Protection Evaluation of a New Attenuated ASFV by Deletion of the L60L and CD2v Genes against Homologous Challenge

African swine fever (ASF) is an acute infectious disease with a high mortality rate in both domestic and wild boars. Commercial vaccines or antiviral drugs for ASF were not available due to the complex diversity of the structure and genome of its pathogen African swine fever virus (ASFV). In recent years, there have been many reports on candidate strains of attenuated vaccines for ASFV. In this study, we obtained a recombinant virus named SY18ΔL60LΔCD2v by simultaneously deleting the <i>L60L</i> gene and <i>CD2v</i> gene from highly virulent strain SY18. In vitro, SY18ΔL60LΔCD2v displayed a decreased growth kinetic compared to that of parental SY18. In vivo, high doses (10⁵ TCID₅₀) of SY18ΔL60LΔCD2v can protect pigs (5/5) from attacks by the parental SY18 strain (10² TCID₅₀). Low doses (10² TCID₅₀) of SY18ΔL60LΔCD2v only protected 20% of pigs (1/5) from attacks by the parental SY18 strain (10² TCID₅₀). The results indicated that the absence of these two genes in SY18 could induce protection against the homologous parental strain, and there were no obvious clinical symptoms or viremia. These results indicate that the SY18ΔL60LΔCD2v strain can serve as a new live attenuated vaccine candidate for the prevention and control of ASFV infection.