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

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.

H19/Mir-130b-3p/Cyp4a14 potentiate the effect of praziquantel on liver in the treatment of Schistosoma japonicum infection

BACKGROUND

Schistosomiasis is a prevalent infectious disease caused by the parasitic trematodes of the genus Schistosoma. Praziquantel (PZQ), a safe and affordable drug, is the recommended oral treatment for schistosomiasis. The main pathologic manifestation of schistosomiasis is liver injury. However, the role and interactions of various RNA molecules in the effect of PZQ on the liver after S. japonicum infection have not been elucidated.

RESULTS

In this study, C57BL/6 mice were randomly divided into the control group, infection group, and PZQ treatment group. Total RNA was extracted from the livers of the mice. High-throughput whole transcriptome sequencing was performed to detect the RNA expression profiles in the three groups. A co-expression gene-interaction network was established based on the significant differentially expressed genes in the PZQ treatment group; messenger RNA (mRNA) Cyp4a14 was identified as a critical hub gene. Furthermore, competitive endogenous RNA networks were constructed by predicting the specific binding relations between mRNA and long noncoding (lnc) RNA and between lncRNA and microRNA (miRNA) of Cyp4a14, suggesting the involvement of the H19/miR-130b-3p/Cyp4a14 regulatory axis. Dual luciferase reporter assay result proved the specific binding of miR-130b-3p with Cyp4a14 3'UTR.

CONCLUSIONS

Our findings indicate the involvement of the H19/miR-130b-3p/Cyp4a14 axis in the effect of PZQ on the liver after S. japonicum infection. Moreover, the expression of mRNA Cyp4a14 could be regulated by the bonding of miR-130b-3p with 3'UTR of Cyp4a14. The findings of this study could provide a novel perspective to understand the host response to PZQ against S. japonicum in the future.

Evaluation of IL-35, as a Possible Biomarker for Follow-Up after Therapy, in Chronic Human Schistosoma Infection

The host response to helminth infections is characterized by systemic and tissue-related immune responses that play a crucial role in pathological diseases. Recently, experimental studies have highlighted the role of regulatory T (Tregs) and B (Bregs) cells with secreted cytokines as important markers in anti-schistosomiasis immunity. We investigated the serical levels of five cytokines (TNFα, IFN-γ, IL-4, IL-10 and IL-35) in pre- and post-treatment samples from chronic Schistosoma infected patients to identify potential serological markers during follow-up therapy. Interestingly, we highlighted an increased serum level of IL-35 in the pre-therapy samples (median 439 pg/mL for Schistosoma haematobium and 100.5 pg/mL for Schistsoma mansoni infected patients) compared to a control group (median 62 pg/mL and 58 pg/mL, respectively, p ≤ 0.05), and a significantly lower concentration in post-therapy samples (181 pg/mL for S. haematobium and 49.5 pg/mL for S. mansoni infected patients, p ≤ 0.05). The present study suggests the possible role of IL-35 as a novel serological biomarker in the evaluation of Schistosoma therapy follow-up.

Praziquantel promotes protection against Schistosoma japonicum infection in mice

Praziquantel (PZQ) is the first line drug for the treatment of schistosomiasis. Several studies have confirmed that PZQ regulates host immunity, and we have recently found that pretreatment with PZQ enhances resistance against Schistosoma japonicum infection in buffaloes. We speculate that PZQ induces physiological changes in mice that prevent S. japonicum infection. To test this hypothesis and provide a practical measure to prevent S. japonicum infection, we determined the effective dose (the minimum dose), protection period and onset time of protection by comparing the worm burden, female worm burden and egg burden in PZQ-pretreated mice and blank control mice. Morphological differences between parasites were observed by measuring the total worm length, oral sucker, ventral sucker and ovary. The levels of cytokines, nitrogen monoxide (NO), 5-hydroxytryptamine (5-HT) and specific antibodies were measured using kits or soluble worm antigens. Hematological indicators on day 0 were analyzed in mice that received PZQ on days -15, -18, -19, -20, -21 and -22. The PZQ concentrations in plasma and blood cells were monitored using high performance liquid chromatography (HPLC). The effective dose was found to be two oral administrations (interval of 24 h) at 300 mg/kg body weight (BW) or one injection at 200 mg/kg BW, and the protection period of PZQ injection was 18 days. The optimal preventive effect was observed at two days post-administration, with a >92% worm reduction rate and significant worm reduction until 21 days after administration. Adult worms from PZQ-pretreated mice were runtish showing a shorter length, smaller organs and fewer eggs in the uteri of females. Detection of cytokines, NO, 5-HT and hematological indicators showed that PZQ induced immune-physiological changes, including higher levels of NO, IFN-γ and IL-2, and a lower level of TGF-β. No significant difference in the anti-S. japonicum specific antibody levels was observed. The PZQ concentrations in plasma and blood cells 8 and 15 days post-administration were lower than the detection limit. Our results confirmed that pretreatment with PZQ promotes the protection of mice against S. japonicum infection within 18 days. Although we observed some immune-physiological changes in the PZQ-pretreated mice, the exact mechanisms involved in the preventive effect require further study.

Praziquantel: An update on the mechanism of its action against schistosomiasis and new therapeutic perspectives

Praziquantel (PZQ) is the drug of choice for the treatment of all forms of schistosomiasis, although its mechanisms of action are not completely understood. PZQ acts largely on adult worms. This narrative literature review describes what is known about the mechanisms of action of PZQ against schistosomes from in vitro and in vivo studies and highlights the molecular targets in parasites and immune responses induced in definitive hosts by this drug. Moreover, new therapeutic uses of PZQ are discussed. Studies have demonstrated that in addition to impacting voltage-operated Ca2 + channels, PZQ may interact with other schistosome molecules, such as myosin regulatory light chain, glutathione S-transferase, and transient receptor potential channels. Following PZQ administration, increased T regulatory type 1 (Tr1) cell differentiation and decreased inflammation were observed, indicating that PZQ promotes immunoregulatory pathways. Although PZQ is widely used in mass drug administration schemes, the existence of resistant parasites has not been proven; however, it is a concern that should be constantly investigated in human populations. In addition, we discuss studies that evaluate health applications of PZQ (other than helminth infection), such as its effect in cancer therapy and its adjuvant action in vaccines against viruses.

The Role of Intestinal Microbial Metabolites in the Immunity of Equine Animals Infected With Horse Botflies

The microbiota and its metabolites play an important role in regulating the host metabolism and immunity. However, the underlying mechanism is still not well studied. Thus, we conducted the LC-MS/MS analysis and RNA-seq analysis on Equus przewalskii with and without horse botfly infestation to determine the metabolites produced by intestinal microbiota in feces and differentially expressed genes (DEGs) related to the immune response in blood and attempted to link them together. The results showed that parasite infection could change the composition of microbial metabolites. These identified metabolites could be divided into six categories, including compounds with biological roles, bioactive peptides, endocrine-disrupting compounds, pesticides, phytochemical compounds, and lipids. The three pathways involving most metabolites were lipid metabolism, amino acid metabolism, and biosynthesis of other secondary metabolites. The significant differences between the host with and without parasites were shown in 31 metabolites with known functions, which were related to physiological activities of the host. For the gene analysis, we found that parasite infection could alarm the host immune response. The gene of “cathepsin W” involved in innate and adaptive immune responses was upregulated. The two genes of the following functions were downregulated: “protein S100-A8” and “protein S100-A9-like isoform X2” involved in chemokine and cytokine production, the toll-like receptor signaling pathway, and immune and inflammatory responses. GO and KEGG analyses showed that immune-related functions of defense response and Th17 cell differentiation had significant differences between the host with and without parasites, respectively. Last, the relationship between metabolites and genes was determined in this study. The purine metabolism and pyrimidine metabolism contained the most altered metabolites and DEGs, which mainly influenced the conversion of ATP, ADP, AMP, GTP, GMP, GDP, UTP, UDP, UMP, dTTP, dTDP, dTMP, and RNA. Thus, it could be concluded that parasitic infection can change the intestinal microbial metabolic activity and enhance immune response of the host through the pathway of purine and pyrimidine metabolism. This results will be a valuable contribution to understanding the bidirectional association of the parasite, intestinal microbiota, and host.

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.

Modulation of mice immune responses against Schistosoma mansoni infection with anti-schistosomiasis drugs: Role of interleukin-4 and interferon-gamma

OBJECTIVE

Schistosoma mansoni (S. mansoni) is endemic in Africa, the Middle East, South America, and the Caribbean. This study investigated the modulation of immune response against S. mansoni through estimation of interleukin-4 (IL-4) (Th2 cytokine) and interferon-gamma (INF-γ) (Th1 cytokine) under the effect of anti-schistosomal drugs.

METHODS

Laboratory bred female albino mice (n = 120) were divided into the following groups: untreated mice, S. mansoni infected mice, S. mansoni infected mice treated with artemisinin (ART), arachidonic acid (ARA), nifedipine or praziquantel (PZQ). Levels of IL-4 and INF-γ cytokines in the serum samples of treated and untreated mice were determined by enzyme-linked immunosorbent assay and the results were further validated by measuring the mRNA levels IL-4 and INF-γ using quantitative real-time polymerase chain reaction.

RESULTS

Anti-schistosomiasis drugs ART and ARA increased the levels of Th2 cytokine IL-4 (P < 0.05), whereas PZQ drug decreased the response of IL-4 (P < 0.05). However, nifedipine was found to be ineffective in modulating the response of IL-4 (P > 0.05). As far as Th-1 cytokine IFN γ was concerned, only PZQ increased its levels (P < 0.05), whereas other tested anti-schistosomiasis drugs; ART, ARA, and nifedipine were found to be infective (P > 0.05).

CONCLUSIONS

These findings indicated that anti-schistosomiasis drugs ART, ARA, and PZQ play a role in the modulation of expression of Th2 cytokines. Whereas, only PZQ may play a role in the modulation of Th1 cytokines. These findings provide a scope for the formulation of novel anti-schistosomal drugs as well as in the therapeutic management of patients infected with S. mansoni.

Influence of schistosomiasis on host vaccine responses

Schistosomiasis is a debilitating helminthiasis which commonly establishes as a chronic infection in people from endemic areas. As a potent modulator of the host immune response, the Schistosoma parasite and its associated products can directly interfere with its host's ability to mount adequate immune responses to unrelated antigens. As a result, increased attention is gathering on studies assessing the influence of helminths, particularly the causal agent of schistosomiasis, on host responsiveness to vaccines. However, to date, no consensus has been drawn regarding the influence of schistosomiasis on host vaccine responses. Here, we review available evidence on the influence of transgenerational and direct Schistosoma parasite exposure on host immune responses to unrelated vaccines. In addition, we evaluate the potential of praziquantel (PZQ) treatment in restoring schistosomiasis-impacted vaccine responses.

Systems Biology Analysis of the Radiation-Attenuated Schistosome Vaccine Reveals a Role for Growth Factors in Protection and Hemostasis Inhibition in Parasite Survival

In spite of several decades of research, an effective vaccine against schistosomiasis remains elusive. The radiation-attenuated (RA) cercarial vaccine is still the best model eliciting high protection levels, although the immune mechanisms have not yet been fully characterized. In order to identify genes and pathways underlying protection we investigated patterns of gene expression in PBMC and skin draining Lymph Nodes (LN) from mice using two exposure comparisons: vaccination with 500 attenuated cercariae versus infection with 500 normal cercariae; one versus three doses. Vaccinated mice were challenged with 120 normal parasites. Integration of PBMC and LN data from the infected group revealed early up-regulation of pathways associated with Th2 skewing and polarization of IgG antibody profiles. Additionally, hemostasis pathways were downregulated in infected mice, correlating with platelet reduction, potentially a mechanism to assist parasite migration through capillary beds. Conversely, up regulation of such mechanisms after vaccination may explain parasite blockade in the lungs. In contrast, a single exposure to attenuated parasites revealed early establishment of a Th1 bias (signaling of IL-1, IFN-γ; and Leishmania infection). Genes encoding chemokines and their receptors were more prominent in vaccinated mice, indicating an enhanced capacity for inflammation, potentially augmenting the inhibition of intravascular migration. Increasing the vaccinations from one to three did not dramatically elevate protection, but there was a clear shift towards antibody-mediated effectors. However, elements of the Th1 bias were still evident. Notable features after three vaccinations were markers of cytotoxicity (including IL-6 and NK cells) together with growth factors and their receptors (FGFR/VEGF/EGF) and the apoptosis pathway. Indeed, there is evidence for the development of anergy after three vaccinations, borne out by the limited responses detected in samples after challenge. We infer that persistence of a Th1 response puts a limit on expression of antibody-mediated mechanisms. This feature may explain the failure of multiple doses to drive protection towards sterile immunity. We suggest that the secretions of lung stage parasites would make a novel cohort of antigens for testing in protection experiments.

Immunological Considerations for Schistosoma Vaccine Development: Transitioning to Endemic Settings

Despite mass drug administration programmes with praziquantel, the prevalence of schistosomiasis remains high. A vaccine is urgently needed to control transmission of this debilitating disease. As some promising schistosomiasis vaccine candidates are moving through pre-clinical and clinical testing, we review the immunological challenges that these vaccine candidates may encounter in transitioning through the clinical trial phases in endemic settings. Prior exposure of the target population to schistosomes and other infections may impact vaccine response and efficacy and therefore requires considerable attention. Schistosomes are known for their potential to induce T-reg/IL-10 mediated immune suppression in populations which are chronically infected. Moreover, endemicity of schistosomiasis is focal whereby target and trial populations may exhibit several degrees of prior exposure as well as in utero exposure which may increase heterogeneity of vaccine responses. The age dependent distribution of exposure and development of acquired immunity, and general differences in the baseline immunological profile, adds to the complexity of selecting suitable trial populations. Similarly, prior or concurrent infections with other parasitic helminths, viral and bacterial infections, may alter immunological responses. Consequently, treatment of co-infections may benefit the immunogenicity of vaccines and may be considered despite logistical challenges. On the other hand, viral infections leave a life-long immunological imprint on the human host. Screening for serostatus may be needed to facilitate interpretation of vaccine responses. Co-delivery of schistosome vaccines with PZQ is attractive from a perspective of implementation but may complicate the immunogenicity of schistosomiasis vaccines. Several studies have reported PZQ treatment to induce both transient and long-term immuno-modulatory effects as a result of tegument destruction, worm killing and subsequent exposure of worm antigens to the host immune system. These in turn may augment or antagonize vaccine immunogenicity. Understanding the complex immunological interactions between vaccine, co-infections or prior exposure is essential in early stages of clinical development to facilitate phase 3 clinical trial design and implementation policies. Besides well-designed studies in different target populations using schistosome candidate vaccines or other vaccines as models, controlled human infections could also help identify markers of immune protection in populations with different disease and immunological backgrounds.