Rotavirus Replication: Gaps of Knowledge on Virus Entry and Morphogenesis

Abstract

In 1973, rotaviruses A (RVAs) were discovered as major causative agents of acute gastroenteritis in infants and young children worldwide. The infectious RV virion is an icosahedral particle composed of three concentric protein layers surrounding the 11 double-stranded (dsRNA) segments. An in vitro replication system for RVs in permanent cell lines was developed in 1982 and expanded to replication in intestinal organoids in 2015. However, the details of rotavirus (RV) entry into cells and particle maturation mechanisms at the molecular level remain incompletely understood. Slowing down human RVA replication in cell culture on ice allowed morphological visualization of virus particle entry and the assembly of triplelayered particles (virion). Although RVAs are non-enveloped viruses, after virus attachment to the cell membrane, the virus enters the cell by perforating the plasma membrane by a fusion mechanism involving VP5* of the cleaved VP4 protein, as the alternative virus entry route besides the receptor-mediated endocytosis which is generally accepted. After assembling double-layered particles (DLPs) in viroplasm or cytoplasm, they appear to be connected with the endoplasmic reticulum (ER) membrane and become coated with outer capsid proteins (VP4 and VP7) in a coating process. The perforation of the ER membrane is caused by an unknown mechanism following interaction between non-structural protein 4 (NSP4) and the inner capsid protein VP6 of the DLPs. The coating process is closely related to the formation of a hetero-oligomeric complex (NSP4, VP4 and VP7). These lines of evidence suggest the existence of novel mechanisms of RV morphogenesis.

Mechanisms of Cell Entry by dsRNA Viruses: Insights for Efficient Delivery of dsRNA and Tools for Improved RNAi-Based Pest Control

“…Rotaviruses exhibit a very distinct tropism and infect primarily differentiated enterocytes at the top of the intestinal villi in the jejunum of the small intestine (Guerrero et al, 2000). As is the case for orthoreoviruses, a major achievement was the establishment of cell culture models, in which simian rotaviruses (e.g., Rhesus rotavirus) could efficiently infect polarized cell lines of renal or intestinal epithelial origin (Estes et al, 1979;Suzuki, 2019). More recently, the technology of human intestinal enteroids has allowed the study of the pathophysiology of human rotaviruses (Saxena et al, 2015).…”

“…Direct cell membrane penetration of rotaviral particles, in the absence of endocytosis, has also been observed ( Suzuki, 2019 ). Using infection of the green monkey kidney cell line BSC-1 by Rhesus rotavirus as a model, the interaction with the host cells of “triple-layered particles” (i.e., virions), that were differentially fluorescently labeled on outer layer and inner layer capsid proteins, was monitored by live cell imaging ( Abdelhakim et al, 2014 ).…”

Alteration of cell junctions during viral infection

“…Rotavirus (RV) is the most common cause of severe vomiting and diarrhea in infants and young children. 34 RV is an enterovirus with a wheel-like structure that is assembled in the lumen of the endoplasmic reticulum (ER); subviral particles germinate until the cells are lysed, with the mature virus remaining in the ER. RV enters cells via receptor-mediated calcium-dependent endocytosis, which causes calcium ions (Ca 2+ ) to move from the endocytic vesicle to the cytoplasm.…”

“…Rotavirus (RV) is the most common cause of severe vomiting and diarrhea in infants and young children . RV is an enterovirus with a wheel‐like structure that is assembled in the lumen of the endoplasmic reticulum (ER); subviral particles germinate until the cells are lysed, with the mature virus remaining in the ER.…”

Goreisan regulates AQP3 expression and improves diarrhea

“…However, there are no effective drugs for treating the disease itself. Generally, when an infection occurs in the intestinal mucosa, the ensuing inflammatory reaction causes a breakdown of the intestinal mucosa barrier function [6][7][8], which disrupts the balance between water secretion and absorption in the intestinal tract, resulting in diarrhea and other symptoms.…”