Protective efficacy of six recombinant proteins as vaccine candidates against Echinococcus granulosus in dogs

Echinococcus granulosus sensu lato control measures: a specific focus on vaccines for both definitive and intermediate hosts

Echinococcosis, a neglected zoonotic disease caused by Echinococcus tapeworms, presents significant public health challenges worldwide. Cystic and alveolar echinococcosis has substantial health and economic impacts, necessitating effective prevention and control strategies. The present review provides a framework to expand our knowledge regarding key components of echinococcosis prevention and control, including phases, options, targets and available tools as well as current gaps and challenges in the field. Furthermore, we discuss the progress made in developing vaccines for the intermediate and definitive hosts and review the limitations and obstacles in vaccine development for definitive hosts. Abundant information is available on various aspects of the Echinococcus vaccine in sheep. Livestock vaccination effectively reduces Echinococcus transmission to sheep, offering a feasible control measure in intermediate hosts. However, vaccine development for the definitive host, i.e. dogs, exhibits significant challenges. Information gaps regarding the immune-mediated protective responses in dogs, repeatability of results, factors influencing the immune response, reinfection resistance, potential age-related decreases in worm burden and factors associated with the antifecundity effect are key challenges that should be addressed in canine vaccine development, and research collaboration, innovative technologies, and a deeper understanding of transmission dynamics are crucial. Multisectoral coordination under the One Health framework, with long-term political commitment and national and international cooperation, is critical for effective control in endemic areas.

RNA sequencing reveals dynamic expression of genes related to innate immune responses in canine small intestinal epithelial cells induced by Echinococcus granulosus protoscoleces

Background

Dogs are definitive hosts of Echinococcus granulosus, with the small intestine being the only site of parasitic infections. However, the immunomodulatory processes that occur during interactions between E. granulosus and its definitive host remain unclear. Therefore, this study aimed to evaluate gene transcription patterns in canine small intestinal epithelial cells (CIECs) following stimulation by E. granulosus protoscoleces (PSCs). Particularly, this study investigated the roles of pattern recognition receptors (PRRs), involved in recognizing pathogen-associated molecular patterns (PAMPs) and mediating the host innate immune response to the tapeworm E. granulosus.

Methods

RNA sequencing (RNA-seq) was used to examine gene transcription patterns in CIECs following stimulation with PSCs for 12 and 24 h. The potential roles of differentially expressed (DE) genes were inferred through Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses.

Results

RNA-seq analysis identified 78,206,492-90,548,214 clean reads in 12 RNA samples. This included six samples stimulated with PSCs for 12 h (PSC1_12h-PSC3_12h) and 24 h (PSC1_24h-PSC3_24h) and six corresponding control samples (PBS1_12h-PBS3_12h and PBS1_24h-PBS3_24h). In the PSC_12h vs. PBS_12h and PSC_24h vs. PBS_24h groups, 3,520 (2,359 upregulated and 1,161 downregulated) and 3,287 (1765 upregulated and 1,522 downregulated) DEgenes were identified, respectively. The expression of 45 PRRs genes was upregulated in the PSC_12h and PSC_24h groups compared to those in the control groups, including 4 Toll-like receptors (TLRs), 4C-type lectin receptors (CLRs), 3 NOD-like receptors (NLRs), 17 G protein-coupled receptors (GPCRs), 4 scavenger receptors (SRs), and 13 leucine-rich repeat-containing proteins (LRRCs). GO enrichment and KEGG analyses revealed that these DEgenes were mainly involved in the regulation of host immune response processes and molecules. These included antigen processing and presentation, Th17, PI3K-Akt, Th1, and Th2 cell differentiation, neutrophil extracellular trap formation, NOD- and Toll-like receptors, TNF, intestinal immune network for IgA production and IL-17 signaling pathway. Furthermore, the identified DEgenes were involved in the regulation of signaling molecules and interaction (e.g., cell adhesion molecules and ECM-receptor interaction).

Conclusion

These preliminary findings provide novel perspectives on the host innate immune response to E. granulosus PSC stimulation, with a focus on the involvement of E. granulosus-specific PRRs in host defense mechanisms against infection.

Proteomics analysis reveals the differential protein expression of female and male adult Toxocara canis using Orbitrap Astral analyzer

BACKGROUND

Toxocara canis, the most prevalent helminth in dogs and other canines, is one of the socioeconomically important zoonotic parasites, particularly affecting pediatric and adolescent populations in impoverished communities. However, limited information is available regarding the proteomes of female and male adult T. canis. To address this knowledge gap, we performed a comprehensive proteomic analysis to identify the proteins with differential abundance (PDAs) and gender-specifically expressed proteins between the two sexes adult T. canis.

METHODS

The comparative proteomic analysis was carried out by the Orbitrap mass spectrometry (MS) with asymmetric track lossless (Astral) analyzer. The difference analysis was conducted using t-test and the proteins verification was achieved through parallel reaction monitoring (PRM). The potential biological functions of identified adult T. canis proteins and PDAs were predicted by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. The domain, transcription factor and subcellular localization of the identified proteins and PDAs were analyzed by InterPro, AnimalTFDB 4.0 and Cell-mPLOC 2.0 databases, respectively.

RESULTS

A total of 8565 somatic proteins of adult T. canis were identified. Compared to male adult, 682 up-regulated PDAs and 844 down-regulated PDAs were identified in female adult with P-values < 0.05 and |log2FC| > 1, including 139 proteins exclusively expressed in female and 272 proteins exclusively expressed in male. The GO annotation analysis using all PDAs revealed that the main biological processes, cellular components and molecular functions corresponded to aminoglycan metabolic process, extracellular region and protein tyrosine phosphatase activity, respectively. The KEGG analysis using all PDAs showed that the pathways were mainly associated with adipocytokine signaling pathway, proximal tubule bicarbonate reclamation and PPAR signaling pathway.

CONCLUSIONS

This study reveals the differential protein expression between female and male adult T. canis, providing valuable resource for developing the novel intervention strategies against T. canis infection in humans and animals, especially from the perspective of sexual development and reproduction.

Evaluation of protective immune responses induced by DNA vaccines encoding Echinococcus granulosus EgM123 protein in Beagle dogs

Introduction

Echinococcus granulosus, known as cystic echinococcosis, is a prominent zoonotic parasitic disease of significant global concern. The definitive hosts serves as the primary reservoir for the transmission of echinococcosis, as well as a main factor in the prevention and control of the disease. Unfortunately, there is currently no commercially available vaccine for these hosts. Nevertheless, DNA vaccines show potential as a feasible strategy for the control and management of parasitic diseases.

Methods

In this study, the EgM123 antigen was selected for its well-documented immunogenic properties to develop a DNA vaccine aimed at combating E. granulosus infection in canines.

Results

The results showed a marked increase in IgG levels in the group vaccinated with pVAX1-EgM123 DNA compared to the PBS group. Additionally, the cytokines IL-1, IFN-γ, IL-4, and IL-6 were significantly upregulated in the pVAX1-EgM123 DNA vaccine group. Furthermore, in comparison to the PBS control group, the EgM123 DNA vaccine group exhibited a notable 87.85% reduction in worm burden and a 65.00% inhibition in segment development.

Discussion

These findings indicate that the pVAX1-EgM123 DNA vaccine shows promising immunogenicity, successfully eliciting a targeted immune response in canines. Moreover, it significantly diminishes the worm burden and hinders the progression of tapeworms in the pVAX1-EgM123 DNA vaccine group. These findings suggest that the pVAX1-EgM123 DNA vaccine holds promise as a potential candidate vaccine for combating E. granulosus infection in dogs.

Effects of annexin B18 from Echinococcus granulosus sensu lato on mouse macrophages

Cystic echinococcosis (CE) is a zoonotic disease, caused by Echinococcus granulosus sensu lato (E. granulosus s. l.), which posed significant public health concern globally. E. granulosus s. l. annexin B18 (EgANXB18) acts as a secretory protein, exerting a crucial influence in mediating host-parasite interactions. Recombinant annexin B18 (rEgANXB18) was expressed by Escherichia coli and the immunoreactivity was assessed by western blotting. The binding affinity between rEgANXB18 and total protein of RAW264.7 cells was assessed by ELISA. The impact of rEgANXB18 on the metabolic activity of RAW264.7 cells was assayed by Cell Counting Kit-8 assay. The mRNA levels of polarization markers (inducible nitrous oxide synthase (iNOS) and arginase 1 (Arg1)) and key cellular factors (IL-1β，IL-6，IL-10 and TNFα) were evaluated by qRT-PCR. rEgANXB18 was successfully expressed and recognized by E. granulosus s.l. infected canine sera, as well as could bind to the total protein of RAW264.7 cells. Additionally, rEgANXB18 could promote metabolic activity at 5, 10, 20, and 40 μg/mL while no significant impact on metabolic activity was observed at 80 μg/mL. Co-culture RAW264.7 cells with rEgANXB18 resulted in significantly upregulation of the transcript levels of polarization markers iNOS and Arg1. Moreover, rEgANXB18 significantly upregulated the transcript levels of IL-1β, IL-6, TNFα, and IL-10, while dose-effect relationship was observed in IL-1β, IL-6, and IL-10. Our results indicated that EgANXB18 showed the potential to regulate immune response of macrophages by shifting the cell polarization and cytokine profile, thereby promoting the parasitism of CE.