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Title: Inhibition of lentivirus replication by aqueous extracts of Prunella vulgaris

Author
item BRINDLEY, MELINDA - UNIVERSITY OF IOWA
item WIDRLECHNER, MARK
item MCCOY, JOE-ANN - BENT CREEK INSTITUTE
item MURPHY, PATRICIA - IOWA STATE UNIVERSITY
item HAUCK, CATHY - IOWA STATE UNIVERSITY
item RIZSHSKY, LUDMILA - IOWA STATE UNIVERSITY
item NIKOLAU, BASIL - IOWA STATE UNIVERSITY
item MAURY, WENDY - UNIVERSITY OF IOWA

Submitted to: Virology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/2/2009
Publication Date: 1/20/2009
Citation: Brindley, M.A., Widrlechner, M.P., Mccoy, J., Murphy, P., Hauck, C., Rizshsky, L., Nikolau, B., Maury, W. 2009. Inhibition of lentivirus replication by aqueous extracts of Prunella vulgaris. Virology Journal. 6:8.

Interpretive Summary: The herb, self-heal (Prunella vulgaris), was traditionally used in Chinese and Native American medicine. Various members of the mint family including self-heal have been reported to have antiviral activity. To investigate whether self-heal also has antiviral activity, we tested water and ethanol extracts for their ability to inhibit the replication of equine infectious anemia virus (EIAV), a serious pathogen of horses. Water extracts contained more antiviral activity than did ethanol extracts, and this was observed both in cell lines as well as in primary cell cultures with little toxicity to the cells. Extracts of self-heal were most effective when added to the experiments during the first four hours of the viral life cycle suggesting that the effects were either on the virus itself or on early entry events. Further analysis showed that extracts did not destroy the viral particles, but instead prevented them from binding to cells. The water extract was fractionated through a process based on molecular size. Different fractions with various components, including both compounds soluble in ethanol and those that were not, displayed profound activity against EIAV. The ability of the water extract to prevent entry of viral particles into cells that would otherwise be receptive to them suggests that these self-heal extracts may function as promising microbicides. This information should be useful to researchers searching for new, antiviral compounds and to practitioners of herbal and conventional medicine for animal health.

Technical Abstract: Prunella vulgaris has been used historically in Chinese and Native American medicine. Various members of the mint family, including Prunella, have been reported to have antiviral activity. To characterize the anti-lentiviral activities of P. vulgaris, we tested water and ethanol extracts for their inhibition of equine infectious anemia virus (EIAV) replication. Aqueous extracts contained more antiviral activity than did ethanol extracts, displaying potent anti-lentiviral activity in cell lines as well as in primary cell cultures with no cytotoxicity. Time-of-addition studies demonstrated that extracts were most effective when added during the first four hours of the viral life cycle suggesting that constituents targeted the virion itself or early entry events. Further analysis showed that extracts did not destroy EIAV virion integrity, but prevented viral particles from binding to surfaces of permissive cells. Modest levels of anti-EIAV activity were also detected when cells were treated with extracts before infection indicating that Prunella constituents could interact with both viral particles and permissive cells to interfere with infectivity. Size fractionation showed that eight of nine fractions generated from water extracts displayed antiviral activity. Ethanol soluble constituents were responsible for antiviral activity in one fraction, whereas ethanol insoluble constituents were key in two other fractions. In three of five fractions that lost activity upon subfractionation, activity was restored upon reconstitution, evidence for synergistic antiviral effects. Our findings indicate that multiple Prunella constituents have profound anti-retroviral activity. The ability of aqueous extracts to prevent entry of viral particles into permissive cells suggests that these extracts may function as promising microbicides against lentiviruses.