Whereas all anti-gB mabs recognized mammalian cell expressed gB aa 1-687, only 40% to 50% of anti-gB antibodies were reactive with a shorter fragment expressing aa 1-447 indicating the presence of epitopes in gB between aa 448 and 687. These antibodies were negative for recognition of the bacterial fusion protein containing AD-1 (aa 484-650). Thus, the location of the antibody binding site(s) remains unknown. There is the possibility that residues 447-484 and 650-687 contain additional epitopes since they are not represented by the AD-1 fusion peptide. However, this seems unlikely. The more plausible explanation for our finding is that the region between aa 447-687 contains additional conformational epitopes that are not formed in the bacterial fusion protein. Our previous analyses have shown that AD-1 induces a multitude of antibodies with different binding characteristics, even when assayed as bacterial fusion proteins or synthetic peptides [33] . Thus, it would be not surprising that this region of gB contains additional epitopes which are present only on the native protein. The large fraction of antibodies falling in this category also supports this possibility. A corresponding protein region of HSV-1 gB was found to contain a ''pseudocontinuous'' epitope, further supporting our interpretation [57] . However, no matter what the underlying mechanism of this finding is, antibodies binding within the 447-687 region of gB were nonneutralizing.