Fig 1.
Inclusion and exclusion criteria of the study participants.
Of the 400 pupils enrolled in the three schools, 269 were included in the analysis.
Table 1.
S. haematobium infection prevalence and intensity determined by the results of pCAA500 and egg detection among 269 pupils.
Fig 2.
Individuals with active S. haematobium infection showed higher IgG levels against the four antigen sets.
Total IgG levels against (a) ShSEA, (b) ShSerpin, (c) RP26, (d) ShSerpin-RP26 mixture were analyzed among individuals from Kwale with active S. haematobium infection (Sh+, n = 141, shown in red dots) and without active infection (Sh-, n = 128, blue dots) determined by the composite reference (CAA Indecisive results regarded as CAA negative, Indec-). The non-endemic control samples are included as the reference (Non endemic, n = 25, black dots). The dotted lines show the cut-off values determined by the geometric mean plus 3 SD of non-endemic controls (Japanese, n = 25)’ unit values. The cut-off value of each antigen was; 0.459 for ShSEA, 0.552 for ShSerpin, 0.165 for RP26, and 0.155 for ShSerpin-RP26 mixture. The antibody levels of the Sh+ and Sh- groups were compared by using Mann-Whitney’s U tests. Statistical significance was set at p < 0.05 and is shown using asterisks: **** = p < 0.0001. The horizontal bars represent the median values of arbitrary units of each group. Sh+: S. haematobium infection positive (pCAA500 positive and/or urine egg positive), shown in red dots (n = 141). Sh-: S. haematobium infection negative (pCAA500 negative and urine egg negative), shown in blue dots (n = 128). NC: non-endemic controls (Japanese), shown in black dots (n = 25).
Fig 3.
The ShSerpin-RP26 mixture capacity detecting active infections was similar to ShSEA.
The ROC curves were generated from the ELISA results of Kwale samples infected (Sh+, n = 141) and uninfected (Sh-, n = 128) with S. haematobium. pCAA500 indecisive results were considered as CAA negative (Inde-). The area under curve (AUC) of ShSEA, ShSerpin, RP26 and ShSerpin-RP26 mixture was 0.884, 0.819, 0.792 and 0.887, respectively.
Table 2.
Diagnostic performance of total IgG detection against ShSEA, ShSerpin, RP26 and ShSerpin-RP26 mix.
Fig 4.
IgG levels against S. haematobium antigens were associated with the infection intensity by plasma CAA.
Total IgG levels against (a) ShSEA, (b) ShSerpin, (c) RP26, (d) ShSerpin-RP26 mixture were analyzed among Kwale samples with different categories of infection intensity determined by plasma CAA concentrations (pCAA500). CAA High: pCAA500 ≥ 100 pg/mL (n = 42); CAA Medium: 10 ≤ pCAA500 < 100 pg/mL (n = 41); CAA Low:1 ≤ pCAA500 < 10 pg/mL (n = 52); CAA Indecisive: 0.5 ≤ pCAA500 < 1 pg/mL (n = 20); CAA Negative: 0 ≤ pCAA500 < 0.5 pg/mL (n = 114). Kruskal-Wallis tests were performed for comparing antibody levels between different infection intensity groups measured by PCAA. Statistical significance was set at p < 0.05 and is shown using asterisks: **** = p < 0.0001. The dotted lines show the cut-off values determined by the geometric mean plus 3 SD of non-endemic controls’ unit values. The cut-off value of each antigen was; 0.459 for ShSEA, 0.552 for ShSerpin, 0.165 for RP26, and 0.155 for ShSerpin-RP26 mixture. The horizontal bars represent the median values of arbitrary units of each group.
Fig 5.
Correlation between the CAA concentration by pCAA500 and the total IgG levels against ShSEA, ShSerpin, RP26 and ShSerpin-RP26 mixture. The correlations between total IgG levels against (a) ShSEA, (b) ShSerpin, (c) RP26, (d) ShSerpin-RP26 mixture and CAA concentrations were analyzed using Spearman’s rank correlation coefficient analyses. The correlation coefficient of ShSEA, ShSerpin, RP26 and ShSerpin-RP26 mixture was 0.729 (95% CI 0.665–0.782), 0.630 (95% CI 0.550–0.699), 0.540 (95% CI 0.447–0.622) and 0.695 (95% CI 0.625–0.754) respectively. For the all antigen sets, the p values were below 0.0001. As the axes are logarithmic, actual CAA concentration + 1 were plotted in the figures.
Fig 6.
Recombinant protein antigens (ShSerpin, RP26 and ShSerpin-RP26 mixture) had lower crosss-reactivity compared to ShSEA.
Total IgG levels against (a) ShSEA, (b) ShSerpin, (c) RP26, (d) ShSerpin-RP26 mix were analyzed among 131 samples with helminthic infections. The samples were from patients with schistosomiasis mansoni (Sm, n = 20), schistosomiasis japonica (Sj, n = 12), paragonimiasis (Pw, n = 20), fascioliasis (Fh, n = 20), clonorchiasis (Cs, n = 10), sparganosis (Se, n = 19), gnathostomiasis (Gd, n = 10) and toxocariasis (Tc, n = 20). The dotted lines show the cut-off values determined by the geometric mean plus 3 SD of non-endemic controls’ unit values. The cut-off value of each antigen was; 0.459 for ShSEA, 0.552 for ShSerpin, 0.165 for RP26, and 0.155 for ShSerpin-RP26 mixture. The horizontal bars represent the median values of arbitrary units of each type of parasite infection.
Table 3.
Number and proportion of cross-reactive samples from different helminthic infections.