CD4 and infection: Although several mice immunized with DIII plasmids survived infection, it remained unclear mechanistically whether this was due to antibodies or possibly, memory CD4+ and CD8+ T cell responses To determine if anti-DIII antibodies alone could afford protection against WNV infection, pooled antiserum from each gene gun vaccinated group was transferred intraperitoneally into naïve 5 week-old C57BL/6 mice, which were then challenged with 102 PFU of WNV (Fig. 6).