Cross-reactivity between Anisakis simplex sensitization and visceral larva migrans by Toxocara canis

Evidence of IgE-Mediated Cross-Reactions between Anisakis simplex and Contracaecum osculatum Proteins

Fish consumers may develop allergic reactions following the ingestion of fish products containing nematode larvae within the genus Anisakis. Sensitized patients may cross-react with proteins from insects, mites and mollusks, leading to allergic reactions even in the absence of the offending food. Potential cross-reactivity in Anisakis-allergic patients with larval proteins from other zoonotic parasites present in freshwater and sea fish should be investigated due to an increasing occurrence in certain fish stocks, particularly Contracaecum osculatum. In this work, we evaluated IgE-cross reactions by in vivo (skin prick tests with parasites extracts) and in vitro methods (IgE-ELISA and IgE-immunoblot). In vivo skin prick tests (SPT) proved the reactivity of Anisakis-sensitized patients when exposed to C. osculatum antigens. Sera from Anisakis-sensitized patients confirmed the reaction with somatic antigens (SA) and excretory/secretory proteins (ES) from C. osculatum. Only anecdotal responses were obtained from other freshwater worm parasites. Consequently, it is suggested that Anisakis-sensitized humans, especially patients with high levels of specific anti-Anisakis antibodies, may react to C. osculatum proteins, possibly due to IgE-mediated cross-reactivity.

Anisakis Sensitization in the Croatian fish processing workers: Behavioral instead of occupational risk factors?

We undertook the first study systematically evaluating the risk of Anisakis-sensitization in Croatian fish-processing workers and potential genetic susceptibility to anisakiasis. Anti-Anisakis IgE seroprevalence and risk factors for 600 employees of Croatian fish processing facilities and 466 blood donor controls, were assessed by indirect ELISA targeted with: recombinant Ani s 1 and Ani s 7 allergens, an Anisakis crude extract, the commercial ImmunoCAP kit, and questionnaires. Genetic susceptibility to anisakiasis was evaluated by genotypisation of human leukocytes alleles (HLA). Anti-Anisakis seropositive and a fraction of negative subjects were also assessed by ELISA and Western Blot (WB) for IgG seroprevalence to Trichinella spp. Overall, the observed anti-Anisakis seroprevalence inferred by indirect ELISA was significantly higher in fish processing workers (1.8%, 95% CI 0.9–3.3%) compared to the controls (0%, 0–0.8%). Seven out of 11 Ani s 1 and Ani s 7-positives and none of selected 65 negative sera, tested positive on whole-Anisakis extract (ImmunoCAP), whereas Anisakis crude extract ELISA detected 3.9% (2.4–6.0%) seropositives in fish processing workers, three (14%) of which showed IgE reactivity to milk proteins. The highest risk associated with Anisakis-sensitization among workers was fishing in the free time, rather than any of attributes related to the occupational exposure. Although no association was observed between anti-Anisakis seropositivity and wearing gloves or protective goggles, the majority of workers (92%) wore protective gloves, minimizing the risk for Anisakis sensitization via skin contact. Six HLA alleles within DRB1 gene were significantly associated with seropositivity under dominant, allelic or recessive models. All sera confirmed negative for anti-Trichinella spp. IgG. The study exhaustively covered almost all marine fish processing workers in Croatia, reflecting real-time Anisakis sensitization status within the industry, already under the influence of wide array of allergens.

Anisakiasis is a human disease caused by ingestion of live Anisakis spp. larvae by raw seafood. Fish processing and aquaculture workers (approximately 60 million people world-wide) are at occupational risk of becoming sensitized to Anisakis. This is the first study systematically evaluating the risk of Anisakis-sensitization in Croatian fish-processing workers and potential genetic susceptibility to anisakiasis in the analysed population. Observed seroprevalence was significantly higher in fish processing workers (1.8%) compared to the controls (0%). Surprisingly, the highest risk associated with Anisakis-sensitization among workers was fishing in their free time, rather than any of attributes related to the occupational exposure. While no association was observed between anti-Anisakis seropositivity and wearing gloves or protective goggles, the majority of workers (92%) wore protective gloves, minimizing the risk for Anisakis sensitization via skin contact. Additionally, seroprevalence to another important food-borne helminth, Trichinella spp. assessed in all Anisakis-positive subjects showed to be negative. Almost all marine fish processing workers in Croatia were part of this research, reflecting real-time Anisakis-sensitization status within the industry. This sets a baseline for the future tracking of sensitization in the sector already under the influence of wide array of allergens.

Prognosis for ocular toxocariasis according to granuloma location

Purpose

To determine the prognosis for ocular toxocariasis (OT) according to the location of the granuloma and to identify factors associated with its recurrence within 1 year.

Methods

OT patients were classified according to the granuloma lesion. After grouping the patients as posterior or peripheral, we compared sex, age, intraocular pressure, best corrected visual acuity (BCVA), degree of inflammation, immunoglobulin E, eosinophil profiles, recurrence, and complications in each group. We also identified factors associated with recurrence within 1 year.

Results

A total of 29 (61.70%) patients had granuloma at the periphery, and 18 (38.30%) patients had granuloma around the posterior pole. There were no significant differences in ocular or systemic evaluations except the initial BCVA. The mean decimal BCVA of the posterior pole granuloma group was worse than that of the peripheral granuloma group (p = 0.042). After treatment, the mean BCVA of the posterior pole granuloma group improved significantly (p = 0.019), and the final mean BCVA was not significantly different between the groups (p = 0.673). Multiple logistic regression analyses revealed that recurrence within a year was associated with age at diagnosis (p = 0.007).

Conclusions

The initial BCVA of OT patients differed according to the location of the granuloma, but the BCVA after treatment was not significantly different between the groups. Younger age was associated with recurrence within 1 year.

Helminthosis and eosinophilia in Spain (1990-2015)

The finding of blood eosinophilia in a patient is a relatively frequent reason to refer him/her to a Clinical Department of Infectious Diseases. The doctor usually intends to rule out a parasitic disease in the autochthonous population, travelers or immigrants. It is uncommon for an eosinophilia to be produced by protozoa infection, whereas helminth parasites are more frequently associated with an increase of eosinophil counts in the infected patient. Eosinophilia can be the only abnormal finding, or it could be part of more complex clinical manifestations suffered by the patient. Furthermore, many, but not all, helminth infections are associated with eosinophilia, and the eosinophil level (low, high) differs according to parasite stages, helminth species, and worm co-infections. The purpose of the present article is to carry out a systematic review of cases and case series on helminth infections and eosinophilia reported in Spain from 1990 to 2015, making a distinction between autochthonous and imported (immigrants and travelers) cases, and studying their relationship with immunodepression situations.

Anisakis/Ascaris IgE ratio improves specificity for the diagnosis of Anisakis simplex sensitization in travellers and immigrants

Anisakis simplex is a fish parasite responsible for human infection and is able to induce IgE-mediated reactions with several clinical manifestations. Laboratory diagnosis of Anisakis allergy is based on the detection of specific IgE using parasite whole antigen. Unfortunately, these diagnostic tools detect cross-reactivities with other nematodes and micro-organisms leading to low specificity of the diagnostic tests. The aim of this retrospective study was to assess the diagnostic value of specific IgE to Anisakis for diagnosis of A. simplex-sensitization in native Spanish residents (IMM, n=766) and subjects coming from tropical and sub-tropical geographic areas (TRO, n=233). Since Ascaris is the human parasite most closely related to Anisakis, specific IgE to Ascaris was also determined to assess Anisakis cross-reaction with other nematodes and the diagnostic value of Anisakis/Ascaris IgE ratio for Anisakis allergy was examined. IMM and TRO groups showed similar specific IgE to Anisakis levels, while TRO had higher levels of specific IgE to Ascaris than IMM group (p=0.001). ROC curve analysis determined that an Anisakis specific IgE threshold of 0.71 kU/L yielded 93% and 82% specificities in IMM and TRO groups, respectively. A cut-off value ≥4.4 for Anisakis/Ascaris IgE ratio increased specificity to 95% for samples having IgE to Ascaris ≥0.35. In conclusion, the ratio of specific IgE to Anisakis and Ascaris improved remarkably the specificity and this parameter easily obtained from the commercially available system could be useful in the diagnosis of hypersensitivity to A. simplex.

Experimental anisakid infections in mice

Anisakidosis is a human parasitic disease caused by infections with members of the Anisakidae family. Accidental infection after fish intake affects the gastrointestinal tract as a consequence of mechanical damage caused by migrating larvae. Infections can also trigger allergies, hives, severe asthma or anaphylaxis with angioedema. Although mouse models of intraperitoneal antigenic stimulation exist, enabling immunological studies, few models using gastric introduction of live larvae are available for the study of immunological and gastrointestinal damage in mice. This study was designed to characterize serum reactivity against Anisakis spp. and Contracaecum spp. in Balb/c mice following orogastric inoculation and to assess gastrointestinal damage. These anisakid species were classified at the Universidade Federal Fluminense (UFF) School of Veterinary Medicine and materials for live larval inoculation were developed at the UFF Immunobiology laboratory. Live larvae were inoculated following injection with a NaCl solution. Blood samples were collected and sera screened for immunoglobulin (Ig)E and IgG anti-larva responses to both nematodes, specific for somatic and excretory/secretory antigens, by enzyme-linked immunosorbent assay (ELISA). The means of the optical densities were analysed using analysis of variance (ANOVA) with Tukey's post-hoc test and the general linear model. This analysis identified the presence of anti-IgG seroreactivity to both somatic and excretory/secretory Anisakis antigens in inoculated animals compared with controls (P< 0.001), and no gastric or intestinal damage was observed. These experiments demonstrated that introduction of live Contracaecum spp. into the gastrointestinal tract did not elicit serum sensitization in animals.

[Evaluation of a purified antigen for the diagnosis of toxocariosis]

Toxocarosis is a zoonotic disease caused by the ingestion of infective eggs of Toxocara spp. The diagnosis is based on the detection of antibodies in serum or other biological fluids. One of the current serological techniques for the diagnosis of toxocariasis is ELISA using excretory - secretory antigens of third stage larvae (ES/L3). These antigens are glycoproteins, which originate in the secretory organs of the parasite and are non species-specific. Sera from patients with other helminthiases and non- parasitic diseases were used to evaluate the specificity of ELISA using the excretory - secretory antigen (ES/L3). The reactivity of these sera was between 11 and 70%. Western blot using patients' sera revealed that the glycoprotein triplet having a molecular weight of 120 kDa was responsible for cross-reactivity. With these results, and for the purpose of purifying the antigen, ion exchange chromatography was performed. When the sera from patients with various parasitic and non-parasitic diseases were analyzed with the purified antigen ES/ L3, they were only reactive between 10 to 20%. The sensitivity of the ELISA test determined by program Epidat 3.0 for the two antigens was 100%, but the following differences in specificity were observed: 84% for the total antigen ES/L3 and 99% for purified ES/L3. Using the ES/L3 purified antigen, it can be considered that the reactive sera, with compatible symptoms correspond to patients who are or were parasitized with Toxocara canis.

The increase in seroprevalence to Toxocara canis in asthmatic children is related to cross-reaction with Ascaris suum antigens

BACKGROUND

It has been suggested that the presence of Toxocara canis larvae in lungs is an underlying factor in the onset of asthma. Although the association of asthma and seropositivity to Toxocara has been observed, there are no studies that indicate whether these antibodies are specific against T. canis antigens.

METHODS

Seroprevalence to T. canis excretion-secretion antigens (TcES Ag) were compared between asthmatic children (n=285) and non-asthmatic children (n=152), using IgG-ELISA and IgE-ELISA. The recognition patterns of TcES Ag were determined using Western blot (WB).

RESULTS

IgG-ELISA seroprevalence was 30.8% for asthmatic children and 19.7% for non-asthmatic children (p<0.05). IgE-ELISA seroprevalence was 7.7% for asthmatic children and 6.5% for non-asthmatic children, respectively (p>0.05). Sera of both groups positive to IgG-ELISA recognised 11 TcES Ag bands for IgG. No differences between the groups were observed regarding recognition patterns; the asthmatic group, however, presented significantly higher cross-reaction to Ascaris suum somatic antigens (AsS Ag) than the non-asthmatic group. Sixty-three sera from asthmatic children positive to IgG-ELISA were evaluated by WB for IgE and 58.7% revealed a recognition pattern for IgE. In the group of non-asthmatic children positive to IgG-ELISA, 80% presented IgE band recognition. No differences were observed between the groups regarding recognition patterns.

CONCLUSIONS

The results observed suggest that differences in seroprevalence determined by IgG-ELISA between groups of asthmatic and non-asthmatic children reported by other authors occur because of a higher frequency of cross-reaction in asthmatic children.

Follow-up of antibody avidity in BALB/c mice infected withToxocara canis

In humanToxocara canisinfection, an association has been shown between high IgG avidity in the chronic phase and low IgG avidity in recently acquired toxocarosis. The evolution of the antibody response in terms of avidity has been carried out through aT. canisinfection in BALB/c mice. Infection withT. canisembryonated eggs (EE) was carried out with single doses (SD) of 6, 12, 50, 100, 200 or 1000 EE/mouse and with multiple doses (MD) of 200 and 1000 EE. Specific antibodies againstT. canis(IgM+G, IgG, IgG1 and IgM) were detected by ELISA and Western Blot (WB) techniques in the presence and absence of urea. With the ELISA method, an increase in the avidity index (AI) of around 50% was detected from days 40–80 p.i. to the end of the study, with all the doses studied. The WB method showed the presence of high avidity antibodies bound to 100 kDa and 75 kDaT. canisproteins in all the cases when the IgM+G and the IgG1 antibodies were investigated. Antibodies of variable avidity were observed in those sera that recognized the group of low molecular weight proteins, between 37 kDa and 25 kDa.

Cloning and characterisation of the Anisakis simplex allergen Ani s 4 as a cysteine-protease inhibitor

Anisakis simplex is a nematode that can parasitise humans who eat raw or undercooked fish containing live L3s. Larvae invading the gastrointestinal mucosa excrete/secrete proteins implicated in the pathogenesis of anisakiasis that can induce IgE mediated symptoms. Misdiagnosis of anisakiasis, due to cross-reactivity, makes it necessary to develop new diagnostic tools. Recombinant allergens have proved to be useful for diagnosis of other parasitoses. Among the Anisakis allergens, Ani s 4 was considered to be a good potential diagnostic protein because of its heat resistance and its importance in the clinical history of sensitised patients. Therefore, the objective of this study was to clone and characterise the cDNA encoding this allergen. The Ani s 4 mRNA sequence was obtained using a PCR-based strategy. The Ani s 4 amino acid sequence contained the characteristic domains of cystatins. Mature recombinant Ani s 4 was expressed in a bacterial system as a His-tagged soluble protein. The recombinant Ani s 4 inhibited the cleavage of a peptide substrate by papain with a Ki value of 20.6 nM. Immunobloting, ELISA, a commercial fluorescence-enzyme-immunoassay and a basophil activation test were used to study the allergenic properties of rAni s 4, demonstrating that the recombinant allergen contained the same IgE epitopes as the native Ani s 4, and that it was a biologically active allergen since it activated basophils from patients with allergy to A. simplex in a specific concentration-dependent manner. Ani s 4 was localised by immunohistochemical methods, using a polyclonal anti-Ani s 4 anti-serum, in both the secretory gland and the basal layer of the cuticle of A. simplex L3. In conclusion, we believe that Ani s 4 is the first nematode cystatin that is a human allergen. The resulting rAni s 4 retains all allergenic properties of the natural allergen, and can therefore be used in immunodiagnosis of human anisakiasis.

Human antibody recognition of Anisakidae and Trichinella spp. in Greenland

High levels of total IgE are observed among children in Greenland. To evaluate the extent to which Anisakidae and Trichinella spp. contribute to the high total IgE level, an ELISA and a western blot were developed for the detection of IgG antibodies to Anisakidae, based on excretory/secretory antigens from Anisakidae larvae. Western blots with Anisakidae and Trichinella antigens discriminated between Anisakidae and Trichinella infections, enabling cross-reactivity between the two parasite infections to be eliminated. Serum samples from 1012 children in Greenland were analysed for specific antibodies to Anisakidae and Trichinella. Eleven children were IgG-positive for Trichinella and nine were IgG-positive for Anisakidae, indicating a relatively low prevalence of both infections among children in Greenland. Faecal samples from 320 children were also examined for other intestinal parasites. Enterobius vermicularis was found in one sample and Blastocystis hominis in 32 samples, but no other intestinal parasites were identified. In total, 304 children had elevated total IgE levels. There was a significant association between Trichinella seropositivity and high levels of total IgE, but not between Anisakidae seropositivity and total IgE. The data indicate that parasitic infections alone do not explain the high level of total IgE observed among children in Greenland.

Cross-reactivity induced by Anisakis simplex and Toxocara canis in mice

The aim of this study was to verify whether cross-reactivity appeared between Toxocara canis and Anisakis simplex in an experimental rodent model. No cross-reactions were detected using sera from mice infected with T. canis eggs. When responses obtained against T. canis ES antigen using sera from BALB/c and C57BL/10 mice infected with T. canis eggs were compared with those obtained by testing sera from mice infected with one A. simplex L3, an increase in cross-reactions was observed using the C57BL/10 strain.

Detection of Anisakis simplex-induced basophil activation by flow cytometry

BACKGROUND

Laboratory diagnosis of anisakidosis is based on specific serum IgE detection. Recently, detection of allergen-induced basophil activation by flow cytometry has been proposed as a valuable tool for allergy diagnosis.

OBJECTIVE

To evaluate if detection of Anisakis-induced basophil activation by flow cytometry is a useful tool in the diagnosis of Anisakis allergy.

METHODS

Patients with Anisakis allergy (A.s.+, n = 37), patients reporting chronic urticaria or abdominal pain unrelated to fish ingestion (A.s.-, n = 51), and healthy controls (n = 12) were studied. Specific IgE to Anisakis simplex (A. simplex) was quantified with CAP-FEIA method, and basophil activation test was performed with three different concentrations of an Anisakis crude extract. Basophil gating was performed with CD123 and HLA-DR, and cellular activation was measured with CD63.

RESULTS

A.s.+ patients showed significantly higher age and total IgE levels than did the A.s.- patients. Specific IgE to A. simplex correlated with the activated basophil percentages obtained with 15 microg/mL (r = 0.80; P < 0.001), 1.5 microg/mL (r = 0.84; P < 0.001), and 0.15 microg/mL (r = 0.82; P < 0.001) of A. simplex crude extract. Nine individuals (3 in the A.s.+ group and 6 in the A.s.- group) were nonresponders to basophil stimulation with anti-IgE. Five A.s.- patients showed positive IgE values to A. simplex while the basophil activation test was negative. According to the receiver operating characteristics curves performed between A.s.+ vs. A.s.- and A.s.+ vs. healthy controls, the cutoff for a positive basophil activation test was >or=21% (specificity = 96%, sensitivity = 100%), and 16% (sensitivity and specificity of 100%) respectively. When nonresponders were included in the A.s.+ vs. A.s.- analysis, sensitivity decreased to 95%. Multivariate logistic analysis showed that the specific basophil activation was a factor independently associated with clinical symptoms of A. simplex allergy.

CONCLUSIONS

Detection of A. simplex-induced basophil activation by flow cytometry is a useful laboratory technique for the diagnosis of anisakidosis, supplementing specific IgE determinations.

Anisakis simplex: sensitization and clinical allergy

PURPOSE OF REVIEW

Whereas gastric anisakiasis has been known for several decades, the implications of Anisakis simplex-related allergic disorders had not been thoroughly studied until the late 1990s. This article reviews recent knowledge of allergic disorders ascribed to A. simplex contact or parasitism.

RECENT FINDINGS

Gastroallergic anisakiasis describes an acute hypersensitivity reaction emerging in the context of an acute parasitism by the nematode A. simplex. But other frequent allergic disorders like chronic urticaria are now being studied for a possible relationship with A. simplex parasitism. In recent investigations, non-IgE mediated mechanisms, such as the involvement of other immunoglobulin isotypes (IgG4), or non-immunological events are discussed.

SUMMARY

The experience of the last several years shows that allergic hypersensitivity symptoms in gastroallergic anisakiasis are clinical events accompanying a wide range of immunologic reactions as a host response against a ubiquitous parasite. The discussed and reviewed studies should motivate allergists around the world to search for this entity. Further studies in the field of allergy could benefit from the experience of this peculiar food-related disorder.