(472a) Targeting C-Type Lectin Receptors On Alveolar Macrophages: A Novel Strategy In the Design of Intranasal Vaccines

The goal of this work is to target C-type Lectin receptor (CLRs) on antigen presenting cells (APCs) using “pathogen-mimicking” carbohydrate-functionalized polyanhydride nanoparticles. Polyanhydride nanoparticles represent a promising platform in the development of effective single dose vaccines, providing an appropriate environment for protein stabilization, sustained release, and modulation of immune response. There is a critical need for the development of efficacious vaccines against respiratory pathogens capable of inducing protective mucosal immune responses. In this context, alveolar macrophages (AMs) are the first phagocytic cells to encounter antigens in the respiratory track and transport them to the lymph nodes draining the lung. Thus, their activation is required for the design of effective vaccines against respiratory pathogens. Our approach is to target CLRs on AMs as a means to enhance antigen presentation and modulate cytokine production. Polyanhydride nanoparticles based on a 50:50 ratio of 1,8-bis(p-carboxyphenoxy)-3,6-dioxaoctane (CPTEG) and 1,6-bis(p-carboxyphenoxy)hexane (CPH) were fabricated by an anti-solvent nano-precipitation method and the particle surface was modified by attaching di-mannose or galactose residues by an amine-carboxylic acid coupling reaction. AMs were harvested from C57BL/6 mice by bronchoalveolar lavage (BAL) and stimulated for 48 h with the nanoparticles. Cell surface marker expression (i.e., MHC I, MHC II, CD40, CD86, CD206, CD209, CD301a/b) was assessed by flow cytometry and cytokine production (i.e., IL-1β, TNF-α, IL-6, IL-12) was evaluated using a multiplexed bead assay. The expression of activation makers was enhanced by di-mannose as well as galactose modified nanoparticles in comparison with the non-modified particles. The data also showed that di-mannose modified nanoparticles selectively upregulated the expression of the macrophage mannose receptor (MMR) and CIRE (also termed as SIGNR5 or mouse DC-SIGN) receptors, while galactose-modified nanoparticles upregulated the expression of macrophage galactose lectin (MGL). In addition, di-mannose functionalization enhanced the production of pro-inflammatory cytokines. In summary, the “pathogen-like” mannose functionalized polyanhydride nanoparticles were shown to possess superior adjuvant properties based on their effective activation of AMs, rendering them as promising components of intranasal vaccines against respiratory infectious diseases.