Reproductive Cycle of an Orthomyxoviridae in a Host Cell

Orthomyxovirus replication is depending on the presence of active host cell DNA, and also the virus RNA. It takes about 6 hours for the replication of the orthomyxovirus.

1. The virus attaches to the cells, which binds to cell membrane, containing acid which are the receptor for virus adsorption.

2. The virus is then engulfed by pinocytosis into endosomes.

3. The acid environemnt of the endosome causes the virus envelope to fuse with the plasma membrane of the endosome, uncoating the nucleocapsid and releasing it into the cytoplasm.

4. A transmembrane protein derived from the matrix gene (M2) forms an ion channel for protons to enter the virion and destabilize protein binding, allowing the nucleocapsid to be transported to the nucleus, where the genome is transcribed to yield viral mRNA.

5. The virus scavenges cap sequences from the nascent mRNA generated in the nucleus by transcription of the host DNA and attaches them to its own mRNA.

6. The viral mRNA was transported to the cytoplasm by those cap sequences, where it is translated by host ribosome.

7. The nucleocapsid is assembled in the nucleus.

8. The viral envelope hemagglutinin is subjected to proteolytic cleavage by host enzymes during budding. This process is necessary for the released particles to be infectious.

9. Newly synthesized virions have surface glycoproteins that contain N acetylneuraminic acid as a part of their carbohydrate structure.

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