Measurement of Aujeszky's disease virus recombination in vitro under conditions of low multiplicity of infection.

The natural development of Aujeszky's disease virus (ADV) vaccine-derived recombinants has been proposed as a conceivable, although unproven, outcome of the practice of using modified-live vaccines on infected herds. Herpesviral recombination has been studied in vitro using high multiplicity of infection (m.o.i.) to maintain synchronous co-infection of target cells and one-step multiplication cycles. However, natural in vivo recombination is unlikely to occur at high m.o.i. with synchronous infection of all available target cells by both parental virus strains. Using a battery of gene-specific polymerase chain reaction assays, an analysis of recombination frequency at comparatively low m.o.i. was performed, which indicates that at low m.o.i. the rate of in vitro genetic recombination can be expressed as a function of the number of virus-cell interactions. This finding indicates that the rate of generation of recombinant ADV genotypes in swine infected by multiple ADV strains would be modulated by factors that affect the distribution of different virus strains to common target cells, thereby limiting or enhancing the likelihood of cellular co-infection. A full description of this study is available (J. gen. Virol., in press).