Mixed ocular infections identify strains of herpes simplex virus for use in genetic studies

Studies on the genetic mechanisms involved in the ocular virulence of herpes simplex virus (HSV) require the careful selection of parental strains. We used the technique of mixed ocular infection in vivo to identify strains of HSV for use in genetic studies. A pair of viruses (OD4 and 994) were identified that cause significantly more severe ocular disease when mixed together and used to infect the eyes of Balb/c mice compared to each strain when used alone. The mixed infection with OD4 and 994 did not result in increased neurovirulence. The technique of mixed ocular infections provides a sensitive screen to identify strains of virus that can act synergistically to cause more severe disease. Marker transfer can then be used to map the genes involved.