Parapoxviruses: potential alternative vectors for directing the immune response in permissive and non-permissive hosts

Parapoxvirus (PPV) represents a genus of the poxviridae, and particularly P PV ovis (Orf virus, OV) seems to offer several potential advantages for the use of vector vaccine. Therefore, we started to investigate the genome of the highly attenuated OV strain D1701, which was only poorly characterised until now. Due to recombination of non-homologous sequences, part of the ri ght hand end of the D1701 genome was duplicated and translocated to the opp osite end of the genome. As a consequence gene deletion had occurred and th e inverted terminal repeat region is increased. Results are described to id entify viral genes, which are non-essential for virus replication and poten tially influence viral pathogenesis, virulence, and host immunity. In more detail, we analysed the expression and functional activity of the OV-specif ic vascular endothelial growth factor (VEGF) gene homologue. Finally the co nstruction and production of a D1701 mutant lacking the VEGF gene homologue is reported. (C) 1999 Elsevier Science B.V. All rights reserved.