Aminoglycoside-driven biosynthesis of selenium-deficient Selenoprotein P.

Selenoprotein biosynthesis relies on the co-translational insertion of selenocysteine in response to UGA codons. Aminoglycoside antibiotics interfere with ribosomal function and may cause codon misreading. We hypothesized that biosynthesis of the selenium (Se) transporter selenoprotein P (SELENOP) is particularly sensitive to antibiotics due to its ten in frame UGA codons. As liver regulates Se metabolism, we tested the aminoglycosides G418 and gentamicin in hepatoma cell lines (HepG2, Hep3B and Hepa1-6) and in experimental mice. In vitro, SELENOP levels increased strongly in response to G418, whereas expression of the glutathione peroxidases GPX1 and GPX2 was marginally affected. Se content of G418-induced SELENOP was dependent on Se availability, and was completely suppressed by G418 under Se-poor conditions. Selenocysteine residues were replaced mainly by cysteine, tryptophan and arginine in a codon-specific manner. Interestingly, in young healthy mice, antibiotic treatment failed to affect Selenop biosynthesis to a detectable degree. These findings suggest that the interfering activity of aminoglycosides on selenoprotein biosynthesis can be severe, but depend on the Se status, and other parameters likely including age and general health. Focused analyses with aminoglycoside-treated patients are needed next to evaluate a possible interference of selenoprotein biosynthesis by the antibiotics and elucidate potential side effects.

Efficient influenza B virus propagation due to deficient interferon-induced antiviral activity in MDCK cells.

Influenza B virus infections are mainly restricted to humans, which is partially caused by the inability of influenza B virus NS1 protein to counteract the innate immune response of other species. However, for cell culture-based influenza vaccine production non-human cells, such as Madin-Darby canine kidney (MDCK) cells, are commonly used. Therefore, the impact of cellular pathogen defence mechanisms on influenza B virus propagation in MDCK cells was analysed in this study. Activation of the cellular antiviral defence by interferon stimulation slowed down influenza B virus replication at early time points but after 48h the same virus titres were reached in stimulated and control cells. Furthermore, suppression of the antiviral host defence by transient expression of a viral antagonist, the rabies virus phosphoprotein, could not increase influenza B virus replication. Finally, canine Myxovirus resistance (Mx) proteins showed no antiviral activity in an influenza B virus-specific minireplicon assay in contrast to the murine Mx1 protein. Taken together, these results indicate that an insufficient antiviral defence in MDCK cells promotes efficient influenza B virus replication favouring the use of MDCK cells in influenza vaccine production.