Iota-carrageenan promotes cell viability and reduces viral titer of influenza A-infected MDCK cells.

<p>MDCK cells grown in 96-well plates were infected with H1N1 A/PR/8/34 virus (A) and H3N2 A/Aichi/2/68 virus (B) (0.01 PFU/cell) in the presence of carrageenans (iota-carrageenan black diamonds, kappa-carrageenan black squares) at concentrations as indicated on the x-axis in µg/ml. Plates were incubated at 37°C until cells in the control (no polymer added) showed >90% damage. Cell proliferation was determined with a Resazurin-based in vitro toxicology assay. Samples were measured fluorometrically by monitoring the increase in fluorescence at a wavelength of 590 nm using an excitation wavelength of 544 nm. Values obtained from mock-infected cells were set to 100%, and the values of cells infected in the absence of polymer were set to 0% (y-axis). (C)-(F) MDCK cells were infected with H1N1 A/PR/8/34 as before and further kept in the presence of iota-carrageenan (circles) or the control polymer CMC (squares) at indicated concentrations and 24 (C), 48 (D), 72 (E), and 96 hours (F) post infection, respectively. Supernatants were harvested, pooled, and subsequently used to determine the TCID50/ml according to the method of Reed and Muench <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0014320#pone.0014320-Reed1" target="_blank">[59]</a>. The points represent the mean of a quadruplicate experiment, the standard deviation is indicated.