Přehled o publikaci

Tick-borne encephalitis virus (TBEV), an enveloped virus belonging to the Flaviviridae family, causes severe central nervous system disease in humans. The virus has a smooth surface covered by envelope proteins (E-proteins), which, along with membrane proteins (M-proteins), are anchored in the viral lipid bilayer. During its life cycle, the immature, non-infectious virus undergoes a maturation process characterized by the proteolytic cleavage of prM and significant rearrangement of the envelope proteins on its surface. We isolated immature TBEV particles from infected tissue culture cells and visualized their structure using cryo-electron microscopy. We solved the high-resolution structure of the E-protein-prM-protein complex, which forms the "spiky" surface of immature particles. Through combination of cryo-electron tomography and single-particle analysis, we demonstrated that TBEV immature particles are asymmetric. Assembly defects often disrupt the symmetric, icosahedral structure of the E-protein-prM-protein spikes on the particle surface. However, these irregularities do not impede the subsequent maturation process, resulting in mature particles with vacant patches in the "herringbone" pattern of the mature viral surface. The findings shed additional light on the viral assembly of TBEV and its maturation process, which may be the subject of future antiviral medication development.