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Abstract

Viruses depend on the metabolic machinery of living cells, which provide energy and macromolecular precursors for their replication. However, there still is a lack of detailed knowledge regarding the impact of virus replication on host cell metabolism. To improve our understanding of virus-host cell interaction and cell response, the activities of 28 key enzymes from central carbon metabolism were analyzed in adherent Madin-Darby canine kidney (MDCK) cells infected with influenza virus A/Puerto Rico/8/34 (H1N1) from the Robert Koch Institute. Adherent MDCK cells were cultured in 6-well plates with glutamine-containing GMEM medium until stationary growth phases were reached (~5 d). The cells were then either mock-infected as control or infected with H1N1 at a multiplicity of infection of 20. Enzyme activities were then determined 9 hours post infection. Significant changes in catalytic activity were found for 9 different enzymes in infected cells compared to mock-infected MDCK cells: glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase from the pentose phosphate pathway, glutaminase and malic enzyme from glutaminolysis, pyruvate carboxylase, citrate synthase, citrate lyase and isocitrate dehydrogenase from the citric acid cycle, and acetate-CoA-ligase. The cells seemed to respond to viral infection with an up-regulation of enzyme activity by at least 20 %. This most likely took place in order to compensate for the metabolic imbalance caused by viral replication. It could be shown that some key enzymes producing NADPH and acetyl-CoA for fatty acid synthesis were increased. Hence, fatty acid synthesis might play a crucial role for the replication of influenza viruses as the viral envelope consists of membrane lipids derived from the host cell membrane. On the one hand the virus potentially forces its host cell to produce new membrane lipids for the budding process and on the other hand the host cell tries to compensate for the membrane loss.