ERdj5 in Innate Immune Cells Is a Crucial Factor for the Mucosal Adjuvanticity of Cholera Toxin

Abstract

Cholera toxin (CT) is one of most strong mucosal adjuvants, but it cannot be clinically used owing to its toxicity. The cytosolic A1 subunit of CT (CTA1) is the molecule responsible for its immunostimulatory activity, which increases the concentration of cyclic AMP and causes the induction of pro-inflammatory cytokines in innate immune cells. However, the importance of endoplasmic reticulum (ER) molecules involved in CTA1 retro-translocation to induce immune responses remained to be investigated. ERdj5 is an ER protein which is expected to transfer CTA1 to the Hrd1 complex for the retro-translocation of CTA1. In this study, we investigated the physiological relevance of ERdj5 in immune stimulation by CT. ERdj5-knockout (ERdj5 KO) mice had decreased production of antigen-specific IgG in the serum and IgA in the mucosal secretion after intranasal immunization with Ag and CT. Especially, IgG2c isotypes were specifically reduced in the absence of ERdj5. ERdj5 KO dendritic cells (DCs) failed to full activation with decreased expression of costimulatory molecules, such as MHC class II, CD80, and CD 86. In ERdj5 KO DCs, secretion of pro-inflammatory cytokines, such as IL-1β, TNF-α, and IL-6, was reduced. The cytokine signatures of several helper T cells were reduced in ERdj5 KO mice following intranasal CT immunization. The absence of ERdj5 affects the immunostimulatory properties of CT but does not affect the response to the CTB pentamer, the response to alum, total antibody production, or cytokine release from DCs exposed to CpG. Interestingly, CT enhanced the expression of ER stress proteins in ERdj5 KO innate immune cells. These results suggested that ERdj5 contributed as a decisive factor to the immunostimulatory capacity of CT via CTA1 retro-translocation.

Fine Epitope Mapping of the <em>Vibrio cholera</em> Toxins A, B, and P and an ELISA Assay

“…CTB is a nontoxic subunit that produces target cells blocking antibodies and is a potent mucosal immunostimulatory adjuvant that can incite potent mucosal and system immune responses [47]. Because of the strong adjuvanticity of CTB, it is applied in different peptide and DNA vaccines such as microbial and cancer [48,49]. In addition to playing a role as an immunostimulatory adjuvant, CTB is also a powerful protective antigen.…”

Desenvolvimento e uso de vacinas mucosas: Potencial e limitações

“…The mucoadhesive delivery systems are quite varied, and their principle is to increase the retention time of antigens in the mucosa, interact with the epithelium of choice and increase the absorption and release of antigens. Delivery systems commonly used in the formulation of mucosal vaccines can be classified into two groups: particulate delivery systems for antigens and solutions (Kim et al, 2019). The first group consists of systems capable of partially protecting the antigen from enzymatic degradation in mucous secretions, involving the antigenic protein, thus making it less vulnerable to attacks by the local innate immune system.…”

“…The first group consists of systems capable of partially protecting the antigen from enzymatic degradation in mucous secretions, involving the antigenic protein, thus making it less vulnerable to attacks by the local innate immune system. Examples are emulsions, liposomes, virosomes, microspheres, immunostimulant compounds (ISCOMs) and pseudo viruses or virus-like particles (VLPs) (Villanova & Oréfice, 2010;Kim et al, 2019). The second group of delivery systems encompasses solutions where the antigen is dissolved or suspended, such as eggs and gels.…”

Immunomodulation as a Novel Strategy for Prevention and Treatment of Bordetella spp. Infections

“…CTA1 is the subunit responsible for the immunomodulatory activity in conjunction with ERdj5 in the endoplasmic reticulum, which is the target for CT. In the absence of ERdj5, mice failed to produce inflammatory cytokines, indicating that CT action requires ERdj5 (183). Similarly, the calcium-binding protein S100A4 is required for efficient antigen presentation and enhanced activity of CT, as it is necessary for the humoral and cellular response (184).…”

“…Similarly, the calcium-binding protein S100A4 is required for efficient antigen presentation and enhanced activity of CT, as it is necessary for the humoral and cellular response (184). CT has been tested as an adjuvant for pertussis vaccine and preliminary data suggests that it substantially improves mucosal protection by augmenting IgA levels (183,185), and it has even been suggested that this adjuvant may be safe for use in humans (186,187). Some studies have revealed that conjugation of CT with pertussis toxoid added to the current acellular vaccine (188) or Fimbriae (Fim2) (189) are highly promising candidates to improve the generation of protective immunity from these vaccines.…”