Differential Cleaving of Specific Substrates for Cathepsin-Like Activity Shows Cysteine and Serine Protease Activities and a Differential Profile BetweenAnisakis simplex s.s.andAnisakis pegreffii, Sibling Species Major Etiologic Agents of Anisakiasis

Molecular characterization of a novel serine proteinase from Trichinella spiralis and its participation in larval invasion of gut epithelium

BACKGROUND

A novel serine proteinase of Trichinells spiralis (TsSPc) has been identified in the excretion/secretion (ES) antigens, but its role in larval invasion is unclear. The aim of this study was to clone and express TsSPc, identify its biological and biochemical characteristics, and investigate its role on larval invasion of gut epithelium during T. spiralis infection.

METHODOLOGY/PRINCIPAL FINDINGS

TsSPc has a functional domain of serine proteinase, and its tertiary structure consists of three amino acid residues (His88, Asp139 and Ser229) forming a pocket like functional domain. Recombinant TsSPc (rTsSPc) was expressed and purified. The rTsSPc has good immunogenicity. On Western blot analysis, rTsSPc was recognized by infection serum and anti-rTsSPc serum, natural TsSPc in crude and ES antigens was identified by anti-rTsSPc serum. The results of qPCR, Western blot and indirect immunofluorescence test (IIFT) showed that TsSPc was expressed at diverse stage worms, and mainly localized at cuticle, stichosome and intrauterine embryos of this nematode. The rTsSPc had enzymatic activity of native serine protease, which hydrolyzed the substrate BAEE, casein and collagen I. After site directed mutation of enzymatic active sites of TsSPc, its antigenicity did not change but the enzyme activity was fully lost. rTsSPc specifically bound to intestinal epithelium cells (IECs) and the binding sites were mainly localized in cell membrane and cytoplasm. rTsSPc accelerated larval invasion of IECs, whereas anti-rTsSPc antibodies and TsSPc-specific dsRNA obviously hindered larval invasion.

CONCLUSIONS

TsSPc was a surface and secretory proteinase of the parasite, participated in larval invasion of gut epithelium, and may be considered as a candidate vaccine target molecule against Trichinella intrusion and infection.

Anisakis infection in anchovies (Engraulis encrasicolus) from Iberian waters, southwestern Europe: Post-mortem larval migration

The Anisakis larvae presence in fish for human consumption is a health risk that needs to be monitored. The anchovy is a fish that is highly appreciated by consumers and that can harbour Anisakis. It is thus necessary to periodically evaluate the presence of anisakid larvae in them. So, anchovies from Iberian Peninsula coasts were analysed. Fish examination for macroscopic nematodes showed L3s of both Anisakis type I and Hysterothylacium aduncum. The Anisakis prevalence varies with the catching area and the fish size. The muscle prevalence was 7.45% (mean intensity 1.75; range 1-5). Molecular analysis showed 110 A. simplex s.s. (17 in muscle), 22 A. pegreffii (3) and 7 hybrid genotype individuals (1). Considering that most of the Iberian Peninsula coasts are a sympatry area between these two Anisakis species, it has been observed that A. simplex s.s./A. pegreffii ratio increases from south to north in a clockwise direction. Also, 19 larvae were detected on the fish surface from the Bay of Biscay, indicating the ability of these larvae to migrate after the fish death. The A. simplex s.s./A. pegreffii larvae proportion found on the anchovy surface is similar to the found in viscera and lower than in muscle, suggesting that most of the larvae migrating to the surface must have come from the visceral package. This confirms the importance of removing fish viscera immediately after capture, for those fish species where this is possible. As both species cause anisakiasis/anisakidosis, these data show a real risk to human health, especially in dishes highly prized in Mediterranean countries prepared with raw or semi-raw anchovies.

Anisakiasis and Anisakis: An underdiagnosed emerging disease and its main etiological agents

Anisakiasis or anisakiosis is a human parasitic infection caused by the third-stage larvae (L3) of nematodes of the genus Anisakis, although the term is also used in medical literature for the much less frequent (<3% of cases) infection by L3 of other genera of anisakids, particularly Pseudoterranova. These parasites have a marine lifecycle. Humans are infected by the L3 through ingesting of fish and squid, the intermediate/paratenic hosts. The live larvae generally penetrate the wall of the stomach or intestine causing, among other symptoms, intense pain or allergic symptoms. These are emerging, cosmopolite illnesses. Diagnosis and treatment is usually by endoscopy and extraction and identification of the larvae. Allergic forms are usually diagnosed by prick-test and/or allergen-specific IgE detection and treated with a suitable anti-allergy treatment. The patient is also warned against further consumption of marine fish or squid, as these may be infected with Anisakis. The most common method of prevention is thermal treatment of the entire fish or squid prior to consumption (>60 °C, >1 min or - 20 °C, >24 h). Useful measures for the control of anisakiasis would be to establish a national register of cases, to initiate educational campaigns for the general public and consciousness-raising and training campaigns for health professionals. These would be complemented by control measures for the relevant sectors of the economy: fish operators, fish farming, fishermen, fishmongers, fish industry and catering facilities. Possible genetic predisposition for allergy to Anisakis and the possible relationship between anisakiasis and cancer would also require further investigation.

Comparative Proteomics Analysis of Anisakis simplex s.s.-Evaluation of the Response of Invasive Larvae to Ivermectin

Ivermectin (IVM), an antiparasitic drug, has a positive effect against Anisakis simplex s.s. infection and has been used for the treatment and prevention of anisakiasis in humans. However, the molecular mechanism of action of IVM on A. simplex s.s. remains unknown. Herein, tandem mass tag (TMT) labeling and extensive liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) analysis were used to identify the effect of IVM on the proteome of A. simplex s.s. in vitro. During the study, 3433 proteins, of which 1247 had at least two protein unique peptides, were identified. Comparative proteomics analysis revealed that 59 proteins were differentially regulated (DRPs) in IVM-treated larvae, of which 14 proteins were upregulated and 38 were downregulated after 12 h of culture, but after 24 h, 12 proteins were upregulated and 22 were downregulated. The transcription level of five randomly selected DRPs was determined by real-time PCR as a supplement to the proteomic data. The functional enrichment analysis showed that most of the DRPs were involved in oxidoreductase activity, immunogenicity, protein degradation, and other biological processes. This study has, for the first time, provided comprehensive proteomics data on A. simplex s.s. response to IVM and might deliver new insight into the molecular mechanism by which IVM acts on invasive larvae of A. simplex s.s.