Developing an effective and safe recombinant vaccine requires microbe-specific antigens combined with an adjuvant/delivery system to strengthen protective immunity. In this study, we designed and expressed a multivalent, recombinant polypeptide antigen (rCpa1) that consists of three previously identified antigens (i.e., Ag2/Pra, Cs-Ag and Pmp1) and 5 pathogen-derived peptides with high affinity for human MHC II molecules. The purified rCpa1 was encapsulated into four types of yeast cell-wall particles containing various compositions of β-glucan, mannan and chitin or mixed with an oligonucleotide (ODN) containing 2 methylated dinucleotide CpG motifs. This multivalent antigen encapsulated into glucan-chitin particles (GCP-rCpa1) showed a significantly elevated reduction of fungal burden for human HLA-DR4 transgenic mice compared to the other tested adjuvant-rCpa1 formulations. Among the tested adjuvants GCPs and GPs were both capable of stimulating a mixed Th1 and Th17 response. Mice vaccinated with GCP-rCpa1 showed elevated IL-17 production in T-cell recall assays and early lung infiltration of activated Th1 and Th17 cells compared to GP-rCpa1-vaccinated mice. Both C57BL/6 and HLA-DR4 transgenic mice that were vaccinated with GCP-rCpa1 vaccine increased surivial compared to the mice received GCPs alone. Concurringly, GCP-rCpa1 vaccine stimulated enhanced infiltration of macrophages to engulf and process the vaccine for antigen presentation in the injection sites compared to GP-rCpa1 injection. This is the first attempt to systematically characterize the presentation of a multivalent coccidioidomycosis vaccine encapsulated with selected adjuvants which enhance protective cellular immune response to infection.

While it was long held that T cells were the primary mediators of multiple sclerosis (MS) pathogenesis, the beneficial effects observed in response to treatment with Rituximab, a monoclonal antibody (mAb) targeting CD20, shed light on a key contributor to MS that had been previously underappreciated: B cells. This has been reaffirmed by results from clinical trials testing the efficacy of subsequently developed B cell-depleting mAbs targeting CD20 as well as studies revisiting the effects of previous disease-modifying therapies (DMTs) on B cell subsets thought to modulate disease severity. In this review, we summarize current knowledge regarding the complex roles of B cells in MS pathogenesis and current and potential future B cell-directed therapies.

While the contribution of autoreactive CD4+ T cells to the pathogenesis of Multiple Sclerosis (MS) is widely accepted, the advent of B cell-depleting monoclonal antibody (mAb) therapies has shed new light on the complex cellular mechanisms underlying MS pathogenesis. Evidence supports the involvement of B cells in both antibody-dependent and -independent capacities. T cell-dependent B cell responses originate and take shape in germinal centers (GCs), specialized microenvironments that regulate B cell activation and subsequent differentiation into antibody-secreting cells (ASCs) or memory B cells, a process for which CD4+ T cells, namely follicular T helper (TFH) cells, are indispensable. ASCs carry out their effector function primarily via secreted Ig but also through the secretion of both pro- and anti-inflammatory cytokines. Memory B cells, in addition to being capable of rapidly differentiating into ASCs, can function as potent antigen-presenting cells (APCs) to cognate memory CD4+ T cells. Aberrant B cell responses are prevented, at least in part, by follicular regulatory T (TFR) cells, which are key suppressors of GC-derived autoreactive B cell responses through the expression of inhibitory receptors and cytokines, such as CTLA4 and IL-10, respectively. Therefore, GCs represent a critical site of peripheral B cell tolerance, and their dysregulation has been implicated in the pathogenesis of several autoimmune diseases. In MS patients, the presence of GC-like leptomeningeal ectopic lymphoid follicles (eLFs) has prompted their investigation as potential sources of pathogenic B and T cell responses. This hypothesis is supported by elevated levels of CXCL13 and circulating TFH cells in the cerebrospinal fluid (CSF) of MS patients, both of which are required to initiate and maintain GC reactions. Additionally, eLFs in post-mortem MS patient samples are notably devoid of TFR cells. The ability of GCs to generate and perpetuate, but also regulate autoreactive B and T cell responses driving MS pathology makes them an attractive target for therapeutic intervention. In this review, we will summarize the evidence from both humans and animal models supporting B cells as drivers of MS, the role of GC-like eLFs in the pathogenesis of MS, and mechanisms controlling GC-derived autoreactive B cell responses in MS.

Coccidioides is the causative agent of San Joaquin Valley fever, a fungal disease prevalent in the semiarid regions of the Americas. Efforts to develop a fungal vaccine over the last 2 decades were unsuccessful. A candidate antigen, Antigen 2 (Ag2), is notoriously difficult to express in Escherichia coli, and this study sought to accumulate the antigen at high levels in maize. Transformed maize lines accumulated recombinant Ag2 at levels >1 g/kg. Mice immunized with this antigen and challenged with live Coccidioides arthroconidia showed a reduction in the fungal load when Ag2 derived from either E. coli or maize was loaded into glucan chitin particles. A fusion of Ag2 to dendritic cell carrier peptide (DCpep) induced a T-helper type 17 response in the spleen when orally delivered, indicative of a protective immune response. The maize production platform and the glucan chitin particle adjuvant system show promise for development of a Coccidioides vaccine, but further testing is needed to fully assess the optimal method of administration.

The regulation of B cell activation and survival is a crucial control point for the maintenance of B cell tolerance in the germinal center (GC) and involves the coordination of several intracellular signaling pathways. Dysregulation of these pathways can lead to the production and survival of autoreactive memory B cells and plasma cells (PCs), resulting in autoimmune disease. The mitogen-activated protein kinase (MAPK) pathway is involved in the transduction of stimulating and apoptotic signals such as those received through the B cell receptor (BCR) and the Fas receptor (CD95), respectively. Extracellular signal regulated kinases 1 and 2 (ERK1/2), important effectors of this pathway, play a major role in B cell activation and survival. Though ERK2 specifically regulates the pro-apoptotic protein, Bmf, its role in regulating GC B cell selection is unknown. Our lab has developed a novel mouse model in which the deletion of Erk2 is accompanied by the expression of the fluorescent reporter protein, eYFP, allowing us to identify and isolate viable Erk2Δ B cells using flow cytometry. Preliminary data using this model has shown that peripheral Erk2Δ B cells express several surface markers associated with follicular T helper cell interactions and immunoglobulin class switching, such as DEC205 and CD80, respectively. Thus we hypothesize that ERK2 is a critical regulator of GC B cell selection. We are currently investigating the ability of Erk2Δ B cells to respond to various activating stimuli in vitro as well as to differentiate into antigen-specific PCs. Our results will contribute to a better understanding of the molecular programs involved in B cell selection, potentially offering new approaches to treating B cell-driven autoimmune diseases.