Herpes simplex virus-induced ribonucleotide reductase: development of antibodies specific for the enzyme

We have previously reported on the characterization of a novel ribonucleotide reductase induced in herpes simplex virus type 2 (HSV-2)-infected mammalian cells. The virus-induced enzyme was partially purified, free of the constitutive cell isozyme, by fractionation of infected cell extracts with ammonium sulphate. In this report we describe a further purification of the virus-induced enzyme and the development of a rabbit antiserum capable of specifically inhibiting its activity. Enzymically active salt fractions from infected cell extracts were sedimented through glycerol gradients; the virus-induced enzyme was found to sediment approximately 2 . 5 times faster than the constitutive, or control, enzyme and was separated from the majority of the protein in the sample. Immunization of rabbits with the partially purified enzyme preparation recovered from gradients resulted in the synthesis of antibodies which completely and specifically inhibited the virus-induced reductase, and precipitated one major polypeptide and a few minor species from both HSV-1- and HSV-2-infected cells. The antibodies, however, exhibited much greater affinity for the HSV-2 than the HSV-1 antigen. These results demonstrate that the virus-induced enzyme differs antigenically, as well as biochemically, from the constitutive cell isozyme and lend further support to the hypothesis that the enzyme is virus-coded.