Recombinant flagellins with deletions in domains D1, D2, and D3: characterization as novel immunoadjuvants.

TABAREAU, JULIEN; MORENO, GRISELDA; PARISI, GUSTAVO; RUMBO, MARTIN; CAYET, DELPHINE; IVI?AK-KOCJAN, KAROLINA; SOULARD, DAPHNÉE; BERGUER, PAULA; BIEDMA, MARINA E.; ROSSI, ANDRÉS H.; ERREA, AGUSTINA; JERALA, ROMAN; SIRARD, JEAN CLAUDE

VACCINE

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2019 vol. 37 p. 652 - 663

0264-410X

Bacterial flagellin activates the innate immune system and ultimately the adaptive immune systemthrough a Toll-like receptor 5 (TLR5)-dependent signaling mechanism. Given that TLR5 is widely distributed in epithelia, flagellin is currently being developed as a mucosal adjuvant. Flagellin FliC fromSalmonella enterica has four domains: the conserved D0 and D1 domains and the hypervariable D2 andD3 domains. The deletion of D3 and partial deletion of D2 in the recombinant FliCD174-400 stronglyimpairs flagellin?s intrinsic antigenicity but does not affect the TLR5-dependent immunostimulationactivity, i.e., the capacity to promote innate responses and adaptive responses to co-administered antigens. Here, we describe the development of novel recombinant flagellins with various deletions encompassing all of D2 and D3, and part of D1. Most of the recombinant molecules conserved an a-helicalsecondary structure that was as resistant to heat denaturation as the native protein. Whereas the recombinant flagellins? ability to trigger TLR5 varied markedly in vitro, most gave equivalent in vivo TLR5-dependent innate immune responses following intranasal administration of 2 lg of flagellin to mice.Concordantly, the recombinant flagellins were also valuable respiratory adjuvants for eliciting antibodyresponses to the foreign antigen ovalbumin, although their intrinsic antigenicity was decreased compared to the native flagellin and not increased compared to FliCD174-400. Our results show that the additional deletions of D2 and the distal part of D1 of FliCD174-400 does not impact on antigenicity and does notsignificantly modify the immunostimulatory adjuvant activity. Altogether, this study generated a novelset of recombinant flagellin that constitutes a portfolio of TLR5-dependent candidate adjuvants forvaccination.