Adenoviruses (Ads) are a family of non-enveloped linear double stranded-DNA viruses infecting a wide range of hosts, including humans. In humans, the 60 serotypes are divided in seven sub- groups (A to G). The first identified adenovirus receptor, called CAR was identified in 1997 and was shown to interact with an elongated protein located at the twelve capsid vertices: the fibre. This receptor is recognized by all sub-groups except subgroup B adenoviruses (B-Ad) which interact with either CD46 (B1-Ads) or desmoglein 2: DSG2 (B2-Ads) which we identified. Until recently, most of Ad vectors used in preclinical and clinical studies were derived from serotype 5 (subgroup C). However, there is a renewed interest in other serotypes, including those belonging to subgroup B because of their different tropism and their ability to escape from serotype 5 pre-existing immunity. However, a major challenge in the use of B-Ads as vectors is the relatively limited understanding of their biology, especially as compared to C-Ad5. In collaboration with Prof. Andre Lieber (Seattle, USA), our team has previously reported that the tropism of B2-Ad (Ad3, Ad7, Ad11 and Ad14) is mainly dictated by their interaction with DSG-2, a desmosomal component.
Biophysically characterizing and solving the high-resolution structure of a new virus/receptor interaction is often challenging, but the results will provide new understanding on how this virus is able to specifically target and interact with host cells. The fundamental data that we will generate on the B2-Ad/DSG2 interaction will not only provide a foundation for understanding virus-receptor interactions, but also facilitate the design of the next generation of cancer–targeted oncolytic adenoviruses. In addition, Pr Lieber team has shown in a collaborative work with our team that B2-Ad can act as a junction opener and thus as adjuvant for chemotherapeutics and monoclonal antibodies (MAbs) already approved in human use. The resolution of the structure of the B2-Ad/DSG2 interaction will enable a better understanding of the mode of action of junction opening and enable the design of improved B2-Ad adjuvants for therapy. Altogether, this integrative project will bridge the gap between fundamental research in virology and applied research in vectorology.
Our research plan will be divided in three mains steps:
1/ Expression and purification of different DSG2 ectodomain constructs by two expression means (mammalian and prokaryotic) and their screening for B2-Ad fibre binding by surface plasmon resonance (SPR) in order to determine the minimal DSG2 domain required for Ad binding (DSG2min)
2/ Co-crystallisation and cryo-EM imaging of the B2-Ad fiber/DSG2min complex to identify at the atomic level which residues of both partners are critical in the interaction
3/ Design of mutations in the Ad-fibre abrogating or increasing DSG2 binding; in vitro characterisation of adenoviral vectors displaying these mutations and their impact in the in vivo bio-distribution in transgenic mice expressing human DSG2 (hDSG2).
Monsieur Pascal Fender (Institut de Biologie Structurale)
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IBS Institut de Biologie Structurale
Vectorologie et thérapeutiques anticancéreuses Unité de recherche
Aide de l'ANR 302 835 euros
Début et durée du projet scientifique : décembre 2018 - 36 Mois