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DAO
Diseases of Aquatic Organisms

    DAO prepress abstract   -  DOI: https://doi.org/10.3354/dao03481

    Advanced vacuolation indicates propagation of Salmonid Alphavirus type 2 isolates from various salmonid species in Acholeplasma-infected BF-2 cells

    O. Schachner*, N. Dinhopl, A. Friedl, H. Soliman, M. El-Matbouli

    *Corresponding author:

    ABSTRACT: At previous routine inspections of Bluegill fry (BF-2) and rainbow trout gonad (RTG-2) cells incubated with organ samples from asymptomatic Arctic char Salvelinus alpinus, brook trout Salvelinus fontinalis and rainbow trout Oncorhynchus mykiss, a distinctive, well reproducible cytopathic effect (CPE) appeared. Originally, the striking CPE, progressive vacuolation shading into slowly proceeding pyknotic degeneration, has been attributed to enhanced growth of Acholeplasma sp. exclusively. At a recent re-examination of re-infected BF-2 cells using electron microscopy (EM), conventional and quantitative real-time PCR (qPCR), virus has been detected additionally. Two days post inoculation (dpi) EM revealed characteristic virions inside cytoplasmic vacuoles and, next to bacteria, outside the cells. The nsP3 gene fragment nucleotide sequences of the virus extracted from supernatants of infected cells were 100% identical and representative for Salmonid Alphavirus type 2 (SAV 2). The 16S RNA gene (16S rDNA) fragment sequences of the Mollicutes-specific PCR product gained from SAV-infected as well as virus free BF-2 control cells were identical with Acholeplasma laidlawii. In addition, results of qPCR indicated enhanced propagation of virus and bacteria increasing with vacuolation between 5 and 8 dpi. Advanced vacuolation can be regarded as CPE of both SAV and A. laidlawii, suggesting a viral impact on the bacterial infection by turning a latent intracellular stage into an apparent degenerative condition.