Lecture 2. Introduction to Viral Replication - Influenza Virus Replication 1 Flashcards
What happens in the attachment stage of viral replication?
Binding to a cell surface receptor; primary determinant of tropism (specificity of what types of cells/what organism a virus can infect)
What happens in the entry stage of viral replication?
Enveloped viruses fuse with cell or endosomal membrane
Non-enveloped viruses endocytosed
What happens in the uncoating stage of viral replication?
Structural proteins of virus disassemble to release genome
What happens in the biosynthesis stage of viral replication?
Genome is replicated
Viral proteins are synthesised
What happens in the assembly stage of viral replication?
Viral proteins form particle structure; genome is packaged; envelope may be acquired
What happens in the exit stage of viral replication?
Viral particles leave cell by budding (normally enveloped viruses), exocytosis, cell lysis; virion maturation may occur (HIV)
How do viruses synthesise their proteins from mRNA?
Viruses use host cell ribosomes and translation machinery
Because different viruses have different genomes, what have the different viruses developed in terms of replication?
They therefore have different strategies for genome replication and synthesis of mRNA
What do almost all viruses carry?
Their own polymerases
What can viral dsDNA be?
Linear e.g. Adenoviruses
Circular e.g. Herpesviruses
Gapped e.g. Hepatitis B virus
What can viral ssDNA be?
+ve or –ve sense e.g. Parvoviruses
What can viral dsRNA be?
Segmented e.g Rotavirus
Non-segmented e.g yeast L-A virus
What can viral ssRNA be?
+ve sense e.g Poliovirus, HIV
-ve sense segmented e.g Influenza
-ve sense non-segmented e.g Measles
Ambisense (some genes coded in one direction and others in a different direction) e.g Arenaviruses
What are Baltimore class 1 viruses, how do they replicate and how are they transcribed?
dsDNA viruses (e.g Herpesvirus)
Replicate self using viral DNA polymerase
Transcribed into +ve sense mRNA by post-cell RNA polymerase
What are Baltimore class 2 viruses, how do they replicate and how are they transcribed?
ssDNA viruses (e.g Paroviruses)
Replicate using dsDNA intermediate from host DNA polymerase
Transcribed into +ve sense mRNA by post-cell RNA polymerase
What are Baltimore class 3 viruses, how do they replicate and how are they transcribed?
dsRNA viruses (e.g Rotavirus)
Replicate using +ve sense mRNA intermediate from host
Transcribed into +ve sense mRNA using own RNA polymerase
What are Baltimore class 4 viruses, how do they replicate and how are they translated?
ssRNA +ve sense viruses (e.g Coronavirus, Poliovirus)
Replicate using dsRNA replicative intermediate
Can be translated directly into protein
What are Baltimore class 5 viruses, how do they replicate and how are they transcribed?
ssRNA -ve sense viruses (e.g Influenza)
Replicate using dsRNA replicative intermediate
Transcribed into +ve sense mRNA using -ve sense ssRNA genome as a template