To obtain insights into the potential role of CEACAM1 in CD8+ T cell responses during chronic viral infection, we challenged C57BL/6 (wild-type, WT) and Ceacam1–/– mice with a viral dose leading to a persistent infection with LCMV-Docile and measured the expression of CEACAM1 on virus-specific CD8+ T cells. This evidence concerns the gene CEACAM1 and infection.