Venestatin from parasitic helminths interferes with receptor for advanced glycation end products (RAGE)-mediated immune responses to promote larval migration.

Parasitic helminths can reside in humans owing to their ability to disrupt host protective immunity. Receptor for advanced glycation end products (RAGE), which is highly expressed in host skin, mediates inflammatory responses by regulating the expression of pro-inflammatory cytokines and endothelial adhesion molecules. In this study, we evaluated the effects of venestatin, an EF-hand Ca2+-binding protein secreted by the parasitic helminth Strongyloides venezuelensis, on RAGE activity and immune responses. Our results demonstrated that venestatin bound to RAGE and downregulated the host immune response. Recombinant venestatin predominantly bound to the RAGE C1 domain in a Ca2+-dependent manner. Recombinant venestatin effectively alleviated RAGE-mediated inflammation, including footpad edema in mice, and pneumonia induced by an exogenous RAGE ligand. Infection experiments using S. venezuelensis larvae and venestatin silencing via RNA interference revealed that endogenous venestatin promoted larval migration from the skin to the lungs in a RAGE-dependent manner. Moreover, endogenous venestatin suppressed macrophage and neutrophil accumulation around larvae. Although the invasion of larvae upregulated the abundance of RAGE ligands in host skin tissues, mRNA expression levels of tumor necrosis factor-α, cyclooxygenase-2, endothelial adhesion molecules vascular cell adhesion protein-1, intracellular adhesion molecule-1, and E-selectin were suppressed by endogenous venestatin. Taken together, our results indicate that venestatin suppressed RAGE-mediated immune responses in host skin induced by helminthic infection, thereby promoting larval migration. The anti-inflammatory mechanism of venestatin may be targeted for the development of anthelminthics and immunosuppressive agents for the treatment of RAGE-mediated inflammatory diseases.

Broad specificity of immune helminth scFv library to identify monoclonal antibodies targeting Strongyloides.

Antibodies have different chemical properties capable of targeting a diverse nature of antigens. Traditionally, immune antibody libraries are perceived to be disease-specific with a skewed repertoire. The complexity during the generation of a combinatorial antibody library allows for a skewed but diverse repertoire to be generated. Strongyloides stercoralis is a parasite that causes strongyloidiasis, a potentially life-threatening disease with a complex diagnosis that impedes effective control and treatment of the disease. This study describes the isolation of monoclonal antibodies against S. stercoralis NIE recombinant protein using an immune antibody phage display library derived from lymphatic filaria-infected individuals. The isolated antibody clones showed both lambda and kappa light chains gene usage, with diverse amino acid distributions. Structural analysis showed that electropositivity and the interface area could determine the binding affinity of the clones with NIE. The successful identification of S. stercoralis antibodies from the filarial immune library highlights the breadth of antibody gene diversification in an immune antibody library that can be applied for closely related infections.

Direct detection of Strongyloides infection via molecular and antigen detection methods.

Laboratory diagnosis of Strongyloides infections can be grouped into direct and indirect detection methods, and a combination of the two methods is often needed to reach an accurate and timely diagnosis. This review focuses on non-conventional direct detection via molecular and antigen detection assays. Conventional PCR is the most commonly used molecular diagnostic for Strongyloides. Real-time PCR is accurate and highly sensitive for quantitative and qualitative analysis. Meanwhile, PCR-RFLP can efficiently distinguish human and dog isolates of S. stercoralis, S. fuelleborni (from monkey), and S. ratti (from rodent). Loop-mediated isothermal amplification (LAMP) amplifies DNA isothermally with high specificity, efficiency, and rapidity, and has potential for point-of-care (POC) translation. As for antigen detection assay, coproantigen detection ELISAs for strongyloidiasis traditionally relied on raising rabbit polyclonal antibodies against the parasite antigens for use as capture or detection reagents. Subsequently, hybridoma technology using animals has enabled the discovery of monoclonal antibodies specific to Strongyloides antigens and was utilised to develop antigen detection assays. In recent times, phage display technology has facilitated the discovery of scFv antibody against Strongyloides protein that can accelerate the development of such assays. Improvements in both direct detection methods are being made. Strongyloides molecular diagnostics is moving from the detection of a single infection to the simultaneous detection of soil-transmitted helminths. Meanwhile, antigen detection assays can also be multiplexed and aptamers can be used as antigen binders. In the near future, these two direct detection methods may be more widely used as diagnostic tools for strongyloidiasis.

Beneficial effects of Strongyloides venezuelensis antigen extract in acute experimental toxoplasmosis.

BACKGROUND: Toxoplasma gondii is a protozoan with worldwide distribution and triggers a strong Th1 immune response in infected susceptible hosts. On the contrary, most helminth infections are characterized by Th2 immune response and the use of helminth-derived antigens to regulate immune response in inflammatory disorders has been broadly investigated. OBJECTIVES: The aim of this study was to investigate whether treatment with Strongyloides venezuelensis antigen extract (SvAg) would alter immune response against T gondii. METHODS: C57BL/6 mice were orally infected with T gondii and treated with SvAg, and parasitological, histological and immunological parameters were investigated. RESULTS: It was observed that SvAg treatment improved survival rates of T gondii-infected mice. At day 7 post-infection, the parasite load was lower in the lung and small intestine of infected SvAg-treated mice than untreated infected mice. Remarkably, SvAg-treated mice infected with T gondii presented reduced inflammatory lesions in the small intestine than infected untreated mice and decreased intestinal and systemic levels of IFN-γ, TNF-α and IL-6. In contrast, SvAg treatment increased T gondii-specific IgA serum levels in infected mice. CONCLUSIONS: S venezuelensis antigen extract has anti-parasitic and anti-inflammatory properties during T gondii infection suggesting as a possible alternative to parasite and inflammation control.

Strongyloides-specific IgA, IgG and IgG immune complex profile in patients with pulmonary tuberculosis.

AIMS: To describe an anti-Strongyloides IgA, IgG and IgG immune complex antibody response profile in patients with pulmonary tuberculosis. METHODS AND RESULTS: Saliva and serum samples were collected from 100 individuals: group I, 50 apparently healthy individuals; and group II, 50 pulmonary tuberculosis patients. The IgA, IgG and IgG immune complex detection were carried out via an ELISA immunoenzymatic test. Optical density medians in saliva samples of IgA antibody (median of 7.21) and IgG-IC (median of 4.95) were significantly higher in tuberculosis group compared to control individuals (median IgA of 3.93 and IgG-IC of 2.38). CONCLUSION: This study presents antibody data to the field of pulmonary tuberculosis and strongyloidiasis coinfection, including saliva samples, and especially IgG immune complex detection.

scFv against HSP60 of Strongyloides sp. and Its Application in the Evaluation of Parasite Frequency in the Elderly.

The present study is aimed at evaluating serological method using scFv anti-Strongyloides sp. and reporting the frequencies of the results with conventional parasitological technique (faeces) in elderly individuals. Among 112 elderly individuals (≥60 years of age), 14.28% were positive for at least one enteroparasite, with one individual positive for S. stercoralis. Sera were evaluated for the presence of anti-Strongyloides sp. antibodies using total or detergent fraction extracts of Strongyloides venezuelensis, which presented positivity rates of 19.64% and 10.71%, respectively. An anti-HSP60 single-chain variable fragment from Strongyloides sp. was used to detect parasite antigens, with 5.36% (6 individuals) of ELISA-positive individuals returning a positive result. While the serological test indicates previous or recent infection and may be limited by antigen purification, the anti-HSP60 method reflects the presence of Strongyloides sp. immune complexes and exhibits greater sensitivity and specificity. Our results demonstrate the variable occurrence of enteroparasites in elderly individuals residing in long-term nursing homes and validate a novel epidemiological tool to describe infection cases by Strongyloides sp.

The effect of maternal Strongyloides venezuelensis infection on mice offspring susceptibility and immune response.

Species of Strongyloides infect a wide range of hosts worldwide. Due to their complex life cycle, it is hard to control the transmission of these parasites. Several species show evidence of vertical transmission; however, the impact of this transmission route on the susceptibility of the offspring has been poorly investigated. Herein, we used Strongyloides venezuelensis infected mice to evaluate transplacental and transmammary parasite transmission and their effect on the susceptibility of offspring. Swiss female mice were infected at the end of the gestation or during the breastfeeding period, and their offspring were examined for the presence of the parasite one week after infection of the mother. Our data showed that female mice infected with S. venezuelensis during gestation did not transmit the parasite to their offspring. On the other hand, all newborn mice breastfeeding in S. venezuelensis infected females got infected. To evaluate the effect of early exposure to the parasite on susceptibility and immune response of the hosts, the offspring of each experimental group (non-infected, gestation-infected, and breastfeeding-infected mothers) received anti-helminth treatment after parasite evaluation and were subcutaneously infected with S. venezuelensis upon reaching adulthood. Mice from the group of breastfeeding-infected mothers showed lower susceptibility to S. venezuelensis in adulthood in comparison with mice from non-infected mothers. The low parasite burden was accompanied by earlier eosinophil and neutrophil activation in the gut and higher serum levels of IgE. In contrast, S. venezuelensis infection in adult mice born from gestation-infected mothers presented with more worms in the intestine and lower levels of parasite-reactive IgM in serum in comparison with mice born from non-infected mothers, thus suggesting that early exposure to parasite antigens may modulate the protective immune response. Altogether, our data confirmed transmammary, but not transplacental, transmission of S. venezuelensis in mice and demonstrated that early exposure to the parasite and/or their antigens has an important effect on host susceptibility to a later infection.

Parasitological and immunological aspects of oral and subcutaneous prednisolone treatment in rats experimentally infected with Strongyloides venezuelensis.

Strongyloides venezuelensis is a model to study human strongyloidiasis, which infects wild rodents and shares common antigenic epitopes with Strongyloides stercoralis. This study aimed to evaluate parasitological and immunological parameters of prednisolone immunosuppression protocols in rats (Rattus novergicus) infected with S. venezuelensis. Rats were divided into six groups (n = 36): untreated and uninfected (-) or infected (+); oral treatment and uninfected (o-) or infected (o+); subcutaneous treatment and uninfected (sc-) or infected (sc+). For oral immunosuppression, 5 mg/mL of water diluted prednisolone were given five days before infection, and in the days 8 and 21 (for 5 days). For subcutaneous immunosuppression, 10 mg/kg of prednisolone were given daily. The infection was established by the subcutaneous injection of approximately 3,000 S. venezuelensis filarioid larvae per animal. All animals from the (+) and (o+) groups survived, while four rats from the (sc+) died prior to necropsy date. Parasitological analysis showed higher egg elimination in (o+) in comparison to (+) and (sc+) on 7, 13 and 26 days post infection (d.p.i.).The recovery of parasitic females at day 30 was significantly higher in (o+), compared to (+). The (+) and (o+) groups showed a clear increase in anti-S. venezuelensis IgG, IgG1 and IgG2 from 13th d.p.i. Oral immunosuppression led to a higher number of adult females and increased egg output while maintaining IgG and subclasses antibody levels comparable to the positive control.

Development of immunochromatographic device as a point-of-care tool for serodiagnosis of human strongyloidiasis cases.

Human strongyloidiasis is an important gastrointestinal disease with an estimated 30 to 100 million people infected. Prevalence is generally underestimated since many infections are asymptomatic, and traditional diagnostic tests based on parasitological examination of stool samples are not adequately sensitive. Serological tests are useful and supportive but are still only available in a reference research setting. We made an immunochromatographic test (ICT) kit for rapid serodiagnosis of human strongyloidiasis. The antigen used in the ICT kit was extracted from larvae of Strongyloides stercoralis. Diagnostic efficacy of the kit was evaluated using human serum samples from strongyloidiasis patients, healthy persons, and those with other parasitoses. When using a cutoff level of 0.5 or above, the diagnostic sensitivity, specificity, and positive and negative predictive values at the prevalence of infection of 34.4%, were 93.3%, 83.7%, 76.7%, and 95.6%, respectively. This ICT kit is easy to use at the point-of-care and a result can be obtained in 15 min. Sophisticated instruments and highly trained staff are not required. It can be used in several diagnostic and public-health settings, e.g., prevalence surveys in endemic areas, confirmation and monitoring of cure post-treatment, diagnosis and screening of infected but asymptomatic individuals, and populations "at risk" for hyperinfection syndrome or disseminated strongyloidiasis if they are given immunosuppressive treatment for other conditions.

Strongyloides venezuelensis-infection alters the profile of cytokines and liver inflammation in mice co-infected with Schistosoma mansoni.

Human co-infection by helminth species is frequent, but their consequences are mostly unknown. Here, we investigate the impact of Strongyloides venezuelensis co-infection on the immune response, schistosome burden, and the associated pathology of schistosomiasis in mice. Co-infection did not alter the schistosome parasite burden, but reduced the IL-4/IL-10 ratio during acute schistosomiasis, indicating induction of modulatory mechanisms. Simultaneous infection with S. venezuelensis and S. mansoni increased the liver concentration of IFN-γ and altered the Th2/Th1 balance, leading to great infiltration of neutrophils and macrophages, which resulted in larger liver inflammation and increased serum transaminase activity in comparison with mono-infected mice. Mice infected with S. venezuelensis at two and four weeks after S. mansoni infection showed significant increase of Th1/Th2/Th17/Treg cytokines and strong cellular infiltration in the liver in comparison with mono-infected mice. However, only in mice co-infected after two weeks of schistosomiasis, the liver immune response leads to more intense Th2 polarization, increased liver inflammation, and transaminase serum activity. S. venezuelensis co-infection during chronic schistosomiasis did not significantly alter liver inflammation. Therefore, S. venezuelensis co-infection affects the host immune responses and morbidity of schistosomiasis, but the effects largely depend on the stage of the S. mansoni infection.

Use of serology in a systematic screening programme for strongyloidiasis in an immigrant population.

OBJECTIVES: The aim of this cross-sectional study was to describe the results of a systematic serological screening programme for strongyloidiasis. METHODS: A prospective serological screening programme for strongyloidiasis was performed between 2009 and 2014 for all immigrant patients attending the Tropical Medicine Unit. Three formalin-ether concentrated stool samples and an ELISA for anti-Strongyloides stercoralis antibodies were used as screening tools. RESULTS: Of 659 patients screened, 79 (12%) were positive for S. stercoralis regardless of the diagnostic method used. The prevalence of infection was 42.9% in East African patients, 16.3% in Central African patients, 10.9% in those from South America, and 10% in the case of West Africa. Univariate analysis showed that infection by S. stercoralis was significantly more frequent in patients from Central Africa (p=0.026; OR 1.72, 95% CI 1.03-2.85) and East Africa (p<0.001; OR 5.88, 95% CI 1.75-19.32). Taking West Africa as the reference (as the area of lowest prevalence among the positive prevalence areas), the statistical analysis showed that the risk of infection was higher in East Africa (p=0.001; OR 6.750, 95% CI 2.127-21.423) and Central Africa (p=0.065; OR 1.747, 95% CI 0.965-3.163). CONCLUSIONS: Due to the potential complications of strongyloidiasis infection, we recommend that immigrant patients from developing countries be routinely screened for S. stercoralis, especially those from East Africa. A serological test is a highly appropriate screening tool.

Highly specific and sensitive anti-Strongyloides venezuelensis IgY antibodies applied to the human strongyloidiasis immunodiagnosis.

Due to the epidemiological problem of the neglected condition of human strongyloidiasis, rapid and effective diagnosis is extremely important, with the development of new diagnostic tools being essential to reduce infections and chronic cases. Avian immunoglobulin Y (IgY) technology is an alternative for antibody production that has high specificity and profitability. This study aimed to produce and fractionate IgY antibodies from the egg yolks of hens that were immunized with the total antigenic extracts of Strongyloides venezuelensis infectious filariform larvae (iL3) and parthenogenetic females (pF). IgY antibodies were then evaluated by their recognition of antigenic proteins, evolutive helminth forms, and serological diagnosis of human strongyloidiasis by the detection of immune complexes in serum samples. Egg yolks were fractionated to obtain IgY antibodies by thiophilic interaction chromatography. Immune complex detection in serum samples showed diagnostic values for anti-iL3 IgY and anti-pF IgY antibodies at 95.56% and 88.89% sensitivity and 95.56% and 91.11% specificity, respectively. Therefore, IgY technology is a promising tool for the detection of blood circulating Strongyloides antigens, with possible application as a serological diagnostic method.

Nematode-Infected Mice Acquire Resistance to Subsequent Infection With Unrelated Nematode by Inducing Highly Responsive Group 2 Innate Lymphoid Cells in the Lung.

The immune responses against helminths have been investigated individually, and it is well-established that infected hosts develop an immunological memory to resist reinfection by the same pathogen. In contrast, it is poorly understood how the host immune system responds to subsequent infection by unrelated parasites after elimination of the first infection. We previously reported that infection of mice with Strongyloides venezuelensis induces the accumulation of group 2 innate lymphoid cells (ILC2s) in the lung. Here, we demonstrated that S. venezuelensis-experienced (Sv-exp) mice became significantly resistant against infection by Nippostrongylus brasiliensis. N. brasiliensis infection induced enhanced accumulation of ILC2s and eosinophils with increased expressions of mRNA for Th2 cytokines in the lungs of Sv-exp mice. The resistance was dependent on ILC2s, and eosinophils but not on CD4+ T cells. Furthermore, pulmonary ILC2s in Sv-exp mice acquired a highly responsive "trained" phenotype; in response to N. brasiliensis infection, they rapidly increased and produced IL-5 and IL-13, which in turn induced the early accumulation of eosinophils in the lungs. IL-33 was required for the accumulation of ILC2s and the resistance of mice against N. brasiliensis infection but insufficient for the induction of trained ILC2s. In conclusion, animals infected with one type of lung-migratory nematodes acquire a specific-antigen-independent resistance to another type of lung-migrating nematodes, providing animals with the capacity to protect against sequential infections with various lung-migratory nematodes.

Acute infection with Strongyloides venezuelensis increases intestine production IL-10, reduces Th1/Th2/Th17 induction in colon and attenuates Dextran Sulfate Sodium-induced colitis in BALB/c mice.

Helminth infection can reduce the severity of inflammatory bowel disease. However, the modulatory mechanisms elicited by helminth infection are not yet fully understood and vary depending on the experimental model. Herein we evaluated the effect of acute infection of BALB/c mice with Strongyloides venezuelensis on the clinical course of ulcerative colitis induced by Dextran Sulfate Sodium (DSS) treatment of these animals. For the experiments, S. venezuelensis-infected BALB/c mice were treated orally with 4% DSS solution for seven days. As controls, we used untreated S. venezuelensis infected, DSS-treated uninfected, and untreated/uninfected BALB/c mice. During DSS treatment, mice from the different groups were compared with regards to the clinical signs related to the severity of colitis and intestinal inflammation. Mice acutely infected with S. venezulensis and treated with DSS had reduced clinical score, shortening of the colon, and tissue inflammation. Moreover, DSS-treated and infected mice showed reduced IL-4, INF-γ, and IL-17 levels and increase of IL-10 production in the colon and/or in the supernatant of mesenteric lymph nodes cell cultures that resulted in lower eosinophil peroxidase and myeloperoxidase activity in colon homogenates, when compared with DSS-treated uninfected mice. DSS-treated infected mice also preserved the intestine architecture and had normal differentiation of goblet cells and mucus production in the colon mucosa. In conclusion, the data indicate that the clinical improvement reported in DSS-treated infected mice was accompanied by the lower production of Th1/Th2/Th17 pro-inflammatory cytokines, stimulation of IL-10, and induction of mucosal repair mechanisms.

Molecular and Immnune Diagnosis: Further Testing for Human Strongyloidiasis.

INTRODUCTION: Detection of Strongyloides stercoralis larvae is particularly challenging because only a small number of larvae are released into the feces, regardless of infection stage. OBJECTIVE: Our objective was to apply conventional polymerase chain reaction (PCR) to the detection of S. stercoralis DNA in feces samples to evaluate its performance in samples of patients with strongyloidiasis and compare results with those of immunodiagnosis. METHODS: Stool, serum, and saliva samples were collected from each individual (n = 48) at the clinic hospital of the State University of Londrina, Brazil, for parasitological, immunological, and molecular tests. Stool samples were processed via parasitological methods. Serum samples were used for immunoglobulin G (IgG) detection and saliva samples for IgA detection by ELISA. RESULTS: For amplification by conventional PCR, two different primers were used: species specific (101 bp) and genus specific (392 bp). The results showed that 34 (97.1%) of the 35 copro-positive individuals for S. stercoralis were positive for serum IgG and 19 (54.3%) were positive for salivary IgA. Regarding molecular analysis, both primers (species and genus specific) demonstrated positivity in 100% of the samples, which was confirmed by sequencing the positive samples. CONCLUSION: Complementary examinations of the parasitological method demonstrated excellent results in the context of the diagnosis of strongyloidiasis, especially in asymptomatic patients with irregular larval release in the feces.

Metaperiodate deglycosylation of Strongyloides venezuelensis larvae: Immunochemical characterization and antigen production for human strongyloidiasis diagnosis.

Strongyloidiasis is an important helminthiasis affecting million people worldwide. The aim of this study was to use sodium metaperiodate (MP) treatment to immunochemically characterize Strongyloides venezuelensis filariform larvae and use MP-treated heterologous antigen to detect IgG and subclasses in serum. Samples from individuals with definitive diagnosis of strongyloidiasis (n = 50), other parasitic diseases (n = 60) and negative endemic (n = 50) were tested. TG-ROC and two-way ANOVA were applied. MP-treatment resulted on differential localization of carbohydrates at larval structure and no carbohydrate content in saline extract (SE). Electrophoretic profiles were similar before and after treatment. ELISA sensitivity and specificity were: 90%; 88.2% for SE and 92.0%; 94.6% for MP, respectively. When using MP treated antigen we observed reduction in IgG1 and IgG3 detection in strongyloidiasis group and decrease of cross reactions in control groups. Our data demonstrate the role of carbohydrate residues in cross reactions and on the recognition of anti-Strongyloides IgG and its subclasses.

Avidity as a criterion for diagnosis of human strongyloidiasis increases specificity of IgG ELISA.

This study evaluates the inclusion of the IgG avidity index in ELISA to detect anti-Strongyloides stercoralis IgG. The ELISA index revealed 70% of specificity. With the inclusion of screening AI, specificity increased to 80%. IgG avidity complemented traditional IgG ELISA by eliminating some of the suspected or false positive cases.

Screening of immunocompromised patients at risk of strongyloidiasis in western Turkey using ELISA and real-time PCR.

BACKGROUND/AIM: Strongyloides stercoralis causes life-threatening hyperinfection or disseminated strongyloidiasis in immunocompromised patients such as HIV-positive, organ transplantation, and cancer patients. This study investigated the presence of strongyloidiasis in immunocompromised patients for the first time in Turkey. MATERIALS AND METHODS: Serum and stool samples were collected from 108 patients (25.9% of them were chronic renal failure and 74.1% were renal transplantation patients) who were admitted to Ege University Medical School in Izmir, located in western Turkey. Serum samples were analyzed by ELISA (DRG, Germany) and the presence of 18S rRNA gene of S. stercoralis was detected in stool samples by real-time PCR. RESULTS: The analysis of serum samples showed that only one patient was anti-S. stercoralis IgG antibody and real-time PCR positive (0.92%). The patient was treated twice with albendazole (400 mg/day for 3 days) at 2-week intervals. Follow up real-time PCR was negative and the patient became seronegative 6 months after the initial diagnosis. CONCLUSION: This screening showed that the prevalence of strongyloidiasis in this small group of patients who were at risk of strongyloidiasis was 0.92%. Overall, the results showed that more systematic studies are required in Turkey to show the prevalence of strongyloidiasis.

Differences in the Importance of Mast Cells, Basophils, IgE, and IgG versus That of CD4+ T Cells and ILC2 Cells in Primary and Secondary Immunity to Strongyloides venezuelensis.

There is evidence that mast cells, basophils, and IgE can contribute to immune responses to parasites; however, the relative levels of importance of these effector elements in parasite immunity are not fully understood. Previous work in Il3-deficient and c-kit mutant KitW/W-v mice indicated that interleukin-3 and c-Kit contribute to expulsion of the intestinal nematode Strongyloides venezuelensis during primary infection. Our findings in mast cell-deficient KitW-sh/W-sh mice and two types of mast cell-deficient mice that have normal c-kit ("Hello Kitty" and MasTRECK mice) confirmed prior work in KitW/W-v mice that suggested that mast cells play an important role in S. venezuelensis egg clearance in primary infections. We also assessed a possible contribution of basophils in immune responses to S. venezuelensis By immunohistochemistry, we found that numbers of basophils and mast cells were markedly increased in the jejunal mucosa during primary infections with S. venezuelensis Studies in basophil-deficient Mcpt8DTR mice revealed a small but significant contribution of basophils to S. venezuelensis egg clearance in primary infections. Studies in mice deficient in various components of immune responses showed that CD4+ T cells and ILC2 cells, IgG, FcRγ, and, to a lesser extent, IgE and FcεRI contribute to effective immunity in primary S. venezuelensis infections. These findings support the conclusion that the hierarchy of importance of immune effector mechanisms in primary S. venezuelensis infection is as follows: CD4+ T cells/ILC2 cells, IgG, and FcRγ>mast cells>IgE and FcεRI>basophils. In contrast, in secondary S. venezuelensis infection, our evidence indicates that the presence of CD4+ T cells is of critical importance but mast cells, antibodies, and basophils have few or no nonredundant roles.