Schistosoma japonicum: construction of phage display antibody library and its application in the immunodiagnosis of infection.
BACKGROUND
A monoclonal antibody would be an effective tool for the detection of circulating antigens in the serum of patients with schistosomiasis, but the traditional way of producing monoclonal antibodies is not cost-effective. The objective of this study was to find a new method for the large-scale production of monoclonal antibodies against Schistosoma japonicum (Sj).


METHODS
A phage display antibody library for Sj was constructed. To obtain a single-chain variable fragment antibody (scFv) against Sj, the library was screened with metabolic antigens from adult Sj worms (Sj-MAg) using enzyme-linked immunosorbent assay. The soluble scFvs selected were used to detect Sj antigens in the serum of acute and chronic schistosomiasis patients.


RESULTS
Six positive clones with good reactivity to Sj-MAg were obtained from the phage display antibody library of about 1.07 x 10(6) individual clones. Only two of these six clones bound specifically to Sj-MAg and were chosen for further analysis. Specific soluble anti-Sj-MAg scFvs were produced by inducing the 2 clones with isopropyl-D-thiogalactopyranoside. The characteristics of the scFvs were then determined. The results of Western blot showed that these scFvs could bind to Sj-MAg specifically and had a molecular weight of about 31 kD. When testing serum from schistosomiasis patients with one of the two specific scFvs, its sensitivity was found to be 60% and 37% in acute and chronic patients, respectively, with a specificity of 90%. When the two specific scFvs were combined, their sensitivity was found to be 75% and 57% in acute and chronic patients, respectively, with a specificity of 85%.


CONCLUSIONS
The results indicate that the scFvs are potentially useful for the diagnosis of schistosomiasis. The library construction also provides a useful tool for the further screening of other antibodies for both diagnostic and immunotherapeutic applications and for epitope analysis and vaccine design.
Chen
Dai-Xiong
DX
Department of Parasitology, Guangzhou Medical College, Guangzhou 510182, China.
He
Ai
A
Zhan
Xi-Mei
XM
Yu
Mu-Hua
MH
Lei
Zhi-Gang
ZG
Meng
Jin-Xiu
JX
Li
Zhuo-Ya
ZY
Liang
Yu
Y
Zhang
Rui-Lin
RL
D000818:Animals; D000909:Antibodies, Helminth / Q000276:immunology*; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000947:Antigens, Helminth / Q000097:blood*; D001483:Base Sequence; D007128:Immunoglobulin Fragments / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D019151:Peptide Library; D011817:Rabbits; D012554:Schistosomiasis japonica / Q000175:diagnosis*; D012680:Sensitivity and Specificity; D012698:Serologic Tests
D000909:Antibodies, Helminth; D000911:Antibodies, Monoclonal; D000947:Antigens, Helminth; D007128:Immunoglobulin Fragments; D019151:Peptide Library; C055966:immunoglobulin Fv