Zinc Salts Block Hepatitis E Virus Replication by Inhibiting the Activity of Viral RNA-Dependent RNA Polymerase

Abstract

Hepatitis E virus (HEV) causes an acute, self-limiting hepatitis in healthy individuals and leads to chronic disease in immunocompromised individuals. HEV infection in pregnant women results in a more severe outcome, with the mortality rate going up to 30%. Though the virus usually causes sporadic infection, epidemics have been reported in developing and resource-starved countries. No specific antiviral exists against HEV. A combination of interferon and ribavirin therapy has been used to control the disease with some success. Zinc is an essential micronutrient that plays crucial roles in multiple cellular processes. Zinc salts are known to be effective in reducing infections caused by few viruses. Here, we investigated the effect of zinc salts on HEV replication. In a human hepatoma cell (Huh7) culture model, zinc salts inhibited the replication of genotype 1 (g-1) and g-3 HEV replicons and g-1 HEV infectious genomic RNA in a dose-dependent manner. Analysis of a replication-defective mutant of g-1 HEV genomic RNA under similar conditions ruled out the possibility of zinc salts acting on replication-independent processes. An ORF4-Huh7 cell line-based infection model of g-1 HEV further confirmed the above observations. Zinc salts did not show any effect on the entry of g-1 HEV into the host cell. Furthermore, our data reveal that zinc salts directly inhibit the activity of viral RNA-dependent RNA polymerase (RdRp), leading to inhibition of viral replication. Taken together, these studies unravel the ability of zinc salts in inhibiting HEV replication, suggesting their possible therapeutic value in controlling HEV infection. Hepatitis E virus (HEV) is a public health concern in resource-starved countries due to frequent outbreaks. It is also emerging as a health concern in developed countries owing to its ability to cause acute and chronic infection in organ transplant and immunocompromised individuals. Although antivirals such as ribavirin have been used to treat HEV cases, there are known side effects and limitations of such therapy. Our discovery of the ability of zinc salts to block HEV replication by virtue of their ability to inhibit the activity of viral RdRp is important because these findings pave the way to test the efficacy of zinc supplementation therapy in HEV-infected patients. Since zinc supplementation therapy is known to be safe in healthy individuals and since high-dose zinc is used in the treatment of Wilson's disease, it may be possible to control HEV-associated health problems following a similar treatment regimen.

Zinc Chelation Specifically Inhibits Early Stages of Dengue Virus Replication by Activation of NF-κB and Induction of Antiviral Response in Epithelial Cells

“…Zinc salts have been shown to inhibit some of the RNA viruses using in vitro assays or infection systems (4)(5)(6)(7)(8)(9). Zinc has been shown to alter various stages of viral infection as in the case of poliovirus and other picornaviruses and hepatitis C virus where zinc salts were shown to inhibit viral protease activity (46,47).…”

“…Previous reports have also shown divergent effects of Zn 2+ on virus replication. Zinc inhibited RNA polymerase activity of a number of viruses including coronavirus, arterivirus, rhinovirus, and hepatitis C virus (4)(5)(6)(7)(8)(9). Dengue virus (DENV), a mosquitoborne, positive-strand RNA virus from the family Flaviviridae, has emerged as one of the major public health concerns in India and recent estimates suggest that over 60 million people globally get infected with DENV every year (10).…”

Recent Advances Towards the Development of a Potent Antiviral Against the Hepatitis E Virus

“…63,64 Zinc salts were shown to block the replication of both genotype 1 and genotype 3 HEV by inhibiting the activity of viral RNA-dependent RNA polymerase in cultured human hepatoma cells. 62 Further, zinc salts did not affect virus entry into the host cell. Zinc also displayed moderate cooperativity with ribavirin in inhibiting viral replication.…”

“…6 | 310-316 MG132 also reduced the cellular RNA and protein levels, indicating its effect to be nonspecific. 61 Zinc A recent report by Kaushik et al 62 has demonstrated the antiviral activity of zinc against HEV. Zinc is an essential micronutrient, which plays a crucial role in multiple cellular processes.…”

Failure to respond to ribavirin despite elevated intra‐erythrocyte zinc level in transplant‐patients with chronic hepatitis E virus infection

“…2 Recently, zinc salt, which is known to reduce infections induced by viruses, was tested in vitro against HEV. 3,4 It has been shown that it inhibits the activity of viral RNA-dependent RNA polymerase (RdRp), leading to inhibition of HEV replication. 3,4 In addition, it has a synergistic effect with ribavirin on HEV replication.…”