Vibrio cholerae ghosts (VCG) exert immunomodulatory effect on dendritic cells for enhanced antigen presentation and induction of protective immunity

Abstract

BackgroundWe previously showed that the Vibrio cholerae ghost platform (VCG; empty V. cholerae cell envelopes) is an effective delivery system for vaccine antigens promoting the induction of substantial immunity in the absence of external adjuvants. However, the mechanism by which these cell envelopes enhance immunity and stimulate a predominantly Th1 cellular and humoral immune response has not been elucidated. We hypothesized that the immunostimulatory ability of VCG involves dendritic cell (DC) activation.ObjectiveThe aims of this study were: a) to investigate the ability of DCs [using mouse bone marrow-derived DCs (BMDCs) as a model system] to take up and internalize VCGs; b) to evaluate the immunomodulatory effect of internalized VCGs on DC activation and maturation and their functional capacity to present chlamydial antigen to naïve and infection-sensitized CD4+ T cells and; c) to evaluate the ability of VCGs to enhance the protective immunity of a chlamydial antigen.ResultsVCGs were efficiently internalized by DCs without affecting their viability and modulated DC-mediated immune responses. VCG-pulsed DCs showed increased secretion of proinflammatory cytokines and expression of co-stimulatory molecules associated with DC maturation in response to stimulation with UV-irradiated chlamydial elementary bodies (UV-EBs). Furthermore, this interaction resulted in effective chlamydial antigen presentation to infection-sensitized but not naïve CD4+ T cells and enhancement of protective immunity.ConclusionsThe present study demonstrated that VCGs activate DCs leading to the surface expression of co-stimulatory molecules associated with DC activation and maturation and enhancement of protective immunity induced by a chlamydial antigen. The results indicate that the immunoenhancing activity of VCG for increased T-cell activation against antigens is mediated, at least in part, through DC triggering. Thus, VCGs could be harnessed as immunomodulators to target antigens to DCs for enhancement of protective immunity against microbial infections.

Chlamydia abortus Pmp18.1 Induces IL-1β Secretion by TLR4 Activation through the MyD88, NF-κB, and Caspase-1 Signaling Pathways

“…Culture of rPmp18.1 with BMDC resulted in the upregulated DC expression of MHC II and co-stimulatory molecules as well as TLR4 and intracellular NLRP3. These findings confirm the results of our previous studies reporting that inactivated chlamydial whole cell and subunit antigens stimulate the in vitro maturation of DCs (Eko et al, 2014 ; Pan et al, 2015 ). Engagement of CD40 on APCs has been demonstrated to lead to the up-regulated expression of MHC-II and CD80 and CD86n and production of inflammatory cytokines, such as TNF-α and IL-12 (Diehl et al, 2000 ).…”

“…A combination of CpG and FL used as a mucosal adjuvant was shown to enhance the immune responses of co-delivered antigens (Fukuyama et al, 2011 ; Asanuma et al, 2012 ). In addition, the Vibrio cholerae ghost (VCG) platform has been demonstrated to be an effective immunomodulator for both subunit and inactivated chlamydial antigens (Eko et al, 2014 ). VCG are empty bacterial cell envelopes derived from V. cholerae cells by protein E-mediated lysis.…”

Shift work influences the outcomes of Chlamydia infection and pathogenesis

“…Determination of concentrations of Chlamydia specific antibody isotypes, Immunoglobulin (Ig) IgG and IgG 2c , in vaginal lavage of ECD or control mice were measured by standard ELISA procedure described previously 13 , 69 . Briefly, 96-well microtiter plates (Nunc Life Technologies, Rochester, NY) were coated with 20 µg/ml of chlamydial antigen (i.e., UV-inactivated C. muridarum elementary bodies) in 50 µl of PBS at 4 °C overnight.…”

Salmonella Typhimurium, the major causative agent of foodborne illness inactivated by a phage lysis system provides effective protection against lethal challenge by induction of robust cell-mediated immune responses and activation of dendritic cells

“…Assessment of the ability of lysed JOL1950 cells to prime immature DCs, which are potent antigen-presenting cells, was used to evaluate the efficacy of the vaccine against Salmonella infection, since mature DCs differentiate by engulfing foreign proteins. It has been reported that BG produced by the expression of the PhiX174 lysis gene results in strong activation of DCs [ 44 , 45 ]. Major antigenic components preserved on BG, which are referred to as pathogen-associated molecular patterns (PAMPs), are recognized by toll-like receptors (TLRs) and other pathogen recognition receptors (PRRs), resulting in activation of mature DCs and subsequent induction of T-cell-related immune responses.…”