The present invention provides genetically engineered cell lines, recombinant vectors, and vaccines. The present invention also provides methods for generating an in vitro system for Varicella zoster virus (VZV), and the in vitro systems generated by these methods. The present invention further provides methods for reactivating VZV, and VZV reactivated by these methods. Finally, the present invention provides a method of screening for an agent for treating VZV infection.