The RT-PCR program consisted of 30 min at 50 °C and 15 min at 95 °C. A three-step cycling protocol was used as follows: 95 °C for 5 s, 58 °C for 15 s, and of 72 °C for 20 s for

45 cycles. In each PCR run a standard curve was included with a known virus concentration. Results of the PCR are expressed as TCID50-equivalents per swab or per gram of tissue. TCID50-equivalents are a relative measure and not necessarily represent live virus. Nasal swabs, oropharyngeal swabs, tissue homogenates and BALF were all tested in a virus isolation Fasudil in vitro with end-titration on MDCK-I-BD5 cells [15]. Samples were initially diluted with the same amount of GMEM/EMEM Modulators medium containing 1% bovine serum albumin and antibiotics (twofold dilution). This initial dilution was serially diluted tenfold in the same medium. The diluted samples (100 μl/well) were mixed with 150 μl of 2 × 105 MDCK-I-BD5 cells/ml and incubated CX-5461 concentration for 48 h at 37 °C and 5% CO2. The monolayers were subsequently washed with PBS, frozen at −20 °C and fixed with 4% cold (4 °C) paraformaldehyde for 10 min. After washing, viral NP-protein-containing cells were stained using HRPO-conjugated monoclonal antibody HB65 and 3-amino-9-ethyl-carbozole (AEC; Sigma–Aldrich,

The Netherlands) as a substrate for HRPO. Samples were tested in eightfold and titres were calculated according to the method of Spearman-Kärber [16]. and Virus titres are expressed as TCID50 per swab or per gram of tissue. The hemagglutination inhibition (HI) test was carried out as described before [17]. Before testing, samples were inactivated for 30 min at 56 °C. Subsequently

they were pre-treated with receptor destroying enzyme (RDE) and chicken red blood cells to remove non-specific agglutinins and hemagglutination inhibitors. Starting at an initial dilution of 1:10, sample were tested in two-fold dilution series. Samples were incubated for 60 min after adding antigen and another 45 min after adding chicken red blood cells and subsequently read. The antigens used in the test were the A/Netherlands/602/2009 (H1N1)v and, for swine influenza, the A/Swine/Best/96 (H1N1) [18] and A/Swine/Gent/7625/99 (H1N2) [19]. All were standardised at 4 hemagglutinating units per 25 μl. The virus neutralisation tests were performed on MDCK-I-BD5 cells [15]. Sera were heat inactivated for 30 min at 56 °C before testing. Twofold serial dilutions of the sera were made in GMEM/EMEM medium containing 1% bovine serum albumin and antibiotics in 96-well plates. The diluted sera (50 μl/well) were mixed with 100 TCID50 of the influenza viruses (50 μl) and incubated at 37 °C and 5% CO2 for 1 h. Thereafter 150 μl of 2 × 105 MDCK-I-BD5 cells/ml were added to each well. The plates were incubated at 37 °C and 5% CO2 for 48 h. The monolayers were washed with PBS, frozen at −20 °C and fixed with 4% cold (4 °C) paraformaldehyde for 10 min.