Forging a Xeno-Free Future for Cell-Culture Based Vaccines and Biopharmaceuticals

Cell lines represent a cornerstone of modern vaccinology, gene therapy, and biopharmaceutical production, serving as platforms for viral propagation, recombinant protein expression, and vector development. Classical lines such as Vero, MDCK, and HEK293 have provided robust systems for vaccine manufacturing, while more recently developed designer lines, including PER.C6, EB66, and HEK clones, offer enhanced yields and defined characteristics suited to regulatory and industrial requirements. Advances in cell engineering, ranging from spontaneous adaptation to suspension culture to targeted genetic modification, have enabled improved scalability, stability, and biosafety, addressing the increasing demand for global vaccine and gene therapy supply. Natural and induced genetic changes, including immortalization strategies, glycoengineering, and viral receptor modulation, have further expanded the versatility of production hosts. Alongside these developments, a critical shift is underway from serum-dependent media to serum-free, chemically defined, and xeno-free alternatives, which minimize variability, reduce contamination risks, and align with Good Manufacturing Practice standards. This review synthesizes the evolution of cell lines in vaccine and gene therapy applications, examines methods of engineering and optimization, and evaluates prospects for serum-free and xeno-free platforms. By integrating historical context with contemporary advances, it highlights both the opportunities and caveats that shape the trajectory of next-generation biomanufacturing.