Structural basis for the binding of the neutralizing antibody, 7D11, to the poxvirus L1 protein

Abstract

Medical countermeasures to prevent or treat smallpox are needed due to the potential use of poxviruses as biological weapons. Safety concerns with the currently available smallpox vaccine indicate a need for research on alternative poxvirus vaccine strategies. Molecular vaccines involving the use of proteins and/or genes and recombinant antibodies are among the strategies under current investigation. The poxvirus L1 protein, encoded by the L1R open reading frame, is the target of neutralizing antibodies and has been successfully used as a component of both protein subunit and DNA vaccines. L1-specific monoclonal antibodies (e.g., mouse monoclonal antibody mAb-7D11, mAb-10F5) with potent neutralizing activity bind L1 in a conformation-specific manner. This suggests that proper folding of the L1 protein used in molecular vaccines will affect the production of neutralizing antibodies and protection. Here, we co-crystallized the Fab fragment of mAb-7D11 with the L1 protein. The crystal structure of the complex between Fab-7D11 and L1 reveals the basis for the conformation-specific binding as recognition of a discontinuous epitope containing two loops that are held together by a disulfide bond. The structure of this important conformational epitope of L1 will contribute to the development of molecular poxvirus vaccines and also provides a novel target for anti-poxvirus drugs. In addition, the sequence and structure of Fab-7D11 will contribute to the development of L1-targeted immunotherapeutics.

Targeting the vaccinia virus L1 protein to the cell surface enhances production of neutralizing antibodies

“…The requirement for disulfide bonds in the interaction of several potently neutralizing monoclonal antibodies, including MAb-7D11 and MAb-10F5, has been reported [30,34]. However, the precise structural role of these bonds in formation of the antibody epitope(s) was not clear until recently when the structural basis for the binding of potentially neutralizing antibodies to the L1 protein was reported [34].…”

“…This is because in the absence of the TM, the protein fails to fold properly leading to the disruption of the critical epitope [44]. Hence, for antigens whose antibody epitopes are highly conformationally dependent, such as L1 [34], retention of the TM region might be critical.…”

“…These disulfide bonds are critical for the interaction of potently neutralizing antibodies [30]. Indeed, the crystal structure of L1 bound by a potently neutralizing antibody MAb-7D11 was recently reported [34]. This structure revealed that potentially neutralizing antibodies bind to a discontinuous epitope consisting of two loop regions held together by a disulfide bond.…”

Disparity between Levels of In Vitro Neutralization of Vaccinia Virus by Antibody to the A27 Protein and Protection of Mice against Intranasal Challenge

“…L1 is a myristylated transmembrane component of the MV (24,69). Considerable information is available regarding its structure and one of its neutralization epitopes (60,61). Although L1 was reported to be essential for virus assembly (55), recent data demonstrate that the primary role of L1 is in virus entry (H. Bisht and B. Moss, unpublished data).…”

Anticorps et bioterrorisme

“…La mélioïdose [14], et surtout la peste [15], sont des maladies bactériennes incluses dans le RBP que des Ac peuvent aider à contrôler. Le virus de la variole peut être neutralisé par des Ac dirigés contre les protéines de surface B5 [16] ou L1 [17]. La neutralisation des toxines botuliques -substances qui sont de loin les plus toxiques connues [18] -est possible par des Ac dont les caractéristiques sont main-SYNTHÈSE REVUES un site d'analyse de séquences (http://imgt.cines.fr) [27] (➜), puis un site de modéli-sation tridimensionnelle des Ac (http://antibody.bath.ac.uk) [28], nous avons pu muter un premier fragment d'Ac de macaque pour le rendre « plus humain » -très exactement, pour le rendre plus proche des séquences germinales humaines (gènes V, (D), J non réarrangés) codant des Ac qu'un Ac issu de tel ou tel donneur humain particulier [29].…”