Development of mixed micellar systems as immunostimulant nanoplatform for novel subunit vaccine formulations

PATRICIO G. MÁRQUEZ; LEONARDO GABRIEL ALONSO; JUAN IGNACIO MARFIA; IGNACIO SMITH; MARÍA VICTORIA MIRANDA; SILVINA NOEMÍ VALDEZ; FEDERICO JAVIER WOLMAN; ROMINA J. GLISONI

CABA

Congreso; LXIX Reunión Anual de sociedades de Biociencias -SAIC-SAFIS-ALACF; 2024

SAIC-SAFIS-ALACF

The use of nanoparticulate systems as adjuvants has gained considerable strength, enhancing the efficacy and safety of subunit vaccines. Polymeric micelles (PMs) based on polyoxyethylene (PEO) and polyoxypropylene (PPO) tri-block copolymers represent a promising nanoplatform for immunostimulant delivery. QS-21, a saponin fraction from Quillaja saponaria, is encapsulated within the AS01 adjuvant system in FDA-approved vaccines to boost immunogenicity and reduce hemotoxicity, though it remains a costly lipid-based platform.Our aim is to develop mixed PMs based on block copolymers (P123) and QS-21 as a novel immunostimulant nanoplatform (P123/QS-21), characterize their physicochemical properties, evaluate in vitro hemotoxicity and in vivo immune response. The P123/QS-21 system was prepared by hydrating its components in PBS at 4°C overnight. Key assembly parameters, including hydrodynamic diameter (Dh), polydispersity index (PDI), and critical micellar concentration (CMC), were determined using dynamic light scattering (DLS). Hemolytic activity was assessed, and the immune response was measured by antibody titers in blood serum and bronchoalveolar lavage (BAL), along with neutralizing antibodies in serum after intramuscular immunization with the SARS-CoV-2 Spike recombinant protein (provided by NANOBIOTEC) formulated with P123/QS-21.The P123/QS-21 system demonstrated effective micellar assembly, with a Dh under 25 nm, PDI < 0.1, and a CMC value intermediate between those of P123 and free QS-21, indicating the formation of a new entity. This formulation showed reduced hemolytic activity compared to free QS-21, and achieved a two-fold increase in anti-Spike antibody titers in serum and a ten-fold increase in BAL. Notably, anti-Spike neutralizing activity was also observed. These findings represent a step forward in the development of novel and cost-effective nanoparticulate adjuvants for subunit vaccine formulations.