Impact of Influenza A Virus Infection on Growth and Metabolism of Suspension MDCK Cells Using a Dynamic Model

Sun Apr 24 11:40:02 CST 2022

Materials and Methods

3.1. Shake Flask Cultivations

Pre-cultures of MDCK.SUS2 suspension cells were grown in shaker flasks (125 mL polycarbonate Erlenmeyer flasks, #431143, Corning®, New York city, NY, USA) with 50 mL working volume (wv), in a Multitron Pro incubator (Infors HT, Bottmingen, Switzerland) at 37 °C and 5% CO2 atmosphere with a shaking frequency of 180 rpm. Cells were passaged every 3–4 days with a seeding density of 0.5–0.8 × 106 cells/mL.

IAV A/Puerto Rico/8/34 (H1N1) seed virus was used for infection, generated in adherent MDCK cells (ECACC # 84121903). The seed virus had a titer of 1.1 × 109 TCID50/mL.

Cells were cultivated in a chemically defined, protein-free and animal component-free medium, Smif8 (Smif8 PGD 2×, supplemented with 5 mM glutamine, and 8 mM pyruvate), specifically developed for the cultivation of suspension MDCK cells [95].

Growth and infection experiments for model validation were performed using 500 mL shaking flasks (#4113-0500, Nalgene™, Thermo Scientific, Waltham, MA, USA) with an initial cultivation volume of 200 mL at 150 rpm. Two cultivations were performed, one mock-infection (Cultivation 1), where cells grew for about 200 h, and one infection (Cultivation 2), where cells were infected with IAV at about 49 h post inoculation. To achieve a synchronous infection of the cell population, a moi = 10 was used. Due to the relatively low cell concentration at time of infection (2.1 × 106 cells/mL) and the high moi used, neither medium replacement nor trypsin addition (for virus activation) was necessary. In both cultivations, sterile Milli-Q water was added before sampling to compensate for water evaporation (1–2 mL/day) since the experiment was performed in a non-hydrated incubator.

Source from:

The FAI climbed 5.9 percent year-on-year in the first 11 months of 2018, quickening from the 5.7-percent growth in Jan-Oct, the National Bureau of Statistics (NBS) said Friday in an online statement.

The key indicator of investment, dubbed a major growth driver, hit the bottom in August and has since started to rebound steadily.

In the face of emerging economic challenges home and abroad, China has stepped up efforts to stabilize investment, in particular rolling out measures to motivate private investors and channel funds into infrastructure.

Friday's data showed private investment, accounting for more than 60 percent of the total FAI, expanded by a brisk 8.7 percent.

NBS spokesperson Mao Shengyong said funds into weak economic links registered rapid increases as investment in environmental protection and agriculture jumped 42 percent and 12.5 percent respectively, much faster than the average.

In breakdown, investment in high-tech and equipment manufacturing remained vigorous with 16.1-percent and 11.6-percent increases respectively in the first 11 months. Infrastructure investment gained 3.7 percent, staying flat. Investment in property development rose 9.7 percent, also unchanged.