Identification of Two Competition-Defined Neutralizing Antibody Groups Targeting the HHV-6B gH/gL/gQ1/gQ2 Complex...

Human herpesvirus 6B (HHV-6B) entry is mediated by the interaction between gH/gL/gQ1/gQ2 complex (tetramer) and CD134 expressed on activated T cells. In this study, we identified and characterized a panel of monoclonal antibodies targeting the HHV-6B tetramer, with particular focus on three antibodies; gHgL J1, gHgL O2, and gHgL F5; that represent anti-gH neutralizing monoclonal antibodies with binding characteristics distinct from the previously described antibody OHV-3. Immunofluorescence and Western blot analyses confirmed recognition of the HHV-6B tetramer in infected and transfected cells. Biolayer interferometry (BLI) demonstrated that these antibodies exhibited dissociation constants (K_D) in the range of 62.52-76.99 nM. We next assessed the effect of antibodies on the interaction between the HHV-6B tetramer and CD134. None of the gH-targeting antibodies inhibited the CD134 binding. Competition analysis using BLI-based antibody-Fab competition assays indicated that gHgL J1, gHgL O2, and gHgL F5 form a competition-defined antigenic cluster distinct from that recognized by OHV-3. Collectively, these findings identify a group of anti-gH antibodies which neutralizes HHV-6B with CD134-binding-independent profiles and suggest the presence of at least two distinguishable antibody-recognition regions within HHV-6B gH. These results expand our understanding of the antigenic organization of the HHV-6B entry complex.