Uptake and disposition of recombinant chimeric immunogens constructed from Streptococcus mutans SBR-CTA2/B at mucosal immune inductive sites (100.35)

Abstract

Abstract Purpose: To investigate cellular pathways of uptake and processing of the recombinant chimeric immunogen SBR-CTA2/B consisting of the saliva-binding region (SBR) of S. mutans AgI/II coupled to cholera toxin A2/B subunits, in comparison with SBR alone. Methods: Amnis ImageStream technology was used to characterize cells from lamina propria (LP), Peyer’s patch (PP), and mesenteric lymph nodes (MLN) of mice before and 2, 4, 16, and 48h after intragastric immunization with FITC-labeled proteins. Dendritic cells (DC) were stained for phenotypic markers and the migration receptor CCR7 using contrasting fluorochromes. Results: LP CD103+, CD11c+, and especially CD103/CD11c double+ DC took up SBR-CTA2/B through 4h, after which the proportion of antigen-containing DC stayed level until 16h, although the number of DCs continued to increase. DCs in PP captured SBR-CTA2/B through 16h. The proportion of LP DCs containing SBR peaked at 2h and declined by 16h. CCR7 expression by CD11c+ LP DCs taking up SBR-CTA2/B rose at 2h and dropped at 4h, whereas CCR7 expression by DC taking up SBR declined from 0h levels. In MLN the number of CD11c+/CD4+ cell doublets dramatically increased at 48 h after SBR-CTA2/B immunization. Conclusions: Compared to SBR alone, the chimeric protein SBR-CTA2/B enhanced the functional activation of DCs in LP and PP, in which most antigen uptake occurred within the first few hours. DCs loaded with protein may then migrate to MLN and intercommunicate with T cells.