title: Immunotargeting of streptavidin to the pulmonary endothelium.
abstract: We have observed previously that monoclonal antibody to angiotensin-converting enzyme (Mab 9B9) accumulates selectively in the lung after intravenous injection. The objective of the present work is the development of a universal system for targeting of drug or radiolabel to the lung, using biotinylated Mab 9B9 and streptavidin.
  
  
  METHODS
  Mab 9B9 was biotinylated with biotin succinimide ester (b-Mab 9B9), while streptavidin (SA) was radiolabeled with 125I. Interaction between b-Mab 9B9 and SA has been estimated in solid-phase radioassay. Radiolabeled SA was conjugated with b-Mab 9B9 or with b-IgG and injected intravenously in rats or perfused in isolated rat lungs.
  
  
  RESULTS
  Radiolabeled b-Mab 9B9 biotinylated at biotin-to-antibody molar ratio 10 (b-Mab 9B9) retains its ability to accumulate in rat lungs after intravenous injection. Radiolabeled SA conjugated with b-Mab 9B9 accumulates in the lung tissue in perfused isolated rat lungs. About 20% of injected SA accumulates in the rat lung 1 hr after intravenous injection (localization ratio is 20, immunospecificity of the conjugate pulmonary uptake is 70). As compared with conjugate injection, stepwise intravenous injection of b-Mab 9B9 and radiolabeled SA leads to a marked reduction of SA pulmonary uptake. Maximal pulmonary uptake of Mab 9B9 has been observed 2-3 hr after intravenous injection, while 24 hr later, radioactivity in the lung was markedly reduced. In contrast to radiolabeled Mab 9B9 alone, radiolabeled SA conjugated with b-Mab 9B9 was retained in the lung for at least 48 hr. In concert with effective blood clearance of the conjugate, its prolonged lung retention leads to a marked increase in its lung-to-blood ratio: 80 for SA-b-Mab 9B9 versus 15-20 for Mab 9B9.
  
  
  CONCLUSIONS
  Conjugation of Mab 9B9 with streptavidin enhances selective pulmonary uptake of the preparation, providing a background for intrapulmonary immunotargeting of various biotinylated agents.
authors.affiliation: Institute of Experimental Cardiology, Russian National Cardiology Research Center, Moscow.
authors.forename: V R
authors.initials: VR
authors.lastname: Muzykantov
authors.forename: E N
authors.initials: EN
authors.lastname: Atochina
authors.forename: V
authors.initials: V
authors.lastname: Gavriljuk
authors.forename: S M
authors.initials: SM
authors.lastname: Danilov
authors.forename: A B
authors.initials: AB
authors.lastname: Fisher
mesh_terms: D000818:Animals; D001426:Bacterial Proteins; D001710:Biotin / Q000031:analogs & derivatives; D004727:Endothelium / Q000000981:diagnostic imaging; D007457:Iodine Radioisotopes; D008168:Lung / Q000000981:diagnostic imaging*; D008297:Male; D016719:Radioimmunodetection / Q000379:methods*; D051381:Rats; D017208:Rats, Wistar; D019809:Streptavidin; D013388:Succinimides; D014018:Tissue Distribution
chemical_list: D001426:Bacterial Proteins; D007457:Iodine Radioisotopes; D013388:Succinimides; C033788:biotinyl N-hydroxysuccinimide ester; D001710:Biotin; D019809:Streptavidin