Identification of Toxocara canis Antigen-Interacting Partners by Yeast Two-Hybrid Assay and a Putative Mechanism of These Host-Parasite Interactions

Proteomic analysis of extracellular vesicles and extracellular vesicle-depleted excretory-secretory products of Toxocara canis and Toxocara cati larval cultures

Toxocara canis and Toxocara cati are parasitic nematodes in the order Ascaridida, which inhabit the small intestines of dogs and cats, respectively, as adults. Although often nonpathogenic as adults, nematodes within this genus are capable of causing widespread disease throughout the host while in a larval stage, during which time larvae migrate throughout the body in a process termed larva migrans. Larvae are also capable of surviving within host tissues in an encysted arrested stage, without immune clearance by the host. The ability of larvae to survive within host tissues during migration and encystment may be attributed to immunomodulatory molecules released by the excretory cells of larvae in excretory-secretory (ES) products. ES products of parasites contain a variety of molecules, including proteins, lipids, and extracellular vesicles (EVs). Toxocara excretory-secretory (TES) products have been studied to some degree, with proteomic analysis of TES proteins described previously; however, investigation of the EVs within TES is lacking, despite the suggested role for these molecules in host interaction and potential immunomodulation. To further characterize the protein cargo within EVs in TES, EVs were isolated from larval cultures of T. canis and T. cati via ultrafiltration, with concurrent collection of EV-depleted TES filtrate for additional study. Isolated EVs and EV-depleted TES from both T. canis and T. cati were submitted for proteomic analysis by liquid chromatography tandem mass spectrometry (LC-MS/MS). Proteomic identification results revealed 140 proteins across all samples, with 16 shared by all samples, and 76 total proteins shared between T. canis and T. cati, present within EVs and EV-depleted TES. There were 17 proteins shared exclusively by EV samples, and 15 were shared exclusively between EV-depleted TES samples. Many shared proteins were associated with the host immune response. Several proteins were specific to either T. canis or T. cati, highlighting the potential use of these proteins as diagnostic tools in the differentiation of etiologic agents in cases of toxocariasis. The results of this study build upon previously reported proteomic evaluations of TES, contributing new information in regards to newly identified proteins, EV protein cargo within TES, and potential immunomodulatory functions of these proteins.

Extracellular traps development in canine neutrophils induced by infective stage Toxocara canis larvae

Neutrophils, a crucial element of the host defense system, develop extracellular traps against helminth parasites. Neutrophils accumulate around the larvae of Toxocara canis (T. canis) in the tissues of the organism. This study aimed to determine the reaction in canine neutrophils after incubation with infective stage T. canis larvae (L3) in vitro. Most L3 were still active and moved between the extracellular traps (NETs) after 60-min incubation. NETs were not disintegrated by L3 movement. The L3 was only immobilized by NETs, entrapped larvae were still motile between the traps at the 24 h incubation. NETs were observed not only to accumulate around the mouth, excretory pole or anus but also the entire body of live L3. The extracellular DNA amount released from the canine neutrophils after being induced with phorbol 12-myristate 13-acetate was not affected by T. canis excretory/secretory products obtained from 250 L3. To the Authors'knowledge, the extracellular trap structures was firstly observed in canine neutrophils against T. canis L3 in vitro. NETs decorated with myeloperoxidase, neutrophil elastase and histone (H3) were observed under fluorescence microscope. There were not significant differences in the amount of extracellular DNA (P > 0.05), but the morphological structure of NETs was different in the live and head-inactivated T. canis larvae.

Molecular investigation of Toxocara infection from the serum of people living with HIV in Alborz, Iran

BACKGROUND

Toxocara infection is one of the most common neglected infections of poverty and a helminthiasis of global importance. Traditional diagnostic methods such as antibodies detection in serum samples are limited due to cross-reactivity and poor sensitivity. The use of molecular base methods for diagnosis of Toxocara infection in Iran has not been fully explored. The purpose of the current study was to estimate the prevalence of Toxocara infection from serum samples of people living with HIV in Alborz province, Iran using serological and molecular methods.

METHODS

Blood samples were collected from 105 people living with HIV. Epidemiological data of participant were obtained through a structured questionnaire to investigate the risk factors. Patients CD4+ T cell count were recorded. Anti-Toxocara IgG antibodies were detected by ELISA, with a cut-off point of 11. PCR was performed to detect genetic material of Toxocara species in the serum samples.

RESULTS

The mean CD4+ count in HIV-infected individuals with positive toxocariasis serology was 255.1 ± 21.6 cells/µL. Seropositivity for Toxocara species was observed in 12/105 (11.4%) people living with HIV. Three samples gave positive results on PCR analysis. Based on the data, a statistically significant relationship was found between anti-Toxocara IgG antibodies seropositivity and underlying conditions (p = 0.017). No significant statistical association was observed between seropositivity for Toxocara and gender, age, exposure to domestic animals or pet keeping, education levels, and occupation (p > 0.05). The findings of PCR confirmed Toxocara DNA in 3/12 (25.0%) serum samples.

CONCLUSION

These findings demonstrated for the first time that people living with HIV from Alborz province, are being exposed to this zoonosis and a relatively high seroprevalence of Toxocara in HIV/AIDS people needs comprehensive health education regarding personal hygiene and how to avoid exposure to this parasite infection, especially in people with an impaired immune system.

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.

Proteomics of Host-Helminth Interactions

Helminth infections in people contribute to the 1 [...].