FIG. 4.

Cross-reactivity assays using sera from rEF- and rLF-immunized mice. (A) IgG anti-EF and anti-LF antibody titers of pooled sera from A/J mice immunized with rEF (day 111 sera) or rLF (day 42 sera) were assessed to quantitate the levels of cross-reactive IgG in each sample. Antibody levels were measured by using a standard ELISA at OD₄₁₀ and OD₄₉₀. (B) The fine specificity of the humoral cross-reactive response was measured using overlapping decapeptides of EF or LF. The data are the antibody responses in sera from rEF (day 111 sera) and rLF (day 42 sera) immunized mice on both EF and LF decapeptide pins. Significant epitopes are defined as the average for the background plus 3 SD. (C) EF (day 111) and LF (day 42) sera (serial twofold dilutions from 1:2 to 1:2,048) were both subjected to LeTx and EdTx in vitro neutralization assays as described in Materials and Methods. EF and LF immune sera neutralized EdTx and LeTx, respectively. The LeTx neutralization titer for LF immune sera was 1,024, and the EdTx neutralization titer for EF immune sera was 256. However, EF sera did not neutralize LeTx, nor did LF sera neutralize EdTx. Control sera are sera from mice immunized with adjuvant alone.