Paramyosin of Clonorchis sinensis (CsPmy) is a myofibrillar
protein localized in subtegumental muscle, tegument, and the muscle layer surrounding the intestine of the parasite. Previously, we have identified that CsPmy reacted with sera of human
clonorchiasis and this
protein had a potential as a candidate
antigen for serodiagnosis of
clonorchiasis. However, we also found that CsPmy is able to bind to human
immunoglobulin G (
IgG) in non-specific manners, which can affect the diagnostic value of the
protein. Here, we mapped CsPmy-specific
IgG binding site on CsPmy to analyze the putative
epitopes recognized by CsPmy-specific
IgG in sera of human
clonorchiasis. The fragmental expression of CsPmy followed by immunoblot analyses with sera from patients with
clonorchiasis and non-specific human
IgG revealed that the middle portion of CsPmy (CsPmyC: 301-600
amino acid residues) had
epitopes responsible for CsPmy-specific
IgG recognition. The precise CsPmy-specific
IgG binding site was further narrowed down to a fragment (CsPmyC-2), which harbors 151
amino acid residues (375-525) of CsPmy. Specific
antibodies for CsPmyC-2 were produced in rats after two-weeks of post-experimental
infection. The CsPmyC-2 showed low levels of cross reactivity against the sera from patients with other helminth parasites. Our results suggested that CsPmyC-2 has real
epitopes recognized by CsPmy-specific
IgG in sera of human
clonorchiasis and the fragment can be useful as a reliable serodiagnostic
antigen to develop a serodiagnostic method for
clonorchiasis.