Antiviral Activities of Hibiscus sabdariffa L. Tea Extract Against Human Influenza A Virus Rely Largely on Acidic pH but Partially on a Low-pH-Independent Mechanism

Influenza A virus (IAV) infection is perennially one of the leading causes of death worldwide. Effective therapy and vaccination are needed to control viral expansion. However, current anti-IAV drugs risk inducing drug-resistant virus emergence. Although intranasal administration of whole inactivate...

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Published in:	Food and environmental virology Vol. 12; no. 1; pp. 9 - 19
Main Authors:	Takeda, Yohei, Okuyama, Yuko, Nakano, Hiroto, Yaoita, Yasunori, Machida, Koich, Ogawa, Haruko, Imai, Kunitoshi
Format:	Journal Article
Language:	English
Published:	New York Springer US 01-03-2020 Springer Nature B.V
Subjects:	Animals Antigenicity Antiviral activity Antiviral agents Antiviral Agents - administration & dosage Antiviral Agents - chemistry Biomedical and Life Sciences Biomedicine Chemistry/Food Science Drug resistance Female Food Science Hemagglutinins Hibiscus - chemistry Hibiscus sabdariffa Humans Hydrogen-Ion Concentration Influenza Influenza A Influenza A virus - drug effects Influenza A virus - growth & development Influenza, Human - drug therapy Influenza, Human - virology Intranasal administration Mice Mice, Inbred BALB C Original Paper pH effects Plant Extracts - administration & dosage Plant Extracts - chemistry Protein structure Protocatechuic acid Roselle Tea Therapy Vaccination Vaccines Virology Viruses Natural substance Anti-human influenza A viral activity Antiviral drug therapy Acidic pH Hibiscus tea extract Whole inactivated vaccine
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Summary:	Influenza A virus (IAV) infection is perennially one of the leading causes of death worldwide. Effective therapy and vaccination are needed to control viral expansion. However, current anti-IAV drugs risk inducing drug-resistant virus emergence. Although intranasal administration of whole inactivated virus vaccine can induce efficient protective immunity, formalin and β-propiolactone are the currently used and harmful inactivating agents. Here, we analyzed the antiviral activity of hibiscus ( Hibiscus sabdariffa L. ) tea extract against human IAV and evaluated its potential as a novel anti-IAV drug and a safe inactivating agent for whole inactivated vaccine. The in vitro study revealed that the pH of hibiscus tea extract is acidic, and its rapid and potent antiviral activity relied largely on the acidic pH. Furthermore, the mouse study showed that the acidic extract was not effective for either therapeutic or vaccination purposes. However, hibiscus tea extract and protocatechuic acid, one of the major components of the extract, showed not only potent acid-dependent antiviral activity but also weak low-pH-independent activity. The low-pH-independent activity did not affect the conformation of immunodominant hemagglutinin protein. Although this low-pH-independent activity is very limited, it may be suitable for the application to medication and vaccination because this activity is not affected by the neutral blood environment and does not lose antigenicity of hemagglutinin. Further study of the low-pH-independent antiviral mechanism and attempts to enhance the antiviral activity may establish a novel anti-IAV therapy and vaccination strategy.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	1867-0334 1867-0342
DOI:	10.1007/s12560-019-09408-x