Single-chain variable fragments in veterinary medicine: Intelligent design, efficient expression, and precision applications.

The development of single-chain variable fragment (scFv) antibodies constitutes a transformative advance in veterinary biologics. However, translation into veterinary practice faces unique constraints that distinguish it from human medicine: stringent cost limitations in food animal production, requirements for long-term stability under variable field conditions, cross-species immunogenicity risks, and a lack of established regulatory frameworks for veterinary antibody products. This review systematically summarizes recent progress in scFv research through three integrated pillars: AI-assisted design tools, efficient expression systems, and precision veterinary applications. We first critically evaluate the paradigm shift enabled by artificial intelligence and computational tools, distinguishing approaches that have been directly validated on scFvs from those established in broader antibody engineering contexts. We then evaluate and compare mainstream expression platforms, including bacterial, yeast, mammalian, plant, and insect cell systems, focusing on their scalability, cost, and suitability for veterinary production. Finally, we map technological advances to concrete veterinary needs, detailing their roles in clinical diagnostics, therapeutics, immunomodulation, and biosecurity. By synthesizing current innovations, identifying translational gaps, and providing an application-oriented framework for platform selection, this review aims to inform the rational development of next-generation scFv-based biologics tailored to animal health requirements and field conditions.