Ricin intoxication: development of monoclonal and recombinant antibodies for diagnostic and therapeutic applications

Loïs Lequesne (1, 2, 3, 4) , Julie Dano (1, 2, 3, 4) , Audrey Rouaix (1, 2, 3, 4) , Camille Kropp (1, 2, 3, 4) , Dorothée Lebert , Nathalie Bosquet (5) , Benoit Delache (5) , Hélène Letscher (5) , Bernard Maillère (1, 6) , Hervé Nozach (1, 6) , Stéphanie Simon (1, 2, 3, 4)

1 MTS - Médicaments et Technologies pour la Santé
2 SPI - Service de Pharmacologie et Immunoanalyse
3 LERI - Laboratoire d'Etudes et de Recherches en Immunoanalyses
4 CEA - CEA- Saclay
5 IDMIT - Infectious Diseases Models for Innovative Therapies
6 SIMoS - Service d'Ingénierie Moléculaire pour la Santé (ex SIMOPRO)

Introduction. Ricin is a protein produced by the plant Ricinus communis, known for its high toxicity. As ricin is readily available in nature, it represents a considerable biothreat. An early diagnosis of ricin intoxication as well as efficient medical countermeasures are therefore urgently needed. In the event of intentional or accidental poisoning, it is essential to treat as quickly as possible. In this context, vaccination, which takes several weeks to several months to achieve the right level of protection, is not appropriate. On the contrary, direct administration of antibodies, provides immediate protection. However, since ricin sequence can differ according to the isoform, developing efficient protective mAbs against ricin is challenging. We have developed and characterized several murine monoclonal antibodies for diagnostic and therapeutic applications. They have enabled the development of a highly sensitive and specific in vitro diagnostic immunoassay (sandwich ELISA) for ricin intoxication, which is now CE-IVD marked and commercially available. Some of these antibodies have been evaluated in in vitro and in vivo models, and have demonstrated excellent protection against ricin poisoning in mice. Materials and Methods. In vitro diagnostic test: monoclonal antibodies were produced by immunizing mice with inactivated ricin. The best antibodies were then selected for their ability to recognize ricin in ELISA. The performance of this test, in its research format, was then evaluated using plasma from ricin-intoxicated animals. An industrial prototype of the test was then designed, and its performance evaluated using human plasma. Medical countermeasures: several generations of ricin antibodies (murine monoclonal and recombinant camelid) were produced and evaluated for their neutralizing capacities in a cellular model. The best ones were then evaluated for their protective activity in an in vivo murine model of intranasal intoxication. Results. In vitro diagnostic test: In its research format, the sandwich ELISA test enables early detection of ricin in the blood of intratracheally poisoned macaques or intranasally poisoned mice. Medical countermeasures: the best antibodies gave intranasally intoxicated mice survival rates of 90% and 50% respectively when administered 6h and 18h post-intoxication. References 1. J. Prigent et al., PLoS ONE. 6(5): e20166. (2011) 2. M.L. Orsini Delgado et al., Toxins. 13(2):100 (2021)

Mots clés: ricin; medical countermeasures; ELISA; diagnostics

Domaines: Sciences du Vivant [q-bio]

Loïs Lequesne, Julie Dano, Audrey Rouaix, Camille Kropp, Dorothée Lebert, et al.. Ricin intoxication: development of monoclonal and recombinant antibodies for diagnostic and therapeutic applications. International Workshop on the Analysis of Chemical Warfare Agents to Mark the 50th Anniversary of VERIFIN, Finnish Institute for Verification of the Chemical Weapons Convention, Nov 2023, Helsinki, Finland. ⟨hal-04458586⟩