Depending on the study, the protection conferred against BVDV infection was evidenced by a reduction in clinical signs such as lymphopenia and lack of pyrexia, reduction in viral shedding, antibody neutralization titers, and an increase in CD4+ and CD8+ lymphocytes along with the cytokine levels for humoral and cellular immune responses (12, 44–49). The gene discussed is CD4; the disease is lymphopenia.