(910) Induction of Robust Immunity Against Hepatitis C Virus Using Rationally Adjuvanted Microneedle Patches Integrating A Secreted Form of E1E2 Heterodimer

Introduction/Rationale: Safe, effective, durable, and broadly deployable vaccines are needed for sustainable control of hepatitis C virus (HCV) that poses a significant global public health threat. We reported the preclinical development of a novel HCV vaccine candidate engineered by formulating a novel native-like secreted E1E2 immunogen and a well-established combinatorial adjuvant of QS-21+3D-(6-acyl) PHAD into our unique microneedle patches (MNPs).

Methods: In C57BL/6 mice, we evaluated (1) the local immunomodulation characteristics by RT-qPCR; (2) the local and systemic reactogenicity; (3) humoral responses by ELISA and pseudovirus neutralization; and (4) cellular responses by antigen-specific stimulation of isolated splenocytes, followed by intracellular cytokine staining and flow cytometry. Intramuscular vaccination (IM) was used as a benchmark group. In human skin explants, we studied the effect of MNP-delivered adjuvant on the subsets and phenotypes of skin-migratory dendritic cells by flow cytometry.

Results: Our HCV vaccine efficiently and safely (with no systemic and local reactogenicity) engineered the skin immune system in mice to induce proinflammatory milieu at the vaccine-targeted tissues with increased Nlrp3, Ifng, and Cxcl10 expression. In human skin explants, our HCV vaccine stimulated the migration of highly immunostimulatory antigen-presenting cells, supported by enhanced expression of co-stimulatory molecules, such as CD86 and CD83. Skin immunization of mice with our HCV vaccine elicited improved humoral (higher binding and neutralizing antibodies with enhanced Th1-skewing) and cellular polyfunctional T-cells responses compared to IM immunization. The formulation preserved potency for 3 months at 40 °C, indicating thermostability.

Conclusion: Unique safety, shelf-stability, innate and adaptive immunogenicity advantages of MNP-based skin immunization would enable the development of clinically translatable and globally accessible HCV vaccines with rationally designed antigens and adjuvants.