Taking in consideration m138 effects on the two co-stimulatory molecules CD80 and ICOSL, we sought to assess the contribution of m138 at later times of the acute infection by comparing the in vivo phenotype of MCMVm138ΔIg2 with that of MCMVΔm138 and MCMVwt under conditions that included depletion of NK cells or combined depletion of NK cells and CD4+ and CD8+ T cells. This evidence concerns the gene CD80 and infection.