Progress in the in vitro propagation of African swine fever virus and implications for vaccine development

Abstract African swine fever (ASF) is a devastating disease of pigs, and control measures are needed worldwide. This review examines advances in the in vitro culture and propagation of ASF virus (ASFV), which are essential for the development of ASF vaccines. As conventional ASFV culture in primary porcine macrophages is challenging in terms of scalability, cost, and biosafety, increasing research has focused on the adaptation of ASFV to different systems, particularly nonporcine or stable porcine cell lines. This adaptation process, which may include serial passaging, results in genetic changes and attenuation in pigs, an important feature for the production of live attenuated vaccines (LAVs). Modern biotechnological tools such as synthetic genomics and reverse genetics have accelerated the development of ASFV strains with specific, advantageous traits. However, a major problem with LAV candidates generated by cell culture adaptation is the possible return to virulence in pigs after back-passage in vivo, which requires careful safety assessment. Nonetheless, the use of continuous cell lines offers a viable route for economical, large-scale ASF vaccine production. Future research should focus on identifying vaccine candidates that offer broad protection and exceptional safety, with an emphasis on cross-protection against different ASFV strains, while ensuring the economic viability of innovative production methods.