Induction of Robust Immunity Against Hepatitis C Virus Using Rationally Adjuvanted Microneedle Patches Integrating A Secreted Form of E1E2 Heterodimer 2259568

Introduction 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.