Study of ribonucleotide reductase in cells infected with six clinical isolates of herpes simplex virus type 2 (HSV-2) with mutations in its larger subunit.

Herpes simplex virus type 2 (HSV-2) induces a novel ribonucleotide reductase (RR) composed of two subunits (140 and 38 kDa) in infected cells. Other investigators have developed a monoclonal antibody, A6, against the 140-kDa subunit of RR and have found, in about 1% of the cases, an inability to detect this protein in cells infected with clinical isolates of HSV-2. We therefore investigated whether in such cases the clinical isolates were capable of inducing viral RR activity and whether the lack of detection of the 140-kDa protein by the monoclonal antibody was due to an alteration in the antigenic site of this protein. Six such isolates were examined and were found to induce RR activity, similar to HSV-2 (strain 333) RR, which did not require ATP for CDP reduction. Western blot analyses using A6 failed to detect the protein. However, R1, a polyclonal antibody raised against viral RR was capable of detecting this subunit. In addition, R1 was also capable of neutralizing RR activity induced by all the isolates and HSV-2 (strain 333). In conclusion, the lack of detection of the large subunit of RR was not due to the lack of induction but was due to an alteration in the antigenic site recognized by A6; this alteration did not appear to affect the properties of the induced RR activity.