Enhancing the Yield and Quality of Influenza Virus-likeParticles (VLPs) Produced in Insect Cells by Inhibiting CytopathicEffects of Matrix Protein M2

To provide broader protection and eliminate the need for annual update of influenza vaccines, biomolecular engineering of influenza virus-like particles (VLPs) to display more conserved influenza proteins such as the matrix protein M2 has been explored. However, achieving high surface density of full-length M2 in influenza VLPs has been left unrealized. In this study, we show that the ion channel activity of M2 induces significant cytopathic effects in Spodoptera frugiperda (Sf9) insect cells when expressed using M2-encoding baculovirus. These effects include altered Sf9 cell morphology and reduced baculovirus replication, resulting in impaired influenza protein expression and thus VLP production. On the basis of the function of M2, we hypothesized that blocking its ion channel activity could potentially relieve these cytopathic effects, and thus restore influenza protein expression to improve VLP production. The use of the M2 inhibitor amantadine indeed improves Sf9 cellular expression not only of M2 (∼3...