Deimmunization of flagellin for repeated administration as a vaccine adjuvant.
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ABSTRACT:
SUBMITTER: Khim K
PROVIDER: S-EPMC8438039 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The activity of the potent nasal adjuvant flagellin depends on initial activation of airway epithelilal cells. This study aims at investigating the immune cells involved in the antigen presentation within the respiratory tract. First, microarrays characterized that activation/recruitment of immune cells was the main signature of flagellin activation in lung. Neutrophils and classical monocytes were strongly recruited into the lungs and take up antigen upon nasal administration of flagellin. In contrast, the numbers of lung CD11b+ or CD103+ DC and alveolar macrophages were not enhanced although these cells were very efficient in antigen uptake. Our experiments showed that CD11b+ DC but not monocytes, PMN, CD103+ DC are not essential for the adjuvant effect. Flagellin signaling enhanced the functional activation of lung CD11b+ conventional DC and their migration to the lymph nodes. Using Cd11c-DTR mice, CD11b+ DC from lymph nodes were identified as the major stimulators of CD4 T cell activation. Finally, the migration and maturation of mucosal DC was independent of direct signaling, highlighting the contribution of epithelial factors in the mucosal adjuvant effect of flagellin. In conclusion, these data demonstrate that adjuvant activity can be dissociated from inflammatory cell recruitment an open new perpectives for improvement of vaccines.
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Project description:Flagellin's potential as a vaccine adjuvant has been increasingly explored over the last three decades. Monomeric flagellin proteins are the only known agonists of Toll-like receptor 5 (TLR5). This interaction evokes a pro-inflammatory state that impacts upon both innate and adaptive immunity. While pathogen associated molecular patterns (PAMPs) like flagellin have been used as stand-alone adjuvants that are co-delivered with antigen, some investigators have demonstrated a distinct advantage to incorporating antigen epitopes within the structure of flagellin itself. This approach has been particularly effective in enhancing humoral immune responses. We sought to use flagellin as both scaffold and adjuvant for HIV gp41 with the aim of eliciting antibodies to the membrane proximal external region (MPER). Accordingly, we devised a straightforward step-wise approach to select flagellin-antigen fusion proteins for gene-based vaccine development. Using plasmid DNA vector-based expression in mammalian cells, we demonstrate robust expression of codon-optimized full length and hypervariable region-deleted constructs of Salmonella enterica subsp. enterica serovar Typhi flagellin (FliC). An HIV gp41 derived sequence including the MPER (gp41607-683) was incorporated into various positions of these constructs and the expressed fusion proteins were screened for effective secretion, TLR5 agonist activity and adequate MPER antigenicity. We show that incorporation of gp41607-683 into a FliC-based scaffold significantly augments gp41607-683 immunogenicity in a TLR5 dependent manner and elicits modest MPER-specific humoral responses in a mouse model.
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