CD4 and viral infectious disease: Since primary virus infection was controlled by all genotypes (Fig. 5D), this suggests the possibility that the combination of a reduced CD8+ T-cell response with impaired CD4+ T-cells and antibody production during the acute response may explain virus control after primary infection even in the Cd4-cre;Parp2f/f;Parp1−/− mice, as these three immune responses are each relevant to control VACV acute infection39, 40.