The dengue virus type 2 envelope protein fusion peptide is essential for membrane fusion

Area of Science:

• Virology
• Molecular Biology
• Structural Biology

Background:

• The flaviviral envelope (E) protein is crucial for virus-mediated membrane fusion, a key step in the viral life cycle.
• Understanding the molecular mechanisms of flavivirus entry and fusion is vital for developing antiviral strategies.

Purpose of the Study:

• To investigate the requirement of specific amino acids (AAs) in the fusion peptide (FP) for optimal flavivirus membrane fusion and virus growth.
• To characterize the impact of FP mutations on viral replication, genetic stability, and infectivity.

Main Methods:

• Introduction of 27 unique mutations into the fusion peptide of a dengue 2 virus infectious cDNA clone.
• Recovery and characterization of seven stable mutant viruses.
• Assessment of fusion efficiency, growth kinetics, genetic stability, infectivity, and antibody reactivity.

Main Results:

• Mutant viruses showed impaired fusion efficiency, confirming the necessity of specific FP AAs for optimal fusion.
• Mutant viruses exhibited varied growth kinetics and genetic stabilities across different cell types and mosquitoes.
• Four lethal mutants could be recovered but were unable to re-infect cells, indicating a post-entry fusion blockade within endosomes.
• FP mutations reduced virus reactivity with flavivirus group-reactive antibodies.

Conclusions:

• Specific amino acids within the flavivirus fusion peptide are indispensable for efficient membrane fusion and productive viral infection.
• Fusion peptide mutations can lead to distinct defects in viral replication and assembly, including endosomal entrapment.
• These findings provide critical insights into flavivirus entry mechanisms and potential therapeutic targets.