The bridging domain (BD) region on hepatitis C virus (HCV) E1E2 glycoprotein complex is a conserved, E1-dependent conformational site of vulnerability formed by E2 residues 646-704. Given its importance for rational vaccine design, here, we characterized the genetic, structural, functional, and epitope features of 25 BD-directed nAbs isolated from HCV-infected individuals or immunized macaques. These antibodies derive from diverse B cell lineages but frequently display recurrent CDRH3 motifs and recognize overlapping epitopes spanning antigenic regions AR4 and AR5, with variable engagement of the E2 back layer (BL) region. A crystal structure of the macaque nAb RM3-26 bound to E2 core domain reveals a BL-directed binding mode analogous to the human nAb hcab40. Importantly, BD-directed nAbs achieve broad neutralization with minimal somatic hypermutation at contact residues and act additively with neutralizing face-directed antibodies. Together, these findings underscore BD as a promising target for rational HCV vaccine design.
Fang Chen, Yen Thi Kim Nguyen, Yi-Zong Lee et al.· Cell Reports· 0 citations
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).
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.
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.
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.
Department of Dermatology, University of Pittsburgh
Vaccines and Immunotherapy (VAC)
Yinuo Zhang, A. Dhayani, Stephen C. Balmert et al.· Journal of Immunology· 0 citations
