Antiviral activity of zinc salts against transmissible gastroenteritis virus in vitro

Abstract

Zinc has been shown to mediate antiviral effects against certain viruses. However, the underlying mechanisms are still largely unknown. We investigated the effects of the two zinc salts, zinc chloride (ZnCl(2)) and zinc sulfate (ZnSO(4)), on infection of swine testicle (ST) cells with transmissible gastroenteritis virus (TGEV) and compared it to the effects of a control salt, magnesium sulfate (MgSO(4)). Virus yield reduction experiments showed that ZnCl(2) and ZnSO(4) did not exhibit direct virucidal effects and did not affect adsorption of TGEV to ST cells. However, ZnCl(2) and ZnSO(4) markedly reduced viral titers as well as TGEV RNA and viral protein synthesis when applied during virus penetration and at different time points after viral cell entry. The results of the study suggest that zinc salts do not interfere with TGEV-cell binding but that they mediate antiviral effects through inhibition of viral penetration or egress or the intracellular phase of the viral life-cycle.

Fig. 1

Determination of virus yields (TCID₅₀ assay) following different Zn salt treatment periods. Cell-free preincubation of Zn salts with TGEV (a), Zn salt treatment for 1–4 hpi (b), for 22–24 hpi (c), for 1–48 hpi (d). Virus titer values indicate the mean values and SEM of three independent experiments.

Fig. 2

Effects of Zn salt treatment on viral RNA synthesis. The relative expression of the TGEV S protein gene was determined by normalizing values against the porcine β-actin gene.

Fig. 3

Influence of Zn salts on viral protein synthesis. Values represent means and SEM and were normalized for the average TGEV protein expression in untreated wells.