The aim of the study was to determine the impact of CyHV-3 on the development of interstitial nephritis and gill necrosis in carp, Cyprinus carpio L., and on the metabolic activity of pronephric macrophages analyzed with respiratory burst activity (RBA) stimulated by PMA and the proliferative response of pronephric lymphocytes stimulated by mitogens ConA and LPS. CyHV-3 isolate was used in the in vitro experimental study and quantified with plaque assay using koi fin cell (KFC) culture incubated at 24°C for 96 h. The macrophage or lymphocyte suspensions were deposited in 96-well culture plates and incubated with CyHV-3 (1 × 106 pfu ml-1 RPMI-1640) at 16, 18, 22, and 2°C. The results indicated that CyHV-3 decreased the level of macrophage respiratory burst activity in comparison with the control at 16, 18, and 22°C, but increased it at 28°C. A similar pattern was observed with lymphocyte proliferation stimulated by ConA and LPS. The results showed that CyHV-3 decreased the proliferative response of pronephric lymphocytes stimulated by ConA and LPS in comparison to the control at 16, 18, and 22°C, while it only increased the proliferative response of lymphocytes stimulated by ConA at 28°C. This preliminary in vitro study demonstrated the strong inhibitory influence of CyHV-3 on macrophage activity and the proliferative response of lymphocytes. This inhibitory effect is determined by temperature.
