An international group of researchers has now shown for the first time that Echinacea purpurea (purple coneflower) develops direct antiviral effects against clinically important influenza viruses in vitro, including the new influenza pathogens (H1N1“swine flu”) . Even after repeated treatment of the influenza virus with the Echinacea fresh-plant extract no build-up of resistances could be seen. Furthermore essential elements of the molecular mechanisms of action of the inhibition could be revealed by the scientists.
It has long been suspected that Echinacea may have direct antiviral or virostatic effects . How effective an Echnacea fresh plant extract can block the replication of relevant respiratory tract pathogens in vitro was part of a very recent study. . The results of this research suggested taking a closer look at the antiviral effect versus influenza viruses, giving particular consideration to the H1N1 strain (swine flu).
In vitro infection model
Tested influenza A viruses
Five influenza A strains were investigated: H3N2 (e.g. “Hong Kong flu” or seasonal influenza), H5N1 (e.g. “bird flu”, human pathogen), H7N7 (e.g. avian influenza, also human pathogen), H1N1 (human influenza) and H1N1 (“Mexico influenza”, swine flu, current pandemic). Infectiousness tests were conducted in a plaque assay with renal epithelial cells (MDCK cells). The cell cultures were treated at different points in time and in varying concentrations with the Echinacea extract, and the extent of infection inhibition was then tested. A standardised alcohol extract of fresh Echinacea purpurea herb (95%) and root (5%) was used (L.) Moench (Echinaforce®, A. Vogel Bioforce AG, Switzerland).
Virus inhibition At doses of 1.6 µg/ml and higher, the Echinacea extract inhibited the infectiousness of all examined influenza viruses by over 99%, including the pathogens of the current pandemic swine flu. The inhibiting effect was also retained at high virus concentrations (e.g. 105 PFU/ml).
Resistance Treatment with Echinacea did not lead to viral resistance in any of the cases, not even following several treatment cycles. In contrast, almost 100% of the viruses were resistant to the conventional Rx antiviral substance, which was tested in parallel, after the third treatment cycle. Even these influenza strains were inhibited over 99.9% by the Echinacea fresh-plant extract.
Mechanisms The results of the haemagglutinin assays (HA), detection of the intracellular ribonucleoprotein (RNP) replication marker and further analyses – e.g. regarding the effects of different incubation periods – suggest that the tested Echinacea extract develops its antiviral effect by acting directly on the viruses very early on during the incubation process. Even prior to the infection of the epithelial cells, Echinacea modifies the viral surface protein haemagglutinin in such a way that the virus is unable to adhere to cellular receptors. The influenza viruses are therefore unable to penetrate and replicate into cells.
Summary In view of the challenges posed by the current swine flu pandemic, each additional prophylactic or therapeutic option is a desirable gain for disease control from a virological point of view. The fact that an established medicinal plant with a known, multiple spectrum of effect is also discovered to have a direct antiviral effect against swine flu and other influenza viruses is surprising. In particular because the pattern of activity resembles the aspects of an innate immune response. The significance of the clinical antiviral effect of Echinaforce in pandemic influenza infections now has to be clarified. The authors of the submitted study are of the opinion that Echinaforce, as a standard preparation, is a useful, easily available, affordable and clinically relevant addition to standard influenza control measures.
• Rainer H. Bubenzer, (Dezember 2009).
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