Activation of the NLRP3 inflammasome by vault nanoparticles expressing a chlamydial epitope

Abstract

The full potential of vaccines relies on development of effective delivery systems and adjuvants and is critical for development of successful vaccine candidates. We have shown that recombinant vaults engineered to encapsulate microbial epitopes are highly stable structures and are an ideal vaccine vehicle for epitope delivery which does not require the inclusion of an adjuvant. We studied the ability of vaults which were engineered for use as a vaccine containing an immunogenic epitope of C. trachomatis, polymorphic membrane protein G (PmpG), to be internalized into human monocytes and behave as a “natural adjuvant”. We here show that incubation of monocytes with the PmpG-1-vaults activates caspase-1 and stimulates IL-1β secretion through a process requiring the NLRP3 inflammasome and that cathepsin B and Syk are involved in the inflammasome activation. We also observed that the PmpG-1-vaults are internalized through a pathway that is transiently acidic and leads to destabilization of lysosomes. In addition, immunization of mice with PmpG-1-vaults induced PmpG-1 responsive CD4+ cells upon re-stimulation with PmpG peptide in vitro, suggesting that vault vaccines can be engineered for specific adaptive immune responses. We conclude that PmpG-1-vault vaccines can stimulate NLRP3 inflammasomes and induce PmpG-specific T cell responses.

Aggregatibacter actinomycetemcomitans Cytolethal Distending Toxin Activates the NLRP3 Inflammasome in Human Macrophages, Leading to the Release of Proinflammatory Cytokines

“…2). It should be noted that the characterization of these cells, including quantification of reduced expression levels relative to those in nontarget control cells, was previously reported (see Materials and Methods) (29)(30)(31)(32). Cdt induced a dose-dependent release of both IL-1␤ and IL-18 in macrophages derived from both wild-type and shRNA control (shCtl) THP-1 cells ( Fig.…”

“…We focused on the NLRP3 inflammasome and determined the requirement for NLRP3 and ASC by also depleting THP-1 cells of these components with specific shRNAs; these cells have been well characterized for reductions in expression levels (see Materials and Methods) (29,32). Macrophages derived from NLRP3-deficient cells produced significantly reduced levels of cytokines relative to the levels observed in shRNA control cells ( Fig.…”

“…Preparation of THP-1 cells stably expressing short hairpin RNA (shRNA) against caspase-1 (shCasp1), NLRP3 (shNLRP3), and ASC (shASC) as well as nontarget controls was previously described (29)(30)(31); these cells have been well characterized, and expression levels were quantified to be reduced Ͼ75% for shNLRP3, Ͼ95% for shASC, and Ͼ90% for shCasp1 cells, with no effect on the nontarget controls (32). THP-1 cells were differentiated into macrophages by incubating cells in the presence of 50 ng/ml phorbol myristate acetate (PMA) for 48 h, at which time the cells were washed and incubated an additional 24 h in medium prior to use.…”

Chlamydial polymorphic membrane proteins: regulation, function and potential vaccine candidates

“…In addition, mice immunized with the PmpG/nanoparticle vaccine induced PmpG-specific CD4+ T cells that were able to be restimulated with PmpG in vitro. 95 Whereas PmpEFGH + MOMP and adjuvants or PmpG + nanoparticles appear to be promising vaccine candidates for protection against C. trachomatis, PmpD may be an interesting candidate for protection against C. abortus which can cause ovine enzootic abortion and poses a risk to pregnant women. 6 Mice immunized with recombinant PmpD in a Vibrio cholerae ghost delivery system elicited a robust antigen-specific IFN-g, IgA and IgG2c immune response after genital C. abortus challenge.…”

Aminated nanomicelles as a designer vaccine adjuvant to trigger inflammasomes and multiple arms of the innate immune response in lymph nodes

“…39 When both BMDMs and BMDCs isolated from NLRP3 −/− mice were treated with aPNMs, the secretion of IL-1β was greatly inhibited (Figure 4A and B). This implies that the NLRP3 inflammasome-inducing pathway is closely related to the production of IL-1β by APCs treated with aPNMs.…”