Neutralizing human monoclonal antibodies bind to a region between residues 100-448 of gB Next, we attempted to map the target sites of antibodies that did not react with the known antigenic sites on gB. To obtain a consistent supply of mabs, the Ig-genes from 10 selected B-cell clones that secreted neutralizing antibodies unreactive with AD-1 and AD-2 were cloned and expressed in recombinant systems as IgG1 molecules (Table 2) . We choose the IgG1 subtype since 8 of the 10 selected B-cell clones secreted IgG1, whereas 2 secreted IgG3. The recombinant antibodies showed comparable neutralizing activity to the B-cell supernatants when tested on fibroblasts as target cells indicating that the Fc-part of the IgG is not significantly contributing to the in vitro neutralizing activity of the antibodies (Fig. 1 ). 50% neutralization was achieved at concentrations of 0.2-1.3 mg/ml (Table 2) . Importantly, the recombinant antibodies were also able to neutralize virus on endothelial, epithelial and dendritic cells with comparable activities. Representative results for Group A mabs (see next paragraph) on endothelial cells and Group B mabs on epithelial cells are shown in Fig. 1 and the data for all mabs are summarized in Table 2 .