Notes animal Virus and Host Cell Interaction

Antiviruses and Complex Host Cells

• Antiviruses are more complex because they target more complex host cells.

• These host cells (eukaryotic) have more machinery.

• Replication happens in different locations within the host cell.

• These host cells have a nucleus and membrane-bound organelles.

Eukaryotic Hosts vs. Bacterial Cells

• In bacterial cells, protein synthesis everything happens in the cytoplasm.

• In eukaryotic hosts (animal cells), protein synthesis, some aspects happen in the nucleus.

• Transcription occurs in the nucleus of a eukaryotic cell.

• Translation happens in the endoplasmic reticulum.

• If a virus infects a eukaryotic cell, different parts of the virus might be synthesized in different locations within the cell.

Stages of Viral Infection

• The five stages (attachment, penetration, biosynthesis, maturation, release) still occur but with increased complexity.

Attachment

• The virus is specific in its attachment.

• It recognizes specific host cell receptors.

• This is based on host specificity, host range, and tissue tropism.

Penetration

• Penetration varies in animal viruses.

• Two methods: endocytosis or fusion.

• Difference from bacteriophage: In animal viruses, the entire nucleocapsid enters the host cell, unlike bacteriophages where only the nucleic acid enters.

Endocytosis vs. Fusion

• Fusion happens specifically for enveloped viruses.

• Enveloped viruses have an outer lipid bilayer layer (envelope) acquired from the host cell membrane.

• Endocytosis can happen in both enveloped and naked (non-enveloped) viruses.

Fusion

• Viral spike proteins on the envelope recognize receptor sites on the host cell.

• Example: COVID uses spike proteins to recognize the ACE2 receptor on the host cell.

• The viral envelope (lipid bilayer) fuses or merges into the host cell membrane (lipid bilayer).

• Analogy: A drop of water (viral envelope) blends into a glass of water (host cell membrane).