Sublingual immunization with recombinant GroEL plus CpG‐ODN inhibits Porphyromonas gingivalis‐induced inflammation and alveolar bone loss

Abstract

It has been reported that GroEL, a heat shock protein (HSP) produced by the representative periodontopathogenic bacterium, Porphyromonas gingivalis, induces inflammation-induced osteoclastogenesis and promotes alveolar bone resorption. In this study, we demonstrated the efficacy of a mucosal vaccine targeting GroEL against bone resorption induced by P. gingivalis. Female BALB/c mice received sublingual CpG oligodeoxynucleotide as an adjuvant with recombinant GroEL (rGroEL) prior to P. gingivalis exposure. Animals were euthanized 30 days after P. gingivalis inoculation.Sublingual immunization (SLI) with rGroEL elicited significant rGroEL-specific serum immunoglobulin (Ig)G and salivary IgA antibody (Ab) responses, and these responses were sustained for approximately 1 year. Interestingly, 10-fold more GroEL-specific IgA Ab-producing cells were detected in the submandibular glands (SMGs) than in the spleen. Antigen (Ag)-specific cells isolated from the spleen and SMGs induced significantly higher levels of IFN-γ expression after Ag restimulation in vitro. Flow cytometry illustrated that the frequency of CD11b + dendritic cells with enhanced expression of CD80, CD86, CD40, and major histocompatibility complex II molecules was significantly increased in the SMGs. Furthermore, SLI with rGroEL significantly suppressed P. gingivalis-induced alveolar bone resorption and P. gingivalis-stimulated tumor necrosis factor-α, interleukin-6, and HSP60 expression in the gingiva.These findings suggest that SLI with rGroEL and CpG oligodeoxynucleotide is a beneficial strategy for preventing periodontal disease, mainly by presenting Ags in the oral region and inducing antibody production in the mucosal and systemic systems.

Porphyromonas gingivalis Vaccine: Antigens and Mucosal Adjuvants

“…Consequently, HSP is viewed as a potential target for periodontal disease vaccines. Studies by Chang et al [ 12 ] and Lee et al [ 62 ] showed that immunization with HSP60 resulted in specific antibody responses, reducing inflammation and bone loss caused by Pg and other periodontal pathogens. This suggests that HSP60 could be a promising candidate for use as a vaccine against periodontal disease induced by various bacterial infections.…”

“…CpG oligodeoxynucleotides (CpG-ODN) are synthetic molecules designed to stimulate TLR9 by mimicking bacterial DNA at CpG sites, activating the natural immune system through this pathway. Studies by Chang et al utilized rGroEL as an antigen and CpG-ODN as an adjuvant for the sublingual immunization of BALB/c mice, showing that CpG-ODN significantly increased levels of rGroEL-specific serum IgG and sIgA antibodies, suggesting that this strategy could be effective in preventing periodontal disease by inducing specific antibodies in mucosal and systemic systems [ 12 ]. Additionally, research by Liu et al [ 92 ] using OMP and Bai et al [ 14 ] using a periodontitis gene vaccine (pVAX1-HA2-fimA) demonstrated that CpG-ODN effectively induced a mucosal sIgA response, inhibited inflammation, and reduced bone loss.…”

“…These studies demonstrated successful delivery of the target protein through the intestinal mucosa. Additionally, various studies have highlighted the efficacy of nasal [ 13 , 20 , 22 , 138 , 139 ] or sublingual [ 12 , 21 , 34 , 56 , 88 ] immunization routes, resulting in high levels of serum-specific IgG, IgA, and salivary sIgA. These antibodies have proven effective in preventing Pg-induced infections and alveolar bone loss.…”

“…As research has progressed, Pg vaccines have diversified in terms of their types and immunization methods. Given that Pg primarily colonizes the oral cavity, many studies focus on mucosal immune pathways [ 12 , 13 , 14 ], highlighting mucosal immunity as a promising approach for preventing Pg infections. This review delves into the three main factors (antigens, adjuvants, and immunization routes) involved in developing Pg vaccines, outlining the challenges encountered in research.…”