Publication: Antiviral Activity Of Microalgae Extracts Against Epstein-Barr Virus
Date
2009-08
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
International Medical University
Abstract
Epstein-Barr virus (EBV) is a class I carcinogen human herpes virus which has infected 90% of humanity and most prevalent among Asians, especially Chinese. After primary infection, EBV establishes the lifelong virus carrier state. EBV can be detected in two different tissues namely, B lymphocytes and epithelial cells. EBV is linked to the pathogenesis of a variety of human tumors and disorders, such as Burkitt’s lymphoma, and nasopharyngeal carcinoma. Algae are a potential source of antiviral compounds; however, there have been very few reports on the antiviral activity of microalgae extracts against EBV. The objective of this study was to investigate the antiviral activity
of extracts from three microalgae, namely Ankistrodesmus convolutus UMACC 101, Synechococcus elongatus UMACC 105 and Spirulina platensis UMACC 161 against EBV in Burkitt’s lymphoma (BL) cell lines. Three EBV-positive BL cell lines, namely Akata, B95-8 and P3HR-1 were used as in vitro study model. A bioassay-guided fractionation approach was used for the screening of antiviral activity. The antiviral activity of the microalgae extracts was elucidated based on their inhibition efficacy in reducing number of cell-free viral particles being released by chemically induced lytic
BL cells. This was assessed by quantifying the cell-free DNA using real-time PCR technique. In addition, the inhibition activity of microalgae extracts against the expression of the viral proteins LMP1, EBNA1 and ZEBRA in BL cells was assessed using immunocytochemistry technique. Two antiviral drugs namely acyclovir and foscarnet were chosen as positive controls. Methanol extracts from Ankistrodesmus convolutus and Synechococcus elongatus displayed low cytotoxicity (IC50 >200 µg/mL) and reduced the cell-free EBV viral load most effectively (EC50 <0.01 µg/mL) and thus, displayed high therapeutic index (>28000). The extracts decreased the expression of EBNA1 (>45%), LMP1 (>38%) and ZEBRA (>67%) effectively in P3HR-1 cells. After column chromatography fractionation, the non-polar fraction of the extract from Synechococcus elongatus (SEF1) reduced the amount of cell-free EBV DNA most effectively (EC50= 2.9μg/mL; therapeutic index >69) with low cytotoxicity (IC50 >200 μg/mL). SEF1 inhibited the expression of EBNA1 and ZEBRA (>40%) effectively in P3HR-1 cells. When SEF1 was further fractionated using HPLC, the sub-fraction SEF1’a was most active in reducing the cell-free EBV DNA (EC50= 1.38µ/mL; therapeutic index >14.5). It inhibited the expression of LMP1 moderately (25%) in P3HR-1 cells. The microalgae extracts did not interact with the cytoskeleton components (actin and tubulin) of BL cells during the release of cell-free EBV particles as revealed by the immunofluorescence study. The active constituents in the microalgae extracts tested might consist of pigments such as chlorophylls, carotenoids, phaeophytins and phycobilins. In conclusion, methanol extracts from Ankistrodesmus convolutus, Synechococcus elongatus and Spirulina platensis showed antiviral activity by inhibiting the release of EBV from the BL cells and the expression of the viral proteins LMP1, EBNA1 and ZEBRA in the host cells. The potential of the microalgae as a source of antiviral drugs against EBV is worth exploring.
Description
Keywords
Antiviral Agents, Microalgae, Herpesvirus 4, Human, Cell Line