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Prophylaxis against influenza is difficult, and current approaches against pandemics may be ineffective because of shortages of the two proven classes of antivirals in the face of a large-scale infection. Herbal/natural products may represent an effective alternative to conventional attempts to protect against infection by avian influenza virus. QR-435, an all-natural compound of green tea extract and other agents, has been developed to provide protection against a wide range of viral infections. The antiviral activities of several QR-435 preparations as well as QR-435 (1) green tea extract were tested against A/Sydney/5/97 and A/Panama-Resvir 17 strains of avian influenza virus H3N2 by means of an assay based on Madin-Darby canine kidney cells. Toxic effects of QR-435 formulations on these cells were also evaluated as were the virucidal properties of a commercially available mask impregnated with QR-435. The efficacy of a QR-435/mask combination was compared with that of the QR control/mask combination, an untreated mask, and no mask. QR-435 had significant in vitro activity against H3N2 at concentrations that were not associated with significant cellular toxic effects. The antiviral activity of QR-435 (1) was similar to that of QR-435. Masks impregnated with QR-435 were highly effective in blocking the passage of live H3N2 virus. These preclinical results warrant further evaluation of the prophylactic use of QR-435 against viral infection in humans.

Background: Prophylaxis against influenza infection can take several forms, none of which is totally effective at preventing the spread of the disease. QR-435, an all-natural compound of green-tea extract and other agents, has been developed to protect against a range of viral infections, including the influenza subtype H3N2., Methods: Several different QR-435 formulations were tested against the two influenza A H3N2 viruses (A/Sydney/5/97 and A/Panama/2007/99) in the ferret model. Most experiments included negative (phosphate-buffered saline) and positive (oseltamivir 5 mg/kg, twice daily) controls. QR-435 and the control were administered 5 minutes after intranasal delivery of the virus as prophylaxis against infection resulting from exposure to infected but untreated ferrets and for prevention of transmission from infected and treated ferrets to untreated animals. Effects of QR-435 on seroconversion, virus shedding, and systemic sequelae of infection (weight loss, fever, reduced activity) were evaluated., Results: QR-435 prevented transmission and provided prophylaxis against influenza virus H3N2. Prophylaxis with QR-435 was significantly more than with oseltamivir in these experiments. Optimal in vivo efficacy of QR-435 requires a horseradish concentration of at least 50% of that in the original formulation, and the benefits of this preparation appear to be dose dependent., Conclusions: QR-435 is effective for both prevention of H3N2 viral transmission and prophylaxis. These preclinical results warrant further evaluation of its prophylactic properties against avian influenza virus infection in humans.