The anti-influenza virus effect of Phellinus igniarius extract.

Herbal medicine has been used in the orient for thousands of years to treat large and small ailments, including microbial infections. Although there are treatments for influenza virus infection, there is no treatment for drug-resistant viruses. It is time that we explored and exploited the multi-component nature of herbal extracts as multi-drug combination therapies. Here, we present data on the anti-influenza virus effect of a medicinal mushroom, Phellinus igniarius. The P. igniarius water extract was effective against influenza A and B viruses, including 2009 pandemic H1N1, human H3N2, avian H9N2, and oseltamivir-resistant H1N1 viruses. Virological assays revealed that the extract may interfere with one or more early events in the influenza virus replication cycle, including viral attachment to the target cell. Therefore, our results provide new insights into the use of P. igniarius as an anti-influenza medicine.

Aronia melanocarpa and its components demonstrate antiviral activity against influenza viruses.

The influenza virus is highly contagious in human populations around the world and results in approximately 250,000-500,000 deaths annually. Vaccines and antiviral drugs are commonly used to protect susceptible individuals. However, the antigenic mismatch of vaccines and the emergence of resistant strains against the currently available antiviral drugs have generated an urgent necessity to develop a novel broad-spectrum anti-influenza agent. Here we report that Aronia melanocarpa (black chokeberry, Aronia), the fruit of a perennial shrub species that contains several polyphenolic constituents, possesses in vitro and in vivo efficacy against different subtypes of influenza viruses including an oseltamivir-resistant strain. These anti-influenza properties of Aronia were attributed to two constituents, ellagic acid and myricetin. In an in vivo therapeutic mouse model, Aronia, ellagic acid, and myricetin protected mice against lethal challenge. Based on these results, we suggest that Aronia is a valuable source for antiviral agents and that ellagic acid and myricetin have potential as influenza therapeutics.

DBA/2 mouse as an animal model for anti-influenza drug efficacy evaluation.

Influenza viruses are seasonally recurring human pathogens. Vaccines and antiviral drugs are available for influenza. However, the viruses, which often change themselves via antigenic drift and shift, demand constant efforts to update vaccine antigens every year and develop new agents with broad-spectrum antiviral efficacy. An animal model is critical for such efforts. While most human influenza viruses are unable to kill BALB/c mice, some strains have been shown to kill DBA/2 mice without prior adaptation. Therefore, in this study, we explored the feasibility of employing DBA/2 mice as a model in the development of anti-influenza drugs. Unlike the BALB/c strain, DBA/2 mice were highly susceptible and could be killed with a relatively low titer (50% DBA/2 lethal dose = 10(2.83) plaque-forming units) of the A/Korea/01/2009 virus (2009 pandemic H1N1 virus). When treated with a neuraminidase inhibitor, oseltamivir phosphate, infected DBA/2 mice survived until 14 days post-infection. The reduced morbidity of the infected DBA/2 mice was also consistent with the oseltamivir treatment. Taking these data into consideration, we propose that the DBA/2 mouse is an excellent animal model to evaluate antiviral efficacy against influenza infection and can be further utilized for combination therapies or bioactivity models of existing and newly developed anti-influenza drugs.

GFP-expressing influenza A virus for evaluation of the efficacy of antiviral agents.

To address its value as a screening tool in the development of antiviral drugs, a recombinant influenza virus expressing green fluorescent protein (rPR8-GFP virus) was investigated in vitro and in vivo. The inhibition of viral growth by a neuraminidase inhibitor in the cells or lower respiratory tracts of mice could be visualized by the level of fluorescence. In addition, the rPR8-GFP virus exhibited high pathogenicity in mice. Taken together, these results suggest that the rPR8-GFP virus can be a useful tool for the rapid identification of antiviral drugs active against influenza viruses.