A single immunization with Ad26.ZIKV.M-Env dose dependently induces humoral immune responses in C57BL/6 mice that are maintained for at least 12 weeks.

Env-specific binding IgG antibody titers (A) or ZIKV-PR neutralization titers (B) were determined in sera of C57BL/6 mice immunized with Ad26.ZIKV.M-Env (n = 5) or Ad26.Empty control vector (n = 3) at the doses indicated, at 4 weeks post immunization. The titer was determined using a commercially available ELISA kit (Alpha Diagnostics) and expressed as the log10 of the inverse first dilution above 2x background values of naïve sera. ZIKV neutralizing antibody titers were measured by FRNT and are reported as the log10 of the inverse serum dilution that reduce the infectivity of input virus by 50% (IC50). The mean responses per group are indicated with a horizontal line. The dotted line shows the lower limit of detection. (C) The ratio (log10) of ZIKV neutralizing and Env-binding antibody titers. (D) The durability of the Env-specific binding IgG antibody responses in sera of C57BL/6 mice immunized once with 108, 109, or 1010 vp Ad26.ZIKV.M-Env or with 1010 vp Ad26.Empty (n = 5 per group) was determined at the indicated time points. Env-specific binding antibody titers were measured using an in-house developed ELISA assay. Relative potency (log10) when compared with a ZIKV Env-specific monoclonal antibody ZV-67 [21] was determined, and displayed as mean +/- standard deviation per group. Lines connect the group mean responses per time point. Asterisks indicate statistically significant trend (*p<0.05, **p<0.01 and ***p<0.001) and “ns” indicates no statistical significant trend.