Application of a single-chain fragment variable (scFv) antibody for the confirmatory diagnosis of hydatid disease in non-endemic areas

Background: Hydatid disease is a serious parasitic disease threatening public health. Because of its rarity in non-endemic coastal areas, determining the nature and origin of a chronic, enlarged liver cystic mass is challenging in these regions. Under these circumstances, physicians need a confirmatory diagnostic tool beyond immunological and radiological examinations. This study investigated a novel human single-chain fragment variable (scFv) antibody for the confirmative diagnosis of 18 atypical hydatid disease cases in non-endemic coastal areas. Results: A scFv antibody against cystic echinococcosis was produced by genetic engineering and then applied to the immunohistochemical diagnosis of 18 cases of cystic echinococcosis presented in non-endemic coastal areas. The diagnosis of these cases by ultrasound and serum-based examinations was inconclusive. The 750 bp scFv antibody gene was expressed in COS-7 cells, and the antibody localized in the cytoplasm. The scFv antibody can detect the germinal layer and protoscolices of actively growing cysts but not of the degenerating protoscolices and has a diagnostic efficiency higher than that of single serum or ultrasound testing (P b 0.05). The combined use of scFv antibodies with serology and ultrasound diagnostics results in a diagnostic efficiency comparable to that of surgery. The scFv antibody can be used as a confirmatory test for the diagnosis of hydatid disease in non-endemic areas, providing a beneficial supplementary diagnostic method that complements traditional immune testing and ultrasonic radiology and thus helping physicians to effectively differentiate hydatid disease.

Imaging atherosclerosis model rabbits with 99Tcm-single chain antibody fragment against vascular cell adhesion molecule-1 / 中华核医学与分子影像杂志

Objective To investigate the imaging performance and feasibility of 99Tcm labeled scFv against VCAM-1(99Tcm-scFv-VCAM-1) on atherosclerosis model rabbits.Methods HYNIC was used as a chelator for 99Tcm labeling.The labeling efficiency and radiochemical purity of 99Tcm-scFv-VCAM-1 were measured by instant thin layer chromatography after PD-10 purification.New Zealand white rabbits were employed for establishing atherosclerotic animal models by endothelia immunity injury and high fat diet, and plaques at aorta lesions were examined by HE staining.Model rabbits were sacrificed after administration of 99Tcm-scFv-VCAM-1 at 1 or 2 h respectively, and tissue samples were measured with gamma counter and weighted to obtain in vivo biodistribution data.Planar imaging was performed 1 and 2 h after the injection of 99Tcm-scFv-VCAM-1 to investigate radioactivity of abdominal aorta.After imaging study, atherosclerosis plaque and VCAM-1 expression at aortas were confirmed by the immunohistochemistry (IHC) study.Two-sample t test was used to analyze data.Results 99Tcm-scFv-VCAM-1 was successfully synthesized.Its labeling efficiency was 75%-83%, radiochemistry purity was (98.54±1.03)% and specific activity was 216 MBq/nmol.Atherosclerosis plaque was confirmed at the aortas of experimental rabbits by HE staining, while no plaque was observed in controls.Biodistribution data indicated that the tracer was cleared mainly through the kidneys.Planar imaging showed that the tracer uptake in abdominal aorta of model rabbits was higher than that of control rabbits, the T/B ratios at 2 h of the model group and control group were statistically different (3.68±0.73 vs 2.42±0.39;t=2.950, P<0.05;n=5).Atherosclerosis plaque and high level of VCAM-1 expression were observed at aortas of model rabbits by IHC study.Conclusions It is feasible and effective to detect vulnerable plaques using 99Tcm-scFv-VCAM-1.It may provide a promising way for early diagnosis and accurate evaluation of atherosclerosis.

Radioimmunoimaging of 131I Labeled Human scFv Against Anaplastic Thyroid Carcinoma in Tumor Bearing Nude Mice / 中国医学影像学杂志

Purpose To study the radioactive purity and activity of 131I labeled human single chain variable fragments antibodies (scFv) against anaplastic thyroid carcinoma (ATC),and to explore its distribution and radioimmunoimaging characteristics in tumor bearing nude mice model in vivo so as to provide a new method for anaplastic thyroid carcinoma diagnosis and treatment.Materials and Methods The nude mice model bearing human anaplastic thyroid carcinoma was constructed.The chloramine T method was used to label scFv with 131I and the Sephadex G25M was used for purification of labeled scFv.Labeling rate was determined by trichloroacetic acid method;radiochemical purity,room temperature stability and serum stability were examined using paper chromatography.131I-scFv was injected via tail vein in mice,and the distribution of 131I-scFv in body tissues and organs was analyzed at 12,24,48,72 h after injection.Static SPECT imaging was performed at 12,24,48,72 h after injection to observe the intratumoral accumulation of radioactivity.The SPECT/CT image fusion was performed when the tumor tissues were clearly visible.Results 131I-scFv was purified,and the labeling rate was 91.64％;the radiochemical purity was (93.3 ±0.3)％.The radiochemical purity of 131l-scFv placed at room temperature and the serum for 1,6,12,24 h were all ＞90％.The radioactive distribution of 131I-scFv in tumor,liver,kidney,intestine and blood was high.SPECT imaging showed 131I-scFv was selectively concentrated in tumor tissue;the target/non-target ratio was the highest at 48 h,and the imaging was most satisfactory.Conclusion 131I-scFv can be successfully prepared.SPECT imaging of 131I-scFv in nude mice model is satisfactory,which lays the foundation for further research in ATC diagnosis and treatment.

Screen of human single chain antibody against N protein of SARS-CoV / 基础医学与临床

Objective To prepare the single chain antibody against N protein of SARS-CoV. Methods With N protein of SARS-CoV expressed in E.coli as antigen, we obtained the single chain antibody against N protein by screening the phage display library of human single chain antibodies. Results The anti-N protein antibody didn’t cross-interacte with BSA and the short peptide containing 6 histidines. The specific interaction between the antibody and N protein was inhibited by the anti-N protein monoclone antibody from immunized mice. ConclusionThe single chain antibody we got is specific to N protein of SARS-CoV,it can be a candidate antibody for fast detection of N protein of SARS-CoV and SARS virus particles in clinical trial study of SARS pathogenesis.