Induction of Reactive Oxygen Species Is Necessary for Efficient Onset of Cyprinid Herpesvirus 2 Replication: Implications for Novel Antiviral Strategy With Antioxidants

Cuiyu Lu,Jixing Zou,Meizhen Su,Ruizhe Tang,Liqun Lu

doi:10.3389/fmicb.2021.792655

Cuiyu Lu, Jixing Zou + Show 3 more

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https://doi.org/10.3389/fmicb.2021.792655

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Abstract

Cyprinid herpesvirus 2 (CyHV-2) has caused great economic loss to the crucian carp breeding industry. Upon viral stimulation, eukaryotic cells generally activate the expression of anti-oxidative genes to maintain the intracellular oxidative balance and resist viral infection. Here, intracellular reactive oxygen species (ROS) levels in CyHV-2-infected cells were monitored to show that CyHV-2 induced the increase of intracellular ROS during early infection, and intracellular excessive accumulation of ROS was ameliorated during late infection, which was accompanied by activated expression of genes related to Nrf2 signaling pathway. In order to explore the interaction between CyHV-2 infection and ROS production, RyuF-2 cells were treated with either antioxidant epigallocatechin-3-gallate (EGCG) or berberine hydrochloride (BBH) and then infected with CyHV-2. Both BBH and EGCG could effectively inhibit the amplification of CyHV-2 while inhibiting the accumulation of intracellular ROS. Consistent with this, the oxidant stress-related genes were up-regulated by CyHV-2 infection and down-regulated in cells treated with either BBH or EGCG, through which the production of intracellular ROS was modulated. These results collectively demonstrated that early ROS accumulation favored the replication of CyHV-2, while antioxidants (BBH and EGCG) could inhibit the amplification of CyHV-2 by inhibiting ROS induction.

Highlights

Cyprinid herpesvirus 2 (CyHV-2), belonging to the genus Cyprinivirus and the family Alloherpesviridae, was first isolated and characterized from juvenile goldfish (Carassius auratus auratus) in Japan (Jung and Miyazaki, 1995)
Primary data analysis of genes involved in the Keap1-Nrf2 pathway indicated that the TPM values of Nrf2, CAT, and superoxide dismutase 2 (SOD2) genes in CyHV-2-infected cells at 48 h post-infection were dramatically higher than those in the negative control (NC), and the values of Keap 1 and GSS were shown to be slightly higher than those of the control (Figure 1)
Infection-initiated oxidative stress plays a key role in the activation of innate immunity to fight off pathogenic microbes, a number of viruses were shown to induce oxidative stress on purpose to facilitate their replication inside the cell, which at least included influenza virus, respiratory syncytial virus (RSV), human metapneumovirus, dengue virus (DENV), rotavirus, herpes simplex virus, Zika virus, and HIV (McCord et al, 2020)

Summary

Introduction

Cyprinid herpesvirus 2 (CyHV-2), belonging to the genus Cyprinivirus and the family Alloherpesviridae, was first isolated and characterized from juvenile goldfish (Carassius auratus auratus) in Japan (Jung and Miyazaki, 1995). Goldfish are regarded as the natural host for CyHV-2, and the symptoms are generally represented by pale gills and swollen spleens and kidneys. CyHV-2 causes high mortality among juvenile goldfish at water temperatures between 15 and 25◦C (Jeffery et al, 2007). Typical symptoms for crucian carp include lethargy and lack of appetite, bleeding and pale gills, pink ascites in the abdominal cavity, and enlarged spleen and kidneys, and death can occur within 1 to 2 days following the onset of clinical signs (Xu et al, 2014). The symptoms of CyHV-2 infection in crucian carp are significantly more severe than those in goldfish. Neither vaccine nor medicine is available for the control of disease caused by CyHV-2 infection

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