A non-neutralizing glycoprotein B monoclonal antibody protects against herpes simplex virus disease in mice

Development of a highly effective combination monoclonal antibody therapy against Herpes simplex virus

BACKGROUND

Infections with Herpes simplex virus (HSV)-1 or -2 usually present as mild chronic recurrent disease, however in rare cases can result in life-threatening conditions with a large spectrum of pathology. Monoclonal antibody therapy has great potential especially to treat infections with virus resistant to standard therapies. HDIT101, a humanized IgG targeting HSV-1/2 gB was previously investigated in phase 2 clinical trials. The aim of this study was to develop a next-generation therapy by combining different antiviral monoclonal antibodies.

METHODS

A lymph-node derived phage display library (LYNDAL) was screened against recombinant gB from Herpes simplex virus (HSV) -1 and HDIT102 scFv was selected for its binding characteristics using bio-layer interferometry. HDIT102 was further developed as fully human IgG and tested alone or in combination with HDIT101, a clinically tested humanized anti-HSV IgG, in vitro and in vivo. T-cell stimulating activities by antigen-presenting cells treated with IgG-HSV immune complexes were analyzed using primary human cells. To determine the epitopes, the cryo-EM structures of HDIT101 or HDIT102 Fab bound to HSV-1F as well as HSV-2G gB protein were solved at resolutions < 3.5 Å.

RESULTS

HDIT102 Fab showed strong binding to HSV-1F gB with Kd of 8.95 × 10-11 M and to HSV-2G gB with Kd of 3.29 × 10-11 M. Neutralization of cell-free virus and inhibition of cell-to-cell spread were comparable between HDIT101 and HDIT102. Both antibodies induced internalization of gB from the cell surface into acidic endosomes by binding distinct epitopes in domain I of gB and compete for binding. CryoEM analyses revealed the ability to form heterogenic immune complexes consisting of two HDIT102 and one HDIT101 Fab bound to one gB trimeric molecule. Both antibodies mediated antibody-dependent phagocytosis by antigen presenting cells which stimulated autologous T-cell activation. In vivo, the combination of HDIT101 and HDIT102 demonstrated synergistic effects on survival and clinical outcome in immunocompetent BALB/cOlaHsd mice.

CONCLUSION

This biochemical and immunological study showcases the potential of an effective combination therapy with two monoclonal anti-gB IgGs for the treatment of HSV-1/2 induced disease conditions.

Protective human antibodies against a conserved epitope in pre- and postfusion influenza hemagglutinin

Phylogenetically and antigenically distinct influenza A and B viruses (IAV and IBV) circulate in human populations, causing widespread morbidity. Antibodies (Abs) that bind epitopes conserved in both IAV and IBV hemagglutinins (HAs) could protect against disease by diverse virus subtypes. Only one reported HA Ab, isolated from a combinatorial display library, protects against both IAV and IBV. Thus, there has been so far no information on the likelihood of finding naturally occurring human Abs that bind HAs of diverse IAV subtypes and IBV lineages. We have now recovered from several unrelated human donors five clonal Abs that bind a conserved epitope preferentially exposed in the postfusion conformation of IAV and IVB HA2. These Abs lack neutralizing activity in vitro but in mice provide strong, IgG subtype-dependent protection against lethal IAV and IBV infections. Strategies to elicit similar Abs routinely might contribute to more effective influenza vaccines.

Antibody attributes, Fc receptor expression, gestation and maternal SARS-CoV-2 infection modulate HSV IgG placental transfer

Antibody-dependent cellular cytotoxicity (ADCC) is associated with protection against neonatal herpes. We hypothesized that placental transfer of ADCC-mediating herpes simplex virus (HSV) immunoglobulin G (IgG) is influenced by antigenic target, function, glycans, gestational age, and maternal severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Maternal and cord blood were collected from HSV-seropositive (HSV+) mothers pre-COVID and HSV+/SARS-CoV-2+ mothers during the pandemic. Transfer of HSV neutralizing IgG was significantly lower in preterm versus term dyads (transfer ratio [TR] 0.84 vs. 2.44) whereas the TR of ADCC-mediating IgG was <1.0 in both term and preterm pre-COVID dyads. Anti-glycoprotein D IgG, which had only neutralizing activity, and anti-glycoprotein B (gB) IgG, which displayed neutralizing and ADCC activity, exhibited different relative affinities for the neonatal Fc receptor (FcRn) and expressed different glycans. The transfer of ADCC-mediating IgG increased significantly in term SARS-CoV-2+ dyads. This was associated with greater placental colocalization of FcRn with FcγRIIIa. These findings have implications for strategies to prevent neonatal herpes.

Antibody effector functions are required for broad and potent protection of neonates from herpes simplex virus infection

The failure of multiple herpes simplex virus (HSV) vaccine candidates that induce neutralizing antibody responses raises the hypothesis that other activities, such as Fc domain-dependent effector functions, may be critical for protection. While neonatal HSV (nHSV) infection result in mortality and lifelong neurological morbidity in humans, it is uncommon among neonates with a seropositive birthing parent, suggesting the potential efficacy of antibody-based therapeutics to protect neonates. We therefore investigated the mechanisms of monoclonal antibody (mAb)-mediated protection in a mouse model of nHSV infection. Both neutralization and effector functions contributed to robust protection against nHSV-1. In contrast, effector functions alone were sufficient to protect against nHSV-2, exposing a functional dichotomy between virus types that is consistent with vaccine trial results. Together, these results emphasize that effector functions are crucial for optimal mAb-mediated protection, informing effective Ab and vaccine design, and demonstrating the potential of polyfunctional Abs as potent therapeutics for nHSV infections.

Greater Durability and Protection against Herpes Simplex Viral Disease following Immunization of Mice with Single-Cycle ΔgD-2 Compared to an Adjuvanted Glycoprotein D Protein Vaccine

Herpes simplex viruses (HSV) cause chronic infections with significant morbidity. Prior vaccines, designed to generate neutralizing antibodies (nAbs) targeting glycoprotein D (gD), failed to provide durable protection. We adopted a different strategy and evaluated a single-cycle virus deleted in gD (ΔgD-2). ΔgD-2elicits antibodies that primarily mediate antibody-dependent cell mediated cytolysis (ADCC) and provides complete protection against clinical isolates of HSV in multiple lethal mouse models. To assess durability, we vaccinated mice (2 doses administered intramuscularly) with ΔgD-2, adjuvanted recombinant gD-2 (rgD-2/Alum-MPL), or uninfected cells as a control, and quantified antibody responses over one year. Mice (n = 5/group) were lethally challenged at 2, 4, 6, 8, and 10-months post-boost. ΔgD-2-vaccinated mice elicited a durable ADCC-mediating response, which provided complete protection against challenge at all timepoints. In contrast, rgD-2/Alum-MPL elicited only nAbs, which declined significantly within 6 months, provided only partial protection at early timepoints, and no protection after 6 months. Serum sampling after viral challenge showed that infection elicited low levels of ADCC-mediating antibodies in rgD-2/Alum-MPL-vaccinated mice and boosted the nAb response, but only after 6 months. Conversely, infection significantly and consistently boosted both the ADCC and nAbs responses in ΔgD-2-vaccinated mice. Results recapitulate clinical trial outcomes with gD vaccines, highlight the importance of ADCC, and predict that ΔgD-2 will elicit durable responses in humans.