Secretory IgA Antibody Responses in Venezuelan Children Infected with Giardia duodenalis

Abstract

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.

Saliva and sera IgA and IgG in Egyptian Giardia-infected children

“…The levels of serum specific IgA were similar in these groups of children, suggesting that the levels of this antibody may reflect previous exposure to parasitic antigens, rather than current infection (Table 2). Similarly, Rodríguez et al (2004) reported that the levels of total and specific anti-Giardia slgA 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). In a study by Cedillo-Rivera et al (2009), positive saliva samples from individuals infected with G. duodenalis contained seven times more sIgA than the saliva samples from non-infected individuals.…”

“…Saliva samples were collected using sterile cotton swabs which were maintained in contact with oral mucosa between the gum and inside of the cheek for 10 min (Rodríguez et al 2004). Saliva secretion was recovered by compression using sterile syringe having 1 ml of cold phosphate-buffered saline (PBS, pH 7.2) into vacutainer tubes with EDTA and stored at −20°C.…”

“…According to Rodríguez et al (2004), Giardia antigen (3 μg/well) was diluted in carbonate-bicarbonate buffer at pH 9.6 and coated onto two 96-well microtitre plates and incubated overnight at 4°C (Rodríguez et al 2004). Excess antigen was washed off with PBS Tween and blocked for 2 h at 37°C with bovine serum diluted 1:30 in PBS.…”

“…The alternative methods of diagnosis as duodenal aspirate examination or intestinal biopsy are more sensitive but they are invasive and risky procedures (Rodríguez et al 2004).…”

“…Also, sIgA was detected on the surface of Giardia trophozoites from jejunal biopsies using direct immunofluorescence technique. This suggests that the production of sIgA antibody occurs during active Giardia infection; therefore, the determination of sIgA may be an important tool for monitoring the course of Giardia infection (Rodríguez et al 2004).…”