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Publication Abstract from PubMed

Canine parvovirus (CPV) is a highly contagious pathogen that causes severe disease in dogs and wildlife. Previously, a panel of neutralizing monoclonal antibodies (MAb) raised against CPV was characterized. An antibody fragment (Fab) of MAb E was found to neutralize the virus at low molar ratios. Using recent advances in cryo-electron microscopy we determined the structure of CPV in complex with Fab E to 4.1 A resolution, which allowed de novo building of the Fab structure. The footprint identified was significantly different than the footprint obtained previously from models fitted into lower resolution maps. Using single chain variable fragments (scFv) we tested antibody residues that control capsid binding. The near atomic structure also revealed that Fab binding had caused capsid destabilization in regions containing key residues conferring receptor binding and tropism, which suggests a mechanism for efficient virus neutralization by antibody. Furthermore, a general technical approach for solving the structures of small molecules is demonstrated, as binding the Fab to the capsid allowed us to determine the 50kDa Fab structure by cryo-EM. SIGNIFICANCE: Using cryo-electron microscopy and new direct electron detector technology we have solved the 4A resolution structure of a Fab molecule bound to a picornavirus capsid. The Fab induced conformational changes to regions of the virus capsid that control receptor binding. The antibody footprint is markedly different from the previous one identified using a 12A structure. This work emphasizes the need for a high-resolution structure to guide mutational analysis and cautions against relying on older low-resolution structures even though they were interpreted with the best methodology possible at the time.

The near-atomic resolution structure of a highly neutralizing Fab bound to canine parvovirus.,Organtini LJ, Lee H, Iketani S, Huang K, Ashley RE, Makhov AM, Conway JF, Parrish CR, Hafenstein S J Virol. 2016 Aug 17. pii: JVI.01112-16. PMID:27535057^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.