Characterization of the biological activity of a panel of TLR5 agonists

MARINA BIEDMA; ANDRES H. ROSSI; JULIEN TABAREAU; PAULA M. BERGUER; JEAN CLAUDE SIRARD; MARTIN RUMBO

Buenos Aires

Congreso; International Joint Meeting between the Latin American Society for Immunodeficiencies (LASID-IV Meeting), the Argentinean Society for Immunology (SAI-LVIII Meeting), and the French Society for Immunology (SFI); 2015

SAI

Flagellin(FliC) activates innate immune responses via its recognition by Toll-likereceptor 5 (TLR5) and adaptive immunity in the host. TLR5 is a receptor widelydistributed in mucosal epithelia and FliC, has been proposed as mucosaladjuvant. The structure of FliC includes four domains, D0 and D1 are involvedin TLR5 activation, whereas D2 and D3 contain the main antigenic sites of themolecule. However, the contribution of D2 and D3 to TLR5 activation has notbeen fully elucidated. In this study, we evaluated 11 different deletionvariants of FliC affecting D2 and D3 domains using wild type FliC as reference.We found that the deletions affect differentially the capacity to trigger TLR5in vitro. Circular dichroism (CD) analysis indicates that FliC mutantsconserved mostly the secondary structure present in the wt molecule andunderwent a reversible thermal transition between 31 and 43 °C. The deletionsin D2-D3 domains resulted in low capacity to elicit anti-flagellin antibodies,however, all variants were able to trigger in vivo innate response activationat dose of 1 ug. Furthermore, to characterize the adjuvant properties, weassessed antibodies responses to OVA following i.n. co-immunizations.Recombinant FliCs present mucosal adjuvant activity that correlates with TLR5activating capacity. The highest adjuvant capacity was shown by variants whichhave a potency to trigger TLR5 activation comparable to flagellin wt. Ourresults indicate that flagellin deletion variants showing maximal TLR5activating capacity have the most promising features to be used as mucosaladjuvants.