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Triazole linker-based trivalent sialic acid inhibitors of adenovirus type 37 infection of human corneal epithelial cells
Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
Interfaculty Institute of Biochemistry, University of Tübingen, Germany.
Interfaculty Institute of Biochemistry, University of Tübingen, Germany.
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2015 (English)In: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 13, no 35, p. 9194-9205Article in journal (Refereed) Published
Abstract [en]

Adenovirus type 37 (Ad37) is one of the principal agents responsible for epidemic keratoconjunctivitis (EKC), a severe ocular infection that remains without any available treatment. Recently, a trivalent sialic acid derivative (ME0322, Angew. Chem. Int. Ed., 2011, 50, 6519) was shown to function as a highly potent inhibitor of Ad37, efficiently preventing the attachment of the virion to the host cells and subsequent infection. Here, new trivalent sialic acid derivatives were designed, synthesized and their inhibitory properties against Ad37 infection of the human corneal epithelial cells were investigated. In comparison to ME0322, the best compound (17a) was found to be over three orders of magnitude more potent in a cell-attachment assay (IC50 = 1.4 nM) and about 140 times more potent in a cell-infection assay (IC50 = 2.9nM). X-ray crystallographic analysis demonstrated a trivalent binding mode of all compounds to the Ad37 fiber knob. For the most potent compound ophthalmic toxicity in rabbits was investigated and it was concluded that repeated eye administration did not cause any adverse effects.

Place, publisher, year, edition, pages
2015. Vol. 13, no 35, p. 9194-9205
National Category
Microbiology in the medical area
Identifiers
URN: urn:nbn:se:umu:diva-100014DOI: 10.1039/C5OB01025JISI: 000360115100007OAI: oai:DiVA.org:umu-100014DiVA, id: diva2:789296
Available from: 2015-02-18 Created: 2015-02-18 Last updated: 2019-08-28Bibliographically approved
In thesis
1. Early host cell interactions and antivirals against ocular adenoviruses
Open this publication in new window or tab >>Early host cell interactions and antivirals against ocular adenoviruses
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Tidiga värd cells interaktioner och antiviraler mot okulära adenovirus
Abstract [en]

Viruses are common causative agents of ocular infection among humans. Epidemic keratoconjuntivitis (EKC) is a severe and contagious ocular disease with reported outbreaks worldwide. It is estimated that this disease affects 20-40 million individuals every year, which leads to huge socioeconomic costs for the affected countries. EKC is characterized by keratitis and conjunctivitis but is also associated with pain, edema, lacrimation, and decreased vision that can prolong for months after the infection and in rare cases years. This disease is caused by human adenoviruses (HAdVs), which belong to the family of Adenoviridae. Currently, there is no available treatment against EKC.

EKC is mainly caused by HAdV-8, HAdV-19, HAdV-37, HAdV-53, HAdV-54, and HAdV-56, which belong to species D HAdVs. HAdV-8, HAdV-19 and HAdV-37 have previously been shown to use sialic acid (SA)-containing glycans as cellular receptors to bind to and infect human corneal epithelial (HCE) cells. To characterize the receptor in more detail, we performed a glycan array, which included SA-containing glycans. A branched hexasaccharide terminating with SA in each arm was identified as a candidate receptor. This glycan corresponds to the glycan motif found on a ganglioside, GD1a. By performing a series of biological and biochemical experiments we confirmed the function of the GD1a glycan as a cellular receptor for EKC-causing HAdVs. However, the glycan used as a receptor was linked to plasma membrane protein(s) through O-glycosidic bonds, rather than to a lipid (as in the ganglioside). X-ray crystallography analysis showed that the two terminal SA:s interacted with two of the three previously identified SA-binding sites on the knob domain of the HAdV-37 capsid protein known as the fiber.

Based on the structural features of the GD1a:HAdV-37 knob interaction, we assumed that a three-armed molecule with each arm terminating with SA would be an efficient inhibitor. Such molecules were designed, synthesized and found to efficiently prevent HAdV-37 binding to and infection of corneal cells. These results indicate that trisialic acids-containing compounds may be used for treatment of EKC.

After binding to its primary receptor, most HAdVs have been shown to interact with αVβ3 and αVβ5 integrins to enter human cells. This interaction occurs through the RGD (arginine-alanine-aspartic acid) motif in the capsid protein known as the penton base. However, it was not clear if corneal epithelial cells express αVβ3 and αVβ5 integrins. Thus, to better understand additional early steps of infection by EKC-causing HAdVs, we performed binding and infection competition experiments using human corneal epithelial cells and siRNA, integrin specific antibodies, peptides and RGD-containing ligands indicating that α3, αV, β1 affected HAdV-37 infection of but not binding to HCE cells. We could also see that HAdV-37 co-localize with α3 and αV at after entry into HCE cells. In situ histochemistry confirmed that the expression of α3 and αV in human corneal tissue. Overall, our results suggest that αV and α3 integrins are important for HAdV-37 infection of corneal cells.

Altogether, these results provide further insight into the biology of HAdVs and open up for development of novel antiviral drugs.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2015. p. 90
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1697
Keywords
Adenovirus, Virus host interactions, Antivirals, Sialic acid, Integrins, Epidemic keratoconjuntivitis
National Category
Microbiology in the medical area
Identifiers
urn:nbn:se:umu:diva-99907 (URN)978-91-7601-211-6 (ISBN)
Public defence
2015-03-13, Hörsal Betula, 6M, Norrlands universitetssjukhus, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2015-02-20 Created: 2015-02-16 Last updated: 2018-06-07Bibliographically approved
2. The glycobiology of human adenovirus infections: implications for tropism and treatment
Open this publication in new window or tab >>The glycobiology of human adenovirus infections: implications for tropism and treatment
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Human adenoviruses (HAdVs) are common human pathogens, causing gastrointestinal, ocular, and respiratory infections on a regular basis. Epidemic keratoconjunctivitis (EKC) is a severe ocular infection for which no approved antivirals are available. HAdV-D37 is one of the causative agents of EKC and uses sialic acid (SA)-containing glycans as cellular receptors. HAdV-D37 interacts with SA via the knob domain of the trimeric virus fiber protein, containing three SA-binding sites. HAdV-D37 also bind to glycosaminoglycans (GAGs), but the outcome of this interaction remains unknown. Here, using biochemical and cell-based assays, the impact of GAGs on HAdV-D37 infection (paper I) was investigated. We found that HAdV-D37 interacts with both soluble and cell-surface sulfated GAGs via the knob domain of the viral fiber protein. Remarkably, removal of heparan sulfate (HS; a type of GAG) from human corneal epithelial (HCE) cells by heparinase III enhanced HAdV-D37 infection. We propose that sulfated GAGs in bodily secretions and on plasma membranes function as decoy receptors that prevent the virus from binding to SA-containing receptors and inhibit subsequent virus infection. We also found abundant HS in the basement membrane of the human corneal epithelium. We suggest that this layer of HS functions as a barrier to sub-epithelial infection of HAdV-D37. Based on this finding, we hypothesized that GAG-mimetics may act as artificial decoy receptors and inhibit HAdV-D37 infection. Here, the antiviral effect of suramin (a known GAG-mimetic) and its analogs against HAdV-D37 (paper II) was evaluated. Interestingly, all compounds displayed antiviral effects by inhibiting the binding of HAdV-D37 to HCE cells. The antiviral effect of suramin was HAdV species-specific. We report for the first time that virus binding to cell-surface decoy receptor constitutes a potential target for antiviral drug development.

HAdVs are the major cause of infectious conjunctivitis, constituting up to 75% of all conjunctivitis cases worldwide. Species B HAdV type 3 (HAdV-B3) causes pharyngoconjunctival fever (PCF), whereas HAdV-D8, -D37, and -D64 cause EKC. Recently, HAdV-D53, -D54, and -D56 have emerged as new EKC-causing agents. HAdV-E4 causes both PCF and EKC. SA-containing glycans have been established as cellular receptors for HAdV-D37. By means of cell-based assays, we investigated if ocular HAdVs other than HAdV-D37 also use SA-containing glycans as receptors on HCE cells (paper III). It was found that SA-containing glycans function as cellular receptors for five (HAdV-D8, -D37, -D53, -D54, and -D64) out of six EKC-causing species D HAdVs. We showed that these viruses interact with SAs via the knob domain of the viral fiber protein. HAdV-E4 and -D56 infection of cells was independent of SAs. Surprisingly, HCE cells were completely refractory to HAdV-B3 infection. A trivalent sialic acid (TSA) derivative ME0462 (compound 17a in paper II), designed to bind to SA-binding sites on HAdV-D37 fiber knob, also showed potent antiviral activity against several EKC-causing HAdVs. This suggests that ME0462 can be used as a broad-spectrum antiviral against known and emerging EKC-causing HAdVs. Surface plasmon resonance (SPR) analysis confirmed a direct interaction between ME0462 and fiber knobs of EKC-causing HAdVs.

Recently, a TSA derivative (ME0322; designed to bind to SA-binding sites on HAdV-D37 fiber knob) was shown potent antiviral against HAdV-D37 in vitro. To improve the antiviral potency of this compound, six new TSA derivatives were synthesized and their inhibitory effects were evaluated against HAdV-D37 (paper IV). Interestingly, the best compound 17a was found approximately three orders of magnitude more potent (IC50 (binding) = 1.4 nM, IC50 (infection) = 2.9 nM) than ME0322 (IC50 in µM range). SPR data showed that HAdV-D37 fiber knob binds to TSA compounds with high affinities. Structural data revealed the trivalent binding mode of all newly synthesized TSA compounds to HAdV-D37 fiber knob. Ophthalmic toxicity of compound 17a (best compound) was also investigated in rabbits without any sign of toxicity.

HAdV-D36 is a member of species D HAdV and has the ability to infect a broad range of animals, which is unusual for HAdVs. Another remarkable feature of HAdV-D36 is that this virus induces obesity in experimental animals. Several epidemiological studies highlighted a link between HAdV-D36 and human obesity. There is no information about the cellular receptor usage by HAdV-D36. Using structural biology and cell-based approaches, we investigated the cellular receptor(s) for HAdV-D36 (paper V).  We show that HAdV-D36 attaches to host cells (via the fiber knob) using the coxsackie and adenovirus receptor (CAR), SA-containing glycans, and one or more unknown proteins or glycoproteins. Using glycan microarray, we found that HAdV-D36 displays binding preference to a rare SA-variant: 4-O,5-N-diacetylneuraminic acid (Neu4,5Ac2), over the more common SA (in humans) i.e. 5-N-acetylneuraminic acid (Neu5Ac). Structural analysis of HAdV-D36 fiber knob:Neu4,5Ac2 complex explained this preference. To date, Neu4,5Achas not been detected in humans, although it is synthesized by many domestic and livestock animals. Our results indicate that HAdV-D36 has evolved to utilize a specialized set of cellular receptors that coincide with a unique host range and pathogenicity profile.

These studies provide insights into multiple roles of glycans in HAdV infection cycle and highlight the therapeutic potential of glycans/glycan-mimetics in HAdV-D37 infection.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2019. p. 111
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 2046
Keywords
denovirus, cellular receptor, glycosaminoglycan, sialic acid, decoy receptors, tropism, epidemic keratoconjunctivitis, antiviral drugs, GAG-mimetic, obesity
National Category
Microbiology in the medical area Infectious Medicine
Research subject
Medical Virology
Identifiers
urn:nbn:se:umu:diva-162709 (URN)978-91-7855-104-0 (ISBN)
Public defence
2019-09-20, Sal E04, byggnad 6A, Umeå, 09:00 (English)
Opponent
Supervisors
Note

I publikationen felaktigt ISBN: 978-91-7601-940-5

Available from: 2019-08-30 Created: 2019-08-26 Last updated: 2019-09-04Bibliographically approved

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Caraballo, RémiSaleeb, MichaelChandra, NareshStorm, Rickard JFrängsmyr, LarsQian, WeixingArnberg, NiklasElofsson, Mikael

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