Toxocara canis: molecular basis of immune recognition and evasion

Alterations of plasma circulating microRNAs in BALB/c mice with Toxocara canis visceral and cerebral larva migrans

BACKGROUND

Human toxocariasis is a neglected parasitic disease characterised by the syndromes visceral, cerebral, and ocular larva migrans. This disease is caused by the migrating larvae of Toxocara roundworms from dogs and cats, affecting 1.4 billion people globally. Via extracellular vesicles (EVs), microRNAs have been demonstrated to play roles in host-parasite interactions and proposed as circulating biomarkers for the diagnosis and follow-up of parasitic diseases.

METHODS

Small RNA-seq was conducted to identify miRNAs in the infective larvae of T. canis and plasma EV-containing preparations of infected BALB/c mice. Differential expression analysis and target prediction were performed to indicate miRNAs involved in host-parasite interactions and miRNAs associated with visceral and/or cerebral larva migrans in the infected mice. Quantitative real-time polymerase chain reaction (PCR) was used to amplify circulating miRNAs from the infected mice.

RESULTS

This study reports host and parasite miRNAs in the plasma of BALB/c mice with visceral and cerebral larva migrans and demonstrates the alterations of these miRNAs during the migration of larvae from the livers through the lungs and to the brains of infected mice. After filtering unspecific changes in an irrelevant control, T. canis-derived miRNAs and T. canis infection-induced differential miRNAs are predicted to modulate genes consistently involved in mitogen-activated protein kinase (MAPK) signalling and pathways regulating axon guidance and pluripotency of stem in the infected mice with visceral and cerebral larva migrans. For these plasma circulating miRNAs predicted to be involved in host-parasite crosstalk, two murine miRNAs (miR-26b-5p and miR-122-5p) are experimentally verified to be responsive to larva migrans and represent circulating biomarker candidates for visceral and cerebral toxocariasis in BALB/c mice.

CONCLUSIONS

Our findings provide novel insights into the crosstalk of T. canis and the mammalian host via plasma circulating miRNAs, and prime agents and indicators for visceral and cerebral larva migrans. A deep understanding of these aspects will underpin the diagnosis and control of toxocariasis in humans and animals.

Comparison of extracellular vesicle isolation methods for the study of exosome cargo within Toxocara canis and Toxocara cati excretory secretory (TES) products

Toxocara is a genus of nematodes, which infects a variety of hosts, principally dogs and cats, with potential zoonotic risks to humans. Toxocara spp. larvae are capable of migrating throughout the host tissues, eliciting eosinophilic and granulomatous reactions, while surviving for extended periods of time, unchanged, in the host. It is postulated that larvae are capable of altering the host's immune response through the release of excretory-secretory products, containing both proteins and extracellular vesicles (EVs). The study of EVs has increased exponentially in recent years, largely due to their potential use as a diagnostic tool, and in molecular therapy. To this end, there have been multiple isolation methods described for the study of EVs. Here, we use nanoparticle tracking to compare the yield, size distribution, and % labelling of EV samples acquired through various reported methods, from larval cultures of Toxocara canis and T. cati containing Toxocara excretory-secretory products (TES). The methods tested include ultracentrifugation, polymer precipitation, magnetic immunoprecipitation, size exclusion chromatography, and ultrafiltration. Based on these findings, ultrafiltration produces the best results in terms of yield, expected particle size, and % labelling of sample. Transmission electron microscopy confirmed the presence of EVs with characteristic cup-shaped morphology. These findings can serve as a guide for those investigating EVs, particularly those released from multicellular organisms, such as helminths, for which few comparative analyses have been performed.

C-type lectin 4 of Toxocara canis activates NF-ĸB and MAPK pathways by modulating NOD1/2 and RIP2 in murine macrophages in vitro

Toxocara canis is a parasitic zoonose that is distributed worldwide and is one of the two pathogens causing toxocariasis. After infection, it causes serious public health and safety problems, which pose significant veterinary and medical challenges. To better understand the regulatory effects of T. canis infection on the host immune cells, murine macrophages (RAW264.7) were incubated with recombinant T. canis C-type lectin 4 (rTc-CTL-4) protein in vitro. The quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot were used to analyze the nucleotide-binding oligomerization domain-containing protein 1/2 (NOD1/2), receptor-interacting protein 2 (RIP2), nuclear factor kappa-light-chain enhancer of activated B cells (NF-κB), and mitogen-activated protein kinase (MAPK) on mRNA level and protein expression level in macrophages. Our results indicated that 10 μg/mL rTc-CTL-4 protein could modulate the expression of NOD1, NOD2, and RIP2 at both the transcriptional and translational levels. The protein translation levels of NF-κB, P-p65, p38, and P-p38 in macrophages were also modulated by rTc-CTL-4 protein. Macrophages were co-incubated with rTc-CTL-4 protein after siRNA silencing of NOD1, NOD2, and RIP2. The expression levels of NF-κB, P-p65, p38, and P-p38 were significantly changed compared with the negative control groups (Neg. Ctrl.). Taken together, rTc-CTL-4 protein seemed to act on NOD1/2-RIP2-NF-κB and MAPK signaling pathways in macrophages and might activate MAPK and NF-κB signaling pathways by regulating NOD1, NOD2, and RIP2. The insights from the above studies could contribute to our understanding of immune recognition and regulatory mechanisms of T. canis infection in the host animals.

The neurotropic schistosome vs experimental autoimmune encephalomyelitis: are there any winners?

The incidences of multiple sclerosis have risen worldwide, yet neither the trigger nor efficient treatment is known. Some research is dedicated to looking for treatment by parasites, mainly by helminths. However, little is known about the effect of helminths that infect the nervous system. Therefore, we chose the neurotropic avian schistosome Trichobilharzia regenti, which strongly promotes M2 polarization and tissue repair in the central nervous system, and we tested its effect on the course of experimental autoimmune encephalomyelitis (EAE) in mice. Surprisingly, the symptoms of EAE tended to worsen after the infection with T. regenti. The infection did not stimulate tissue repair, as indicated by the similar level of demyelination. Eosinophils heavily infiltrated the infected tissue, and the microglia number increased as well. Furthermore, splenocytes from T. regenti-infected EAE mice produced more interferon (IFN)-γ than splenocytes from EAE mice after stimulation with myelin oligodendrocyte glycoprotein. Our research indicates that the combination of increased eosinophil numbers and production of IFN-γ tends to worsen the EAE symptoms. Moreover, the data highlight the importance of considering the direct effect of the parasite on the tissue, as the migrating parasite may further tissue damage and make tissue repair even more difficult.

Convergence between helminths and breast cancer: intratumoral injection of the excretory/secretory antigens of the human parasite Toxocara canis (EST) increase lung macro and micro metastasis

Introduction

Worldwide, breast cancer is the most important cancer in incidence and prevalence in women. Different risk factors interact to increase the probability of developing it. Biological agents such as helminth parasites, particularly their excretory/secretory antigens, may play a significant role in tumor development. Helminths and their antigens have been recognized as inducers or promoters of cancer due to their ability to regulate the host's immune response. Previously in our laboratory, we demonstrated that chronic infection by Toxocara canis increases the size of mammary tumors, affecting the systemic response to the parasite. However, the parasite does not invade the tumor, and we decided to study if the excretion/secretion of antigens from Toxocara canis (EST) can affect the progression of mammary tumors or the pathophysiology of cancer which is metastasis. Thus, this study aimed to determine whether excretion/secretion T. canis antigens, injected directly into the tumor, affect tumor growth and metastasis.

Methods

We evaluated these parameters through the monitoring of the intra-tumoral immune response.

Results

Mice injected intratumorally with EST did not show changes in the size and weight of the tumors; although the tumors showed an increased microvasculature, they did develop increased micro and macro-metastasis in the lung. The analysis of the immune tumor microenvironment revealed that EST antigens did not modulate the proportion of immune cells in the tumor, spleen, or peripheral lymph nodes. Macroscopic and microscopic analyses of the lungs showed increased metastasis in the EST-treated animals compared to controls, accompanied by an increase in VEGF systemic levels.

Discussion

Thus, these findings showed that intra-tumoral injection of T. canis EST antigens promote lung metastasis through modulation of the tumor immune microenvironment.

Dynamics of ex vivo cytokine transcription during experimental Toxocara canis infection in Balb/c mice

The cytokine microenvironment is crucial in generating and polarizing the immune response. A means of monitoring this environment would be of great value for better understanding Toxocara canis immune modulation. The aim of this study was to analyze the dynamics of cytokine transcription ex vivo, during early (24-48 hours) and late (15-30 days) times post-infection, in the mesenteric lymph nodes, spleen and intestinal mucosa of Balb/c mice experimentally infected with T. canis larvae. Mice in the treated group were infected with 100 third-stage larvae (L3), whereas mice in the control group were not infected. Analyses were performed at different times: 24-48 hours post-infection (HPI), 15-30 days post-infection (DPI). IL4, IL10, IL12 and Ym1 mRNA transcriptions were analyzed through qPCR. This study showed cytokine transcription mediated by migrating larvae in the mesenteric lymph nodes and spleen at 24-48 HPI, whereas cytokine transcription in the intestinal mucosa was observed only at late times (15-30 DPI). These results suggest that the T. canis larvae migration during infection might play a role in cytokine dynamics. Since the cytokine microenvironment is crucial in modulating immune response, knowledge of cytokine dynamics during T. canis infections pave the way to better understand its interaction with the host.

Effects of metformin on parasitological, pathological changes in the brain and liver and immunological aspects during visceral toxocariasis in mice

There are currently insufficient anthelmintic medications available for the treatment of toxocariasis. For instance, Albendazole (ABZ) is the preferred medication, but its effectiveness against tissue-dwelling parasites is limited. In addition, Metformin (MTF) is a widely used oral antidiabetic medication that is considered to be safe for treatment. This study aimed to investigate any potential effects of MTF, alone or in combination with ABZ, on mice infections caused by Toxocara canis (T. canis). The efficacy of the treatment was assessed in the acute and chronic phases of the infection by larval recovery and histopathological, immunohistochemical, and biochemical studies. The results showed that combined therapy significantly reduced larval counts in the liver, brain, and muscles and ameliorated hepatic and brain pathology. It reduced oxidative stress and TGF-β mRNA expression and increased FGF21 levels in the liver. It decreased TNF-α levels and MMP-9 expression in the brain. In addition, it increased serum levels of IL-12 and IFN-γ and decreased serum levels of IL-4 and IL-10. In the acute and chronic phases of the infection, the combined treatment was more effective than ABZ alone. In conclusion, this study highlights the potential role of MTF as an adjuvant in the treatment of experimental T. canis infection when administered with ABZ.

The immunomodulatory effects of the C-type lectin protein of Toxocara canis on experimental autoimmune encephalomyelitis

Toxocara canis is a global zoonosis infection that can cause chronic and long-term toxocariasis in their paratenic host. The excretory-secretory (ES) products of T. canis larvae are considered to be responsible for the Th2 polarization and regulatory immune responses in toxocariasis. The C-type lectin family is one of the most prominent components of ES products of T. canis infective larvae. This study aimed to investigate the ameliorative effect of a T. canis C-type lectin recombinant protein (rCTL), on experimental autoimmune encephalomyelitis (EAE) which is a T-cell-mediated autoimmune disease of the central nervous system. C57BL/6 mice were subcutaneously treated with 30 μg rCTL, three times at an interval of 1 week. EAE was induced by myelin oligodendrocyte glycoprotein 35-55 peptide (MOG35-55 peptide) immunization, and weight and clinical scores were evaluated. Real time polymerase chain reaction was performed to evaluate the expression levels of T-bet, Gata3, and Foxp3 in splenocytes. In addition, the levels of interleukin 4, interferon gamma, and tumour growth factor-β (TGF-β) were quantified by enzyme-linked immunosorbent assay in splenocyte culture supernatants. The results indicated that the rCTL decreased clinical disability scores and delayed the onset of EAE. Furthermore, the data showed that rCTL treatment modulated the immune response, which was associated with upregulation of the mRNA expression of the Foxp3 gene and higher production of TGF-β in rCTL-treated mice. This study demonstrated that rCTL might be a potential agent to ameliorate EAE symptoms by stimulating anti-inflammatory responses.

Who Let the Dogs Out? Unmasking the Neglected: A Semi-Systematic Review on the Enduring Impact of Toxocariasis, a Prevalent Zoonotic Infection

Toxocariasis remains an important neglected parasitic infection representing one of the most common zoonotic infections caused by the parasite Toxocara canis or, less frequently, by Toxocara cati. The epidemiology of the disease is complex due to its transmission route by accidental ingestion of embryonated Toxocara eggs or larvae from tissues from domestic or wild paratenic hosts. Even though the World Health Organization and Centers for Disease Control classified toxocariasis amongst the top six parasitic infections of priority to public health, global epidemiological data regarding the relationship between seropositivity and toxocariasis is limited. Although the vast majority of the infected individuals remain asymptomatic or experience a mild disease, the infection is associated with important health and socioeconomic consequences, particularly in underprivileged, tropical, and subtropical areas. Toxocariasis is a disease with multiple clinical presentations, which are classified into five distinct forms: the classical visceral larva migrans, ocular toxocariasis, common toxocariasis, covert toxocariasis, and cerebral toxocariasis or neurotoxocariasis. Anthelmintic agents, for example, albendazole or mebendazole, are the recommended treatment, whereas a combination with topical or systemic corticosteroids for specific forms is suggested. Prevention strategies include educational programs, behavioral and hygienic changes, enhancement of the role of veterinarians, and anthelmintic regimens to control active infections.

The Role of Some Free-Ranging Animals in the Transmission of Multi-Host Species of Cryptosporidium Spp

Background

We aimed to characterize Cryptosporidium spp. in rats, cats, pigeons, and crows.

Methods

Fifty-five animal origin Cryptosporidium spp. genome were identified, genotyped and confirmed by nested PCR and of RFLP-PCR analysis as well as sequenced based on 18s rRNA and gp60 genes in Tehran (2012-2019). Finally, the phylogenetic analysis was performed by MEGA software (version 7).

Results

By the molecular method, Cryptosporidium spp. were detected in 24 (15.2%), 15 (15%), 2 (2%) and 13 (13%) cases of wild rats, cat, pigeon, and crow, respectively. Among the identified species by the RFLP pattern, most isolates were identified as C. parvum (24/157) 17.8% in rats, (15/100) 15% in cats, (13/100) 13%in crew and (2/100) 2% in pigeons; and the rest of the cases were C. muris and C. felis. The results of sequencing did not prove the existence of C. parvum, C. felis, C. muris, and rat genotype. Subtyping of C. parvum was indicated that the dominant subtype family belongs to the IId family and the subtype A20G1 was the most common subtype detected in all hosts while A19G1 was detected in one isolate of cat and pigeon.

Conclusion

Free-ranging animals are infected by species/subtype of Cryptosporidium, which can infect humans. This shows by itself the hygienic importance of the free-ranging animals in urban ecosystems. In the transmission of human cryptosporidiosis, the multi-host Cryptosporidium species such as C. parvum, C. felis, and C. muris can be transferred potentially from these animals to humans.

Potential roles of Toxocara canis larval excretory secretory molecules in immunomodulation and immune evasion

Toxocara canis larvae invade various tissues of different vertebrate species without developing into adults in paratenic host. The long-term survival of the larvae despite exposure to the well-armed immune response is a notable achievement. The larvae modulate the immune response to help the survival of both the host and the larvae. They skew the immune response to type 2/regulatory phenotype. The outstanding ability of the larvae to modulate the host immune response and to evade the immune arms is attributed to the secretion of Toxocara excretory-secretory products (TESPs). TESPs are complex mixture of differing molecules. The present review deals with the molecular composition of the TESPs, their interaction with the host molecules, their effect on the innate immune response, the receptor recognition, the downstream signals the adaptive immunity and the repair of tissues. This review also addresses the role of TESPs molecules in the immune evasion strategy and the potential effect of the induced immunomodulation in some diseases. Identification of parasite components that influence the nematode-host interactions could enhance understanding the molecular basis of nematode pathogenicity. Furthermore, the identification of helminths molecules with immunomodulatory potential could be used in immunotherapies for some diseases.

LARVICIDE ACTIVITY OF LACTOBACILLUS SPP. AND SACCHAROMYCES BOULARDII SUPERNATANTS ON TOXOCARA CANIS

Experimental studies have demonstrated the potential of probiotics to control visceral toxocariasis, which is a tissue parasitosis that is difficult to treat. This study evaluated the in vitro activity of probiotics and their supernatants on Toxocara canis larvae. The probiotics Lactobacillus rhamnosus (ATCC 7469), Lactobacillus paracasei (ATCC 335), Saccharomyces boulardii, Saccharomyces cerevisiae, and Bacillus cereus var. toyoi were tested in the following preparations: probiotic (P) 1 × 102 to 1 × 109 colony-forming units (CFUs), inactivated probiotic (IP) 1 × 102 to 1 × 109 CFUs, supernatant probiotic (SUpP), and inactivated probiotic supernatant (SupIP). The probiotics and their respective supernatants were separately incubated with 100 T. canis larvae per well using microculture plates with RPMI-1640 medium for 48 hr at 37 C and 5% CO2. The evaluation of the in vitro tests was based on the viability of T. canis larvae, through morphologic integrity, positive motility, and the absence of trypan blue stain. Only culture supernatants (SUpP and SUpIP) of Lactobacillus spp. resulted in 100% dead larvae, whereas S. boulardii showed larvicidal activity in T. canis >70%. The rest of the tests did not show larvicide activity. Therefore, it is important to investigate the supernatant effects of Lactobacillus spp. and S. boulardii in vivo on T. canis visceral infections, their mechanisms of action, and major metabolites involved.

Evaluation of new Toxocara canis chimeric antigens as an alternative to conventional TES-Ag for anti-Toxocara antibodies detection

Human toxocariasis is one of the neglected helminthiases and it is caused by the zoonotic roundworm species Toxocara canis and Toxocara cati. Diagnosis of human toxocariasis is based on the combination of clinical, parasitological, and epidemiological criteria, as well as serology tests that detect anti-Toxocara antibodies. Notwithstanding, due to the absence of pathognomonic symptoms and signs of the disease, serology is the key evidence to support a conclusive diagnosis. TES-ELISA is the most widely used serological test for diagnosis. However, cross-reaction of TES antigens with antibodies produced to other helminth antigens is a major drawback for its application in countries with high parasitic prevalence. T. canis recombinant antigens have been described as an alternative to native TES for diagnosis. Nevertheless, the selection of antigenic proteins is a complex process that requires validation. In this paper, we developed an eGFP carrier-based system to express and purify blocks of recombinant polypeptides of T. canis antigenic proteins. Intense cross-reaction polypeptides were detected by Immunoblot and avoided to finally produce a chimeric prototype protein. Additionally, a control chimeric protein that harbors the complete tested proteins was produced. Purified chimeric antigens were tested in ELISA and Immunoblot assays with 310 sera samples of negative and positive control individuals. Our results showed that chimeric rCHITC0 and rCHITC1 antigens (with sensitivities of 62% 58%, 38% and 16% in IB-rCHITC0, ELISA-rCHITC0, ELISA-rCHITC1 and IB-rCHITC1 respectively for OLMS) can perform better in terms of specificity (being 91%, 89%, 87% and 76% for ELISA-rCHITC1, IB-rCHITC1, ELISA-rCHITC0 and IB-rCHITC0 respectively for OLMS) than T. canis TES-ELISA (with 61% specificity), giving a higher signal with serum samples of infected individuals as well the possibility to discriminate false positive cases with other parasitic infections. Our data suggest that T. canis chimeric proteins, represent candidate antigens for phase II studies.

Lipidomic changes in the liver of beagle dogs associated with Toxocara canis infection

A global lipidomic analysis using liquid chromatography–tandem mass spectrometry was performed on the liver of beagle dogs infected with Toxocara canis to profile hepatic lipid species at 12 h post-infection (hpi), 24 hpi, and 36 days post-infection (dpi). This analysis identified six categories and 42 subclasses of lipids, including 173, 64, and 116 differentially abundant lipid species at 12 hpi, 24 hpi, and 36 dpi, respectively. Many of the identified lysophospholipids, such as lysophosphatidylglycerol, lysophosphatidylserine, and lysophosphatidylcholine, may contribute to the migration and development of T. canis during the early infection stage. Pathway analysis revealed significant alterations of several immune-inflammatory pathways, such as the B-cell receptor signaling pathway, the NF-kappa B signaling pathway, and the C-type lectin receptor signaling pathway at 12 and 24 hpi. These findings demonstrate the value of lipidomic profiling in revealing the extent of changes in the composition and abundance of hepatic lipidome caused by T. canis infection and their relevance to the pathophysiology of toxocariasis in beagle dogs.

The non-glycosylated protein of Toxocara canis MUC-1 interacts with proteins of murine macrophages

Toxocariasis is a neglected parasitic disease caused predominantly by larvae of Toxocara canis. While this zoonotic disease is of major importance in humans and canids, it can also affect a range of other mammalian hosts. It is known that mucins secreted by larvae play key roles in immune recognition and evasion, but very little is understood about the molecular interactions between host cells and T. canis. Here, using an integrative approach (affinity pull-down, mass spectrometry, co-immunoprecipitation and bioinformatics), we identified 219 proteins expressed by a murine macrophage cell line (RAW264.7) that interact with prokaryotically-expressed recombinant protein (rTc-MUC-1) representing the mucin Tc-MUC-1 present in the surface coat of infective larvae of T. canis. Protein-protein interactions between rTc-MUC-1 and an actin binding protein CFL1 as well as the fatty acid binding protein FABP5 of RAW264.7 macrophages were also demonstrated in a human embryonic kidney cell line (HEK 293T). By combing predicted structural information on the protein-protein interaction and functional knowledge of the related protein association networks, we inferred roles for Tc-MUC-1 protein in the regulation of actin cytoskeletal remodelling, and the migration and phagosome formation of macrophage cells. These molecular interactions now require verification in vivo. The experimental approach taken here should be readily applicable to comparative studies of other ascaridoid nematodes (e.g. T. cati, Anisakis simplex, Ascaris suum and Baylisascaris procyonis) whose larvae undergo tissue migration in accidental hosts, including humans.

Toxocariasis is a neglected parasitic disease of humans caused mainly by larvae of Toxocara canis. Given that T. canis is zoonotic and can infect a range of mammals, there has been substantial interest in host-parasite relationships, with studies showing that T. canis larvae secrete abundant mucins that effect/modulate immune responses and disease pathogenesis. To improve the understanding of immunomolecular interactions, we investigated the role(s) of the protein component of a mucin (Tc-MUC-1) secreted by infective larvae using a well-defined murine macrophage line (RAW264.7). The non-glycosylated recombinant protein of Tc-MUC-1 (designated rTc-MUC-1) was shown to interact with at least 219 proteins of RAW264.7 cells, particularly with the actin binding protein (CFL1) and a fatty acid binding protein (FABP5), which are involved in cell migration and phagocytosis, respectively. Based on these findings, we propose that Tc-MUC-1 regulates cytoskeletal organisation and signal transduction in host macrophages. It would be interesting to establish, using the integrative experimental approach employed here, whether the role(s) of Tc-MUC-1 protein homologues of related ascaridoids are conserved.

RNA sequencing reveals dynamic expression of spleen lncRNAs and mRNAs in Beagle dogs infected by Toxocara canis

BACKGROUND

Toxocara canis is a cosmopolitan parasite with a significant adverse impact on the health of humans and animals. The spleen is a major immune organ that plays essential roles in protecting the host against various infections. However, its role in T. canis infection has not received much attention.

METHODS

We performed sequencing-based transcriptome profiling of long noncoding RNA (lncRNA) and messenger RNA (mRNA) expression in the spleen of Beagle puppies at 24 h post-infection (hpi), 96 hpi and 36 days post-infection (dpi). Deep sequencing of RNAs isolated from the spleen of six puppies (three infected and three control) at each time point after infection was conducted.

RESULTS

Our analysis revealed 614 differentially expressed (DE) lncRNAs and 262 DEmRNAs at 24 hpi; 726 DElncRNAs and 878 DEmRNAs at 96 hpi; and 686 DElncRNAs and 504 DEmRNAs at 36 dpi. Of those, 35 DElncRNA transcripts and 11 DEmRNAs were detected at all three time points post-infection. Many DE genes were enriched in immune response, such as ifit1, ifit2 and rorc. Kyoto Encyclopedia of Genes and Genomes enrichment analysis revealed that some genes (e.g. prkx and tnfrsf11a) were involved in the T cell receptor signaling pathway, calcium signaling pathway, Ras signaling pathway and NF-κB signaling pathway.

CONCLUSIONS

The findings of this study show marked alterations in the expression profiles of spleen lncRNAs and mRNAs, with possible implications in the pathophysiology of toxocariasis.

Toxocara canis Infection Alters mRNA Expression Profiles of Peripheral Blood Mononuclear Cells in Beagle Dogs at the Lung Infection Period

Simple Summary

Toxocariasis is one of the most neglected zoonoses in the world. Toxocara canis is the main pathogen causing toxocariasis in humans and animals, threatening public health. To date, the mechanism by which the larvae of T. canis escape the attack of immune cells in the blood is still poorly understood. Using RNA-seq technology, the transcriptional alterations of Beagle dog peripheral blood mononuclear cells (PBMCs) between the presence and absence of T. canis infection were analyzed during the lung infection period, and 1066 upregulated genes and 1076 downregulated genes were identified (padj < 0.05 and |log₂ (FoldChange)| > 1). In addition, many immune- or inflammation-related GO terms and KEGG signaling pathways were significantly altered during T. canis infection by GO annotation and KEGG enrichment analysis. The present study revealed that T. canis infection can alter the mRNA profiles of PBMCs in Beagle dogs during the lung infection period, which has important implications for a better understanding of the interaction mechanism between T. canis and host immune cells.

Abstract

Toxocara canis is a neglected zoonotic roundworm distributed all over the world, causing toxocariasis in humans and animals. However, so far, the immune mechanism of T. canis infection in definitive hosts remains to be clarified. In this study, the transcriptional alterations of Beagle dogs’ peripheral blood mononuclear cells (PBMCs) induced by T. canis infection during the lung infection period were analyzed using RNA-seq technology. A total of 2142 differentially expressed genes were identified, with 1066 upregulated genes and 1076 downregulated genes. Many differentially expressed genes participated in the biological process of intracellular signal transduction, as well as the immune- or inflammation-related KEGG signaling pathway, such as the Notch signaling pathway, Toll-like receptor signaling pathway, and NF-kappa B signaling pathway, through KEGG enrichment analysis. This study indicated that T. canis infection could suppress the biological function of Beagle dogs’ PMBCs and provided basic data to further clarify the interaction mechanism between T. canis and host immune cells.

Changes in the expression of miR-103a and miR-21: a functional diagnosis of toxocariasis in rats

Introduction. Toxocariasis is a zoonotic parasitic disease caused by migrating nematode worms, Toxocara species larvae, within tissues. MicroRNAs (miRNAs) are small RNA molecules that regulate gene expression at a post-transcriptional level.Hypothesis/Gap Statement. miRNA-based diagnostic biomarkers for toxocariasis are emerging, but there is limited information about the role of many miRNAs and a more detailed diagnostic evaluation of miRNA expression patterns is needed to understand their immunobiological function.Aim. We investigated the expression levels of circulating miRNA 21 and miRNA 103a as potential biomarkers for the prediction and diagnosis of toxocariasis in Wistar rats infected with Toxocara canis.Methodology. Thirty Wistar rats were inoculated orally with 2500 T. canis embryonated eggs via gavage. Serum samples were collected from infected animals and were tested against T. canis antigens for 60 days post-infection. The plasma samples were isolated for quantitative real-time PCR (qPCR) assays and qPCR was used to assess transcription levels of miRNA 21 and miRNA 103a.Results. The prevalence of anti-Toxocara IgG was detected in 7/30 (23.3 %) infected rats. Molecular analysis of miRNAs 21 and 103a showed that expression levels of miRNAs in both groups of Toxocara-positive and negative samples were the same without significant association. The ratio of housekeeping gene expression (U6) to gene expression of miRNAs 21 and 103a indicated the rate of change (1/1.38 ≈ 0.75 and 1/0.751 ≈ 1.3, respectively).Conclusion. Our study revealed that miRNAs 21 and 103a might play fundamental roles as biomarkers and diagnostic tools for toxocariasis. However, the changes in expression of these miRNAs were not adequate to be used as biomarkers in diagnosis.

Cytokine Profile in Aqueous Humor of Patients With Ocular Toxocariasis

Purpose

Ocular toxocariasis (OT) is a vision-threatening disease with a largely unknown intraocular pathogenesis. Herein, we determined the cytokine expression profile in aqueous humor (AH) of patients with OT.

Methods

This is a retrospective case-control study of cytokine levels in AH of patients with OT and uveitis and control subjects. Thirty samples from eyes with OT, 23 from eyes with non-OT uveitis, and 25 from eyes with age-related cataract were analyzed using a multiplexed magnetic bead immunoassay. Thirty-one cytokines were detected and classified into 5 categories: T-helper type 1 (Th1) -associated cytokines, Th2-associated cytokines, Th17 cytokine, proinflammatory mediators, and growth factors.

Results

In the 31 cytokines, 9 cytokines were undetectable, including IL-1a, IL-1b, IL-2, IL-3, IL-12p70, IL-17A, TGF-a, TNF-β, and IFN-g. From the 22 cytokines, 13 exhibited significantly increased expression in the OT group than in the control group, including TNF-a, IFN-a2, IL-4, IL-5, IL-6, IL-9, IL-10, IL-13, sCD40L, PDGF-AA, PDGF-AB/BB, FLT3l, and EGF. There were 5 cytokines exhibited significantly increased expression in the OT group than in non-OT group, including IL-5, IL-9, IL-10, IL-13, and PDGF-AA. There was no significantly decreased expression in any cytokines in the OT group when compared with control or non-OT groups. To the 5 cytokines that showed significant difference in OT group alone, IL-10 and IL-13 exhibited more than 13-fold increase, and IL-5 showed the most obvious as 27-fold increase in OT patients, when compared with that in control group.

Conclusion

The cytokine profile expression in aqueous humor from patients with ocular toxocariasis was investigated, and our findings suggest that Th1 and Th17 cytokine responses are not enhanced, whereas the cytokine status was polarized toward a Th2 response. Our findings also suggest the involvement of IL-5, IL-10, and IL-13 in the immunopathogenesis of ocular toxocariasis.

Interstitial pneumonia and diffuse alveolar damage in domestic animals

Classification of pneumonia in animals has been controversial, and the most problematic pattern is interstitial pneumonia. This is true from the gross and histologic perspectives, and also from a mechanistic point of view. Multiple infectious and noninfectious diseases are associated with interstitial pneumonia, all of them converging in the release of inflammatory mediators that generate local damage and attract inflammatory cells that inevitably trigger a second wave of damage. Diffuse alveolar damage is one of the more frequently identified histologic types of interstitial pneumonia and involves injury to alveolar epithelial and/or endothelial cells, with 3 distinct stages. The first is the “exudative” stage, with alveolar edema and hyaline membranes. The second is the “proliferative” stage, with hyperplasia and reactive atypia of type II pneumocytes, infiltration of lymphocytes, plasma cells, and macrophages in the interstitium and early proliferation of fibroblasts. These stages are reversible and often nonfatal. If damage persists, there is a third “fibrosing” stage, characterized by fibrosis of the interstitium due to proliferation of fibroblasts/myofibroblasts, persistence of type II pneumocytes, segments of squamous metaplasia of alveolar epithelium, plus inflammation. Understanding the lesion patterns associated with interstitial pneumonias, their causes, and the underlying mechanisms aid in accurate diagnosis that involves an interdisciplinary collaborative approach involving pathologists, clinicians, and radiologists.

Therapy and Prevention for Human Toxocariasis

For the last four decades, knowledge about human toxocariasis with regard to its epidemiology, pathophysiology, clinical spectrum, and imaging or laboratory diagnosis has substantially progressed. Knowledge about specific therapy with anthelmintics has lagged behind. To date, only four drugs are registered for human use, and their efficacy has rarely been assessed in prospective controlled trials. It is likely that the repurposing of potent anthelmintics from veterinary medicine will improve this situation. Due to its wide availability and a lack of major side effects during short regimens, albendazole has become the drug of choice. However, its efficacy should be more precisely assessed. The role of anthelmintics in the treatment of neurological or ocular toxocariasis remains to be clarified. Prophylactic measures in humans or companion animals are efficient and represent first-line treatments for the control of this zoonosis. Unfortunately, their implementation in areas or countries where toxocariasis epidemiology is driven by poverty is quite difficult or unrealistic.

Acute and chronic immunomodulatory response mechanisms against Toxocara canis larvae infection in mice

Abstract The objective of this work was to evaluate the early and late immunological modulation of an experimental infection of T. canis larvae in mice. Mice were infected with 100 infective larvae and euthanized at different period: 24, 48 hours post infection (HPI), 15- and 30 days post infection (DPI). The humoral response was evaluated by indirect ELISA. Quantitative RT–PCR (qPCR) was used to quantify the mRNA transcription of cytokines IL4, IL10, IL12 and Ym1 in the early and late infection periods. Infection with T. canis was able to generate specific total IgG at 15- and 30- DPI. Analyzing the IgG isotype revealed a significant differentiation for IgG1 compared with IgG2a, IgG2b and IgG3, characterizing a Th-2 response. Evaluating the gene transcription at the early phase of infection, higher transcription levels of IL10, IL4 and Ym1 and a downregulation of IL12 were observed. By the late phase, increased transcription levels of IL4, Ym1 and IL12 were observed, and downregulation of IL-10 transcription was observed. The data obtained suggest that during experimental infection with T. canis, the participation of the IL4, IL10, IL12 cytokines and Ym1 can play an important role in T. canis immunomodulation.

Excretory/secretory proteins of adult Toxocara canis induce changes in the expression of proteins involved in the NOD1-RIP2-NF-κB pathway and modulate cytokine production in mouse macrophages

Dog roundworm (Toxocara canis) is the major causative agent of toxocarosis, a parasitic disease of both veterinary and medical importance. Knowledge gaps in fundamental and applied aspects hinder the control of this important zoonotic disease. To have a better understanding of Toxocara infection and host immune responses, mouse macrophages were exposed to excretory/secretory (ES) proteins released by adult worms of T. canis in vitro. The messenger RNA transcription and protein expression of nucleotide-binding oligomerization domain-containing protein 1 (NOD1), receptor interacting protein 2 (RIP2) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) in macrophages were analysed using quantitative real-time PCR (qRT-PCR) and Western blot. The levels of tumour necrosis factor alpha (TNF-ɑ), interleukin-1 beta (IL-1β) and IL-6 released by the stimulated macrophages were analysed using enzyme-linked immunosorbent assay. It was found that 20 μg/mL ES proteins of adult T. canis induced the expression of NOD1, RIP2 and NF-κB in mouse macrophages at both transcriptional and translational levels after 9 h of incubation in vitro. Incubation with 20 μg/mL ES proteins also modulated the production of pro-inflammatory cytokines TNF-ɑ, IL-1β and IL-6 by the macrophages. Taken together, ES proteins of adult T. canis appeared to be able to affect the macrophage NOD1-RIP2-NF-κB signalling pathway, which might play a role in regulating the production of proinflammatory cytokines. Further investigation of these aspects should lead to a better understanding of immune recognition of and modulation by Toxocara canis in host animals.

An international seroprevalence survey of the IgE sensitisation to the Dermatophagoides farinae house dust mite and two of its major allergens (Der f 2, Zen 1) in atopic dogs

BACKGROUND

Dogs with atopic dermatitis are often immunoglobulin (Ig)E-sensitised to Dermatophagoides farinae (Df) house dust mites, yet limited data exist on the sensitisation rates to the individual Df allergens, Der f 2 and Zen 1.

OBJECTIVES

To determine the IgE sensitisation rates to Df, Der f 2 and Zen 1 in atopic dogs from geographically diverse countries.

ANIMALS

Serum was collected from 32 laboratory dogs in Japan, and 837 atopic dogs from 11 countries from five continents: Asia (Japan, Thailand, Taiwan), Europe (Italy, Latvia, the Netherlands, UK), North America (USA), South America (Argentina, Brazil) and Africa (South Africa).

METHODS AND MATERIALS

We determined Df-, Der f 2- and Zen 1-specific IgE levels by ELISA. Correlations between the IgE values for these three allergens were calculated.

RESULTS

The IgE seropositivity rates for Df varied between 74% (Argentina) and 100% (the Netherlands, Thailand, South Africa), those for Der f 2 between 12% (Argentina) and 88% (South Africa), and for Zen 1 between 70% (Argentina) and 100% (the Netherlands). Apart from the especially low seropositivity rate for Der f 2-specific IgE in Argentina, the percentage of IgE sensitisation varied little between countries. There was significant correlation between the IgE levels to these three allergens which was highest between Df and Zen 1, and lowest between Zen 1 and Der f 2.

CONCLUSIONS AND CLINICAL RELEVANCE

The IgE sensitisation to Df is geographically widespread. Der f 2 and Zen 1 are major allergens for dogs in almost all countries where this was evaluated.

A Zinc Metalloprotease nas-33 Is Required for Molting and Survival in Parasitic Nematode Haemonchus contortus

Molting is of great importance for the survival and development of nematodes. Nematode astacins (NAS), a large family of zinc metalloproteases, have been proposed as novel anthelmintic targets due to their multiple roles in biological processes of parasitic nematodes. In this study, we report a well conserved nas-33 gene in nematodes of clade V and elucidate how this gene is involved in the molting process of the free-living nematode Caenorhabditis elegans and the parasitic nematode Haemonchus contortus. A predominant transcription of nas-33 is detected in the larval stages of these worms, particularly in the molting process. Knockdown of this gene results in marked molecular changes of genes involved in cuticle synthesis and ecdysis, compromised shedding of the old cuticle, and reduced worm viability in H. contortus. The crucial role of nas-33 in molting is closely associated with a G protein beta subunit (GPB-1). Suppression of both nas-33 and gpb-1 blocks shedding of the old cuticle, compromises the connection between the cuticle and hypodermis, and leads to an increased number of sick and dead worms, indicating essentiality of this module in nematode development and survival. These findings reveal the functional role of nas-33 in nematode molting process and identify astacins as novel anthelmintic targets for parasitic nematodes of socioeconomic significance.

Expression of Ascaris lumbricoides putative virulence-associated genes when infecting a human host

BACKGROUND

Ascaris lumbricoides is the most common causative agent of soil-transmitted helminth infections worldwide, with an estimated 450 million people infected with this nematode globally. It is suggested that helminths are capable of evading and manipulating the host immune system through the release of a spectrum of worm proteins which underpins their long-term survival in the host. We hypothesise that the worm overexpresses these proteins when infecting adults compared to children to cirvumvent the more robust defence mechanisms of adults. However, little is known about the parasite's genes and encoded proteins involved during A. lumbricoides infection. Hence, this study was conducted to assess the expression profile of putative virulence-associated genes during an active infection of adults and children.

METHODS

In this study, quantitative PCR was performed to evaluate the expression profile of putative virulence-associated genes in A. lumbricoides isolated from infected children and adults. The study was initiated by collecting adult worms expelled from adults and children following anthelminthic treatment. High-quality RNA was successfully extracted from each of six adult worms expelled by three adults and three children, respectively. Eleven putative homologues of helminth virulence-associated genes reported in previous studies were selected, primers were designed and specific amplicons of A. lumbricoides genes were noted. The expression profiles of these putative virulence-associated genes in A. lumbricoides from infected adults were compared to those in A. lumbricoides from infected children.

RESULTS

The putative virulence-associated genes VENOM, CADHERIN and PEBP were significantly upregulated at 166-fold, 13-fold and fivefold, respectively, in adults compared to children. Conversely, the transcription of ABA-1 (fourfold), CATH-L (threefold) and INTEGRIN (twofold) was significantly suppressed in A. lumbricoides from infected adults.

CONCLUSIONS

On the basis of the expression profile of the putative virulence-associated genes, we propose that the encoded proteins have potential roles in evasion mechanisms, which could guide the development of therapeutic interventions.

Toxocara canis and Toxocara cati Somatic and Excretory-Secretory Antigens Are Recognised by C-Type Lectin Receptors

Toxocara canis and Toxocara cati, the worldwide occurring intestinal roundworms of canids and felids, represent an important public health threat due to various disease manifestations in humans. Host recognition of pathogens is mediated by pattern recognition receptors (PRRs). Myeloid C-type lectin receptors (CLRs) are PRRs and recognise carbohydrate structures of various pathogens. As Toxocara excretory-secretory products (TES) are predominantly composed of glycoconjugates, they represent suitable targets for CLRs. However, the range of host-derived CLRs recognising Toxocara spp. is still unknown. Using a CLR-hFc fusion protein library, T. canis and T. cati L3 somatic antigens (TSOM) were bound by a variety of CLRs in enzyme-linked immunosorbent assay (ELISA), while their TES products interacted with macrophage galactose-type lectin-1 (MGL-1). Two prominent candidate CLRs, MGL-1 and macrophage C-type lectin (MCL), were selected for further binding studies. Immunofluorescence microscopy revealed binding of MGL-1 to the oral aperture of L3. Immunoblot experiments identified distinct protein fractions representing potential ligands for MGL-1 and MCL. To evaluate how these interactions influence the host immune response, bone marrow-derived dendritic cell (BMDC) assays were performed, showing MCL-dependent T. cati-mediated cytokine production. In conclusion, MGL-1 and MCL are promising candidates for immune modulation during Toxocara infection, deserving further investigation in the future.

Identification and Immunological Characterization of Somatic Proteins from Adults of Toxocara cati by Proteomics Technique

Background:

Toxocara cati is considered as one of the main etiological agents of toxocariasis with global and regional importance. As there is no information on proteomics of T. cati, herein, we reported the results obtained by proteomic analysis of somatic proteins extract, using a mass spectrometry (LC–MS/MS) approach.

Methods:

Somatic extract fractions were separated by two-dimensional SDS-PAGE and were electro blotted on to PVDF membranes for immunoblot analysis, then collected the immunogenic spots which response of antibodies of the paratenic hosts (mice) to the antigens (Mashhad, 2017), and analyzed by LC–MS/MS. The LC-MS/MS data were analyzed by Mascot database, Taxonomy Toxocara, and common contaminants, in Omics Center, Biotechnology Medical University of Graz (Austria, 2018).

Result:

The protein spots were isolated between 15–140 kDa ranges using 3–10 non-linear IPG strips and Brilliant Blue Coomassie. Ten proteins were characterized as immunogenic proteins, seven of them were identified and three of them were unknown proteins.

Conclusion:

This study provided additional information about the somatic antigens of T. cati, which can lead to the development of new strategies for novel immuno-modulators, drug targets, subunit vaccines and immunodiagnostic kits for toxocariasis.

Protective effect of the probiotic Lactobacillus acidophilus ATCC 4356 in BALB/c mice infected with Toxocara canis

Human toxocariasis consists of chronic tissue parasitosis that is difficult to treat and control. This study aimed to evaluate the action of the probiotic Lactobacillus acidophilus ATCC 4356 on larvae of Toxocara canis and the effect of IFN-γ cytokine on parasite-host in vivo (1.10⁹ CFU) and in vitro (1.10⁶, 1.10⁷, 1.10⁸, 1.10⁹ CFU) interactions. Four groups of six BALB/c mice were formed: G1 - L. acidophilus supplementation and T. canis infection; G2 - T. canis infection; G3 - L. acidophilus supplementation; and G4 - PBS administration. Mice were intragastrically suplemented with probiotics for 15 days before inoculation and 48 h after inoculation with 100 T. canis eggs. The inoculation of T. canis was also perfomed intragastrically. The recovery of larvae took place through digestion of liver and lung tissues; the evaluation of IFN-γ gene transcription in leukocytes was performed by qPCR. The in vitro test consisted of incubating the probiotic with T. canis larvae. The supplementation of probiotics produced a reduction of 57.7% (p = 0.025) in the intensity of infection of T. canis larvae in mice, whereas in the in vitro test, there was no larvicidal effect. In addition, a decrease in the IFN-γ gene transcription was observed in both, T. canis-infected and uninfected mice, regardless of whether or not they received supplementation. The probiotic L. acidophilus ATCC 4356 reduced T. canis infection intensity in mice, however, the probiotic did not have a direct effect on larvae, demonstrating the need of interaction with the host for the beneficial effect of the probiotic to occur. Yet, the proinflammatory cytokine IFN-γ did not apparently contributed to the observed beneficial effect of probiotics.

Proteomic alterations in the plasma of Beagle dogs induced by Toxocara canis infection

Toxocara canis causes ocular larva migrans and visceral larva migrans in humans. Knowledge about the molecular mechanism of T. canis-hosts interaction is limited. The proteomic alterations in the plasma of Beagle dogs induced by T. canis infection were studied by the quantitative mass spectrometry-based data-independent acquisition (DIA). 418, 414 and 411 plasma proteins were identified at 24 h post-infection (hpi), 96 hpi and 36 days post-infection (dpi), including 6, 5 and 23 proteins with differential abundance, respectively. At 24 hpi, the altered proteins, retinoic acid receptor responder protein 2 (RARRES2), WD repeat-containing protein 1 (WDR1), moesin and filamin-A, may participate in pro-inflammatory reaction or promote larvae migration. At 96 hpi, the altered protein C and fibroleukin may maintain the stability of the coagulation system to protect the lung. At 36 dpi, the alterations of C-reactive protein (CRP), ficolin (FCN), complement factor H-related protein 5 (CFHR5) and other complements can affect the three traditional complement system, including the classic pathway, lectin pathway and alternative pathway. These proteins may play important roles in the interaction between T. canis and its definitive hosts. Further study on these altered proteins triggered by T. canis infection may discovery novel therapeutic or diagnostic targets for toxocariasis. SIGNIFICANCE OF THE STUDY: Toxocara canis is one of the globally distributed soil-transmitted helminths, which causes ocular larva migrans and visceral larva migrans in humans and a wide range of warm-blooded animals. T. canis adapts to different microenvironments by resisting and adjusting various biological processes of the hosts. Knowledge about the molecular mechanism of T. canis-hosts interaction is limited. Plasma proteins are good marker for monitoring the occurrence and development of diseases. The proteomic alterations in the plasma of Beagle dogs induced by T. canis infection were studied by the quantitative mass spectrometry-based data-independent acquisition (DIA) in this study. A total of 418, 414 and 411 plasma proteins were identified at 24 h post-infection (hpi), 96 hpi and 36 days post-infection, respectively. Ten protein with differential abundances were validated by using parallel reaction monitoring (PRM). Collectively, our deep proteomic analysis of plasma revealed that proteins alterations were affected by disease development, and proteomic analysis is an ideal method for quantifying changes in circulating factors on a global scale in response to pathophysiological perturbations such as T. canis infection.

Ivermectin: An Anthelmintic, an Insecticide, and Much More

Here we tell the story of ivermectin, describing its anthelmintic and insecticidal actions and recent studies that have sought to reposition ivermectin for the treatment of other diseases that are not caused by helminth and insect parasites. The standard theory of its anthelmintic and insecticidal mode of action is that it is a selective positive allosteric modulator of glutamate-gated chloride channels found in nematodes and insects. At higher concentrations, ivermectin also acts as an allosteric modulator of ion channels found in host central nervous systems. In addition, in tissue culture, at concentrations higher than anthelmintic concentrations, ivermectin shows antiviral, antimalarial, antimetabolic, and anticancer effects. Caution is required before extrapolating from these preliminary repositioning experiments to clinical use, particularly for Covid-19 treatment, because of the high concentrations of ivermectin used in tissue-culture experiments.

"Begging the Question"-Does Toxocara Infection/Exposure Associate with Multiple Sclerosis-Risk?

Although the cause of multiple sclerosis (MS) is unclear, infectious agents, including some parasitic roundworms (nematodes), have been proposed as possible risk factors or contributors. Here, we conducted a systematic review and meta-analysis of published observational studies to evaluate whether there is a possible association between infection with, or exposure to, one or more members of the genus Toxocara (phylum Nematoda; superfamily Ascaridoidea) and MS. We undertook a search of public literature databases to identify relevant studies and then used a random-effects meta-analysis model to generate the pooled odds ratio (OR) and 95% confidence intervals (CIs). This search identified six of a total of 1371 articles that were relevant to the topic; these published studies involved totals of 473 MS patients and 647 control subjects. Anti-Toxocara IgG serum antibodies were detected in 62 MS patients and 37 controls, resulting in respective seroprevalences of 13.1% (95% CI: 8.2-20.3) and 4.8% (95% CI: 2.5-9.2), indicating an association (pooled OR, 3.01; 95% CI: 1.46-6.21). Because of the publication bias identified (six eligible studies), well-designed and -controlled studies are required in the future to rigorously test the hypothesis that Toxocara infection/exposure has an association with MS.

Global profiling of lncRNAs-miRNAs-mRNAs reveals differential expression of coding genes and non-coding RNAs in the lung of beagle dogs at different stages of Toxocara canis infection

The roundworm Toxocara canis causes toxocariasis in dogs and larval migrans in humans. Better understanding of the lung response to T. canis infection could explain why T. canis must migrate to and undergoes part of its development inside the lung of the definitive host. In this study, we profiled the expression patterns of long non-coding RNAs (lncRNAs), microRNAs (miRNAs), and mRNAs in the lungs of Beagle dogs infected by T. canis, using high throughput RNA sequencing. At 24 h p.i., 1,012 lncRNAs, 393 mRNAs and 10 miRNAs were differentially expressed (DE). We also identified 883 DElncRNAs, 264 DEmRNAs and 20 DEmiRNAs at 96 h p.i., and 996 DElncRNAs, 342 DEmRNAs and eight DEmiRNAs at 36 days p.i., between infected and control dogs. Significant changes in the levels of expression of transcripts related to immune response and inflammation were associated with the antiparasitic response of the lung to T. canis. The remarkable increase in the expression of scgb1a1 at all time points after infection suggests the need for consistent moderation of the excessive inflammatory response. Also, upregulation of foxj1 at 24 h p.i., and downregulation of IL-1β and IL-21 at 96 h p.i., suggest an attenuation of the humoral immunity of infected dogs. These results indicate that T. canis pathogenesis in the lung is mediated through contributions from both pro-inflammatory and anti-inflammatory mechanisms. Competing endogenous RNA (ceRNA) network analysis revealed significant interactions between DElncRNAs, DEmiRNAs and DEmRNAs, and improved our understanding of the ceRNA regulatory mechanisms in the context of T. canis infection. These data provide comprehensive understanding of the regulatory networks that govern the lung response to T. canis infection and reveal new mechanistic insights into the interaction between the host and parasite during the course of T. canis infection in the canine.

Humoral immune response of pigs infected with Toxocara cati

Toxocara cati is one of the causative agents of human toxocariasis. Serological methods are used for diagnosis in paratenic hosts like humans but the humoral immune response triggered by this parasite is unknown. We characterized the humoral immune response to T. cati excretory-secretory antigens (TES) in pigs as animal model during the acute and chronic stages of infection. ELISA and Western Blot techniques were used to determine antibody response. Pigs were experimentally inoculated with 100,000 infective Toxocara cati eggs. Blood was collected at 7, 14, 21 and 28 days post-inoculation (d.p.i.) to assess the acute stage of infection and 90, 120 and 180 d. p.i. for chronic stage analysis. ELISA showed values higher than the cut-off of specific IgM and IgG at 7 d. p.i. with significant differences at 0 and 7 d. p.i. for IgM and at 14, 21 and 28 d. p.i. for IgG in the acute stage. Higher and stable levels were detected in the chronic stage. Western Blot showed bands from 102 to 38 kDa detected by specific IgM and IgG. More immunogenic bands were identified by specific IgG. In the chronic stage of infection a band near 31 kDa was the only band detected by IgM until 150 d. p.i. Specific IgG recognized bands between 102 and 31 kDa. This study demonstrates how the humoral immune response evolves in the acute and chronic stages of infection and provides evidence on the role of the pig as a paratenic host of T. cati.

Proteomic analysis of soluble protein extract of adult Toxocara cati

Toxocara cati is a cat roundworm and the causative agent of toxocariasis as a cosmopolitan zoonotic disease. As no information has been reported so far, identification of T. cati proteins can be useful for the development of new diagnostic strategies. This study was conducted to identify the major proteins in the adult T. cati tegument using bi-dimensional electrophoresis (2-DE) and shotgun proteomics. A total proteins were identified, among them the metabolic enzymes were the largest group, including: Enolase, triose phosphate isomerase, fructose-bisphosphate aldolase, aldehyde dehydrogenase. The other important protein groups recognized in T. cati, belong to the HSP-family, the structure and motor proteins, such as actin. The role of these proteins have been implicated in parasite-host interactions and modulating cellular immune response, immune regulation in evasion mechanisms of the host immune response. Characterizing T. cati adult proteins play a key role not only in host-parasite interactions, but also in the discovery of drug targets, subunit vaccines against toxocariasis, immunodiagnostic kits for toxocariasis and the identification of novel immuno-modulators that can form the next generation of therapeutic possibilities for inflammatory diseases.

Excretory/Secretory Metabolome of the Zoonotic Roundworm Parasite Toxocara canis

Toxocariasis is a zoonotic disease affecting humans that is predominantly caused by Toxocara canis and T. cati, primarily parasites of dogs and cats, respectively. Toxocara generally establishes long-term infections by co-opting its host's physiological processes, while at the same time exploiting the nutritional environment. Adult stage T. canis reside in the gut of the definitive canine host where they employ a suite of strategies to combat intestinal immune responses by actively producing and releasing excretory-secretory products (ESPs). The protein component of T. canis ESPs has been widely studied, but characterisation of the non-protein ESP complement remains neglected. To characterize the secreted metabolome of Toxocara ESPs and to shed light on the parasite's metabolic processes, we profiled the ESPs of T. canis using both gas chromatography (GC) and liquid chromatography (LC) mass spectrometry approaches. We successfully identified 61 small molecules, including 41 polar metabolites, 14 medium-long chain fatty acids (MLCFAs) and six short chain fatty acids (SCFAs). We identified talose, stearic acid and isovalerate as the major compounds belonging to the polar, MLCFA and SCFA chemical classes, respectively. Most of the 61 identified metabolites appear to have been produced by T. canis via three distinct metabolic pathways - fatty acid, amino acid and carbohydrate metabolism. The majority of the identified ESPs have known biological properties, especially as immunomodulators. However, there is limited/no information on the biological roles or applications of 31 ESP biomolecules, suggesting that these may have novel activities that merit further investigation.

Potential Novel Risk Factor for Breast Cancer: Toxocara canis Infection Increases Tumor Size Due to Modulation of the Tumor Immune Microenvironment

Worldwide, breast cancer is the most important type of cancer in women with regard to incidence and prevalence. Several risk factors interact to increase the probability of breast cancer development. Biological environmental contaminants such as infectious agents play a significant role in tumor development, and helminths have been recognized as cancer enhancers or inducers due to their ability to regulate the host immune response. Toxocara canis is a zoonotic and cosmopolite nematode with immuno-regulatory abilities. T. canis infection has been related to T helper type-2 cell (Th2 or type 2) and regulatory responses. Type 2 and regulatory immune responses may favor the development of comorbidities that are usually controlled or eliminated through a type 1 response such as cancer. The aim of this study was to determine whether T. canis infection alters mammary tumor growth through modulation of the immune response. Infected mice developed larger tumors. Tumor immune cell milieu analysis revealed that infection reduced the proportions of CD8⁺ lymphocytes and increased the proportions of F4/80⁺ macrophages and CD19⁺ B cells. These changes were accompanied by a type 2 local response represented by increased amounts of IL-4 and VEGF and a regulatory microenvironment associated with higher IL-10 levels. Thus, this study demonstrates that T. canis infection enhances tumor development and suggests that this is through modulation of the tumor immune microenvironment.

Infection with Toxocara canis Inhibits the Production of IgE Antibodies to α-Gal in Humans: Towards a Conceptual Framework of the Hygiene Hypothesis?

α-Gal syndrome (AGS) is a type of anaphylactic reaction to mammalian meat characterized by an immunoglobulin (Ig)E immune response to the oligosaccharide α-Gal (Galα1-3Galβ1-4GlcNAc-R). Tick bites seems to be a prerequisite for the onset of the allergic disease in humans, but the implication of non-tick parasites in α-Gal sensitization has also been deliberated. In the present study, we therefore evaluated the capacity of helminths (Toxocara canis, Ascaris suum, Schistosoma mansoni), protozoa (Toxoplasma gondii), and parasitic fungi (Aspergillus fumigatus) to induce an immune response to α-Gal. For this, different developmental stages of the infectious agents were tested for the presence of α-Gal. Next, the potential correlation between immune responses to α-Gal and the parasite infections was investigated by testing sera collected from patients with AGS and those infected with the parasites. Our results showed that S. mansoni and A. fumigatus produce the terminal α-Gal moieties, but they were not able to induce the production of specific antibodies. By contrast, T. canis, A. suum and T. gondii lack the α-Gal epitope. Furthermore, the patients with T. canis infection had significantly decreased anti-α-Gal IgE levels when compared to the healthy controls, suggesting the potential role of this nematode parasite in suppressing the allergic response to the glycan molecule. This rather intriguing observation is discussed in the context of the 'hygiene hypothesis'. Taken together, our study provides new insights into the relationships between immune responses to α-Gal and parasitic infections. However, further investigations should be undertaken to identify T. canis components with potent immunomodulatory properties and to assess their potential to be used in immunotherapy and control of AGS.

Toxocara "omics" and the promises it holds for medicine and veterinary medicine

Toxocariasis is one of the most neglected worldwide zoonoses that is caused by larval nematode parasites of the genus Toxocara, Toxocara canis, and to a lesser extent, Toxocara cati, whose migration mechanism is still largely unknown. Fortunately, some advanced tools have been employed, such as genomics, transcriptomics, and proteomics, to better understand the molecular biology and regulatory mechanisms of Toxocara. Using genomics and transcriptomics, we can identify a large number of genes that participate in the development of Toxocara and the interaction of parasites and their hosts and can predict the functions of unknown genes by comparing them with other relevant species. Using proteomics, we can identify somatic proteins and excretory and secretory (ES) proteins that perform specific biological functions in tissue degradation, pathogen invasion, immune evasion or modulation. These "omics" techniques also can contribute enormously to the development of new drugs, vaccines and diagnostic tools for toxocariasis. In a word, by utilizing "omics", we can better understand the Toxocara and toxocariasis. In this review, we summarized the representative achievements in Toxocara and the interaction between Toxocara spp. and their hosts based on expressed sequence tags (ESTs), microarray gene expression, next-generation sequencing (NGS) technologies and liquid chromatography-tandem mass spectrometry (LC-MS/MS), hoping to better understand the molecular biology of Toxocara, and contribute to new progress in the application areas of new drugs, vaccines and diagnostic tool for toxocariasis in the future.

Nematode larva migrans caused by Toxocara cati in the North Island brown kiwi (Apteryx mantelli)

Sporadic cases of visceral and neural nematode larva migrans have been diagnosed at necropsy in the endangered New Zealand kiwi (Apteryx spp.), but the causative organisms have not yet been definitively identified. From an initial group of five affected kiwi, PCR was performed on DNA extracted from archival formalin-fixed paraffin-embedded tissue sections in which larval nematodes had been histologically identified. Sequencing of positive results from four out of the five kiwi aligned with sequences from Toxocara cati, a nematode parasite whose definitive host is the domestic cat. PCR was then performed on a second group of 12 kiwi that had histologic inflammatory lesions consistent with larva migrans, but variable larval presence. Repeatable positive PCR results were only achieved in one tissue, in which larval organisms were histologically confirmed. This study supports the use of PCR as an alternative or adjunct to the morphological identification of nematode larvae in formalin-fixed histopathological samples, as well as showing that in investigation of larva migrans, PCR has greatest chance of success from sections where nematode larvae are evident histologically. The identification of Toxocara cati from lesions of larva migrans in kiwi reflects an indirect, parasite-mediated effect of an invasive mammalian species on a native species.

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Cases of nematode larva migrans have been diagnosed in the New Zealand kiwi.

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PCR was performed on archival formalin-fixed paraffin-embedded tissue blocks.

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Results identified Toxocara cati, a parasite of cats, as the causative agent.

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PCR had greatest success from tissues where larvae were identifiable histologically.

Toxocara-induced neural larva migrans (neurotoxocarosis) in rodent model hosts

Neural larva migrans (NLM), or neurotoxocarosis, induced by Toxocara canis or Toxocara cati results from migrating and persisting larvae in the central nervous system of paratenic hosts, including humans. As the diagnosis of NLM in humans is not straightforward, most knowledge on the disease is derived from only a few published clinical cases. To improve our understanding of human NLM, studies on the pathogenesis and clinical symptoms in laboratory animal model systems are indispensable, and rodents have been accepted as the most appropriate model organisms for NLM. As research has mostly focused on neuroinvasive T. canis-larvae, information regarding the pathogenesis of T. cati-induced NLM remains scarce. This review summarises the current state of knowledge on neuroinvasion by both T. canis and T. cati in different rodent model hosts, the resulting behavioural changes, and histopathological alterations during the course of NLM as well as the potential molecular pathogenic mechanisms.

Pathogenesis of cerebral toxocariasis and neurodegenerative diseases

Toxocara canis belongs to one of zoonotic parasites that commonly infects canines worldwide, and its eggs in host faeces may contaminate the food, water, soil and their fur as well as the larvae entrapped in the granuloma can infect paratenic hosts including mice and humans. Survivability of T. canis embryonated eggs under moist, cool conditions may be as long as 2-4 years or more. In paratenic hosts such as mice and humans, T. canis L3 larvae neither moult, grow, nor replicate and will wander through a number of internal organs in humans so as to cause Th2-dominant pathology in various internal organs as leading to neurotoxocariasis (NT), ocular toxocariasis (OT), or visceral larva migrans (VLM). Although the systemic immune response to T. canis has been widely reported, the immune response in the brain has received little attention. Differential cytokine expression and other brain injury-associated biomarkers or neurodegeneration-associated factors have been observed in infected versus uninfected outbred and inbred mice. Preliminary data have also suggested a possible link between significant memory impairment and cytokine production associated with T. canis infection in the hippocampus which has been long recognised as being responsible for learning and memory functions. Notably, it remains an enigma concerning cerebral invasion by T. canis larvae rarely induces a recognisable neurological syndrome or its involvement in neuropathological disorders in humans. Exploration of the relationship between host and parasite in the brain may elucidate the cryptic symptoms of human cerebral toxocariasis, with patients presenting with mental retardation, epilepsy, neurodegeneration and other central nervous system (CNS) disorders.

Human Toxocara Infection: Allergy and Immune Responses

BACKGROUND

Toxocariasis is a cosmopolitan infection that occurs in various regions worldwide, more frequently in developing countries. Chronic infections with Toxocara species in humans are associated with the production of high levels of specific and non-specific antibodies of all isotypes and IgG subclasses and a cytokine response characterized by the production of Th2 cytokines including IL-4, IL-5 and IL-13 by Peripheral Blood Monocytes (PBMCs) and Leukocytes (PBLs) in whole blood cultures. Other Th2 effector responses are also prominent during infection, reflected by elevated numbers of peripheral blood eosinophils and increased expression of eosinophil degranulation products. The production of IFN-γ by PBMCs/PBLs stimulated with Toxocara-secreted proteins is not prominent in toxocariasis but IL-10 production may be increased in infected individuals. The relationship between Toxocara species with allergic reactions was reported in the recent century. Experimental and epidemiological investigations revealed that toxocariasis with this parasite led to the development of allergic symptoms, such as asthma. However, the findings are conflicting since in other investigations no association between these two immunopathologies has been reported.

CONCLUSION

The present review endeavours to summarize the data on Toxocara species and findings from studies on the relationship of toxocariasis with symptoms and signs of allergy. Furthermore, the mechanisms of immune responses and the factors associated between allergy and Toxocara infection are discussed.

A Dual Role for Macrophages in Modulating Lung Tissue Damage/Repair during L2 Toxocara canis Infection

Macrophages that are classically activated (M1) through the IFN-γ/STAT1 signaling pathway have a major role in mediating inflammation during microbial and parasitic infections. In some cases, unregulated inflammation induces tissue damage. In helminth infections, alternatively activated macrophages (M2), whose activation occurs mainly via the IL-4/STAT6 pathway, have a major role in mediating protection against excessive inflammation, and has been associated with both tissue repair and parasite clearance. During the lung migratory stage of Toxocara canis, the roles of M1 and M2 macrophages in tissue repair remain unknown. To assess this, we orally infected wild-type (WT) and STAT1 and STAT6-deficient mice (STAT1^-/- and STAT6^-/-) with L2 T. canis, and evaluated the role of M1 or M2 macrophages in lung pathology. The absence of STAT1 favored an M2 activation pattern with Arg1, FIZZ1, and Ym1 expression, which resulted in parasite resistance and lung tissue repair. In contrast, the absence of STAT6 induced M1 activation and iNOS expression, which helped control parasitic infection but generated increased inflammation and lung pathology. Next, macrophages were depleted by intratracheally inoculating mice with clodronate-loaded liposomes. We found a significant reduction in alveolar macrophages that was associated with higher lung pathology in both WT and STAT1^-/- mice; in contrast, STAT6^-/- mice receiving clodronate-liposomes displayed less tissue damage, indicating critical roles of both macrophage phenotypes in lung pathology and tissue repair. Therefore, a proper balance between inflammatory and anti-inflammatory responses during T. canis infection is necessary to limit lung pathology and favor lung healing.

Immune response to chronic Toxocara canis infection in a mice model

AIMS

The zoonotic nematode Toxocara canis causes larva migrans syndrome that induces an immune response characterized by the production of antibodies and eosinophilia. A Th2 polarization has been associated with the infection, but there are still details of the cellular and humoral immune response that need to be described. Thus, the aim of this study was to describe the systemic host immune response to T canis chronic infection in a mouse model.

METHODS AND RESULTS

BALB/c mice were inoculated once with 500 T canis embryonated eggs, per os. After 49 days, the amounts of larval found in brain and muscle tissues were statistically two and four times higher, respectively, than the amounts found in lung, liver, kidney or heart tissues. Splenic proportions of F4/80⁺ cells, as well as B, cytotoxic T and CD4⁺ Foxp3⁺ lymphocytes, were statistically higher (P ≤ .05, P ≤ .01, P ≤ .001 and P ≤ .001, respectively) as compared with control mice. In lymph nodes, some of these proportions changed, with the exception of F4/80⁺ cells. IgG1 levels in infected mice sera were increased. IL-4, IL-10 and VEGF levels were statistically higher in spleen (P ≤ .05, all) and sera (P ≤ .01, P ≤ .05 and P ≤ .05, respectively) in the infected mice. Also, in infected animals, IL-5 serum levels were increased (P ≤ .01).

CONCLUSION

These results suggest that T canis chronic infection in BALB/c mice results in a type 2 response with an incipient regulatory response.

Human toxocariasis - A look at a neglected disease through an epidemiological 'prism'

Toxocariasis, a disease caused by infection with larvae of Toxocara canis, T. cati and/or congeners, represents clinical syndromes in humans including visceral and ocular larva migrans, neurotoxocariasis and covert/common toxocariasis. It is reported to be one of the most widespread public health and economically important zoonotic parasitic infections that humans share with dogs, wild canids, including foxes, and possibly other mammals. Humans become infected by accidental ingestion of embryonated Toxocara eggs, or larvae from tissues from domestic or wild paratenic hosts. Most infections are asymptomatic, and human disease may go unnoticed, as clinical investigation is often not pursued and/or diagnostic testing not conducted. Sometimes toxocariasis can be associated with complications, such as allergic and/or neurological disorders, possibly including cognitive or developmental delays in children. There is no anti-toxocariasis vaccine, and chemotherapy in humans varies, depending on symptoms and location of larvae, and may include the administration of albendazole or mebendazole, together with anti-inflammatory corticosteroids. Some recent studies indicate that toxocariasis is having an increased, adverse impact on human health in some, particularly underprivileged, tropical and subtropical communities around the world. Although tens of millions of people, especially children, are expected to be exposed to, or infected with Toxocara species, there is limited precise epidemiological data or information on the relationship between seropositivity and disease (toxocariasis) on a global scale. To gain an improved insight into this area, the present article reviews salient clinical aspects of human toxocariasis and the epidemiology of this disease, with particular reference to seroprevalence, and discusses future research and approaches/measures to understand and prevent/control this socioeconomically important, yet neglected zoonosis.

Neuroinvasion of Toxocara canis- and T. cati-larvae mediates dynamic changes in brain cytokine and chemokine profile

Background

Neurotoxocarosis (NT) is induced by larvae of the dog or cat roundworm (Toxocara canis or T. cati) migrating and persisting in the central nervous system of paratenic hosts, including humans, and may be accompanied by severe neurological symptoms. Host- or parasite-induced immunoregulatory processes contribute to the pathogenesis, but detailed data on pathogenic mechanisms and involvement of signalling molecules during cerebral Toxocara species infections are scarce.

Methods

To elucidate alterations in immunomodulatory mediator pattern, comprehensive multiplex bead array assays profiling comprising 23 different cytokines and chemokines were performed during the course of T. canis- and T. cati-induced NT. To this end, cerebra and cerebella of experimentally infected C57Bl/6 J mice serving as paratenic host models were analysed at six different time points (days 7, 14, 28, 42, 70 and 98) post infectionem (pi).

Results

Brain-body mass ratios of T. canis and T. cati-infected mice were significantly lower than those of the uninfected control group at day 14 pi, and also at day 28 pi for T. canis-infected mice. Both infection groups showed a continuous decrease of pro-inflammatory cytokine concentrations, including TNF-α, IFN-γ, GM-CSF and IL-6, in the cerebrum over the course of infection. Additionally, T. canis but not T. cati-induced neurotoxocarosis was characterised by significantly elevated levels of anti-inflammatory IL-4 and IL-5 in the cerebrum in the acute and subacute phase of the disease. The higher neuroaffinity of T. canis led to a prominent increase of eotaxin and MIP-1α in both the cerebrum and cerebellum, while in T. cati-infected mice, these chemokines were significantly elevated only in the cerebellum.

Conclusions

The direct comparison of T. canis- and T. cati-induced NT provides valuable insights into key regulatory mechanisms of Toxocara species in paratenic hosts. The cerebral cyto-/chemokine milieu is shifted to a predominantly anti-inflammatory immune response during NT, possibly enabling both survival of the parasite and the neuroinfected paratenic host. Alteration of eotaxin and MIP-1α concentrations are congruent with the higher neuroaffinity of T. canis and species-specific tropism of T. canis to the cerebrum and T. cati to the cerebellum.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1537-x) contains supplementary material, which is available to authorized users.

An innovative approach in the detection of Toxocara canis excretory/secretory antigens using specific nanobodies

Human toxocariasis is a zoonosis resulting from the migration of larval stages of the dog parasite Toxocara canis into the human paratenic host. Despite its well-known limitations, serology remains the most important tool to diagnose the disease. Our objective was to employ camelid single domain antibody fragments also known as nanobodies (Nbs) for a specific and sensitive detection of Toxocara canis excretory/secretory (TES) antigens. From an alpaca immune Nb library, we retrieved different Nbs with specificity for TES antigens. Based on ELISA experiments, these Nbs did not show any cross-reactivity with Ascaris lumbricoides, Ascaris suum, Pseudoterranova decipiens, Anisakis simplex and Angiostrongylus cantonensis larval antigens. Western blot and immunocapturing revealed that Nbs 1TCE39, 1TCE52 and 2TCE49 recognise shared epitopes on different components of TES antigen. The presence of disulphide bonds in the target antigen seems to be essential for recognition of the epitopes by these three Nbs. Three separate sandwich ELISA formats, using monovalent and bivalent Nbs, were assessed to maximise the detection of TES antigens in solution. The combination of biotinylated, bivalent Nb 2TCE49 on a streptavidin pre-coated plate to capture TES antigens, and Nb 1TCE39 chemically coupled to horseradish peroxidase for detection of the captured TES antigens, yielded the most sensitive ELISA with a limit of detection of 0.650 ng/ml of TES antigen, spiked in serum. Moreover, the assay was able to detect TES antigens in sera from mice, taken 3 days after the animals were experimentally infected with T. canis. The specific characteristics of Nbs make this ELISA not only a promising tool for the detection of TES antigens in clinical samples, but also for a detailed structural and functional study of TES antigens.

Aquaporin 1 is located on the intestinal basolateral membrane in Toxocara canis and might play a role in drug uptake

Background

Aquaporins (AQPs) are a family of integral membrane channel proteins that facilitate the transport of water and other small solutes across cell membranes. AQPs appear to play crucial roles in parasite survival and represent possible drug targets for novel intervention strategy. In this work, we investigated the tissue distribution and biological roles of an aquaporin TcAQP1 in the neglected parasitic nematode Toxocara canis.

Methods

Recombinant C-terminal hydrophilic domain of AQP1 of T. canis (rTcAQP1c) and polyclonal antibody against rTcAQP1c were produced to analyse the tissue expression of native TcAQP1 in adult (female and male) worms using an immunohistochemical approach. RNA interference (RNAi), quantitative real-time PCR (qRT-PCR) and nematocidal assays were performed to investigate the functional roles of TcAQP1 in the adult stage of T. canis.

Results

Immunofluorescence analysis showed that TcAQP1 was localised predominantly in the epithelial linings of the reproductive tract and basolateral membrane of the intestine in the adult stage (female and male) of T. canis, indicating important roles in reproduction, nutrient absorption and/or osmoregulation. Treatment with silencing RNA for 24 h resulted in a significant reduction of Tc-aqp-1 mRNA level in adult T. canis, though no phenotypical change was observed. The efficient gene knockdown compromised the nematocidal activity of albendazole in vitro, suggesting the role of TcAQP1 in drug uptake.

Conclusions

The findings of this study provide important information about tissue expression and functional roles of TcAQP1 protein in adult T. canis. Understanding the biological functions of this protein in other developmental stages of T. canis and related parasitic nematodes would contribute to the discovery of novel diagnostic or anthelmintic targets.