As a naturally occurring nanocapsule abundantly expressed in nearly all-eukaryotic cells, the barrel-shaped vault particle is perhaps an ideal structure to engineer for targeting to specific cell types. Recombinant vault particles self-assemble from 96 copies of the major vault protein (MVP), have dimensions of 72.5 × 41 nm, and have a hollow interior large enough to encapsulate hundreds of proteins. In this study, three different tags were engineered onto the C-terminus of MVP: an 11 amino acid epitope tag, a 33 amino acid IgG-binding peptide, and the 55 amino acid epidermal growth factor (EGF). These modified vaults were produced using a baculovirus expression system. Our studies demonstrate that recombinant vaults assembled from MVPs containing C-terminal peptide extensions, display these tags at the top and bottom of the vault on the outside of the particle, and can be used to specifically bind the modified vaults to epithelial cancer cells (A431) via the epidermal growth factor receptor (EGFR), either directly (EGF modified vaults) or as mediated by a monoclonal antibody (anti-EGFR) bound to recombinant vaults containing the IgG-binding peptide. The ability to target vaults to specific cells represents an essential advance towards using recombinant vaults as delivery vehicles.

BackgroundGeneration of robust cell-mediated immune responses at mucosal surfaces while reducing overall inflammation is a primary goal for vaccination. Here we report the use of a recombinant nanoparticle as a vaccine delivery platform against mucosal infections requiring T cell-mediated immunity for eradication.Methodology/Principal FindingsWe encapsulated an immunogenic protein, the major outer membrane protein (MOMP) of Chlamydia muridarum, within hollow, vault nanocapsules (MOMP-vaults) that were engineered to bind IgG for enhanced immunity. Intranasal immunization (i.n) with MOMP-vaults induced anti-chlamydial immunity plus significantly attenuated bacterial burden following challenge infection. Vault immunization induced anti-chlamydial immune responses and inflammasome formation but did not activate toll-like receptors. Moreover, MOMP-vault immunization enhanced microbial eradication without the inflammation usually associated with adjuvants.Conclusions/SignificanceVault nanoparticles containing immunogenic proteins delivered to the respiratory tract by the i.n. route can act as “smart adjuvants” for inducing protective immunity at distant mucosal surfaces while avoiding destructive inflammation.

SummaryInfection of epithelial cells by the intracellular pathogen, Chlamydia trachomatis , leads to activation of NFk B and secretion of pro-inflammatory cytokines. We find that overexpression of a dominant-negative Nod1 or depletion of Nod1 by RNA interference inhibits partially the activation of NF-k B during chlamydial infection in vitro , suggesting that Nod1 can detect the presence of Chlamydia . In parallel, there is a larger increase in the expression of pro-inflammatory genes following Chlamydia infection when primary fibroblasts are isolated from wild-type mice than from Nod1 -deficient mice. The Chlamydia genome encodes all the putative enzymes required for proteoglycan synthesis, but proteoglycan from Chlamydia has never been detected biochemically. Since Nod1 is a ubiquitous cytosolic receptor for peptidoglycan from Gram-negative bacteria, our results suggest that C. trachomatis and C. muridarum do in fact produce at least the rudimentary proteoglycan motif recognized by Nod1. Nonetheless, Nod1 deficiency has no effect on the efficiency of infection, the intensity of cytokine secretion, or pathology in vaginally infected mice, compared with wild-type controls. Similarly, Rip2, a downstream mediator of Nod1, Toll-like receptor (TLR)-2, and TLR4, increases only slightly the intensity of chlamydial infection in vivo and has a very mild effect on the immune response and pathology.Thus, Chlamydia may not produce sufficient peptidoglycan to stimulate Nod1-dependent pathways efficiently in infected animals, or other receptors of the innate immune system may compensate for the absence of Nod1 during Chlamydia infection in vivo .