Precision Glycoengineering of an HCV Envelope-Based Nanoparticle Vaccine

ABSTRACTGlobally, more than 71 million people are infected with Hepatitis C virus (HCV), with 1-2 million new infections occurring each year. This major health concern necessitates the development of an effective vaccine. Since HCV rapidly accumulates mutations, vaccines must elicit the production of broadly neutralizing antibodies (bnAbs) in a reproducible fashion. The viral envelope E1E2 glycoprotein is a natural target of neutralizing antibodies. However, two major challenges in production of envelope proteins such as E1E2 are as follows. First, as the candidate protein advances, it will be critical to obtain a product with stable, reproducible, homogenous glycoforms that show high potential for yielding a potent and broadly neutralizing antibody response. This ensures an optimally potent vaccine with comparable efficacy across batches in preclinical and clinical trials, and makes it easier to retain the glycan profile through manufacturing. However, variation across host cells, even clones, can lead to substantial variation in glycosylation. Second, upon identifying a glycoform that provides the desired broadly neutralizing antibody response, it can be difficult to obtain an effective expression host that can economically produce the vaccine subunit proteins in a functional form. Here we are addressing these challenges by producing a well-characterized novel native-like secreted E1E2 (sE1E2) complex in a panel of glycoengineered mammalian cell lines to obtain more homogeneous glycosylation with predictable and defined structures. After production of preclinical material of all glycoforms, the most effective glycoforms will be identified by rigorous bioanalytical analysis, coupled to nanoparticles, and subjected to immunological assessment of polyclonal sera from animals immunized with sE1E2 produced in glycoengineered CHO cell lines, wild-type CHO cell lines, and HEK 293 and Huh7 control cell lines. Thus, this proposed research will identify optimal glyforms and help establish a platform cell line for manufacturing an effective pan-HCV vaccine.