Two types of functionally distinct fiber containing structural protein complexes are produced during infection of adenovirus serotype 5.

Bo Zhang,Liang Ran,Andre Lieber,Hongyu Lin,Xiaolong Fan,Xiaoyan Zhang,Jin Liu,Zongyi Li,Chao Xi,Jie Jin,Yuhua Yan

doi:10.1371/journal.pone.0117976

Bo Zhang, Liang Ran + Show 9 more

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https://doi.org/10.1371/journal.pone.0117976

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Abstract

Adenoviruses are common pathogens. The localization of their receptors coxsackievirus and adenovirus receptor, and desmoglein-2 in cell-cell junction complexes between polarized epithelial cells represents a major challenge for adenovirus infection from the apical surface. Structural proteins including hexon, penton base and fiber are excessively produced in serotype 5 adenovirus (Ad5)-infected cells. We have characterized the composition of structural protein complexes released from Ad5 infected cells and their capacity in remodeling cell-cell junction complexes. Using T84 cells as a model for polarized epithelium, we have studied the effect of Ad5 structural protein complexes in remodeling cell-cell junctions in polarized epithelium. The initial Ad5 infection in T84 cell culture was inefficient. However, progressive distortion of cell-cell junction in association with fiber release was evident during progression of Ad5 infection. Incubation of T84 cell cultures with virion-free supernatant from Ad5 infected culture resulted in distortion of cell-cell junctions and decreased infectivity of Ad5-GFP vector. We used gel filtration chromatography to fractionate fiber containing virion–free supernatant from Ad5 infected culture supernatant. Fiber containing fractions were further characterized for their capacity to inhibit the infection of Ad5-GFP vector, their composition in adenovirus structural proteins using western blot and LC-MS/MS and their capacity in remolding cell-cell junctions. Fiber molecules in complexes containing penton base and hexon, or mainly hexon were identified. Only the fiber complexes with relatively high content of penton base, but not the fiber-hexon complexes with low penton base, were able to penetrate into T84 cells and cause distortion of cell-cell junctions. Our findings suggest that these two types of fiber complexes may play different roles in adenoviral infection.

Highlights

Human adenoviruses (HAdVs) are nonenveloped viruses causing a variety of infections in respiratory, ocular and enteric systems
In vitro studies have demonstrated that the majority of HAdVs utilize coxsackievirus and adenovirus receptor (CAR) as a receptor to initiate the infection [2]
Fiber molecules are expected to bind to CAR, which is a component of tight junction (TJ) complexes

Summary

Introduction

Human adenoviruses (HAdVs) are nonenveloped viruses causing a variety of infections in respiratory, ocular and enteric systems. The adenoviral capsid is composed of three major structural proteins: hexon, penton base and fiber. The infection of host cells by HAdVs is initiated by fiber binding to its receptors on the surface of host cells. In vitro studies have demonstrated that the majority of HAdVs utilize coxsackievirus and adenovirus receptor (CAR) as a receptor to initiate the infection [2]. HAdVs of subgroup B utilize either CD46 [3,4], or Desmoglein 2 (DSG-2) [5] to initiate infection. Ad37 (subgroup D), a leading cause of epidemic keratoconjunctivitis, utilizes GD1a glycan [6]. The binding of fiber molecules to receptors mediates the attachment of viral particle to host cells, which is followed by penton base-mediated interactions with integrin molecules for internalization of adenoviral particles [7]

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