Coxsackievirus B3—Its Potential as an Oncolytic Virus

Oncolytic virotherapy represents one of the most advanced strategies to treat otherwise untreatable types of cancer. Despite encouraging developments in recent years, the limited fraction of patients responding to therapy has demonstrated the need to search for new suitable viruses. Coxsackievirus B3 (CVB3) is a promising novel candidate with particularly valuable features. Its entry receptor, the coxsackievirus and adenovirus receptor (CAR), and heparan sulfate, which is used for cellular entry by some CVB3 variants, are highly expressed on various cancer types. Consequently, CVB3 has broad anti-tumor activity, as shown in various xenograft and syngeneic mouse tumor models. In addition to direct tumor cell killing the virus induces a strong immune response against the tumor, which contributes to a substantial increase in the efficiency of the treatment. The toxicity of oncolytic CVB3 in healthy tissues is variable and depends on the virus strain. It can be abrogated by genetic engineering the virus with target sites of microRNAs. In this review, we present an overview of the current status of the development of CVB3 as an oncolytic virus and outline which steps still need to be accomplished to develop CVB3 as a therapeutic agent for clinical use in cancer treatment.

MAGI-1 PDZ2 domain blockade averts adenovirus infection via enhanced proteolysis of the apical coxsackievirus and adenovirus receptor

Adenoviruses (AdV) are etiologic agents for gastrointestinal, heart, eye, and respiratory tract infections that can be lethal for immunosuppressed people. Many AdV use the coxsackievirus and adenovirus receptor (CAR) as a primary receptor. The CAR isoform resulting from alternative splicing that includes the eighth exon, CAREx8, localizes to the apical surface of polarized epithelial cells and is responsible for the initiation of AdV infection. We have shown that the membrane level of CAREx8 is tightly regulated by two MAGI-1 PDZ domains; PDZ2, and PDZ4, resulting in increased or decreased AdV transduction, respectively. We hypothesized that targeting the interactions between the MAGI-1 PDZ2 domain and CAREx8 would decrease apical CAREx8 expression level and prevent AdV infection. Decoy peptides that target MAGI-1 PDZ2, were synthesized (TAT-E6, TAT-NET1). PDZ2 binding peptides decreased CAREx8 expression and reduced AdV transduction. CAREx8 degradation was triggered by activation of the regulated intramembrane proteolysis (RIP) pathway through the disintegrin and metalloproteinase (ADAM17) and γ-secretase. Further analysis revealed that ADAM17 interacts directly with the MAGI-1 PDZ3 domain and blocking the PDZ2 domain enhanced the accessibility of ADAM17 to the substrate (CAREx8). Finally, we validated the efficacy of TAT-PDZ2 peptides in protecting the epithelia from AdV transduction in vivo using a novel transgenic animal model. Our data suggest that TAT-PDZ2 binding peptides are novel anti-AdV molecules that act by enhanced RIP of CAREx8 and decreased AdV entry. This strategy has an additional translational potential for targeting other viral receptors which have PDZ binding domains such as the angiotensin-converting enzyme-2 receptor. IMPORTANCE Adenovirus is a common threat in immunosuppressed populations and military recruits. There are no currently approved treatments/prophylactic agents that protect from most AdV infections. Here, we developed peptide-based small molecules that can suppress AdV infection of polarized epithelia by targeting the AdV receptor, coxsackievirus, and adenovirus receptor (CAREx8). The newly discovered peptides target a specific PDZ domain of the CAREx8 interacting protein MAGI-1 and decreased AdV transduction in multiple polarized epithelia models. Peptides-induce CAREx8 degradation is triggered by extracellular domain shedding through ADAM17 followed by γ-secretase-mediated nuclear translocation of the C-terminal domain. The enhanced shedding of CAREx8 ECD further protected the epithelium from AdV infection. Taken together, these novel molecules protect the epithelium from AdV infection. This approach may be applicable to the development of novel antiviral molecules against other viruses that use a receptor with a PDZ binding domain.

Porphyromonas gingivalis induces penetration of lipopolysaccharide and peptidoglycan through the gingival epithelium via degradation of coxsackievirus and adenovirus receptor

Porphyromonas gingivalis is a major pathogen in severe and chronic manifestations of periodontal disease, which is one of the most common infections of humans. A central feature of P. gingivalis pathogenicity is dysregulation of innate immunity at the gingival epithelial interface. We previously showed that junctional adhesion molecule 1 (JAM1) was specifically degraded by P. gingivalis, leading to epithelial barrier breakdown in gingival tissues. Whereas, the involvement of the other JAM family protein(s) in the epithelial barrier dysregulation by P. gingivalis remains unknown. Here we show that Arg-specific or Lys-specific cysteine proteases named gingipains produced by P. gingivalis specifically degrade coxsackievirus and adenovirus receptor (CXADR), a tight junction associated protein, at R145 and K235 in gingival epithelial cells. A P. gingivalis strain lacking gingipains was impaired in degradation of CXADR. Knockdown of CXADR in a three-dimensional multilayered tissue model increased permeability to 40 kDa dextran, lipopolysaccharide, and proteoglycan. Inversely, overexpression of CXADR in a gingival epithelial tissue model prevented penetration by these agents following P. gingivalis infection. Our findings strongly suggest that P. gingivalis gingipains disrupt barrier function of stratified squamous epithelium via degradation of CXADR as well as JAM1, efficiently allowing bacterial virulence factors to penetrate into subepithelial tissues.

Induction of the Coxsackievirus and Adenovirus Receptor in Macrophages During the Formation of Atherosclerotic Plaques

Multiple viruses are implicated in atherosclerosis, but the mechanisms by which they infect cells and contribute to plaque formation in arterial walls are not well understood. Based on reports showing the presence of enterovirus in atherosclerotic plaques we hypothesized that the coxsackievirus and adenovirus receptor (CXADR/CAR), although absent in normal arteries, could be induced during plaque formation. Large-scale microarray and mass spectrometric analyses revealed significant up-regulation of CXADR messenger RNA and protein levels in plaque-invested carotid arteries compared with control arteries. Macrophages were identified as a previously unknown cellular source of CXADR in human plaques and plaques from Ldr−/−Apob100/100 mice. CXADR was specifically associated with M1-polarized macrophages and foam cells and was experimentally induced during macrophage differentiation. Furthermore, it was significantly correlated with receptors for other viruses linked to atherosclerosis. The results show that CXADR is induced in macrophages during plaque formation, suggesting a mechanism by which enterovirus infect cells in atherosclerotic plaques.

Spectrum-Wide Exploration of Human Adenoviruses for Breast Cancer Therapy

Oncolytic adenoviruses (Ads) are promising tools for cancer therapeutics. However, most Ad-based therapies utilize Ad type 5 (Ad5), which displays unsatisfying efficiency in clinical trials, partly due to the low expression levels of its primary coxsackievirus and adenovirus receptor (CAR) on tumor cells. Since the efficacy of virotherapy strongly relies on efficient transduction of targeted tumor cells, initial screening of a broad range of viral agents to identify the most effective vehicles is essential. Using a novel Ad library consisting of numerous human Ads representing known Ad species, we evaluated the transduction efficiencies in four breast cancer (BC) cell lines. For each cell line over 20 Ad types were screened in a high-throughput manner based on reporter assays. Ad types featuring high transduction efficiencies were further investigated with respect to the percentage of transgene-positive cells and efficiencies of cellular entry in individual cell lines. Additionally, oncolytic assay was performed to test tumor cell lysis efficacy of selected Ad types. We found that all analyzed BC cell lines show low expression levels of CAR, while alternative receptors such as CD46, DSG-2, and integrins were also detected. We identified Ad3, Ad35, Ad37, and Ad52 as potential candidates for BC virotherapy.