Variability of tropism and replicative capacity of two naturally occurring influenza A H9N2 viruses in cell cultures from different tissues

ABSTRACTStudies carried out on cell permissivity are of great interest to understand virus replication and pathogenicity. We described the results of a comparative analysis of replication efficiency of two naturally occurring influenza A H9N2 variants isolated from poultry and wild birds, differing by only two substitutions Q226L and T384N, in the receptor-binding site of haemagglutinin and the 380 loop region of NA proteins, respectively. Considering the overall growth of both viruses, lung cultures ensured the most efficient growth of TUN12L226N384 strain with titres up to 109 TCID50/ml whereas small intestine culture was highly susceptible to the TUN51Q226T384 virus reaching a titre of 106 TCID50/ml. The lowest replication was shown in liver cells. The addition of trypsin was essential for the replication of either virus in primary fibroblasts, but it had a marginal positive effect on virus replication in the four other culture types with maximum titres of 108 TCID50/ml. This means that in chicken, the...