Exceptionally potent human monoclonal antibodies are effective for prophylaxis and treatment of tetanus in mice
Marco Pirazzini, … , Antonio Lanzavecchia, Cesare Montecucco
Marco Pirazzini, … , Antonio Lanzavecchia, Cesare Montecucco
Published October 7, 2021
Citation Information: J Clin Invest. 2021;131(22):e151676. https://doi.org/10.1172/JCI151676.
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Research Article Neuroscience

Exceptionally potent human monoclonal antibodies are effective for prophylaxis and treatment of tetanus in mice

Abstract

We used human monoclonal antibodies (humAbs) to study the mechanism of neuron intoxication by tetanus neurotoxin and to evaluate these antibodies as a safe preventive and therapeutic substitute for hyperimmune sera to treat tetanus in mice. By screening memory B cells from immune donors, we selected 2 tetanus neurotoxin–specific mAbs with exceptionally high neutralizing activities and extensively characterized them both structurally and functionally. We found that these antibodies interfered with the binding and translocation of the neurotoxin into neurons by interacting with 2 epitopes, whose identification pinpoints crucial events in the cellular pathogenesis of tetanus. Our observations explain the neutralization ability of these antibodies, which we found to be exceptionally potent in preventing experimental tetanus when injected into mice long before the toxin. Moreover, their Fab derivatives neutralized tetanus neurotoxin in post-exposure experiments, suggesting their potential for therapeutic use via intrathecal injection. As such, we believe these humAbs, as well as their Fab derivatives, meet the requirements to be considered for prophylactic and therapeutic use in human tetanus and are ready for clinical trials.

Authors

Marco Pirazzini, Alessandro Grinzato, Davide Corti, Sonia Barbieri, Oneda Leka, Francesca Vallese, Marika Tonellato, Chiara Silacci-Fregni, Luca Piccoli, Eaazhisai Kandiah, Giampietro Schiavo, Giuseppe Zanotti, Antonio Lanzavecchia, Cesare Montecucco

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Figure 2

Preliminary screening for TeNT neutralization by TT humAbs assayed in vitro and in vivo.

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Preliminary screening for TeNT neutralization by TT humAbs assayed in vi...
(A) TeNT (50 pM) was diluted in complete culture medium alone (positive control) or supplemented with a 100X molar excess of the indicated humAb. The mixture was then added to CGNs for 12 hours, and TeNT activity was evaluated by monitoring the cleavage of VAMP-2 with an antibody recognizing only the intact form. SNAP-25 was used as a loading control. (B) Effect of different TeNT/humAbs ratios for the humAbs displaying toxin-neutralizing activity on CGNs. (C) Immunofluorescence analysis performed with an antibody specific for intact VAMP-2 (green) to assay for the TeNT-neutralizing activity of TT39, TT104, TT109, and TT110 preincubated with TeNT (100:1 molar ratio) and added to the primary culture of CGNs. Control CGNs (NC) are labeled in green, whereas neurons treated with TeNT alone (PC) do not display this signal because of the complete cleavage of VAMP-2. CGNs treated with the indicated humAbs displayed intermediate signals depending on the neutralization activity of the humAbs. Images are representative of 3 independent experiments. Scale bars: 25 μm. (D) Mice were injected i.p. with TeNT (4 ng/kg, black trace) alone or preincubated with the indicated molar ratios of humAb/TeNT, and survival is plotted as a function of time after toxin injection. P values are shown in the panels and were determined by Mantel-Cox test. The number of mice in each group is indicated in the panels. NC, negative control; PC, positive control.