Rat cytomegalovirus infection enhances type II collagen arthritis in rats

The effect of rat cytomegalovirus (RCMV) infection on type II collagen‐induced arthritis was studied in DA rats. Rats were infected with RCMV 5 days before, simultaneously with, or 5 days after immunization with calf type II collagen. Control rats were either given type II collagen alone or were injected with normal rat salivary gland (NRSG) simultaneously with collagen immunization. Severity of arthritis in each limb was graded on a scale of 1–4 (maximum score 16). In 5 experiments, peak arthritis scores in the RCMV groups were twice those of the control groups which received NRSG or collagen only (8–9 versus 4–6). Radiographs of involved joints showed greater destruction of cartilage and articular bone in the RCMV rats than in the NRSG control group. Repeated attempts to culture RCMV from joint tissues were unsuccessful. Our results indicate that RCMV infection enhances the arthritic process in this experimental model of an autoimmune arthritis.