Different Th1/Th2 responses to Anisakis simplex are related to distinct clinical manifestations in sensitized patients

Anisakidae and Anisakidosis: A Public Health Perspective

Fish and seafood are increasingly recognised as safe and nutritiously valuable foods of animal origin, being a source of about 17% of animal protein globally. Novel culinary trends encourage the consumption of raw or thermally lightly processed fishery products. At the same time, consumers prefer wild, fresh and whole fish over farmed or processed fish. However, the consumption of raw or undercooked fish and other marine organisms poses a risk of contracting parasitic infections, potentially representing a public health risk. Among the most common seafoodborne parasites are members of the Anisakidae family, especially the genus Anisakis, which can cause potentially detrimental effects to human health. These parasites are the causative agent of a zoonosis termed anisakidosis that is prevalent in countries with high per capita fish consumption. Although the number of annual clinical cases varies among countries and regions and is generally not high, sensitisation to this parasite in the general population seems to be considerably higher. Therefore, anisakidosis is still significantly underreported and misdiagnosed globally, making it a disease of rising public health concerns. To prevent infection and mitigate potential negative effects on human health, proper preventive measures such as gutting the fish, freezing or thermal processing are needed. Moreover, a holistic approach implementing One Health principles together with educational campaigns towards the general public and primary care physicians can extend the knowledge on the occurrence of these parasites in their natural hosts and the diagnosis and incidence of anisakidosis, with a final goal to minimize risks for human health and reducing costs for health systems.

Screening of Anisakis-Related Allergies and Associated Factors in a Mediterranean Community Characterized by High Seafood Consumption

Dietary changes expose consumers to risks from Anisakis larvae in seafood, leading to parasitic diseases and allergies. Anisakis is recognized by EFSA as a significant hazard, with potential oncogenic implications. Diagnostic advancements, like the Basophil Activation Test (BAT), enhance sensitivity and accuracy in identifying Anisakis sensitization, complementing traditional IgE tests. We conducted a cross-sectional study on patients with allergic symptoms from April 2021 to April 2023 at two outpatient clinics in western Sicily. Our goal was to assess the prevalence of Anisakis-related allergies and to identify risk profiles using specific Anisakis IgE and the BAT, especially in regions with high raw fish consumption. The study evaluated specific Anisakis IgE as a screening tool for Anisakis sensitization, using questionnaires, blood samples, and immuno-allergology analyses. Anisakis-specific IgE values were compared with the BAT results, with statistical analyses including Fisher's exact test and logistic regression. The results showed an 18.5% seroprevalence of Anisakis IgE, while the BAT as a second-level test showed 4.63%, indicating the BAT's superior specificity and accuracy. The study highlighted the importance of the BAT in diagnosing Anisakis sensitization, especially in cases of cross-reactivity with Ascaris and tropomyosin. The findings confirm the BAT's exceptional specificity in identifying Anisakis sensitization and support using Anisakis-specific IgE for population-based risk profiling. The BAT can effectively serve as a confirmatory test.

Immune response evaluation in Balb/c mice after crude extract of Anisakis typica sensitization

BACKGROUND AND AIM

Anisakis is a global challenge for a fish product which may lead to a decrease in economic value and consumers' preference. Skipjack (Katsuwonus pelamis) in Kupang, Nusa Tenggara Timur, Indonesia, have important economic value for local fisheries. Anisakis typica is one of the Anisakis species which potent to induce an allergic reaction. However, the study about A. typica involved in the dendritic cells (DCs), T helper 1 (Th1), T helper 2 (Th2), and regulatory T cells (Tregs) is still limited. This study aimed to analyze the dynamic changed of the immune system including DCs, CD4+ T cells, and Tregs after 1 week of A. typica sensitization.

MATERIALS AND METHODS

Twenty-four male Balb/C mice were randomly divided into four groups (n=6), mice treated with crude A. typica extract (CAE) 50, 75, and 100 mg/kg BW, respectively. CAE was given orally per day for a week. At the end of the experiment, the animals were sacrificed and the spleen was collected. DCs were labeled as CD11c+ interleukin-6+ (IL-6+); CD4+ T cells were distinguished as Th1 (CD4+ interferon-γ+ [IFN-γ+]) and Th2 (CD4+ IL-4+ and CD4+ IL-5+); Tregs were labeled as CD4+CD25+CD62L+. The expression of each cell was determined by flow cytometry.

RESULTS

Our result described that CAE elicits CD11c+ IL-6+, CD4+ IFN-γ+, CD4+ IL-4+, and CD4+ IL-5+ and reduces CD4+CD25+CD62L+ significantly (p<0.05) in dose-dependent manner in mice after A. typica infection.

CONCLUSION

The Th1/Th2 ratio after A. typica crude extract treatment exhibits a mixed pattern rather than the classical model allergy to food antigens. Our study is expected as a basic understanding of the changes in immune response after A. typic a infection.

Interplay between proinflammatory cytokines, miRNA, and tissue lesions in Anisakis-infected Sprague-Dawley rats

Background

Anisakiasis is an emerging public health problem, caused by Anisakis spp. nematode larvae. Anisakiasis presents as variable and unspecific gastrointestinal and/or allergic clinical symptoms, which accounts for the high rate of misdiagnosed cases.

Methodology/Principal findings

The aim of this study was to characterize the early cellular (6–72 h p.i.) and molecular (6 h p.i.) immune response and general underlying regulatory mechanism in Anisakis infected rats. Each Sprague-Dawley rat was infected with 10 Anisakis spp. larvae by gastric intubation. Tissues with visible lesions were processed for: i) classic histopathology (HE), immunofluorescence (CD3, iNOS, S100A8/A9), and transmission electron microscopy (TEM); ii) target genes (Il1b, Il6, Il18, Ccl3, Icam1, Mmp9) and microRNA (Rat Immunopathology MIRN-104ZF plate, Quiagen) expression analysis; and iii) global DNA methylation. Histopathology revealed that Anisakis larval migration caused moderate to extensive hemorrhages in submucosal and epimysial/perimysial connective tissue. In stomach and muscle, moderate to abundant mixed inflammatory infiltrate was present, dominated by neutrophils and macrophages, while only mild infiltration was seen in intestine. Lesions were characterized by the presence of CD3⁺, iNOS⁺, and S100A8/A9⁺ cells. The greatest number of iNOS⁺ and S100A8/A9⁺ cells was seen in muscle. Il6, Il1b, and Ccl3 showed particularly strong expression in stomach and visceral adipose tissues, but the order of expression differed between tissues. In total, three miRNAs were differentially expressed, two in stomach (miRNA-451 and miRNA-223) and two in intestine (miRNA-451 and miRNA-672). No changes in global DNA methylation were observed in infected tissues relative to controls.

Conclusions/Significance

Anisakis infection induces strong immune responses in infected rats with marked induction of specific proinflammatory cytokines and miRNA expression. Deciphering the functional role of these cytokines and miRNAs will help in understanding the anisakiasis pathology and controversies surrounding Anisakis infection in humans.

Anisakiasis is a zoonotic disease (infection transmitted between animals and humans) contracted by consumption of raw or undercooked seafood contaminated with Anisakis spp. nematode larvae. Anisakiasis usually presents with variable and unspecific gastrointestinal and/or allergic symptoms, which accounts for the high rate of misdiagnosed cases. Due to changes in dietary habits, such as eating raw or undercooked seafood, anisakiasis is considered an emerging public health problem. Despite the increase in number of reported cases worldwide, mechanisms of immune response to this unspecific human pathogen are poorly known. We have shown that in experimentally infected rats, Anisakis larvae cause severe hemorrhages and necrotic changes of affected tissues in the early phase of infections. Neutrophils and macrophages were abundantly present in tissue lesions, while eosinophils, hallmark of helminth infections, were scarcely present. We have also demonstrated particularly strong expression of several inflammatory genes. Moreover, we give for the first-time insight into putative regulatory mechanism mediated via a distinct class of RNA molecules. Our study may provide new opportunities for better understanding of cellular and molecular response to Anisakis spp., aiming at development of more specific therapeutics and alleviation of pathologies associated with Anisakis spp. infection.

Molecular and Cellular Response to Experimental Anisakis pegreffii (Nematoda, Anisakidae) Third-Stage Larval Infection in Rats

Background: Anisakiasis is a zoonotic disease caused by accidental ingestion of live Anisakis spp. third-stage larvae present in raw or undercooked seafood. Symptoms of this emerging infectious disease include mild-to-severe abdominal pain, nausea, and diarrhea. Some patients experience significant allergic reactions. Aims: In order to better understand the onset of anisakiasis, we aimed to: (i) histopathologically describe severe inflammatory/hemorrhagic infection site lesions in Sprague-Dawley rats experimentally infected with Anisakis pegreffii larvae; and (ii) qualitatively and quantitatively characterize the transcriptomes of affected tissues using RNA-Seq. Methodology: The experiment was performed on 35 male rats, sacrificed at 5 time points (6, 10, 18, 24, and 32 h post-infection). Gastric intubation was performed with 10 A. pegreffii larvae (N = 5 infected rats per time point) or 1.5 ml of saline (external control N = 2 rats). 16 pools, seven for muscle tissues and nine for stomach tissues, were created to obtain robust samples for estimation of gene expression changes depicting common signatures of affected versus unaffected tissues. Illumina NextSeq 500 was used for paired-end sequencing, while edgeR was used for count data and differential expression analyses. Results: In total, there were 1372 (855 up and 517 down) differentially expressed (DE) genes in the Anisakis-infected rat stomach tissues, and 1633 (1230 up and 403 down) DE genes in the muscle tissues. Elicited strong local proinflammatory reaction seems to favor the activation of the interleukin 17 signaling pathway and the development of the T helper 17-type response. The number of DE ribosomal genes in the Anisakis-infected stomach tissue suggests that A. pegreffii larvae might induce ribosomal stress in the early infection stage. However, the downstream pathways and post-infection responses require further study. Histopathology revealed severe inflammatory/hemorrhagic lesions caused by Anisakis infection in the rat stomach and muscle tissues in the first 32 h. The lesion sites showed infiltration by polymorphonuclear leukocytes (predominantly neutrophils and occasional eosinophils), and to a lesser extent, macrophages. Conclusion: Understanding the cellular and molecular mechanisms underlying host responses to Anisakis infection is important to elucidate many aspects of the onset of anisakiasis, a disease of growing public health concern.

Eosinophils from Physiology to Disease: A Comprehensive Review

Despite being the second least represented granulocyte subpopulation in the circulating blood, eosinophils are receiving a growing interest from the scientific community, due to their complex pathophysiological role in a broad range of local and systemic inflammatory diseases as well as in cancer and thrombosis. Eosinophils are crucial for the control of parasitic infections, but increasing evidence suggests that they are also involved in vital defensive tasks against bacterial and viral pathogens including HIV. On the other side of the coin, eosinophil potential to provide a strong defensive response against invading microbes through the release of a large array of compounds can prove toxic to the host tissues and dysregulate haemostasis. Increasing knowledge of eosinophil biological behaviour is leading to major changes in established paradigms for the classification and diagnosis of several allergic and autoimmune diseases and has paved the way to a "golden age" of eosinophil-targeted agents. In this review, we provide a comprehensive update on the pathophysiological role of eosinophils in host defence, inflammation, and cancer and discuss potential clinical implications in light of recent therapeutic advances.

Anisakis - immunology of a foodborne parasitosis

Anisakis species are marine nematodes which can cause zoonotic infection in humans if consumed in raw, pickled or undercooked fish and seafood. Infection with Anisakis is associated with abdominal pain, nausea and diarrhoea and can lead to massive infiltration of eosinophils and formation of granulomas in the gastrointestinal tract if the larvae are not removed. Re-infection leads to systemic allergic reactions such as urticarial or anaphylaxis in some individuals, making Anisakis an important source of hidden allergens in seafood. This review summarizes the immunopathology associated with Anisakis infection. Anisakiasis and gastroallergic reactions can be prevented by consuming only fish that has been frozen to -20°C to the core for at least 24 hours before preparation. Sensitization to Anisakis proteins can also occur, primarily due to occupational exposure to infested fish, and can lead to dermatitis, rhinoconjunctivitis or asthma. In this case, exposure to fish should be avoided.

New Perspectives on the Diagnosis of Allergy to Anisakis spp

PURPOSE OF REVIEW

To compare the prevalence of sensitization in different countries based on specific IgE values and to evaluate the use of isolated native or recombinant allergens for diagnosis.

RECENT FINDINGS

Isolated allergens help in the diagnosis of truly sensitized patients avoiding false positives due to cross-reactions. Their use is therefore highly recommended, especially when used as a combination of several relevant allergens. The use of purified allergens allows an accurate diagnosis and this has led to three important findings: (1) in addition to the digestive route of sensitization, occupational and non-digestive exposure seems to be clinically relevant. (2) The parasite appears as an important agent for chronic urticaria. And (3) in endemic countries, the amount of highly sensitized subjects in the general population could be as high as 7%. Adequate information to asymptomatic patients on fish consumption habits would avoid new contacts with parasite allergens and decrease their specific IgE levels and consequently the appearance of acute or chronic episodes induced by the parasite.

Identification of autoclave-resistant Anisakis simplex allergens

Anisakis simplex is a fish parasite able to induce allergic reactions in humans infected when eating raw or undercooked fish parasitized with viable third-stage larvae. Some authors claim that exposure to nonviable Anisakis material can result in allergic symptoms in previously sensitized patients, indicating that parasite allergens are resistant to the thermal treatments of usual cooking procedures. Furthermore, some patients report symptoms after eating canned fish. The aim of this work was the analysis of parasite allergen stability in heating to 121 °C in an autoclave to simulate the thermal process applied to canned fish. Third-stage larvae were subjected to autoclaving for 20, 40, and 80 min, and parasite crude extracts were analyzed by electrophoresis, immunoblotting, and a flow-cytometric basophil activation test. Allergens resistant to autoclaving were separated by reversed-phase high-performance liquid chromatography and identified by ion trap mass spectrometry. Protein analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that autoclaving considerably reduced the number and intensity of identifiable protein bands in a time-dependent manner. Several allergens were detected by immunoblotting with a pool of A. simplex allergic patients' sera after autoclaving. Allergens of 9 and 14 kDa resistant to autoclaving were identified as Ani s 4 and Ani s 1 allergens, respectively. Functional analysis showed that allergens retain their capacity to activate basophils even after autoclaving for 80 min. In conclusion, some relevant A. simplex allergens retain their capacity to bind immunoglobulin E and activate basophils after being subjected to autoclaving, which is a method equivalent to that used in industrial canning processes.

Gnathostoma spinigerum: immunodepression in experimental infected mice

Mice were infected with 8- or 25-infective worms of advanced third stage Gnathostoma spinigerum larvae (L3) which were obtained from natural infected eels. On day 14, 60 and 200 post infections (PI), spleen cells of infected mice were tested for lymphoproliferative responses in vitro against the mitogen and specific L3 somatic antigen in order to clarify the cellular immune status of the host upon this nematode infection. Reduced responsiveness to Con A was observed in infected mice. These depressed responses were more pronounced in chronically infected mice (day 200, PI) than in day 14 and day 60, PI. There was no significant difference of lymphoproliferative response between groups of high (25 L3) and low (8 L3)-infective dose in the chronic readily stage. Regarding to the L3 somatic Ag stimulation, the depressed response was obviously detected in high dose and chronic infection. Our results demonstrated that in this G. spinigerum-mouse system T-cell response is defective. The depression could be reversible and was associated with active infection because it was abolished by anthelmintic (ivermectin) treatment. This study shows the involvement of Th-2 response to this nematode in regulating T cell proliferation.

Fish immune responses against endoparasitic nematodes - experimental models

Vertebrates mount a series of immune reactions when invaded by helminths but antihelmintic immune strategies allow, in many cases, the first invaders of the non-immune host to survive for prolonged periods, whereas subsequent larval invaders of the same parasite species face increased host resistance and thereby decreased colonization success. This concomitant immunity may represent a trade-off between adverse side effects (associated with killing of large helminths in the host tissue) and the need for future protection against invasion. Encapsulation and isolation of large live endoparasitic larvae may be associated with less pathology compared to coping with excess dead parasite tissue in host organs. Likewise, live adult nematodes may be accepted in tissues at a certain activity level for the same reasons. Various host cell receptors bind helminth molecules after which signal-transducing events lead to mobilization of specific reaction patterns depending on the combination of receptors and ligands involved. Both innate and adaptive responses (humoral and cellular) are prominent actors, but skewing of the Th1 lymphocyte response towards a Th2 type is a characteristic element of antihelminthic responses in mammalian hosts. Similar patterns may be expected also to occur in at least some fish species, such as salmonids, producing relevant cytokines, MHCII and CD4+ cells required for these lymphocyte subpopulations. Atlantic cod, Gadus morhua L., is without these immunological elements that indicate that alternative reaction pathways exist in at least some fish groups. Recent achievements within teleost immunology have made it possible to track these host responses in fish and the present work outlines the main immune reactions in fish against helminths and suggests three experimental fish models for exploration of these immune pathways in fish infected with nematodes.