Secreted NS1 Protects Dengue Virus from Mannose-Binding Lectin-Mediated Neutralization

Area of Science:

• Virology
• Immunology
• Glycobiology

Background:

• Flavivirus nonstructural protein 1 (NS1) is crucial for viral replication and pathogenesis.
• The secretion and properties of NS1 in insect cells remain incompletely understood.

Purpose of the Study:

• To confirm and characterize the secretion of NS1 from insect cells during dengue virus (DENV) infection.
• To investigate the biochemical and functional properties of insect cell-derived NS1.
• To explore the interaction of NS1 with complement proteins and its role in immune evasion.

Main Methods:

• Culturing DENV-infected insect cells and analyzing secreted NS1.
• Characterizing N-linked glycans, physical properties, and oligomerization of NS1.
• Performing binding assays with complement proteins (C1s, C4, C4-binding protein, MBL).
• Detecting NS1 and DENV in Aedes aegypti mosquito saliva.

Main Results:

• Confirmed secretion of NS1 from DENV-infected insect cells.
• Insect cell-derived NS1 contains high mannose glycans, unlike mammalian NS1.
• Insect cell NS1 exhibits smaller, heterogeneous sizes and less stable hexamers.
• NS1 binds to C1s, C4, C4-binding protein, and mannose-binding lectin (MBL).
• NS1-MBL binding protects DENV from MBL-mediated neutralization.
• Secreted NS1 and DENV were found together in mosquito saliva.

Conclusions:

• Insect cell-derived NS1 possesses distinct glycan profiles and physical characteristics.
• NS1 interaction with MBL represents a novel viral immune evasion strategy.
• NS1 secretion in mosquito saliva suggests a mechanism for early-stage viral transmission and immune evasion.