Effect of influenza virus infection on key metabolic enzyme activities in MDCK cells

Background Influenza, or “flu”, is an upper respiratory tract infection caused by a virus belonging to the family of Orthomyxoviridae. Influenza can pose a serious risk to the health of mainly the elderly, the very young, and to people suffering from medical conditions (e.g. weak immune system). For example, seasonal influenza strains are fatal to more than 50,000 people annually in the United States alone [1]. The most effective measure for preventing influenzarelated morbidity and mortality is annual vaccination. Seasonal influenza vaccines are almost exclusively produced using the traditional egg-based manufacturing process. However, the main limitation of egg-based technology (especially in the case of a pandemic) is the time-consuming production process (~6 months). Furthermore, people with serious egg allergy cannot be vaccinated when trace amounts of egg protein remain in the final formulation. Therefore, new production processes using continuous cell lines for influenza vaccine manufacturing are currently being established [2]. Influenza viruses take advantage of the host cell metabolism to replicate their genetic material and to synthesize viral proteins. The influenza virus particle consists of three major parts: the ribonucleocapsid, the matrix protein M1, and the envelope, which is derived from the plasma membrane of the host cell. The lipid bilayer contains the ion channel protein M2 and the immunogenic glycoproteins hemagglutinin and neuraminidase [3]. The replication cycle of influenza viruses including entry, uncoating, genome transcription and replication, assembly and release has been studied extensively with type A strains [4]. So far, only few studies have characterized the influence of influenza infection on the central carbon metabolism of host cells [5]. Madin-Darby canine kidney (MDCK) cells are considered a suitable substrate for cell culture-based influenza vaccine manufacturing [2,6]. In this study, key metabolic enzyme activities were analyzed in MDCK cells infected with an influenza A virus strain to improve our understanding of virus-host cell interaction and cell response.