Bispecific antibodies targeting herpes simplex virus glycoproteins B and D

Background Herpes simplex viruses (HSV-1 and HSV-2) can be transmitted both orally and sexually and cause lifelong morbidity and, in some cases, meningitis and encephalitis. Although several clinical trials using subunit antigens have been conducted, no vaccine exists. One problem in viral treatment is the emergence of drug resistance through mutations, thereby conferring resistance. Treatment with antibodies targeting multiple epitopes, such as antibody cocktails or bispecific antibodies (BsAbs), should reduce the likelihood of viral escape. Methods We screened pairs of antibodies targeting key functional sites on glycoproteins B (gB) and D (gD), which are crucial for HSV entry. Murine hybridoma cells expressing anti-gD and anti-gB Mabs were sequenced. Recombinant antibodies, mono- and bispecific, were purified from supernatants of 293T transfected cells. Results From a panel of gD-gB monoclonal antibodies (Mabs), we selected MC2 (anti-gD) and C226 (anti-gB) for the design of BsAbs: MC2/C226sc and a simpler version in which the C226scFv was cloned at the C-terminus of MC2 Fc, which we termed BD Tetra. Notably, both MC2/C226sc and BD Tetra BsAbs simultaneously recognized and bound gB and gD and had a marked synergistic effect on inhibiting cell-cell fusion, virus entry, and plaque formation. Although MC2 is HSV-2 specific, both MC2/C226sc and BD Tetra showed activity against HSV-1. The Fc domains of these two BsAbs were equally effective at binding to mouse Fcγ receptors RI or RIV in vitro . Discussion The data presented here demonstrate the generation, characterization, and potential of bispecific antibodies targeting two distinct glycoproteins to enhance neutralization of herpes simplex virus compared with monoclonal antibodies. BsAbs offer a potential avenue for herpes therapeutics, but their design and mechanism of action require careful consideration for optimal efficacy. Engineering different formats of BsAbs will not only enable optimal protective and therapeutic outcomes but also aid in the study of the spatial relationships between key glycoproteins involved in HSV infection. We propose that targeting distinct steps of the fusion cascade will yield a BsAb that is highly effective.