Isolation of herpes simplex virus clones and drug resistant mutants in microcultures.

Suitable dilutions of herpes simplex virus (HSV) preparations inoculated into microcultures of confluent monolayers of human foreskin or Vero cells, in individual wells of plastic "microplates", induced viral cytopathic effects that resulted from the infection of the cultures by single virus particles. The clonal nature of the viral progeny in isolated wells was supported by visual control over the development of viral foci and by statistical analysis. The method has the advantage of speed and economy, while it also yields a large primary clonal virus stock. HSV clones resistant to phosphonoacetic acid (PAA) and 5-iodo-2'-deoxyuridine (IUdR) could be readily isolated by the described technique.