A Clonorchis sinensis-specific
antigen in excretory-secretory product of C. sinensis (CsE) was assessed in human
clonorchiasis by immunoblot. Thirty and 7 kDa
antigens of CsE2, one of four different batches of CsEs reacted strongly with
infection sera from
clonorchiasis patients; however, the
antigens reacted weakly with 6-month post-treatment sera from
praziquantel-cured cases, but were still highly detected by the sera from
praziquantel-failed patients, indicating that the 30 and 7 kDa
antigens can detect
antibodies during an active
infection. The 30 kDa
antigen showed some cross reactions with sera from patients with Paragonimus westermani and Metagonimus yokogawai, while the 7 kDa
antigen did not, suggesting that the 7 kDa
antigen has high specificity. The 30 kDa
antigen reacted with some past
clonorchiasis sera, whereas the 7 kDa
antigen did not, supporting that
antibodies to the 7 kDa
antigen are not present in sera from past
clonorchiasis patients. In an endemic area, 92% (23/25) of active
clonorchiasis patients and 91% (10/11) of
mixed infection patients with C. sinensis and M. yokogawai had
IgG antibodies to the 7 kDa
antigen, while 40% (6/15) of past
clonorchiasis individuals and 43% (3/7) of
metagonimiasis patients cross-reacted to the
antigen. These data suggest that the 7 kDa
antigen in an excretory-secretory
antigen may serve as a marker of an active
clonorchiasis with reliable specificities in past
clonorchiasis,
paragonimiasis and
metagonimiasis.