The Intranasal Application of Zanamivir and Carrageenan Is Synergistically Active against Influenza A Virus in the Murine Model

<div><p>Background</p><p>Carrageenan is a clinically proven and marketed compound for the treatment of viral upper respiratory tract infections. As infections caused by influenza virus are often accompanied by infections with other respiratory viruses the combination of a specific anti-influenza compound with the broadly active antiviral polymer has huge potential for the treatment of respiratory infections. Thus, the combination of the specific anti-influenza drug Zanamivir together with carrageenan in a formulation suitable for intranasal application was evaluated <i>in-vitro</i> and <i>in-vivo</i>.</p><p>Principal Findings</p><p>We show <i>in-vitro</i> that carrageenan and Zanamivir act synergistically against several influenza A virus strains (H1N1(09)pdm, H3N2, H5N1, H7N7). Moreover, we demonstrate in a lethal influenza model with a low pathogenic H7N7 virus (HA closely related to the avian influenza A(H7N9) virus) and a H1N1(09)pdm influenza virus in C57BL/6 mice that the combined use of both compounds significantly increases survival of infected animals in comparison with both mono-therapies or placebo. Remarkably, this benefit is maintained even when the treatment starts up to 72 hours post infection.</p><p>Conclusion</p><p>A nasal spray containing carrageenan and Zanamivir should therefore be tested for prevention and treatment of uncomplicated influenza in clinical trials.</p></div

Therapeutic efficacy in influenza H1N1(09)pdm lethally infected mice.

<p>Mice (n = 20 per group) were lethally intranasally infected without anesthesia on day 0 and intranasally treated twice per day either with placebo or a combination of carrageenan and Zanamivir (1 mg/kg BW/day). Treatment started either 48 hpi or 72 hpi and continued for 5 days. On the y-axis the survival of mice [%] and on the x-axis the time post infection [days] is given. Placebo treated uninfected control mice showed 100% survival (data not shown). Statistical analyses were conducted using log rank test and are shown beneath the graphs. Values of p<0.05 were considered statistically significant.</p

IC₅₀ values of carrageenan and Zanamivir for influenza A viruses of human and animal origin.

<p>^a IC₅₀ values were calculated in comparison to untreated infected cells. Each value represents the mean IC₅₀ of 6 replicates/assay and their standard deviation.</p><p>IC₅₀ values of carrageenan and Zanamivir for influenza A viruses of human and animal origin.</p

Isobologram of compound interaction.

<p>Comparison of the combination of different doses of both compounds necessary to reach 50% replication inhibition of (A) H7N7 and (B) H1N1(09)pdm (◆) to a model of dose additivity that would represent a curve progression of 1 (□). Dose response was tested with an adapted plaque reduction assay with semi-liquid overlay in MDCK cells. On the x-axis the concentration of Zanamivir and on the y-axis the concentration of carrageenan is presented. The concentrations (determined as mean of 3 replicates) are given as the fraction of the respective IC₅₀ values of the different viruses with the particular compound (IC₅₀ = 1).</p