Cationic pH-Responsive Polycaprolactone Nanoparticles as Intranasal Antigen Delivery System for Potent Humoral and Cellular Immunity against Recombinant Tetravalent Dengue Antigen

Research on amalgamation of an antigen with a delivery system for developing a potent mucosal vaccine that elicits both cellular and humoral response has captured immense attention these days. Cationic delivery systems being the first choice for mucosal antigen delivery, despite being effective, are associated with inherent problems like cytotoxicity. Therefore, the quest for developing a precise system that can effectively deliver antigen to immune cells without adverse toxic effect has led to the use of partial cationic systems which are mostly humoral immune mediators. The art of fine-tuning cationic nature, avoiding side effects, and being immune responsive are the needs of the hour. Herein, we try to optimize the cationic nature of polycaprolactone (USFDA approved) by conjugating it with hydrazine. The polymer was modified using two stoichiometry ratios (5 and 10 equiv) of hydrazine monohydrate and characterized using FTIR and XRD. Free amine quantification of the modified polymers concluded that both the modified polymers had 232 and 457 μM/mg amine groups, respectively. A cytotoxicity assay performed using RAW 264.7 macrophages proved the safety of cationic polymers. In vitro assays for antigen colocalization and cross-presentation have revealed that the modified polymers could effectively execute the anticipated function. In vivo evaluation in BALB/c mice using recombinant dengue antigen for intranasal immunization affirmed that the modified polymer having 457 μM/mg of free amine groups effectively stimulated humoral and potent cellular immune response. The overall data suggests that the modified polymeric nanoparticleswith their cationic, pH-responsive, and adjuvanting characteristicsproved to be a versatile system for effective mucosal antigen delivery.