The 5G3 paratope comprises three complementary determining regions (CDRs): L1 (residues 31C33), L3 (residues 98 and 100), and H2 (residues 51 and 54). directly from the copyright holder. To view Gsk3b a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. This article has been cited by other articles in PMC. Associated Data Supplementary MaterialsSupplementary Information 41421_2021_264_MOESM1_ESM.pdf (3.4M) GUID:?CE5A48D5-FC14-4D5D-89F6-CB1338D90E13 Data Availability StatementThe atomic coordinates of E3 F-, EC- and EE-particles as well as E3 (F-particle)-, E3 (EE-particle)-5G3 complexes have been submitted to the Protein Data Bank with accession numbers: 7C9X, 7EAI, 7EAH, 7EAK, and 7EAJ, respectively. Their corresponding cryo-EM maps have been deposited in the Electron Microscopy Data Bank under accession codes: EMD-30320, EMD-31044, EMD-31043, EMD-31046, and EMD-31045, respectively. All the other materials and data involved in Lisinopril this study will be available on request. Dear Editor, Human enteroviruses (HEVs) are ubiquitous pathogens responsible for multiple human diseases, ranging from hand-foot-and-mouth disease (HFMD), meningitis, to poliomyelitis, encephalitis, etc1. HEVs comprise four main groups, Enterovirus ACD (HEV-A, B, C, and D), among which HEV-B is the largest group, including coxsackievirus A9 (CVA9), coxsackievirus B1C6 (CVB1C6), and over 30 serotypes Lisinopril of echoviruses. Echovirus 3 (E3), a serotype of HEV-B, first isolated in 1953, leads to highly contagious and severe diseases in humans, such as aseptic meningitis, myocarditis, and anicteric hepatitis2. Infection in neonates and infants within the first few weeks of life can be fatal. Currently, there are no approved vaccines or antiviral drugs for treating infections caused by viruses belonging to the HEV-B group. Although the atomic structures for numerous HEVs have been studied3C8, large gaps in our knowledge concerning structural determinants for specificity between the serotypes/subgroups and immunogenic characteristics for serotype-specific or cross-reactive epitopes within HEV-Bs still exist. Therefore, an in-depth understanding of the structural, immunogenic features and key epitopes of E3 should be useful in providing guidance for the rational drug design against HEV-B infections. We obtained the E3 virus (genotype HNWY-01 strain) from the Jiangsu Provincial Center for Disease Control and Prevention (CDC) and propagated it in RD cells. Following rounds of purifications and analyses, three types of particles were identified, one containing significant amounts of viral RNA characterized as mature virus (or full particle, F-particle) and the other two being empty inside with substantially different sizes defined as expanded and compact empty particles (EE- and EC-particles) (Supplementary Fig. S1). Cryo-electron microscopic (cryo-EM) structures of the three types of particles: F-particle (~?64%), EC-particle (~?3%), and EE-particle (~?33%) were reconstructed to 3.2??, 3.8??, and 3.1?? resolution, respectively (Fig. ?(Fig.1a;1a; Supplementary Figs. Lisinopril S2a and S3aCc and Table S1). The external surfaces of the F- and EC-particles with a diameter of ~?325?? are indistinguishable, apart from some disorder on the inside of the EC-particle, including N-termini of VP1 and VP0 (Fig. ?(Fig.1a).1a). By contrast, the EE-particle exhibits a typical expanded form with a ~?4.5% increase in diameter (~?340??) and notable perforations at the icosahedral two-fold axes (Fig. ?(Fig.1a;1a; Supplementary Figs. S4 and S5d). Superimposition of the asymmetric units (protomers) verifies the similarity in capsid structures of the F- and EC-particles and reveals substantially conformational differences between F- and EE-particles in several exposed loops, such as VP1 BC, DE, EF and HI loops, VP3 EF and GH loops (Supplementary Figs. S4 and Lisinopril S5aCc). Remarkably, most of these loops are key determinants for immunogenicity in HEVs, indicating that EC-particle, rather than EE-particle, has more potential as candidates for the development of a vaccine. Incorporation of EE-particles in the vaccine would require a rational strategy to facilitate the structural transition from the expanded to the compact state. Open in a separate window Fig. 1 Structural, biochemical, and immunogenic analysis of E3 particles.a Surface representations of E3 F-, EC-, and EE-particles and thin slices of the corresponding central sections viewed along the two-fold axes, respectively. The surface of the virus is colored by rainbow-color based on the distance of the viral elements from the center, starting with blue.