Truncated flagellin lacking the hypervariable region: A structural basis for improved immune responses and...

Area of Science:

• Immunology
• Vaccinology
• Microbial Pathogenesis

Background:

• Bacterial flagellins are potent immunomodulators with vaccine adjuvant potential.
• Flagellins activate innate and adaptive immunity via Toll-like receptor 5 (TLR5) and NLRC4 inflammasome signaling.
• Understanding flagellin structure-function relationships is key to optimizing adjuvant properties.

Purpose of the Study:

• To investigate the impact of truncated flagellin derivatives on TLR5 activation.
• To evaluate the adjuvant properties of flagellin mutants lacking specific domains.
• To identify flagellin domains critical for immune activation and adjuvant efficacy.

Main Methods:

• Generation of truncated flagellin mutants from Escherichia coli (EHEC EDL933).
• In vitro assessment of TLR5 activation by flagellin derivatives.
• In vivo evaluation of immunoadjuvant effects using a model antigen.

Main Results:

• Flagellin variants lacking the hypervariable region (HVR) but retaining terminal domains (FliC_H7, FliC_NC, FliC_H7-FaeG, FliC_NC-FaeG) significantly enhanced TNF-α and IL-8 production.
• The FliC_NC mutant showed TLR5 activation comparable to native flagellin.
• Truncated flagellins induced higher antibody titers when used as adjuvants or fusion proteins.

Conclusions:

• The HVR is not essential for flagellin's immunoadjuvant activity.
• Conserved terminal regions are crucial for TLR5 activation.
• Optimized flagellin derivatives, particularly those lacking the HVR, offer a potent platform for vaccine development to enhance immune responses.