Targeting retrovirus to cancer cells expressing a mutant EGF receptor by insertion of a single chain antibody variable domain in the envelope glycoprotein receptor binding lobe

We have investigated targeting of retroviral vectors to a mutant EGF recept or (EGFRvIII) that is expressed in cancers of the brain, breast, lung and o vary, but is not found in any normal tissues. An expression plasmid was mad e in which a single chain Fv antibody specific for EGFRvIII was inserted at a novel position within a disulphide-bonded surface loop near the native r eceptor binding site of the Moloney leukemia virus ecotropic envelope glyco protein. This fusion protein was expressed and incorporated into retroviral particles as efficiently as normal envelope glycoprotein. Retroviral vecto rs made with the fusion protein were able to bind peptide antigen and EGFRv III expressed on the surface of human glioblastoma cells. The retroviral ve ctors had normal levels of infectivity on mouse cells, showing that the env elope glycoprotein tolerated a large insertion at this site, but did not sh ow significant infectivity to human cells expressing EGFRvIII. Thus we were able to redirect retrovirus binding to this tumour-specific target without perturbing the normal function of the ecotropic envelope glycoprotein, but this was not sufficient to mediate infectivity via this receptor. (C) 2000 Elsevier Science BN. All rights reserved.