The aim of this study was to evaluate total IgG, IgG1, IgG4, and IgE antibody responses in human strongyloidiasis by enzyme-linked immunosorbent assay (ELISA) using Strongyloides ratti saline extract as heterologous antigen for a possible clinical utility of the assay. A total of 40 serum samples of patients who were shedding Strongyloides stercoralis larvae in feces (group I), 30 sera from patients with other intestinal parasites (group II), and 30 sera from subjects with negative results in three parasitological assays (group III) were analyzed to detect total IgG, IgG1, IgG4, and IgE to Strongyloides spp. by ELISA and expressed in ELISA index. Levels of total IgG anti-Strongyloides spp. were significantly higher in patients of group I than in groups II (p=0.0005) and III (p<0.0001). Levels of specific IgG1, IgG4, and IgE of group I were also significantly higher than in groups II and III, respectively. There was a significant positive correlation between specific IgE and IgG4 (r=0.6524; p=0.0084) and IgG1 and IgG4 (r=0.5398; p=0.0171). It can be concluded that the detection of specific IgE, IgG1, and IgG4 subclasses rather than total IgG antibodies to Strongyloides spp. using the S. ratti antigen showed to be an additional tool for improving the serodiagnosis of human strongyloidiasis.

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Strongyloidiasis is a human parasitic disease caused by the helminth Strongyloides stercoralis whose treatment is particularly difficult in immunosuppressed patients due to their low responsiveness to conventional therapy. Carica papaya and its isolated compounds benzyl isothiocyanate, carpaine and carpasemine are promising compound for the treatment of Strongyloides infections due to their anthelmintic action. This study aims to examine the in vitro ovicidal and larvicidal activity of C. papaya seed hexane extract against Strongyloides venezuelensis, using egg hatching tests and larval motility tests as efficiency markers. The crude extract at the concentrations of 566 – 0.0566 mg/mL or the control with albendazole (0.025 mg/mL) and negative controls (water and PBS) were incubated with an equal volume of egg suspension (± 50 specimens) followed by counting of the specimens after 48 h. The same extract and dilutions were added to L3 larvae suspensions (±50 specimens) followed by analysis of larvae viability after 24, 48, and 72 h. The extract inhibited egg hatching with high efficiency at concentrations of 56.6 mg/mL (95.74%) and 5.66 mg/mL (92.16%). At the concentrations of 566 mg/mL (100%) and 56.66 mg/mL (97.32%), the extract inhibited larval motility as effectively as ivermectin (0.316 mg/mL; 100%), and more effectively than the other dilutions and the negative controls. The larvicidal effect depended on the extract concentration, but not on the treatment period. Therefore, C. papaya seed hexane extract has anthelmintic potential against S. venezuelensis and is a promising compound for the development of phytotherapies to treat strongyloidiasis.

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