title: Soluble coxsackievirus adenovirus receptor is a putative inhibitor of adenoviral gene transfer in the tumor milieu.
abstract: OBJECTIVE
  Several barriers that collectively restrict gene delivery by viral vectors in vivo have been described. Previously, we identified soluble chondroitin sulfate-proteoglycans/glycosaminoglycans in malignant pleural effusions (MPEs) as inhibitors of retroviral vector transduction. Soluble components of MPE also inhibited adenoviral (Ad) gene transfer, and the factors were characteristically filterable, titrable, stable at 56 degrees C, and blocked the binding of Ad to target cells. Depleting immunoglobulin from MPE, partially reversed the block to Ad transduction, instigating a search for additional factors that bound Ad in MPE.
  
  
  METHODS
  Vector-protein interactions were identified after the resolution of MPE-components by SDS-PAGE. Viral overlays and immunoblots delineated significant interactions, and the potential relevance of those interactions was tested in transduction efficiency bioassays.
  
  
  RESULTS
  Immunoglobulin is the predominant factor inhibiting Ad gene transfer in MPE. Albumin also interacted with Ad, although at predicted serum concentrations, it did not effect Ad transduction efficiency in vitro. Soluble coxsackievirus-Ad receptor (sCAR) was then identified in MPE. In a survey of 18 MPE, the mean concentration of sCAR was variable and estimated to be 3.51 +/- 5.02 ng/ml by ELISA. The impact of sCAR on transduction efficiency in this milieu was next assessed. Whereas immunodepletion of sCAR from MPE by affinity chromatography resulted in enhanced gene transfer within MPE, the inhibition of adenoviral gene transfer was not evident when the predicted concentrations of recombinant sCAR were added into the transduction medium.
  
  
  CONCLUSIONS
  These studies indicate that, in addition to anti-Ad antibodies, other specific and nonspecific factors interact with viral vectors and may impair gene transfer in the tumor milieu. The presence of sCAR in MPE puts forward the notion that in certain contexts (e.g., within the extracellular matrix of solid tumors) the concentrations of secreted (or shed) CAR may be high enough to effectively compete with Ad gene delivery.
authors.affiliation: Department of Medicine, The University of California at Los Angeles (UCLA)/ Wadsworth Pulmonary Immunology and Gene Medicine Laboratory, Los Angeles, CA 90073, USA.
authors.forename: Ray M
authors.initials: RM
authors.lastname: Bernal
authors.forename: Sherven
authors.initials: S
authors.lastname: Sharma
authors.forename: Brian K
authors.initials: BK
authors.lastname: Gardner
authors.forename: Joanne T
authors.initials: JT
authors.lastname: Douglas
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Bergelson
authors.forename: Steven M
authors.initials: SM
authors.lastname: Dubinett
authors.forename: Raj K
authors.initials: RK
authors.lastname: Batra
mesh_terms: D000256:Adenoviridae / Q000235:genetics*; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics / Q000378:metabolism*; D062727:Coxsackie and Adenovirus Receptor-Like Membrane Protein; D004591:Electrophoresis, Polyacrylamide Gel; D004770:Enterovirus / Q000235:genetics*; D004797:Enzyme-Linked Immunosorbent Assay; D015870:Gene Expression; D018014:Gene Transfer Techniques; D015316:Genetic Therapy; D005822:Genetic Vectors; D006801:Humans; D007763:Lac Operon / Q000502:physiology; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D010996:Pleural Effusion / Q000378:metabolism; D011991:Receptors, Virus / Q000276:immunology / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; C568771:CLMP protein, human; C568772:CLMP protein, mouse; D062727:Coxsackie and Adenovirus Receptor-Like Membrane Protein; D011991:Receptors, Virus