Plant-based vaccines against influenza

Abstract

Influenza is an infectious disease with a high worldwide impact on human health, caused by RNA viruses of the family Orthomyxoviridae. Influenza spreads around the world in seasonal epidemics that occur in most of the cases during the fall or winter, resulting in about three to five million cases of severe illness yearly and about 250,000-500,000 deaths yearly rising up to millions in some pandemic years. The high rate of rearrangements and genetic recombination as well as the accumulation of mutations through replication cycles result in the generation of new strains every season, a capacity that evolves this pathogen to a pandemic behavior and thus demands a periodic development of strain-specific vaccines. Vaccine development for new strains takes between 6 and 8 months, which limits the establishment of rapid immunization programs against the emerging strains. In view of these particular immunization needs, the concept of plant-based vaccines has been vastly applied to influenza during the past decade, mainly by means of transient expression systems. This has allowed for the successful production of virus-like particles (VLPs) at high enough levels to be purified and used to formulate parenteral vaccines. These platforms have yielded highly immunogenic and immunoprotective formulations, assessed in test animals and phase I clinical trials. Some of the candidates are under phase II clinical evaluation and manufacturing at the pilot level. Therefore, influenza plant-based vaccines have reached an advanced degree of development and some candidates seem to be the closest plant-derived vaccines to be marketed in the near future; thus, overcoming the valley of death is almost a reality for these candidates.