Date of Award

Spring 5-14-2016

Degree Type

Dissertation

Degree Name

PhD Molecular Bioscience

Department

Biology

Advisor

Tin-Chun Chu, Ph.D

Committee Member

Lee H. Lee, Ph.D

Committee Member

Jane L. Ko, Ph.D

Committee Member

Edward Tall, Ph.D

Committee Member

Angela V. Klaus,

Keywords

green tea, black tea, HSV, theaflavins, epigallocatechin gallate (EGCG), palmitoyl-EGCG (p-EGCG)

Abstract

Green tea and black tea originate from the leaves of Camellia Sinensis plant and contain antioxidants known to possess antiviral properties, including anti-HSV (Herpes Simplex Virus). There is no cure for the diseases caused by HSV infections. While there is a rising concern over the increase in resistant HSV strains, new effective agents for prevention are in critical need to be developed. Green tea’s polyphenol epigallocatechin gallate (EGCG), and its modification palmitoyl-EGCG (p-EGCG), along with black tea theaflavins TF1, TF2, TF3 have been used to study their antiviral effect against HSV type 1 (HSV-1) and HSV type 2 (HSV-2). These compounds with concentrations of 0, 6.25, 12.5, 25, 50, and 75 μM were used on Vero and A549 cells to determine cell viability and cytotoxicity, and were shown to have no significant toxic effect in either one of the cell lines. Plaque assay, flow cytometric assay, fluorescence microscopy, polymerase chain reaction (PCR), and quantitative real-time PCR (qPCR) all demonstrated that EGCG and p-EGCG are effective in inhibiting HSV-1, with p-EGCG being the most efficient. Furthermore, binding assay suggests that p-EGCG is able to block viral glycoprotein(s) and efficiently inhibit the binding of HSV-1 to host receptors. Similar results were seen when cells were infected with HSV-2; plaque assay, flow cytometric assay, and fluorescence microscopy showed that p-EGCG is very effective in inhibiting HSV-2 (> 99%).

Black tea theaflavins were also efficient in preventing HSV-1 and HSV-2 infection in both cell lines. Plaque assay, flow cytometric assay, fluorescence microscopy, qPCR and scanning electron microscopy (SEM) demonstrated that all three theaflavins have strong antiviral capabilities, with TF3 being the most efficient. Binding and penetration assays also suggest that theaflavins are able to block viral binding of HSV to host cell receptors.

Overall, results indicated that all of the compounds used are effective anti- HSV-1 and HSV-2 agents, with p-EGCG being the most efficient from green tea and TF3 being the most efficient from black tea. Several experimental approaches used here showed that a concentration of 50 μM and above of p-EGCG and TF3 were sufficient to inhibit > 99% of HSV-1 and HSV-2 virions in both of the cell lines used. Finally, binding and penetration assays suggest that the antiviral activity of p-EGCG and TF3 may be through blocking the virus’ ability to bind/penetrate host cells and in turn prevent infection. Thus, green tea polyphenols and black tea theaflavins may serve as novel antiviral treatments that can substitute or complement current anti-HSV medications.

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