Rapid diagnosis of varicella-zoster virus infection by detection of viral deoxythymidine kinase in serum and vesicle fluid.

A sensitive enzyme assay utilizing [125I]iododeoxyuridine as the substrate and CTP as the phosphate donor in combination with isozyme-specific antisera was used for direct detection and typing of herpesvirus deoxythymidine kinase (dTk) in clinical specimens. An investigation of 16 coded vesicle fluid specimens, taken in connection with varicella-zoster virus (VZV) and herpes simplex virus infections, revealed viral dTk activity in 14 samples. All positive samples except one were taken within 5 days after the onset of illness. Serological typing of the dTk activities easily established whether the vesicles were caused by VZV, herpes simplex virus type 1, or herpes simplex virus type 2. The results were obtainable within 5 h and were in agreement with the results achieved by immunofluorescence tests or by virus isolation when positive. Acute- and convalescent-phase sera from patients with VZV infections were analyzed with regard to dTk isozyme composition. All sera collected within 5 days after the onset of varicella were found to contain elevated levels of dTk activity. By the use of isozyme-specific antisera and gel electrophoresis, it was possible to show the presence of both cellular and VZV dTk's. Among the 13 acute-phase sera from zoster patients, only 2 were found to be VZV dTk positive. Convalescent sera, in most cases collected 15 days or more after the onset of illness, were also found to be devoid of VZV dTk. The relevance of the results and the possible use of these methods for viral diagnostics are discussed.