(b) PGA-co-PDL NPs prepared at pH 7
(b) PGA-co-PDL NPs prepared at pH 7.0 by double emulsion with encapsulated PspA4Pro. lungs. PGA-co-PDL/HCl-CS (291 nm) or CM-CS (281 nm) NPs produced smaller sizes compared to PLGA/HCl-CS (310 nm) or CM-CS (299 nm) NPs. Moreover, NPs formulated with HCl-CS possessed a positive charge (PGA-co-PDL +17 mV, PLGA + 13 mV) compared to those formulated with CM-CS (PGA-co-PDL ?20 mV, PLGA ?40 mV). PspA released from NPs formulated with HCl-CS preserved the integrity and biological activity, but CM-CS affected PspA binding to lactoferrin and antibody recognition. PspA adsorbed in PGA-co-PDL/HCl-CS NPs stimulated CD80+ and CD86+ cells, but this was lower compared to when PspA was encapsulated in PLGA/HCl-CS NPs, which also stimulated CD40+ and MHC II (I-A/I-E)+ cells. Despite no differences in IgG being observed between immunized animals, PGA-co-PDL/HCl-CS/adsorbed-PspA protected 83% of mice after lethal pneumococcal challenge, while 100% of mice immunized with PLGA/HCl-CS/encapsulated-PspA were protected. Therefore, this formulation is a promising vaccine strategy, which has beneficial properties for mucosal immunization and could potentially provide serotype-independent protection. is a bacteria pathogen and the leading cause of lower respiratory tract infections [1]. Despite the existence of vaccines, the global burden of pneumococcal diseases remains high, and new vaccines with greater efficacy are needed [2]. Pneumococcal pneumonia causes significant morbidity, accounting for 5C15% of pneumonia cases in the US [3] and 19% in Europe [4]. The estimated 30-day mortality of invasive pneumococcal diseases (IPD) is 16.7% and can reach 26.5% in patients with meningitis plus other IPD [5]. Pneumococcal diseases have a significant impact on health-related quality of Pf4 life [6]. All current vaccines are based on the protection offered by a few capsular polysaccharides from prevalent serotypes. However, there are more than 100 known serotypes of [7], and serotype replacement has occurred after the introduction of pneumococcal conjugate vaccines (PCV), due to the selective pressure caused by vaccination. For instance, serotype 14 was the most common in children before vaccination in Brazil, while after PCV introduction, serotype 3 became the most frequent in children aged 5 years, followed by serotypes 19A, 6A, 12F, and 6C, and serotypes 12F, 3, 8 and 9N in 5 years [8]. These phenomena mitigate the benefits of the vaccines [9], and hence, recombinant pneumococcal protein antigens are considered promising candidates for new serotype-independent vaccines. However, several protein-based or whole-cell vaccines have failed to progress in clinical trials, highlighting the importance of exploring new approaches, especially those that have the potential to block pneumococcal carriage [10], such as mucosal immunization. To provide an adequate immune response, protein antigens are often formulated into a delivery system crucial for mucosal immunization. The lung mucosa is a very promising immunization route for respiratory pathogens such as pneumococcus, since mucosal vaccines could offer local and Rivastigmine systemic immune responses and protect against pneumococcal colonization at the body entry sites [11]. Rivastigmine Among the delivery systems, nanoparticles (NPs) are especially attractive for mucosal immunization because they can protect the antigen from degradation, act as an adjuvant, and enhance the uptake by antigen presenting cells (APCs) [12,13]. Polymeric NPs have the advantages of biocompatibility and versatility to be formulated in different sizes and shapes, and incorporate other molecules besides the antigen, which confer additional characteristics to the particles; for example, mucoadhesive substances such as chitosans to improve residence time and antigen presentation at mucosal surfaces and to facilitate the crossing of tight gap junctions between epithelial cells [14,15]. Chitosans also have intrinsic adjuvant properties, which can activate the cGASCSTING pathway and NLRP3 inflammasome [16]. Hence, an effective delivery system should guarantee the antigen presentation to the immune system and stimulate innate and adaptive immune responses. APCs have a central role in the initiation of the innate and adaptive immune responses, and dendritic cells (DCs) are considered the main population of APCs. DCs Rivastigmine exhibit high phagocytic capacity and are involved in the initiation of the adaptive immune responses that lead to memory and protection. Polymeric NPs and chitosans have intrinsic properties that stimulate immunogenicity through the uptake of NPs by DCs, which can occur through all four endocytosis pathways [17]. The interactions between NPs and DCs depend on the NP physicochemical properties, such as.