A scalable cell-free manufacturing platform for two-step bioproduction of immunogenic conjugate vaccines

Abstract

Rapid and decentralized vaccine production is essential to ensure global preparedness against emerging and re-emerging infectious diseases. Cell-free gene expression systems, which can be freeze-dried for long-term storage and re-activated for point-of-use synthesis, offer a promising solution to address this need. However, scalable cell-free production of conjugate vaccines--highly effective tools against bacterial infections--has been hindered by low yields and inefficient glycosylation. Here, we present an optimized, modular cell-free platform for the synthesis and purification of conjugate vaccines. By decoupling cell-free protein expression from in vitro glycosylation in a two-step approach, we achieve >85% glycosylation efficiency and up to [~]450 mg/L of glycoprotein. We apply this platform to manufacturing protein-polysaccharide conjugates composed of vaccine carrier proteins covalently modified with polysaccharide antigens from enterotoxigenic Escherichia coli O78 and Streptococcus pneumoniae serotype 4. Our workflow produced conjugate vaccine candidates in under 5 days with >87% product purity and low endotoxin levels suitable for preclinical evaluation. Immunization of mice with the pneumococcal conjugate vaccine induced a strong IgG response against the S. pneumoniae serotype 4 capsular polysaccharide, confirming the immunogenicity of the conjugate. We anticipate that this cell-free platform will advance efforts in decentralized manufacturing and rapid response to bacterial disease threats.