In control animals, upon establishment of infection (19-26 weeks), higher percentages of CD8α+ and CD4–CD8α+ cells in the absence of significantly higher values of memory CD4+CD8+low cells demonstrate that total CD8+ cells were mainly constituted by cytotoxic effector cells (likely NK cells, γ/δ T and cytotoxic T lymphocytes) which were not previously primed. The gene discussed is CD4; the disease is infection.