Approaches to the identification of non-essential genes of African swine fever virus

Abstract

It is poorly understood why vaccines could not be developed for the control and prevention of African swine fever (ASF) virus infection. The aim of our study was to identify genes non-essential for ASF virus replication because there were indications that certain viral gene products, which apparently parently are non-essential for viral replication, conferred protection from death due to ASF. A cosmid library representing the genome of ASF virus strain France 64 was established and characterized. Then, in order to inactivate viral genes by insertion, the β-galactosidase (β-gal) gene was introduced either randomly or at specific locations of selected cloned DNA fragments. These constructions were tranfected into cells which had been previously infected with a cell-culture-adapted viral strain in order to allow the generation of recombinant progeny virus. Viable recombinant progeny was identified by at least one of the following means: (1) expression of β-gal; (2) detection of β-gal specific DNA by plaque hybridization, and (3) absence of a functional product of the inactivated gene. Presently, we are characteriaing a recombinant virus with an insertionally activated thymidine kinase gene.