The Study On Technetium-99m Labeled Anti-Aspergillus Monoclonal Antibody For Detection Of Aspergillus Fumigatus In Lungs

Objective:The aim of this study was to evaluate the feasibility of using a technetium-99m(^99mTc)-labeled anti-Aspergillus monoclonal antibody?WF-AF-1?for the detection of A.fumigatus in lungs.Methods:^99mTc-WF-AF-1 was prepared with indirect-labeling method using NHS-MAG3 as bifunctional chelating agent.The labeling efficiency and radiochemical purity were identified using thin layer chromatography.SDS-PAGE was performed to confirm the radiochemical purity of the labeled Mab-WF-AF-1.The stability of the radiolabeled protein in vitro was evaluated in PBS and serum.In vitro binding experiments were performed to determine the specificity of the labeled antibody to A.fumigatus.Biodistribution analysis and scintigraphy were carried out in healthy mice and in mice intratracheally instilled with A.fumigatus conidia to assess in vivo targeting efficiency.The relationship between the tracer uptake by the lung and the amount of A.fumigatus conidia instilled in the mice was also evaluated.Results:The labeling efficiency reached up to 95%and the radiochemical purity determined by radio-TLC is basically consistent with the result of SDS-PAGE.The radiolabeled Mab-WF-AF-1 was stable in both PBS and serum at room temperature.In vitro binding study showed the binding percentage to A.fumigatus?10.32±0.21%?were significantly higher?P<0.05 for both?than Staphylococcus aureus?1.88±0.45%?or Candida albicans?1.67±0.29%?,which indicating ^99mTc-WF-AF-1 preferentially bound to A.fumigatus.Biodistribution and scintigraphy showed significant accumulation of radioactivity in A.fumigatus conidia-instilled lungs.For biodistribution,the ratio of lung accumulation of the conidia-instilled to healthy lungs increased steadily from 2 h to 7 h?1.95 at 2 h,2.25 at 4 h,and 3.09 at 7 h?.Furthermore,the uptake of the tracer in lungs was significantly correlated with the logarithmic value of total amount of viable A.fumigatus conidia instilled in mice?R²=0.824,P<0.05?.The scintigraphic images obtained at 4 h after injection of the radiolabeled antibody clearly showed higher uptake of the radiotracer in the lungs of the A.fumigatus-instilled mice than in those of the control mice.Conclusions:^99mTc-WF-AF-1 was successfully prepared with satisfactory characteristics and showed high specificity of binding to A.fumigatus in vitro.^99mTc-WF-AF-1 could concentrate specifically in the lungs of A.fumigatus instilled mice and showed an amount-dependence of radio-tracer uptake,indicating that it may not only be useful for the detection of A.fumigatus in lungs but also for assessing the severity of disease.