The Respiratory Commensal Bacterium Corynebacterium pseudodiphtheriticum as a Mucosal Adjuvant for Nasal Vaccines

Abstract

Previously, we demonstrated that nasally administered Corynebacterium pseudodiphteriticum 090104 (Cp) or its bacterium-like particles (BLPs) increase the resistance of mice against bacterial and viral respiratory pathogens by modulating the innate immunity. In this work, we evaluated the ability of Cp and BLPs to stimulate alveolar macrophages, and to enhance the humoral immune response induced by a commercial vaccine against Streptococcus pneumoniae. In the first set of experiments, Cp or the BLPs were incubated with primary cultures of murine alveolar macrophages and the phagocytic activity, and the production of cytokines was evaluated. The results revealed that Cp and BLPs were efficiently phagocyted by respiratory macrophages and that both treatments triggered the production of TNF-α, IFN-γ, IL-6, and IL-1β. In the second set of experiments, 3-week-old Swiss mice were intranasally immunized at days 0, 14, and 28 with the pneumococcal vaccine Prevenar®13 (PCV), Cp + PCV, or BLPs + PCV. On day 33, samples of bronco-alveolar lavages (BAL) and serum were collected for the study of specific antibodies. In addition, immunized mice were challenged with S. pneumoniae serotypes 6B or 19F on day 33 and sacrificed on day 35 (day 2 post-infection) to evaluate the resistance to the infection. Both Cp + PCV and BLPs + PCV groups had higher specific serum IgG and BAL IgA antibodies than the PCV control mice. In addition, the mice that were immunized with Cp + PCV or BLPs + PCV had lower lung and blood pneumococcal cell counts as well as lower levels of BAL albumin and LDH, indicating a reduced lung damage compared to the control mice. Improved levels of anti-pneumococcal antibodies were also detected in the serum and BAL samples after the challenges with the pathogens. The results demonstrated that C. pseudodiphteriticum 090104 and its bacterium-like particles are capable of stimulating the respiratory innate immune system serving as adjuvants to potentiate the adaptive humoral immune response. Our study is a step forward in the positioning of this respiratory commensal bacterium as a promising mucosal adjuvant for vaccine formulations aimed at combating respiratory infectious diseases.

Bacterium-like Particles from Corynebacterium pseudodiphtheriticum as Mucosal Adjuvant for the Development of Pneumococcal Vaccines

“…This observation aligns with our earlier findings, which focused on early infection assessed at day 2 post-challenge [11]. The protective effect can be credited to the bolstering of innate immunity and the heightened activation of antigen-presenting cells [11,13], resulting in a strengthening of both humoral and cellular adaptive immune responses. The impact of Cp 090104 and CP-derived BLPs on adaptive immunity was apparent in the increased levels of antibodies, TNF-α, IFN-γ, and IL-4 found in the respiratory mucosa and bloodstream of the treated mice compared with the control mice.…”

“…(b) Cp 090104 and CP-derived BLPs enhance the adaptive immune responses induced by pneumococcal vaccines and boost resistance to primary pneumococcal infection. Our previous research showed that nasal priming with Cp 090104 and CP-derived BLPs enhances the effectiveness of the pneumococcal conjugate vaccine Prevenar ® 13 (PCV) by acting as mucosal adjuvants [13]. This study aimed to further investigate the adjuvant properties of Cp 090104 or CP-derived BLPs.…”

“…Subsequently, the bacteria were suspended in sterile PBS [11]. The production of BLPs ensued through a heat-chemical treatment, and was executed in adherence to previously delineated protocols [13]. Briefly, the Cp 090104 strain underwent a thorough wash with sterile water (13,000× g for 10 min) and was then immersed in 0.1 M HCl before being boiled 45 min in a water bath.…”

“…Recently, we evaluated the capacity of Cp 090104 and CP-derived BLPs, when coadministered with the pneumococcal vaccine Prevenar ® 13 via the nasal route, to improve the protection of mice against pneumococcal infection [13]. It was found that the Cp 090104 strain and the CP-derived BLPs stimulated the respiratory innate immune system, serving as adjuvants to enhance the specific antibody response against the vaccine, which contains 13 pneumococcal capsular polysaccharides all conjugated to the CRM197 carrier protein.…”

“…It was found that the Cp 090104 strain and the CP-derived BLPs stimulated the respiratory innate immune system, serving as adjuvants to enhance the specific antibody response against the vaccine, which contains 13 pneumococcal capsular polysaccharides all conjugated to the CRM197 carrier protein. This immunomodulatory effect of Cp 090104 and the CP-derived BLPs correlated with significantly lower lung and blood counts of the pathogen in the mice challenged with S. pneumoniae serotypes 6B or 19F [13]. In this work, we aimed to advance the characterization of the adjuvant properties of Cp 090104 and the CP-derived BLPs and their capacities to enhance mucosal and systemic responses to pneumococcal vaccines.…”