Multiplication of infectious pancreatic necrosis virus (IPNV) in head kidney and blood leucocytes isolated from Atlantic salmon, Salmo salar L.

Abstract

Abstract. Blood and head kidney (HK) leucocytes were isolated from Atlantic salmon, Salmo salar L., carrying infectious pancreatic necrosis virus (IPNV), and the cells were separated into adherent and non‐adherent populations. Significant increases in both intra‐ and extracellular IPNV titres, and in the number of IPNV‐positive fluorescent cells were detected in adherent HK leucocytes during 7 days in culture, and demonstrated that IPNV multiplied in these cells. Infectious virus was not detected in culture medium collected from blood leucoeytes, and only occasionally, in very low titres, from non‐adherent HK leucocytes. No IPNV‐positive fluorescent cells were detected in these cell populations. IPNV infection of adherent leucocytes isolated from non‐carrier fish indicated that adherent blood leucocytes (mainly monocytes) could become productively infected in vitro, but to a lesser degree than adherent HK leucocytes (mainly macrophages). The present results suggest a major role for adherent HK leucocytes in maintaining the IPNV carder state in Atlantic salmon.