Increasing the intracellular Zn(2+) concentration with zinc-ionophores like pyrithione (PT) can efficiently impair the replication of a variety of RNA viruses, including poliovirus and influenza virus. For some viruses this effect has been attributed to interference with viral polyprotein processing. In this study we demonstrate that the combination of Zn(2+) and PT at low concentrations (2 µM Zn(2+) and 2 µM PT) inhibits the replication of SARS-coronavirus (SARS-CoV) and equine arteritis virus (EAV) in cell culture. The RNA synthesis of these two distantly related nidoviruses is catalyzed by an RNA-dependent RNA polymerase (RdRp), which is the core enzyme of their multiprotein replication and transcription complex (RTC). Using an activity assay for RTCs isolated from cells infected with SARS-CoV or EAV--thus eliminating the need for PT to transport Zn(2+) across the plasma membrane--we show that Zn(2+) efficiently inhibits the RNA-synthesizing activity of the RTCs of both viruses. Enzymatic studies using recombinant RdRps (SARS-CoV nsp12 and EAV nsp9) purified from E. coli subsequently revealed that Zn(2+) directly inhibited the in vitro activity of both nidovirus polymerases. More specifically, Zn(2+) was found to block the initiation step of EAV RNA synthesis, whereas in the case of the SARS-CoV RdRp elongation was inhibited and template binding reduced. By chelating Zn(2+) with MgEDTA, the inhibitory effect of the divalent cation could be reversed, which provides a novel experimental tool for in vitro studies of the molecular details of nidovirus replication and transcription.
Background: Routine zinc supplementation is a potential intervention for the prevention of acute lower respiratory infections in developing countries. However discrepant findings from recent randomized trials remain unexplained.
Methods: Single centre, single arm, prospective non-randomized, open label interventional study, of effect of zinc supplementation in zinc deficient children aged 6 months to 5 years. 465 healthy children aged 6 months to 5 years were enrolled in the study. The primary outcome was the prevalence of serum zinc deficiency. Children having zinc deficiency were recruited for the study of effect of oral administration of zinc 20 mg for 2 weeks. The secondary outcomes were incidence and duration of acute upper respiratory and acute lower respiratory infections per child-year and side effects after giving zinc therapy.
Results: There was significant difference in mid arm circumference in between zinc deficient and non-zinc deficient groups (p < 0.001). Also the number of episodes of acute upper respiratory infections (AURI) and mean duration of AURI and acute lower respiratory infections (ALRI) was significantly different in the two groups (p < 0.001). There was no significant difference in ALRI episodes in two groups. After zinc supplementation in zinc deficient children, there was significant decrease in the number of episodes and mean duration of AURI (p < 0.001) and ALRI (p < 0.001) in six months after supplementation as compared to preceding six months before supplementation.
Conclusion: This study sheds light on the efficacy of short course prophylactic zinc supplementation in reducing the burden of ARI among zinc deficient children. Future studies should assess the effectiveness of delivering prophylactic zinc supplementation at scale, comparing the feasibility and cost benefit of short course and continuous regimens.
Clinical Trial Number: As it was a Non Randomized observational single arm study, study was not registered. Only RCT needs to be registered.
Funding Statement: This study was funded by All India Institute of Medical Sciences (AIIMS), Manuscript Jodhpur, India, as a part of Intramural project conducted in the department of Pediatrics, AIIMS Jodhpur.
Declaration of Interests: We declare no competing interests.
Ethics Approval Statement: The study was approved by Institutional Ethics committee of All India Institute of Medical Sciences, Jodhpur, India. The study was conducted in accordance with ICH-GCP and other applicable regulatory guidelines.
This 2020 review highlighted earlier clinical data on zinc:
“Zinc is known to modulate antiviral and antibacterial immunity and regulate inflammatory response.
Zinc possesses anti-inflammatory activity by inhibiting NF-κB signaling and modulation of regulatory T-cell functions.
The most critical role of zinc is demonstrated for the immune system.
Zinc regulates proliferation, differentiation, maturation, and functioning of leukocytes and lymphocytes.
Alteration of zinc status significantly affects immune response resulting in increased susceptibility to inflammatory and infectious diseases including acquired immune deficiency syndrome, measles, malaria, tuberculosis, and pneumonia. Zinc status is associated with the prevalence of respiratory tract infections in children and adults.
In view of the high prevalence of zinc deficiency worldwide (up to 17%), its impact on population health is considered as a significant issue. Certain groups of people, including infants, especially preterm ones, and elderly, are considered to be at high risk of zinc deficiency and its adverse effects.
Zinc was shown to have a significant impact on viral infections through modulation of viral particle entry, fusion, replication, viral protein translation and further release for a number of viruses including those involved in respiratory system pathology. Increasing intracellular Zn levels through application of Zn ionophores significantly alters replication of picornavirus, the leading cause of common cold.
The results of systematic analysis confirmed the efficiency of intake of at least 75 mg/day Zn in reduction of pneumonia symptom duration but not severity, with the response being more pronounced in adults than in children.”
Josef Penninger is the founder and a shareholder of Apeiron, the company that makes rhACE2. Arthur Slutsky has been a paid consultant for Apeiron. No other conflicts of interested have been reported.
BACKGROUND: Airway epithelium is the first line of defense against a variety of exposures. Inflammatory processes, hyperresponsiveness and zinc deficiency cause epithelial damage. Zinc is involved in apoptosis and microtubule formation. However, its role in the integrity of bronchial mucosa and cilia is unclear.
METHODS: To assess the effect of zinc on the integrity of the bronchial epithelium, 24 male Rattus norvegicus strain Wistar rats were randomized into four experimental groups: normal zinc diet group without zinc supplementation, normal zinc diet group with 60 ppm zinc supplementation, zinc deficient diet group without zinc supplementation, and zinc deficient diet group with 120 ppm zinc supplementation. Bronchial mucosal integrity was measured with the number of epithelial cells, and the number and length of cilia.
RESULTS: Number of cell in normal zinc diet group was 8.8±1.82, while it was only 8.1±1.08 in zinc deficient diet group (p<0.001). Number of cilia per cell was 4.6±1.08 in normal zinc diet group, compared to 4.0±0.79 in zinc deficient diet group (p<0.001). Ciliary length also differ by 7.68±0.66 μm in normal zinc diet group and only 5.16±0.91 μm in zinc deficient diet group (p<0.001).
CONCLUSION: Zinc supplementation of the normal zinc diet group affected the length of bronchial cilia. Zinc supplementation of the zinc deficient diet group affected the integrity of the bronchial epithelium, which was shown by the number and length of cilia, and the number of epithelial cells.