We standardized and evaluated an ELISA technique for the detection of total and specific anti-Giardia duodenalis secretory IgA antibodies (sIgA). Samples of saliva and serum of 161 Venezuelan schoolchildren were analysed. After stool examination, 66 children were diagnosed to be infected with Giardia duodenalis, 22 with other protozoa, and 73 non-parasitized. The mean (+ 2 SD) values of secretory IgA in the non-parasitized group was considered as the criterion of positivity. The levels of total and specific anti-Giardia sIgA were significantly higher in children with Giardia compared with the group with other protozoa (p < 0.01) and the non-parasitized group (p < 0.001). The ELISA technique developed showed values of sensitivity and specificity of 74 and 94 per cent, respectively, a predictive value of 92 per cent for positive samples and 80 per cent for negative samples. Specific anti-Giardia IgA serum levels showed a low sensitivity (57 per cent) and a predictive value for negative samples (53 per cent). Our results suggest that secretory anti-Giardia IgA levels measured in saliva samples may reflect local intestinal IgA responses elicited by these parasites. Thus, determinations of the levels of sIgA anti-Giardia could be a useful diagnostic tool for giardiasis in children.

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Innate lymphoid cells (ILCs) are classified by the expression of specific transcription factors: ILC1 depending on T‐bet for IFN‐γ production; ILC2 depending on GATA3 for IL‐5 and IL‐13; and ILC3 depending on ROR‐γτ and AHR for IL‐17 and IL‐22. This study aimed to determine circulating ILCs in 23 patients with localized (LCL) = 7, mucocutaneous (MCL) = 10, intermediate (ICL) = 3 and diffuse (DCL) = 3 cutaneous leishmaniasis and 17 healthy controls from endemic area (EC) = 9 and non‐endemic area (HC) = 8. Results evidenced a higher proportion of ILC1 in LCL than controls and MCL. ILC2 was higher in DCL compared with controls. ILC3 s were abundant in MCL and DCL concerning controls. A prevalence ratio was calculated to approach cell plasticity: in LCL, the ratio showed a prevalence of ILC1/ILC3 (plasticity 1), in contrast to DCL, and controls, where ILC2/ILC3 (plasticity 3) is prevalent. Also, MCL and ICL showed higher ILC1/ILC2 (plasticity 2). These results suggest that ILC1 and ILC3 in LCL are associated with disease control and regulation of inflammation, while MCL and ICL are related to immunopathology and uncontrolled inflammation. In DCL, ILC2 is associated with the tolerogenic state of these patients.

We investigated the influence of nutritional status, as determined from anthropometric measurement, and of helminthic infections on the immune response of children of low socioeconomic status in two rural communities in Venezuela: El Cardón in the state of Nueva Esparta and San Daniel in the state of Miranda. A total of 125 boys and girls between 2 and 15 years old participated in the study. Their socioeconomic stratum was determined by a modified Graffar method. A physical examination was performed, as was also an anthropometric evaluation that took into account three indicators--weight-for-height, weight-for-age, and height-for-age--according to parameters established by the World Health Organization. Other examinations included feces, secretory IgA in saliva, total serum IgE, and anti-Ascaris-specific immunoglobulins. The children in both of the communities were in strata IV and V of the of Graffar scale, with a significantly greater number of stratum V inhabitants in San Daniel (P < 0.001). The results suggest that exposure level and individual susceptibility to the parasites are determining factors in parasitic infection and immune system behavior. The intensity of the parasitic burden plays an important role in stimulating polyclonal IgE, which diminishes the effectiveness of the specific response to those infections. On the other hand, nutritional deficiencies could change the immune mechanisms of the mucous membranes, negatively influence the synthesis of secretory IgA, and stimulate the production of polyclonal IgE. Poor sanitary and socioeconomic conditions promote more exposure to gastrointestinal parasites and a deficient nutritional status, which modulates the immune response and affects serum IgE and secretory IgA production mechanisms.

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