Effect of the turbot aquareovirus on fish macrophages using an in vitro model

Abstract

The turbot aquareovirus TRV has an invasive behaviour, as the virus spreads throughout most fish organs and tissues. In the present study the presence of TRV inside macrophages of both naturally and experimentally infected turbot was demonstrated, and the ability of the virus to resist killing and to replicate within turbot macrophages in vitro was evaluated. The virus survived and replicated in the phagocytic cells, as demonstrated by electron microscopy and growth curve. Superoxide anion (O2-) production of phorbol 12-myristate 13-acetate (PMA)-stimulated macrophages infected with TRV was similar to that of normal macrophages. However, the levels of O2- produced by macrophages infected with a non-virulent Aeromonas salmonicida strain lacking the A-layer were clearly reduced when phagocytic cells had been previously incubated with TRV, but this reduction did not modified the ability of infected macrophages to kill the bacteria. These results indicate that the viral agent eludes the recognition system of the macrophages and the bactericidal capacity of these phagocytic cells is not affected by the presence of the virus, although the interaction with the virus must affect the mechanism of reduction of molecular oxygen into O2-.