1. Cap-snatching: The influenza virus lacks its cap structure necessary for initiating transcription. Instead, it steals the 5' cap structure from host cell mRNAs through a process called cap-snatching. This allows the viral RNA to be recognized by the host cell's translation machinery and efficiently translated into viral proteins.
2. Multipartite genome: The influenza virus genome consists of eight separate RNA segments. This segmentation allows for genetic reassortment between different viral strains, which contributes to the rapid evolution and emergence of new influenza viruses.
3. Error-prone RNA polymerase: The influenza virus RNA polymerase lacks proofreading activity, leading to a high mutation rate in the viral RNA. This genetic variation generates diversity within the viral population, facilitating adaptation to changing host environments and immune responses.
4. Nuclear export of viral RNA: After transcription in the nucleus, viral RNA must be efficiently exported to the cytoplasm for translation and replication. Influenza viruses encode specific viral proteins, such as the nuclear export protein (NEP), that mediate the nuclear export of viral RNA.
5. Regulation of host cell transcription and translation: Influenza viruses manipulate host cell transcription and translation to favor viral RNA synthesis and replication. They achieve this by interfering with host mRNA splicing, translation initiation, and protein degradation pathways, leading to the shutdown of host cell processes and the redirection of cellular resources toward viral replication.
6. Assembly of the viral replication complex: The influenza virus forms specialized replication complexes within the cytoplasm of infected cells. These complexes consist of viral RNA, viral proteins (including the RNA-dependent RNA polymerase), and host factors. The replication complex provides an organized environment for efficient viral RNA replication and transcription.
7. Immune evasion: Influenza viruses have evolved mechanisms to evade the host immune response, including the ability to rapidly change their surface proteins, hemagglutinin (HA), and neuraminidase (NA). These changes help the virus escape recognition by antibodies and allow for persistent infection and transmission.
Collectively, these mechanisms enable the influenza virus to efficiently replicate its RNA genome, produce new viral particles, and spread within the host, leading to the symptoms of influenza infection.
