of the frequency of CD3+IFN-β+ T cells in sample of severe patients was seen with TLR8 and TLR7 agonists (both p = 0.002). The frequency of CD3+IFN-γ+ T cells was significantly increased upon stimulation with TLR agonists in cell from patients with moderate and severe COVID-19, compared with HC (all p < 0.01), except with TLR7 and TLR8 agonists. The TLR8 agonist did not significantly increase the frequency of CD3+IFN-γ+ T cells in PBMCs of severe patients, but did so in cells from patients with moderate disease (p = 0.01). Moreover, IFN-β gene expression was significantly upregulated in CD3+T cells from moderate (p < 0.0001) and severe (p = 0.002) COVID-19 patients, compared to HC after stimulation with the TLR8 agonist, while, stimulation of T cells with SP, significantly up-regulated IFN-β mRNA expression in cells from patients with moderate (p = 0.0003), but not severe disease.

CONCLUSION

Stimulation of PBMCs from COVID-19 patients, especially patients with moderate disease, with TLR8 agonist and SP increased the frequency of IFN-β-producing T cells and IFN-β gene expression.

Schistosomiasis in Gabon from 2000 to 2021 - A review

INTRODUCTION

Schistosomiasis is a public health issue of concern in Gabon, with the disease being reported from all regions of the country. The topic has been of interest for the local researchers and physicians for over two decades. The objective of this narrative review was to provide an overview of the research activities in the area from 2000 to early 2021.

METHODS

We performed a narrative literature review. The search strategy was designed to get a broad overview of the different research topics on schistosomiasis and the national control programme, and included grey literature.

RESULTS

A total of 159 articles was screened, and 42 were included into the review in addition to the grey literature. During the past two decades, the work on schistosomiasis originated from five out of the nine provinces of the country, with diverse aspects of the disease investigated; including immunology, epidemiology, diagnosis and treatment. Several studies investigated various aspects of schistosomiasis-related morbidity in the respective study populations. The body of work demonstrates that much effort was made to understand the details of the host immune response to schistosomiasis, and the immune profile changes induced in patients treated with praziquantel. Although some MDA campaigns were conducted in the country; little, however, is known on the epidemiological situation of the disease, particularly of its distribution within the population, as well as co-infections with other parasitic diseases also endemic in the area.

CONCLUSION

Progress has been made over the past two decades in the understanding of schistosomiasis in the country, including disease-related morbidity and its interaction with other parasitic infections, and the immunology and epidemiology of the disease. However, for optimising control of the disease, there is a need to fine-tune these findings with detailed local epidemiological and malacological data. We call for such studies to accomplish the knowledge of schistosomiasis in the country, particularly in areas of moderate or high endemicity, and recommend this approach to comparable schistosomiasis-endemic areas elsewhere.

Activity of the Toll-like receptor ligands in children with high and low socioeconomic backgrounds

BACKGROUND

Adjuvants are essential in the induction of immunity by vaccines and interact with receptors, including the Toll-like receptors (TLRs). Responsiveness of these receptors differs between and within populations, which impacts vaccine effectiveness.

OBJECTIVE

Here we examine how the innate cytokine response towards TLR ligands differs between high and low socioeconomic status (SES) school-aged children from Makassar, Indonesia.

METHODS

We stimulated whole blood from children, of which 27 attended a high SES school and 27 children a low SES school, with ligands for TLR-2/1, -2/6, -3, -4, -5, -7, -9 and measured pro- (TNF) and anti-inflammatory (IL-10) cytokines released.

RESULTS

In the low SES there is an increased pro-inflammatory response after 24 h stimulation with TLR-2/1 ligand Pam3 and TLR-4 ligand LPS compared to the high SES. Comparison of the response to LPS after 24 h versus 72 h stimulation revealed that the pro-inflammatory response in the low SES after 24 h shifts to an anti-inflammatory response, whereas in the high SES the initial anti-inflammatory response shifts to a strong pro-inflammatory response after 72 h stimulation.

CONCLUSION

We observed differences in the TLR-mediated innate immune response between children attending low and high SES schools, which can have important implications for vaccine development.

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.

The Regulatory Roles of Toll-Like Receptor 4 in Secretions of Type 1/Type 2 Relative Cytokines by Splenocytes and Dendritic Cells Exposed to Clonorchis sinensis Excretory/Secretory Products

The roles of TLR4 in mediation of innate immune response and in regulation of adaptive immune responses triggered by Clonorchis sinensis remain unknown. In the present study, splenocytes derived from C3H/HeN (TLR4 ^wild ) and C3H/Hej mice (TLR4 ^mut ) that were infected with 45 metacercariae of C. sinensis were harvested, then stimulated by C. sinensis excretory/secretory products (ESP) or medium (control) for 48 h, respectively. Meanwhile, bone marrow-derived dendritic cells (BMDCs) from normal C3H/HeN and C3H/Hej mice were prepared and stimulated with medium, ESP, LPS, or ESP+LPS for 24 h, respectively. The supernatants were collected, and the concentrations of type 1 and type 2 relative cytokines were determined by ELISA. The maturation of BMDCs indicated by surface markers of CD80, CD86, and MHC II was evaluated by flow cytometry. The results showed that the levels of IFN-γ, IL-6, TNF-α, and IL-10 in the splenocytes from C. sinensis-infected TLR4 ^mut mice were significantly lower than those from TLR4 ^wild mice when they were further exposed to ESP. For BMDCs, the productions of the cytokines IL-12p70 and IL-10, but not IL-4, in the BMDCs from TLR4 mutation mice were predominantly decreased compared with those from TLR4 ^wild mice when the BMDCs were co-stimulated by ESP combined with LPS. Flow cytometry analysis showed that ESP could significantly decrease the high levels of CD80, CD86, and MHC II which were elevated by LPS. In conclusion, these data suggest that TLR4 may play a regulatory role in type 1 immune responses during C. sinensis infection.

Cytokine and chemokine profile of the innate and adaptive immune response of Schistosoma haematobium and Plasmodium falciparum single and co-infected school-aged children from an endemic area of Lambaréné, Gabon

BACKGROUND

Helminths and malaria are among the most prevalent infectious diseases in the world. They both occur in tropical area where they often affect the same populations. There are studies suggesting an effect of helminths on malariometric indices. For example, malaria attacks as well as disease severity has been shown to be influenced by a concurrent chronic helminth infection. However, there are also studies that show no effect of concurrent helminth infections on malarial outcomes. To start addressing this issue, the effect of chronic Schistosoma haematobium infection on both the innate and adaptive immune response of Plasmodium falciparum-infected subjects was assessed in an area endemic for both these infections in Gabon.

METHOD

Subjects infected with S. haematobium and or P. falciparum, as well as a control group with neither of these infections, were recruited. For innate immune response, heparinized blood was obtained and cultured for 24 hours with a panel of TLR ligands. For adaptive immune response, PBMC was isolated and stimulated with SEB for 72 hours. Cytokines and chemokines were measured in supernatants using a multiplex beads array immunoassay. Principal Component analysis was used to assess pattern of cytokine and chemokine responses representing the innate and adaptive components of the immune system.

RESULTS

Overall it was observed that the presence of P. falciparum infection was marked by an increase in innate and adaptive immune responsiveness while S. haematobium infection was characterized by an increased chemokine profile, with at the same time, lower pro inflammatory markers. When the study subjects were split into single infected and co-infected groups no effect of S. haematobium on the immune response of P. falciparum infected subjects was observed, neither for the innate nor for the adaptive component of the immune response.

CONCLUSION

This study provides original information on the cellular immune response of S. haematobium and/or P. falciparum in infected subjects. It rules out an effect of S. haematobium on the cytokine profile of subjects co-infected with P. falciparum.

Assessment of the effect of Schistosoma haematobium co infection on malaria parasites and immune responses in rural populations in Gabon: study protocol

Background

Malaria and helminth co infection are common in tropical and subtropical areas where they affect the life of millions of people. While both helminth and malaria parasites have immunomodulatory activities, little is known about the consequence of co-infections on malaria antigen specific immune responses.

Method/Design

This study will be conducted in two rural areas of the Moyen Ogooué province in Gabon, endemic for both Plasmodium falciparum and Schistosoma haematobium infections. Participants, 5 to 50 years old, will be enrolled and grouped according to their infection status. S. haematobium and malaria parasites will be detected, demographic and clinical data will be recorded and blood will be collected for hematological as well as for immunological assays. The level of antibody specific to Plasmodium falciparum blood stage and gametocyte antigens will be measured using ELISA. PBMC will be isolated for phenotyping of different T cell subsets ex vivo by flow cytometry and for culture and cytokine response assessment.

Discussion

We will provide a comprehensive picture of the interaction between schistosomes and malaria parasites which co-localize in peripheral blood. We will test the hypothesis that schistosome infection has an impact on specific humoral as well as on cellular immune responses to malaria antigens.

Schistosomes and snails: a molecular encounter

Biomphalaria glabrata snails play an integral role in the transmission of Schistosoma mansoni, the causative agent for human schistosomiasis in the Western hemisphere. For the past two decades, tremendous advances have been made in research aimed at elucidating the molecular basis of the snail/parasite interaction. The growing concern that there is no vaccine to prevent schistosomiasis and only one effective drug in existence provides the impetus to develop new control strategies based on eliminating schistosomes at the snail-stage of the life cycle. To elucidate why a given snail is not always compatible to each and every schistosome it encounters, B. glabrata that are either resistant or susceptible to a given strain of S. mansoni have been employed to track molecular mechanisms governing the snail/schistosome relationship. With such snails, genetic markers for resistance and susceptibility were identified. Additionally, differential gene expression studies have led to the identification of genes that underlie these phenotypes. Lately, the role of schistosomes in mediating non-random relocation of gene loci has been identified for the first time, making B. glabrata a model organism where chromatin regulation by changes in nuclear architecture, known as spatial epigenetics, orchestrated by a major human parasite can now be investigated. This review will highlight the progress that has been made in using molecular approaches to describe snail/schistosome compatibility issues. Uncovering the signaling networks triggered by schistosomes that provide the impulse to turn genes on and off in the snail host, thereby controlling the outcome of infection, could also yield new insights into anti-parasite mechanism(s) that operate in the human host as well.

De novo assembly and transcriptome characterization: novel insights into the natural resistance mechanisms of Microtus fortis against Schistosoma japonicum

BACKGROUND

Microtus fortis is a non-permissive host of Schistosoma japonicum. It has natural resistance against schistosomes, although the precise resistance mechanisms remain unclear. The paucity of genetic information for M. fortis limits the use of available immunological methods. Thus, studies based on high-throughput sequencing technologies are required to obtain information about resistance mechanisms against S. japonicum.

RESULTS

Using Illumina single-end technology, a de novo assembly of the M. fortis transcriptome produced 67,751 unigenes with an average length of 868 nucleotides. Comparisons were made between M. fortis before and after infection with S. japonicum using RNA-seq quantification analysis. The highest number of differentially expressed genes (DEGs) occurred two weeks after infection, and the highest number of down-regulated DEGs occurred three weeks after infection. Simultaneously, the strongest pathological changes in the liver were observed at week two. Gene ontology terms and pathways related to the DEGs revealed that up-regulated transcripts were involved in metabolism, immunity and inflammatory responses. Quantitative real-time PCR analysis showed that patterns of gene expression were consistent with RNA-seq results.

CONCLUSIONS

After infection with S. japonicum, a defensive reaction in M. fortis commenced rapidly, increasing dramatically in the second week, and gradually decreasing three weeks after infection. The obtained M. fortis transcriptome and DEGs profile data demonstrated that natural and adaptive immune responses, play an important role in M. fortis immunity to S. japonicum. These findings provide a better understanding of the natural resistance mechanisms of M. fortis against schistosomes.

Differences in innate cytokine responses between European and African children

Although differences in immunological responses between populations have been found in terms of vaccine efficacy, immune responses to infections and prevalence of chronic inflammatory diseases, the mechanisms responsible for these differences are not well understood. Therefore, innate cytokine responses mediated by various classes of pattern-recognition receptors including Toll-like receptors (TLR), C-type lectin receptors (CLRs) and nucleotide-binding oligomerisation domain-like receptors (NLRs) were compared between Dutch (European), semi-urban and rural Gabonese (African) children. Whole blood was stimulated for 24 hours and the pro-inflammatory tumor necrosis factor (TNF) and the anti-inflammatory/regulatory interleukin-10 (IL-10) cytokines in culture supernatant were measured by enzyme-linked immunosorbent assay (ELISA). Gabonese children had a lower pro-inflammatory response to poly(I:C) (TLR3 ligand), but a higher pro-inflammatory response to FSL-1 (TLR2/6 ligand), Pam3 (TLR2/1 ligand) and LPS (TLR4 ligand) compared to Dutch children. Anti-inflammatory responses to Pam3 were also higher in Gabonese children. Non-TLR ligands did not induce substantial cytokine production on their own. Interaction between various TLR and non-TLR receptors was further assessed, but no differences were found between the three populations. In conclusion, using a field applicable assay, significant differences were observed in cytokine responses between European and African children to TLR ligands, but not to non-TLR ligands.

Posttreatment changes in cytokines induced by Schistosoma mansoni egg and worm antigens: dissociation of immunity- and morbidity-associated type 2 responses

Background. Human type 2 cytokine responsiveness to schistosome antigens increases after treatment; due either to removal of the immunosuppressive effects of active infection or immunological boosting by antigens released from dying parasites. We determined the responsiveness to Schistosoma mansoni over a 2-year period, when reinfection was restricted by interrupting transmission.

Methods. The proinflammatory and type 2 responses of Kenyan schoolchildren were measured before, and 1 year and 2 years posttreatment in whole blood cultures stimulated with soluble egg antigen (SEA) or soluble worm antigen (SWA). The site of S. mansoni transmission was molluscicided throughout.

Results. Pretreatment proinflammatory responses to SEA were high but reduced 1 and 2 years posttreatment, whereas type 2 responses were low pretreatment and increased 1 and 2 years posttreatment. Type 2 responses to SWA were high pretreatment and increased at 1 year, with no further increases at 2 years posttreatment. Children infected at follow-up had lower SEA, but not SWA, posttreatment type 2 responsiveness. Increases at 1 year in type 2 SWA, but not SEA, responsiveness correlated with pretreatment egg counts.

Conclusions. Removal of immunosuppressive effects of active infection increases SEA type 2 responsiveness; long-term SWA type 2 responsiveness is due to treatment-induced immunological boosting. Dissociation of type 2 responses potentially protects against severe egg-associated immunopathology during infection, while allowing worm-antigen derived immunity to develop.

Macroparasites at peripheral sites of infection are major and dynamic modifiers of systemic antimicrobial pattern recognition responses

Immune defences and the maintenance of immunological homeostasis in the face of pathogenic and commensal microbial exposures are channelled by innate antimicrobial pattern recognition receptors (PRRs) such as toll-like receptors (TLRs). Whilst PRR-mediated response programmes are the result of long-term host-pathogen or host-commensal co-evolutionary dynamics involving microbes, an additional possibility is that macroparasitic co-infections may be a significant modifier of such interactions. We demonstrate experimentally that macroparasites (the model gastrointestinal nematode, Heligmosomoides) at peripheral sites of infection cause substantial alteration of the expression and function of TLRs at a systemic level (in cultured splenocytes), predominantly up-regulating TLR2, TLR4 and TLR9-mediated cytokine responses at times of high standing worm burdens. We consistently observed such effects in BALB/c and C57BL/6 mice under single-pulse and trickle exposures to Heligmosomoides larvae and in SWR and CBA mice under single-pulse exposures. A complementary long-term survey of TLR2-mediated tumour necrosis factor-alpha responses in wild wood mice (Apodemus sylvaticus) was consistent with substantial effects of macroparasites under some environmental conditions. A general pattern, though, was for the associations of macroparasites with TLR function to be temporally dynamic and context-dependent: varying with different conditions of infection exposure in the field and laboratory and with host genetic strain in the laboratory. These results are compelling evidence that macroparasites are a major and dynamic modifier of systemic innate antimicrobial responsiveness in naturally occurring mammals and thus likely to be an important influence on the interaction between microbial exposures and the immune system.

Relationship between carotid intima media thickness and helminth infections on Flores Island, Indonesia

Objective

To examine the association between helminth infections and atherosclerosis.

Background

Chronic helminth infection, which can lead to poor nutritional status and anti-inflammatory response, might protect against the development of atherosclerosis.

Methods

A cross-sectional study was performed in Flores, Indonesia, an area highly endemic for soil-transmitted helminths (STH). Stool samples from 675 participants aged 18–80 years were collected and screened for Trichuris trichiura by microscopy and for Ascaris lumbricoides, Necator americanus, Ancylostoma duodenale, and Strongyloides stercoralis by qPCR. We collected data on body mass index (BMI), waist to hip ratio (WHR), blood pressure, fasting blood glucose (FBG), lipid, high sensitive C-reactive protein (hs-CRP), total immunoglobulin-E (TIgE) and Escherichia coli lipopolysaccharide stimulated cytokines (tumor necrosis factor and interleukin-10). In a subset of 301 elderly adults (≥40 years of age) carotid intima media thickness (cIMT) was measured.

Results

Participants with any STH infection had lower BMI (kg/m2) (mean difference −0.66, 95%CI [−1.26, −0.06]), WHR (−0.01, [−0.02, −0.00]), total cholesterol (mmol/L) (−0.22, [−0.43, −0.01]) and LDL-cholesterol (mmol/L) (−0.20, [−0.39, −0.00]) than uninfected participants. After additional adjustment for BMI the association between helminth infection and total cholesterol (mean difference −0.17, 95%CI [−0.37, 0.03]) as well as LDL-cholesterol (−0.15, [−0.33, 0.04]) was less pronounced. BMI, WHR, and total cholesterol were negatively associated with number species of helminth co-infections. Participants with high TIgE, an indicator of exposure to helminths, had lower FBG, TC, and HDL. The association between TIgE and TC and HDL remained significant after adjustment with BMI. No clear association was found between STH infection or TIgE and mean cIMT.

Conclusions

This cross-sectional study presents evidence that helminth infections were negatively associated with risk factors for cardiovascular disease, an association at least partially mediated by an effect on BMI. The significance of this finding needs to be determined.

Parasitic infections and immune function: effect of helminth infections in a malaria endemic area

According to the hygiene hypothesis, reduced exposure to infections could explain the rise of atopic diseases in high-income countries. Helminths are hypothesised to alter the host's immune response in order to avoid elimination and, as a consequence, also reduce the host responsiveness to potential allergens. To elucidate the effect of current helminth infections on immune responsiveness in humans, we measured cytokine production in a rural Ghanaian population in an area with multiple endemic parasites including malaria, intestinal helminths and protozoa. Multiplex real-time PCR in stool samples was used for the detection of four gastrointestinal helminths, of which only Necator americanus was commonly present. A similar assay was used to test for Giardia lamblia in stool samples and malaria infection in venous blood samples. Levels of the cytokines interleukin (IL)-10, tumour necrosis factor (TNF)-α, IL-17, IL-6, IL-13, and interferon (IFN)-γ were determined in whole-blood samples ex vivo-stimulated either with lipopolysaccharide (LPS) and zymosan (for innate cytokine production) or the T-cell mitogen phytohaemagglutinin (PHA). There were no significant differences in either innate or PHA-stimulated cytokine production dependent on current N. americanus infection. Plasmodium falciparum malarial infection was associated with a pro-inflammatory response indicated by increased innate production of TNF-α, IL-17 and IL-6. There was no clear pattern in cytokine responses dependent on G. lamblia-infection. In conclusion, in this rural Ghanaian population current N. americanus infections are not associated with altered immune function, while infection with P. falciparum is associated with pro-inflammatory innate immune responses.