Life Cycle of the Dengue Fever Virus — HHMI BioInteractive Video

Summary

The dengue virus, an RNA virus, infects immune cells by binding to receptors and entering via endocytosis. Its genome is translated into proteins, initiating replication within the host's cells. The virus matures, assembling new particles that bud off and travel to the cell surface, ready to infect other cells.

Takeaways

• 🦠 Dengue virus is an RNA virus with an outer lipid bilayer envelope and envelope proteins.
• 🔒 The virus targets immune cells and uses two key cell surface receptor molecules for infection: the cognate receptor and the Fc receptor.
• 🔗 The envelope protein of the virus binds to the cognate receptor, initiating receptor-mediated endocytosis.
• 🌡️ The lowered pH within the endosome triggers a conformational change in the envelope proteins, forming spike-like structures.
• 💉 The hydrophobic tips of the spikes penetrate the endosome's membrane, leading to the release of the capsid into the cytoplasm.
• 🧬 The viral RNA is a positive-sense strand, which can be directly translated into proteins by the host cell's machinery.
• 🔄 The viral RNA forms a circular structure, enabling it to be used as a template for both negative-sense and positive-sense RNA synthesis.
• 🛠️ Viral proteins, including a protease enzyme, are activated and aggregate to form the RNA replication complex.
• 🔗 The viral genome is translated as a single poly-protein chain, which is then cleaved into functional proteins.
• 🌐 New virus particles assemble with envelope proteins and capsid proteins, with viral RNA packaged inside, eventually maturing and being released to infect other cells.

Q & A

What type of virus is the Dengue virus?

The Dengue virus is an RNA virus.

What are the two cell surface receptor molecules important in Dengue infection?

The two important cell surface receptor molecules in Dengue infection are the cognate receptor and the Fc receptor.

What phenomenon is the Fc receptor involved in?

The Fc receptor is involved in a phenomenon called antibody-dependent enhancement.

How does the virus enter the host cell?

The virus enters the host cell through a process called receptor-mediated endocytosis, where it is internalized in a structure called the endosome.

What happens to the virus when the pH of the endosome interior is lowered by proton pumps?

When the pH of the endosome interior is lowered, the virus responds by changing the conformation of the envelope proteins to form spike-like structures.

How does the virus's envelope protein facilitate the release of the capsid into the cytoplasm?

The tips of the spikes formed by the envelope proteins are hydrophobic, allowing them to penetrate the endosome's membrane, leading to the fusion of the endosome's and virus's membranes and the release of the capsid into the cytoplasm.

Where does the viral RNA travel to after being released from the capsid?

After being released from the capsid, the viral RNA travels to the rough endoplasmic reticulum.

How is the viral RNA translated into proteins?

The viral RNA, being a positive-sense strand, can be directly translated into proteins. The ends of the RNA form structures that bind to translation initiation proteins, which attach to the ribosome to initiate translation.

What is the role of the protease enzyme in the viral replication process?

In the cytoplasm, a protease enzyme, which is one of the viral proteins, activates all the other proteins in the poly-protein chain, leading to the formation of the RNA replication complex.

How does the virus's RNA form a circle during replication?

The ends of the viral RNA fold up, allowing the RNA to form a circle, which then attaches to the replication complex to start the first round of synthesis.

What is the final step in the maturation of new Dengue viruses before they are released from the cell?

The final step in the maturation of new Dengue viruses is the processing of the pre-membrane protein before the virus reaches the cell surface, which allows the virus to become mature and be released to infect other cells.