title: Immune responses result in misdiagnosis of Schistosoma japonicum by immunodiagnosis kits in egg-positive patients living in a low schistosomiasis transmission area of China.
abstract: BACKGROUND
  In recent field surveys, we failed to detect the presence of specific antibody against Schistosoma japonicum in some egg-positive patients by commonly used immunodiagnostic kits. To find out whether low levels of specific antibody truly exist among egg-positive individuals and elucidate the underlying immune mechanisms, we carried out a cross-sectional epidemiologic study in a S. japonicum low transmission endemic area of Poyang Lake region, China and compared the humoral and cellular immune characteristics between S. japonicum high and low antibody responders.
  
  
  METHODS
  Kato-Katz thick smear assay was used to determine the schistosomiasis status of 3,384 participants residing in two Poyang Lake region villages, Jiangxi, China. Among the 142 stool egg-positive participants, we identified low and high S. japonicum antibody responders with soluble egg antigen (SEA) and adult worm antigen (AWA) specific IgG levels by adopting ROC curve analysis. To compare the humoral and cellular immune responses between high and low S. japonicum antibody responders, serum specific antibody levels as well as the percentage of T lymphocyte subpopulation in PMBC, and cell stimulated cytokines (IFN- gamma and interlukin-10) were detected.
  
  
  RESULTS
  Eight S. japonicum egg-positive participants were defined as low antibody responders. Although the percentage of CD3⁺T cells in low responders was slightly higher and the percentage of CD4⁺ T cells, CD8⁺ T cells, the ratio of CD4⁺/CD8⁺ and CD4⁺ CD25⁺ Treg cells were lower than those in high responders, the differences between the two groups were not significant (P > 0.05). AWA -stimulated interlukin-10 level was significantly higher in high responders, while other cytokines did not show differences between two groups. For antibody profiles, except AWA specific IgA, significant differences of each antibody isotype between low and high responders were detected (P < 0.05).
  
  
  CONCLUSIONS
  Our study confirmed that there are S. japonicum antibody low responders among schistosome egg-positive residents in S. japonicum low-transmission areas in China. Thus, mis-diagnosis using immune-diagnosis kits do exist. Significant differences of responding antibody levels between low and high responders were detected, while no major cellular response changes were observed.
authors.forename: Shu-Ying
authors.initials: SY
authors.lastname: Xie
authors.forename: Min
authors.initials: M
authors.lastname: Yuan
authors.forename: Min-Jun
authors.initials: MJ
authors.lastname: Ji
authors.forename: Fei
authors.initials: F
authors.lastname: Hu
authors.forename: Zhao-Jun
authors.initials: ZJ
authors.lastname: Li
authors.forename: Yue-Min
authors.initials: YM
authors.lastname: Liu
authors.forename: Xiao-Jun
authors.initials: XJ
authors.lastname: Zeng
authors.forename: Hong-Gen
authors.initials: HG
authors.lastname: Chen
authors.forename: Hai-Wei
authors.initials: HW
authors.lastname: Wu
authors.affiliation: Jiangxi Provincial Institute of Parasitic Diseases, Nanchang, Jiangxi 330046, China. jxlindandan@163.com.
authors.forename: Dan-Dan
authors.initials: DD
authors.lastname: Lin
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D002681:China; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010063:Ovum / Q000502:physiology*; D011933:Reagent Kits, Diagnostic / Q000592:standards*; D012554:Schistosomiasis japonica / Q000175:diagnosis* / Q000276:immunology*; D055815:Young Adult
chemical_list: D011933:Reagent Kits, Diagnostic