To determine whether host immune responses to viral infection could be promoted by enhancing 4-1BB co-stimulation, in this study, we produced transgenic pig clones expressing an extra copy of the 4-1BB gene by clustered regularly interspaced short palindromic repeats/CRISPR-associated gene 9-mediated homologous recombination at the Rosa26 locus. Here, TNFRSF9 is linked to viral infectious disease.