Human Adenovirus Type 37 Uses α_Vβ₁and α₃β₁Integrins for Infection of Human Corneal Cells

Abstract

Epidemic keratoconjunctivitis (EKC) is a severe, contagious ocular disease that affects 20 to 40 million individuals worldwide every year. EKC is mainly caused by six types of human adenovirus (HAdV): HAdV-8, -19, -37, -53, -54, and -56. Of these, HAdV-8, -19, and -37 use sialic acid-containing glycans as cellular receptors. αVβ3, αVβ5, and a few additional integrins facilitate entry and endosomal release of other HAdVs. With the exception of a few biochemical analyses indicating that HAdV-37 can interact physically with αVβ5, little is known about the integrins used by EKC-causing HAdVs. Here, we investigated the overall integrin expression on human corneal cells and found expression of α2, α3, α6, αV, β1, and β4 subunits in human corneal in situ epithelium and/or in a human corneal epithelial (HCE) cell line but no or less accessible expression of α4, α5, β3, or β5. We also identified the integrins used by HAdV-37 through a series of binding and infection competition experiments and different biochemical approaches. Together, our data suggest that HAdV-37 uses αVβ1 and α3β1 integrins for infection of human corneal epithelial cells. Furthermore, to confirm the relevance of these integrins in the HAdV-37 life cycle, we developed a corneal multilayer tissue system and found that HAdV-37 infection correlated well with the patterns of αV, α3, and β1 integrin expression. These results provide further insight into the tropism and pathogenesis of EKC-causing HAdVs and may be of importance for future development of new antiviral drugs.IMPORTANCE Keratitis is a hallmark of EKC, which is caused by six HAdV types (HAdV-8, -19, -37, -53, -54, and -56). HAdV-37 and some other HAdV types interact with integrin αVβ5 in order to enter nonocular human cells. In this study, we found that αVβ5 is not expressed on human corneal epithelial cells, thus proposing other host factors mediate corneal infection. Here, we first characterized integrin expression patterns on corneal tissue and corneal cells. Among the integrins identified, competition binding and infection experiments and biochemical assays pointed out αVβ1 and α3β1 to be of importance for HAdV-37 infection of corneal tissue. In the absence of a good animal model for EKC-causing HAdVs, we also developed an in vitro system with multilayer HCE cells and confirmed the relevance of the suggested integrins during HAdV-37 infection.

The roles of tetraspanins in bacterial infections

“…Although it was shown that host cell entry, assembly and release of various viruses are mediated by the Tspans in a dependent or independent manner (through their partners such as integrins), there is currently no evidence, other than the FimH/Tspan21 complex, that bacteria interact with Tspans directly. The major function of Tspans during bacterial infection may rely on connecting bacterial ligands to additional surface proteins belonging to TEMs platforms, such as integrins (Rajan et al, 2018; Storm et al, 2017; TerBush, Hafkamp, Lee, & Coscoy, 2018). Thus, further work is required to unravel the contribution of individual Tspans or their cognate partners in the different processes leading to bacterial colonisation of the host.…”

Identification of chicken CAR homology as a cellular receptor for the emerging highly pathogenic fowl adenovirus 4 via unique binding mechanism

“…Most AdVs have one unique fibre that attaches to variable cellular receptors. HAdV-2 and HAdV-5 in subgroup C use the high-affinity human coxsackie and adenovirus receptor (CAR) as the cellular receptor to infect host cells [13,14], HAdV-37 uses integrins to infect human corneal cells [15], mouse adenovirus type 1 utilizes integrin and heparin sulfate as cellular receptors [16], bovine adenovirus serotype 3 utilizes sialic acid as a receptor for viral entry [17], and porcine adenovirus serotype 3 internalization is independent of CAR and integrin, but uses some other receptors [18]. However, HAdV-52, HAdV-40 [19], and HAdV-41 [20] are equipped with two different fibre proteins, only the long fibre type is inserted into each penton and binds the CAR, whereas the short fibre binds to sialylated glycoproteins during infection [21,22].…”

Human adenovirus binding to host cell receptors: a structural view

“…Interactions with integrins stimulate integrin clustering signalling for endocytosis, and virus entry into the host cell via the endocytic pathway is thought to be promoted through such receptor clustering. The integrin most extensively studied in the context of HAdV entry is α v β 3 [22], although other integrins, such as α v β 5 , α v β 1 and α 3 β 1 [22,56] can also function in the same manner.…”