Therapeutic effects of Csk virus injection on rat adjuvant arthritis. All rats were immunized with adjuvant in the right foot-pad (day 0). Viruses were intra-articularly injected into ankles on day 7. Data are shown as mean ± SD. (a) Effects of Csk virus injection into right ankles, as evaluated by arthritis score. The arthritis score of the Csk group (n = 10) was significantly lower than that of the WT (n = 10) and LacZ (n = 10) groups on days 21, 28, and 35 (*P < 0.01 Csk vs. LacZ, Csk vs. WT [day 21]; **P < 0.001 Csk vs. LacZ, Csk vs. WT [days 28 and 35]). (b) Effects of Csk virus injection into right ankles, as evaluated by increase in paw volume. The increase in paw volume of the Csk group was significantly less than that of the WT and LacZ groups on days 14, 21, 28, and 35 (*P < 0.05 Csk vs. WT; ^#P < 0.01 Csk vs. LacZ [day 21]; **P < 0.01 Csk vs. WT, Csk vs. LacZ [day 14]; ^##P < 0.001 Csk vs. WT, Csk vs. LacZ [days 28 and 35]). (c) Effects of Csk virus injection into left ankles, as evaluated by arthritis score. The arthritis score of the Csk group (n = 10) was significantly lower than that of the WT (n = 10) and LacZ (n = 10) groups on days 28 and 35 (*P < 0.05 Csk vs. LacZ; ^#P < 0.05 Csk vs. WT). (d) Effects of Csk virus injection into left ankles, as evaluated by increase in paw volume. The increase in paw volume of the Csk group was significantly less than that of the WT and LacZ groups (*P < 0.05 Csk vs. WT; ^#P < 0.05 Csk vs. LacZ). (f) On day 35, the right ankles of WT virus–injected rats showed the radiological findings of severe joint destruction — joint space narrowing, erosion, periarticular osteoporosis, and bone spur formation — compared with a normal rat ankle (e). (g) Radiological examination of Csk virus–injected right ankles showing minimal destructive changes. (j) The radiological score of Csk virus–injected right ankles was significantly decreased in comparison with WT and LacZ groups (*P < 0.001 Csk vs. WT, Csk vs. LacZ). (h) Pathohistological findings of WT virus–injected right ankles. Hyperplasia of synovial membrane occupied the articular spaces of talo-tibial (arrowhead a), talo-calcaneal (arrowhead b), and calcaneo-navicular (arrowhead c) joints. (i) Pathohistological findings of Csk virus–injected right ankles. Synovial hyperplasia and invasion into subchondral bone were markedly suppressed. (k) The pathological score of Csk virus–injected right ankles was significantly decreased in comparison with WT and LacZ groups (*P < 0.001 Csk vs. WT, Csk vs. LacZ).