Partial susceptibility of the SSN-1 fish cell line to a crustacean virus: a defective replication study

This study evaluated the possible use of the fish SSN-1 cell line to investigate the development of Macrobrachium rosenbergii nodavirus (MrNV). Cells were incubated with viral particles and cytopathic effects were observed. De novo synthesis of viral capsid proteins was shown by immuno-fluorescence labelling and a sandwich ELISA test. Viral genomic replication was demonstrated by RT-PCR using primers specific to RNA-1 as well as by quantitative RT-PCR (RT-qPCR). Using electron microscopy, only a few empty particles were observed and attempts to isolate complete infectious particles or to re-infect healthy cells (second passage) were unsuccessful. As complete viral particles were rarely observed, it appeared that defaults in MrNV virogenesis might arise resulting in the formation of scarce and non-infectious particles. SSN-1 cells were found to be partially permissive to MrNV infection that induced cell lysis, but key elements for viral infection were lacking such as regulatory factors for gene replication or post-translational modifications.