Viral vectors: a look back and ahead on gene transfer technology

The virus life cycle has two main steps: infection and replication. Infection starts with recognition of the target cell, proceeds with virus entry into the cell (and neutralization of various host defenses) to terminate with the release of the viral genome in a cell location suitable for replication. Replication starts with the expression cascade of viral genes to proceed with the synthesis of viral genome copies. Viral proteins and genomes are then conveyed to a specific “meeting point” where