1. ¹Got-A-Gene AB, Östra Kyviksvägen 18, Kullavik, Sweden
2. ²Department of Microbiology and Immunology, Institute for Biomedicine, University of Göteborg, Göteborg, Sweden
3. ³Laboratoire de Virologie et Pathogénèse Virale, Faculté de Médecine RTH Laennec, Université Claude Bernard de Lyon & CNRS UMR-5537, Lyon Cedex, France
4. ⁴Department of Clinical Virology, Institute for Biomedicine, University of Göteborg, Göteborg, Sweden
5. ⁵Department of Biotechnology, Kungl Tekniska Högskolan (KTH), Albanova University Center, Stockholm, Sweden
6. ⁶Laboratoire de Virologie Est, Domaine Rockefeller, Hospices Civils de Lyon, 8, Lyon Cedex, France

Correspondence: Dr S-S Hong, Laboratoire de Virologie et Pathogénèse Virale, CNRS UMR 5537, Faculté de Médecine RTH Laennec, 7 Rue Guillaume Paradin, 69372 Lyon Cedex 8, France. E-mail: sawsee.hong@sante.univ-lyon1.fr

Received 16 May 2006; Revised 3 August 2006; Accepted 24 August 2006; Published online 12 October 2006.

Abstract

In this study, a prototype Adenovirus type 5 (Ad5) vector deleted of the fiber knob domain and carrying an Affibody molecule as the targeting ligand showed decreased susceptibility to human pre-existing antibodies. This vector, Ad5/R7-Z_taqZ_taq, has short fibers carrying seven shaft repeats, a non-native trimerization signal and an affibody molecule (Z_taq) reactive to Taq polymerase. Ad5/R7-Z_taqZ_taq could be specifically targeted to 293 cells stably expressing membrane-bound anti-Z_taq idiotypic affibody called Z_ztaq (293Z_ztaq). Sera from 50 blood donors were analyzed for neutralization activity (NA) against the parental Ad5/Fiwt vector and knobless Ad5/R7-Z_taqZ_taq on 293Z_ztaq cells. Twenty-three sera had NA titers (1:64) against Ad5/Fiwt (46%) and only two against Ad5/R7-Z_taqZ_taq (4%). Characterization of sera with NA titers showed that the knob domain is one of the targets of the antibodies. Neutralization assays using sera pre-adsorbed on knob and hexon proteins showed that the NA of the sera was carried mainly by anti-knob and anti-hexon antibodies, but in certain sera the anti-hexon antibodies represent the major population of the neutralizing antibodies (NAbs). Our results suggested that a combination of knob deletion and hexon switching could be an effective strategy for Ad vectors to better evade the anti-Ad NAbs.