ABSTRACT
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.
ABSTRACT
Early detection and accurate evaluation of vulnerable plaques is important to clinical prevention and in time intervention of atherosclerosis plaque rupture,which is the main reason of cardiovascular and cerebrovascular emergency events.Molecular imaging reveals the formation and progression mechanisms of atherosclerosis at the molecular level,and thus has obvious superiority in early detection and evaluation of vulnerable plaques.Suitable targets are the major contents of molecular probe research.Probes of different imaging modalities have been used to detect vulnerable plaques.The targets including low density lipoprotein,macrophage,adhesion molecule,micro calcification,activated protease,apoptosis,proliferation gene,integrin and thrombus.The mechanism of detecting different targets is different,and the effectiveness varies as well.This review summarizes the development of imaging probes for molecular detection of atherosclerosis vulnerable plaques.
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Objective To screen out single chain variable fragment antibody (scFv)specific to vascular cell adhesion mole‐cule 1(Vcam‐1)from phage recombinant antibody library ,and to evaluate its activity and compare its activity with full‐length monoclonal antibody.Methods Amplification of Vcam‐1 was performed by PCR and Vcam‐1 gene plasmid was transferred into eukaryotic cells to express Vcam‐1 antigen protein.Immune cuvette was coated with purified Vcam‐1 antigen ,and the positive clones were screened out by 4 rounds of “adhesion‐elution‐proliferation” process with gradually increasing pressure.The posi‐tive clones were tested by ELISA method and high titer clones were chosen for gene sequencing.Then the high‐titer clones were transferred into E.coli ,and the clone with the highest expression was regarded as the final requisite one.Competent cells were infected by the final requisite clone and scFv was expressed.After purification ,the activity of scFv was tested by ELISA and its affinity was evaluated.Results Molecular weight of Vcam‐1 antigen protein was 85-90 kD.Positive clones were screened out by taking Vcam‐1 protein as the antigen ,and 9 high titer clones were obtained by single phage ELISA.Gene sequencing of these clones was carried out and 3 sequences were obtained ,1 of which got the highest expression.Molecular weight of the expressed scFv was about 30 kD.The scFv got high affinity to Vcam‐1 antigen according to ELISA ,in spite of its lower activity than full‐length monoclonal antibody.Conclusion scFv antibody specific to Vcam‐1 was successfully obtained from phage display librar‐y ,which laid the foundation of subsequent in vivo diagnosis and therapy.
ABSTRACT
Objective: To study the therapeutic effect of secondary lymphoid tissue chemokine (SLC) combined with CpG oligodeoxynucleotide (CpG-ODN) in treatment of implanted mouse melanoma and the possible mechanism. Methods: SLC-Fc fusion protein was prepared and its chemotaxis of lymphocytes was detected by chemotaxis assay. Implanted melanoma mouse models were established and randomly divided into 4 groups: control group, SLC-Fc group, CpG-ODN group, and SLC-Fc+CpG-ODN group. The growth of implanted tumors in each group was observed after treatment. Subtype and infiltration of lymphocytes in implanted tumor tissues were examined by flow cytometry. Results: SLC-Fc protein was successfully prepared, and it dose-dependently attracted lymphocytes (0.03, 0.3, and 3 μg/L). Intra-tumor injection SLC-Fc and CpG-ODN alone or in combination significantly inhibited growth of B16-implanted tumors. Tumor size in SLC-Fc+CpG-ODN group was significantly smaller than that in control group (P<0.01), and animals in SLC-Fc+CpG-ODN group survived longer. Tumor-infiltrated CD4~+ T, CD~8+ T, and dendritic cells (DCs) in SLC-Fc+CpG-ODN group were markedly increased as compared with those in control group (P<0.05), and tumor draining lymph nodes were dramatically enlarged. Conclusion: SLC combined with CpG-ODN can inhibit the growth of implanted melanoma by attracting CD4~+ T and CD8~+ T and promoting proliferation of DCs.