Recombinant and chimeric viruses: Evaluation of risks associated with changes in tropism Ben P.H. Peeters Animal Sciences Group, Wageningen University and Research Centre, Division of Infectious Diseases, P.O. Box 65, 8200 AB Lelystad, The Netherlands. May 2005 This report represents the personal opinion of the author. The interpretation of the data presented in this report is the sole responsibility of the author and does not necessarily represent the opinion of COGEM or the Animal Sciences Group. Dit rapport is op persoonlijke titel door de auteur samengesteld. De interpretatie van de gepresenteerde gegevens komt geheel voor rekening van de auteur en representeert niet de mening van de COGEM, noch die van de Animal Sciences Group. Advisory Committee Prof. dr. R.C. Hoeben (Chairman) Leiden University Medical Centre Dr. D. van Zaane Wageningen University and Research Centre Dr. C. van Maanen Animal Health Service Drs. D. Louz Bureau Genetically Modified Organisms Ing. A.M.P van Beurden Commission on Genetic Modification Recombinant and chimeric viruses 2 INHOUDSOPGAVE RECOMBINANT AND CHIMERIC VIRUSES: EVALUATION OF RISKS ASSOCIATED WITH CHANGES IN TROPISM Executive summary............................................................................................................................... 5 Introduction............................................................................................................................................ 7 1. Genetic modification of viruses .................................................................................................9 2. Recombinant and chimeric viruses ......................................................................................... 11 3. Applications of recombinant and chimeric viruses ............................................................... 13 3.1. Fundamental studies of host-pathogen interactions ........................................................... 13 3.2. Gene therapy....................................................................................................................... 13 3.3. Cancer gene therapy........................................................................................................... 14 3.4. Vaccination .......................................................................................................................... 15 3.5. Immune modulation ............................................................................................................. 15 4. Recent developments in virus retargeting.............................................................................. 17 4.1. Adenovirus........................................................................................................................... 17 4.2. Adeno-associated virus ....................................................................................................... 22 4.3. Retrovirus en lentivirus ........................................................................................................ 24 4.4. Hybrid virus vectors ............................................................................................................. 27 4.5. Herpesvirus.......................................................................................................................... 28 4.6. Negative-stranded RNA viruses .......................................................................................... 29 4.7. Other viruses ....................................................................................................................... 31 5. Chimeric viruses containing foreign viral surface proteins.................................................. 35 5.1. Chimeric poxviruses ............................................................................................................ 35 5.2. Chimeric herpesviruses....................................................................................................... 36 5.3. Chimeric negative-stranded RNA viruses ........................................................................... 38 5.4. Chimeric flaviviruses............................................................................................................ 42 5.5. Other chimeric viruses......................................................................................................... 44 6. Viral factors and host factors that determine host-range and tropsim ............................... 49 6.1. Receptor and co-receptor usage......................................................................................... 49 6.2. Entry and transport .............................................................................................................. 50 3 Recombinant and chimeric viruses 6.3. Nuclear import ..................................................................................................................... 51 6.4. Interference with interferon responses ................................................................................ 52 6.5. Interference with general immune responses ..................................................................... 54 6.6. Host restriction factors......................................................................................................... 57 6.7. Viral host range genes......................................................................................................... 58 6.8. Host proteases required for processing of viral proteins..................................................... 59 6.9. Host transcription factors..................................................................................................... 61 6.10. Other factors........................................................................................................................ 63 7. Potential risks associated with the use of recombinant and chimeric viruses .................. 65 7.1 Increase in pathogenicity and virulence .............................................................................. 65 7.2. Changes in host tropism...................................................................................................... 68 7.3. Immunopathology ................................................................................................................ 70 7.4. Conclusions ......................................................................................................................... 71 8. References ................................................................................................................................. 75 RECOMBINANT EN CHIMAERE VIRUSSEN: EVALUATIE VAN RISICO’S TEN GEVOLGE VAN VERANDERINGEN IN TROPISME Opdracht............................................................................................................................................... 99 Verantwoording ................................................................................................................................... 99 Leeswijzer .......................................................................................................................................... 100 Management samenvatting .............................................................................................................. 101 Nederlandse samenvatting............................................................................................................... 103 Inleiding...................................................................................................................................... 103 1. Genetische modificatie van virussen .................................................................................... 103 2. Recombinant en chimaere virussen...................................................................................... 103 3. Toepassingen van recombinant en chimaere virussen ........................................................ 104 4. Recente ontwikkelingen op het gebied van de sturing van het tropisme van virussen ........ 105 5. Chimaere virussen met heterologe oppervlakte eiwitten...................................................... 107 6. Virale factoren en gastheer factoren die tropisme bepalen .................................................. 108 7. Evaluatie van risico’s ten gevolge van veranderingen in tropisme....................................... 112 Bijlage 1: Beschrijving van het project ........................................................................................... 117 Recombinant and chimeric viruses 4 EXECUTIVE SUMMARY With molecular biological techniques the genetic make-up of virtually any (micro-)organism can be modified. This process is know as ‘genetic modification’. The availability of cloned copies of viral genomes facilitates the generation of genetically-modified recombinant and chimeric viruses. A chimeric virus is a recombinant virus that contains at least one functional gene from another virus. Such viruses become increasingly important for vaccine development, experimental gene therapy and for scientific research purposes. Virus particles bind and enter living cells via specific receptors at the cell surface. These and other host factors determine whether the host is permissive for this virus. Rare spontaneous mutations in the viral genome can alter the cell-, tissue-, and host-specificity of a virus. Hardly ever this leads to an extension of the host range of a virus. However, in rare cases this may lead to new viral diseases. HIV, influenza virus,