Diagnostic potentials of whole and fragmented major egg protein for human schistosomiasis

Heat shock proteins are known to be antigenic due to their high conservation. A 40 kDa heat shock protein, considered a major egg protein, was identified as a potential candidate antigen for diagnosing schistosomiasis. Consequently, this study aims to evaluate the diagnostic potential of SjMEP-40 for detecting human schistosomiasis. SjMEP-40 was fragmented into three distinct portions—SjMEP-40 N (N-terminal), SjMEP-40 M (middle), and SjMEP-40C (C-terminal)—to determine which segment provides the best diagnostic performance compared to the whole antigen (SjMEP-40 W) for both IgG and IgM detection. Enzyme-linked immunosorbent assay (ELISA) was used to analyze archived samples from various endemic areas in the Philippines, all previously confirmed either positive or negative for Schistosoma japonicum infection through microscopy or stool PCR. Additionally, cross-reactivity tests were conducted with other parasitic infections, including paragonimiasis, clonorchiasis, and opisthorchiasis. IgG ELISA results revealed that SjMEP-40 M has the sensitivity (82.24 %) and specificity (95.97 %). On the other hand, SjMEP-40 N showed the highest sensitivity (85.5 %) and positivity rates in IgM ELISA with both microscopy and PCR-positive samples. Overall, SjMEP-40 M showed the best diagnostic results for IgG evaluation, whereas SjMEP-40 N is the fragment responsible for antigen detection at the early stage of the disease, as shown by the IgM ELISA results. The fragmented antigens might be useful in differentiating early and chronic disease.