To protect against human immunodeficiency virus (HIV-1) infection, broadly neutralizing antibodies (bnAbs) must be active at the portals of viral entry in the gastrointestinal or cervicovaginal tracts. The localization and persistence of antibodies at these sites is influenced by the neonatal Fc receptor (FcRn)1,2, whose role in protecting against infection in vivo has not been defined. Here, we show that a bnAb with enhanced FcRn binding has increased gut mucosal tissue localization, which improves protection against lentiviral infection in non-human primates. A bnAb directed to the CD4-binding site of the HIV-1 envelope (Env) protein (denoted VRC01)3 was modified by site-directed mutagenesis to increase its binding affinity for FcRn. This enhanced FcRn-binding mutant bnAb, denoted VRC01-LS, displayed increased transcytosis across human FcRn-expressing cellular monolayers in vitro while retaining FcγRIIIa binding and function, including antibody-dependent cell-mediated cytotoxicity (ADCC) activity, at levels similar to VRC01 (the wild type). VRC01-LS had a threefold longer serum half-life than VRC01 in non-human primates and persisted in the rectal mucosa even when it was no longer detectable in the serum. Notably, VRC01-LS mediated protection superior to that afforded by VRC01 against intrarectal infection with simian–human immunodeficiency virus (SHIV). These findings suggest that modification of FcRn binding provides a mechanism not only to increase serum half-life but also to enhance mucosal localization that confers immune protection. Mutations that enhance FcRn function could therefore increase the potency and durability of passive immunization strategies to prevent HIV-1 infection.
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We thank M. Roederer for advice on the design and statistical analysis of animal studies. This research was supported by the Intramural Research Program of the Vaccine Research Center, National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), and in part by a grant from the Foundation for the National Institutes of Health with support from the Collaboration for AIDS Vaccine Discovery (CAVD), award OPP1039775, from the Bill & Melinda Gates Foundation. R.S.B. is supported by the NIH (DK044319, DK051362, DK053056 and DK088199) and the Harvard Digestive Diseases Center (DK0034854). T.R. is supported by the German research foundation (DFG; RA 2040/1-1). The findings and conclusions in this report are those of the authors and do not necessarily reflect the views of the funding agencies.
The authors declare no competing financial interests.
Extended data figures and tables
Extended Data Figure 1 Enhanced FcRn-binding mutants of VRC01 are released from human FcRn at pH 7.4.
VRC01 or the indicated FcRn-binding mutants were injected in PBS (pH 6.0) at a concentration of 100 nM over human-FcRn-immobilized Biacore CM5 sensor chips (∼500 response units (RU)) and were dissociated using PBS at pH 6.0 followed by PBS at pH 7.4.
Extended Data Figure 2 Mutants with enhanced human FcRn binding persist at higher serum concentrations than VRC01 in the human-FcRn(276)-transgenic mouse.
The indicated VRC01-derived monoclonal antibodies (2 mg kg−1) were injected intravenously into 6–8-week-old human-FcRn(276)-transgenic mice (n = 4, male and female mice evenly distributed). Serum concentrations were assessed by indirect ELISA against RSC3 over time. The percentage of the monoclonal antibodies remaining in the serum is shown compared with the percentage on day 1 (set at 100%).
Extended Data Figure 3 Binding of VRC01, VRC01-LS and other FcRn-binding mutants to FcγRIIa and FcγRIIb.
Binding to the indicated human Fc receptors was evaluated by ELISA as described in Methods.
Extended Data Figure 4 Serum pharmacokinetics, rectal tissue accumulation and mucosal secretion of VRC01-derived monoclonal antibodies in cynomolgus macaques.
VRC01 or VRC01-LS (10 mg kg−1) were injected intravenously into cynomolgus macaques. a, The serum levels (n = 4) were analysed over time. b, c, The amounts of monoclonal antibody per mg of total tissue protein in rectal biopsy samples (b) and per mg of total IgG in rectal secretions (c) from each monoclonal-antibody-injected cynomolgus macaque (n = 2 per group) were quantitated and are shown over time. The values for each macaque and the mean values for the groups are shown as dotted lines and heavier solid lines, respectively (b). Pharmacokinetic parameters were calculated with a two-compartment model (VRC01 versus VRC01-LS, half-life, 9.0 versus 30.3 days; clearance, 15.7 versus 3.7 ml day−1 kg−1; area under the curve (AUC), 896 versus 2,812 day × µg ml−1).
Extended Data Figure 5 Viral load measurements over time after passive antibody transfer and SHIV challenge of non-human primates.
The indicated monoclonal antibodies (0.3 mg kg−1) were administered intravenously to rhesus macaques (n = 12). Macaques were challenged with SHIV BaLP4 5 days later, and the plasma viral loads were measured over time. Normal human IgG was given to the control group. Five of 12 VRC01-LS-injected macaques and 10 of 12 VRC01-injected macaques were infected (P = 0.0447, one-tailed Fisher’s exact test).
a, VRC01 or VRC01-LS (10 mg kg−1) were injected intravenously into female cynomolgus macaques (n = 2). The monoclonal antibody concentration per mg of total tissue protein in vaginal biopsy samples was quantitated at the indicated times. The values for each macaque and the mean values for the groups are shown as dotted and solid lines, respectively. b, VRC01 (20 mg kg−1) was injected intravenously into rhesus macaques (n = 2), and vaginal biopsy samples were taken and processed. Immunohistochemical staining was performed before and after the antibody dosing. The arrows indicate VRC01 (RSC3 staining, red) in basal and parabasal epithelial cells. The sections are representative of the sections assessed for two macaques. Scale bar, 50 µm.
VRC01 or VRC01-LS (10 mg kg−1) was injected intravenously into Indian rhesus macaques (n = 4). a, Anti-VRC01 antibody responses (left) or anti-VRC01-LS antibody responses (right) were evaluated by ELISA. b, Sera from animals that were administered VRC01 or VRC01-LS were absorbed with 20 µg ml−1 VRC01, and binding to VRC01-LS was then evaluated by ELISA.
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Ko, S., Pegu, A., Rudicell, R. et al. Enhanced neonatal Fc receptor function improves protection against primate SHIV infection. Nature 514, 642–645 (2014). https://doi.org/10.1038/nature13612
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