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Hu CT, Diaz K, Yang LC, Sharma A, Greenberg HB, Smith JG. Corrected and republished from: "VP4 Is a Determinant of Alpha-Defensin Modulation of Rotaviral Infection". J Virol 2023; 97:e0096223. [PMID: 37787534 PMCID: PMC10617384 DOI: 10.1128/jvi.00962-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Accepted: 06/29/2023] [Indexed: 10/04/2023] Open
Abstract
IMPORTANCE Rotavirus is a leading cause of severe diarrhea in young children. Like other fecal-oral pathogens, rotaviruses encounter abundant, constitutively expressed defensins in the small intestine. These peptides are a vital part of the vertebrate innate immune system. By investigating the impact that defensins from multiple species have on the infectivity of different strains of rotavirus, we show that some rotaviral infections can be inhibited by defensins. We also found that rotaviruses may have evolved resistance to defensins in the intestine of their host species, and some even appropriate defensins to increase their infectivity. Because rotaviruses infect a broad range of animals and rotaviral infections are highly prevalent in children, identifying immune defenses against infection and how they vary across species and among viral genotypes is important for our understanding of the evolution, transmission, and zoonotic potential of these viruses as well as the improvement of vaccines.
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Affiliation(s)
- Ciara T. Hu
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, USA
| | - Karina Diaz
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, USA
| | - Linda C. Yang
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, USA
| | - Anjali Sharma
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, USA
| | - Harry B. Greenberg
- Department of Medicine, Stanford School of Medicine, Stanford, California, USA
- Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, California, USA
| | - Jason G. Smith
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, USA
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Porter JM, Oswald MS, Sharma A, Emmanuel S, Kansol A, Bennett A, McKenna R, Smith JG. A Single Surface-Exposed Amino Acid Determines Differential Neutralization of AAV1 and AAV6 by Human Alpha-Defensins. J Virol 2023; 97:e0006023. [PMID: 36916912 PMCID: PMC10062168 DOI: 10.1128/jvi.00060-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Accepted: 02/21/2023] [Indexed: 03/16/2023] Open
Abstract
Adeno-associated viruses (AAVs) are being developed as gene therapy vectors due to their low pathogenicity and tissue tropism properties. However, the efficacy of these vectors is impeded by interactions with the host immune system. One potential immune barrier to vector transduction is innate immune host defense peptides, such as alpha-defensins, which are potent antiviral agents against other nonenveloped viruses. To investigate the interaction between AAVs and alpha-defensins, we utilized two closely related AAV serotypes, AAV1 and AAV6. Although their capsids differ by only six residues, these two serotypes exhibit markedly different tissue tropisms and transduction efficiencies. Using two abundant human alpha-defensins, enteric human defensin 5 (HD5) and myeloid human neutrophil peptide 1 (HNP1), we found both serotype-specific and defensin-specific effects on AAV infection. AAV6 infection was uniformly neutralized by both defensins at low micromolar concentrations; however, inhibition of AAV1 infection was profoundly influenced by the timing of defensin exposure to the virus relative to viral attachment to the cell. Remarkably, these differences in the defensin-dependent infection phenotype between the viruses are completely dictated by the identity of a single, surface-exposed amino acid (position 531) that varies between the two serotypes. These findings reveal a determinant for defensin activity against a virus with unprecedented precision. Furthermore, they provide a rationale for the investigation of other AAV serotypes not only to understand the mechanism of neutralization of defensins against AAVs but also to design more efficient vectors. IMPORTANCE The ability of adeno-associated viruses (AAVs) to infect and deliver genetic material to a range of cell types makes them favorable gene therapy vectors. However, AAV vectors encounter a wide variety of host immune factors throughout the body, which can impede efficient gene delivery. One such group of factors is the alpha-defensins, which are a key component of the innate immune system that can directly block viral infection. By studying the impact that alpha-defensins have on AAV infection, we found that two similar AAV serotypes (AAV1 and AAV6) have different sensitivities to inhibition. We also identified a single amino acid (position 531) that differs between the two AAV serotypes and is responsible for mediating their defensin sensitivity. By investigating the effects that host immune factors have on AAV infection, more efficient vectors may be developed to evade intervention by the immune system prior to gene delivery.
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Affiliation(s)
- Jessica M. Porter
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, USA
| | - Mackenzi S. Oswald
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, USA
| | - Anjali Sharma
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, USA
| | - Shanan Emmanuel
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Austin Kansol
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Antonette Bennett
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Robert McKenna
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Jason G. Smith
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, USA
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3
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The Inhibition of DNA Viruses by the Amphibian Antimicrobial Peptide Temporin G: A Virological Study Addressing HSV-1 and JPCyV. Int J Mol Sci 2022; 23:ijms23137194. [PMID: 35806198 PMCID: PMC9266403 DOI: 10.3390/ijms23137194] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Revised: 06/24/2022] [Accepted: 06/25/2022] [Indexed: 12/17/2022] Open
Abstract
Herpes simplex virus type-1 (HSV-1) and John Cunningham polyomavirus (JCPyV) are widely distributed DNA viruses causing mainly asymptomatic infection, but also mild to very severe diseases, especially when these viruses reach the brain. Some drugs have been developed to inhibit HSV-1 replication in host cells, but their prolonged use may induce resistance phenomena. In contrast, to date, there is no cure for JCPyV. The search for alternative drugs that can reduce viral infections without undermining the host cell is moving toward antimicrobial peptides (AMPs) of natural occurrence. These include amphibian AMPs belonging to the temporin family. Herein, we focus on temporin G (TG), showing that it strongly affects HSV-1 replication by acting either during the earliest stages of its life cycle or directly on the virion. Computational studies have revealed the ability of TG to interact with HSV-1 glycoprotein B. We also found that TG reduced JCPyV infection, probably affecting both the earliest phases of its life cycle and the viral particle, likely through an interaction with the viral capsid protein VP1. Overall, our results are promising for the development of short naturally occurring peptides as antiviral agents used to counteract diseases related to HSV-1 and JCPyV.
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Hu CT, Diaz K, Yang LC, Sharma A, Greenberg HB, Smith JG. VP4 Is a Determinant of Alpha-Defensin Modulation of Rotaviral Infection. J Virol 2022; 96:e0205321. [PMID: 35285683 PMCID: PMC9006894 DOI: 10.1128/jvi.02053-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 01/31/2022] [Indexed: 11/20/2022] Open
Abstract
Fecal-oral pathogens encounter constitutively expressed enteric alpha-defensins in the intestine during replication and transmission. Alpha-defensins can be potently antiviral and antibacterial; however, their primary sequences, the number of isoforms, and their activity against specific microorganisms often vary greatly between species, reflecting adaptation to species-specific pathogens. Therefore, alpha-defensins might influence not only microbial evolution and tissue tropism within a host but also species tropism and zoonotic potential. To investigate these concepts, we generated a panel of enteric and myeloid alpha-defensins from humans, rhesus macaques, and mice and tested their activity against group A rotaviruses, an important enteric viral pathogen of humans and animals. Rotaviral adaptation to the rhesus macaque correlated with resistance to rhesus enteric, but not myeloid, alpha-defensins and sensitivity to human alpha-defensins. While mouse rotaviral infection was increased in the presence of mouse enteric alpha-defensins, two prominent genotypes of human rotaviruses were differentially sensitive to human enteric alpha-defensins. Furthermore, the effects of cross-species alpha-defensins on human and mouse rotaviruses did not follow an obvious pattern. Thus, exposure to alpha-defensins may have shaped the evolution of some, but not all, rotaviruses. We then used a genetic approach to identify the viral attachment and penetration protein, VP4, as a determinant of alpha-defensin sensitivity. Our results provide a foundation for future studies of the VP4-dependent mechanism of defensin neutralization, highlight the species-specific activities of alpha-defensins, and focus future efforts on a broader range of rotaviruses that differ in VP4 to uncover the potential for enteric alpha-defensins to influence species tropism. IMPORTANCE Rotavirus is a leading cause of severe diarrhea in young children. Like other fecal-oral pathogens, rotaviruses encounter abundant, constitutively expressed defensins in the small intestine. These peptides are a vital part of the vertebrate innate immune system. By investigating the impact that defensins from multiple species have on the infectivity of different strains of rotavirus, we show that some rotaviral infections can be inhibited by defensins. We also found that some, but not all, rotaviruses may have evolved resistance to defensins in the intestine of their host species, and some even appropriate defensins to increase their infectivity. Because rotaviruses infect a broad range of animals and rotaviral infections are highly prevalent in children, identifying immune defenses against infection and how they vary across species and among viral genotypes is important for our understanding of the evolution, transmission, and zoonotic potential of these viruses as well as the improvement of vaccines.
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Affiliation(s)
- Ciara T. Hu
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, USA
| | - Karina Diaz
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, USA
| | - Linda C. Yang
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, USA
| | - Anjali Sharma
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, USA
| | - Harry B. Greenberg
- Department of Medicine and Department of Microbiology and Immunology, Stanford School of Medicine, Stanford, California, USA
| | - Jason G. Smith
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, USA
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Diaz K, Hu CT, Sul Y, Bromme BA, Myers ND, Skorohodova KV, Gounder AP, Smith JG. Defensin-driven viral evolution. PLoS Pathog 2020; 16:e1009018. [PMID: 33232373 PMCID: PMC7723274 DOI: 10.1371/journal.ppat.1009018] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 12/08/2020] [Accepted: 10/02/2020] [Indexed: 01/06/2023] Open
Abstract
Enteric alpha-defensins are potent effectors of innate immunity that are abundantly expressed in the small intestine. Certain enteric bacteria and viruses are resistant to defensins and even appropriate them to enhance infection despite neutralization of closely related microbes. We therefore hypothesized that defensins impose selective pressure during fecal-oral transmission. Upon passaging a defensin-sensitive serotype of adenovirus in the presence of a human defensin, mutations in the major capsid protein hexon accumulated. In contrast, prior studies identified the vertex proteins as important determinants of defensin antiviral activity. Infection and biochemical assays suggest that a balance between increased cell binding and a downstream block in intracellular trafficking mediated by defensin interactions with all of the major capsid proteins dictates the outcome of infection. These results extensively revise our understanding of the interplay between defensins and non-enveloped viruses. Furthermore, they provide a feasible rationale for defensins shaping viral evolution, resulting in differences in infection phenotypes of closely related viruses. Defensins are potent antimicrobial peptides that are found on human mucosal surfaces and can directly neutralize viruses. They are abundant in the small intestine, which is constantly challenged by ingested viral pathogens. Interestingly, non-enveloped viruses, such as adenovirus, that infect the gastrointestinal system are unaffected by defensins or can even appropriate defensins to enhance their infection. In contrast, respiratory adenoviruses are neutralized by the same defensins. How enteric viruses overcome defensin neutralization is not well understood. Our studies are the first to show that defensins can drive the evolution of non-enveloped viruses. Furthermore, we identify important components within human adenovirus that dictate sensitivity to defensins. This new insight into defensin-virus interactions informs our understanding of mucosal immunity to viral infections.
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Affiliation(s)
- Karina Diaz
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, United States of America
| | - Ciara T. Hu
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, United States of America
| | - Youngmee Sul
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, United States of America
| | - Beth A. Bromme
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, United States of America
| | - Nicolle D. Myers
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, United States of America
| | - Ksenia V. Skorohodova
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, United States of America
| | - Anshu P. Gounder
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, United States of America
| | - Jason G. Smith
- Department of Microbiology, University of Washington School of Medicine, Seattle, Washington, United States of America
- * E-mail:
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6
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Abstract
Defensins are a major family of host defense peptides expressed predominantly in neutrophils and epithelial cells. Their broad antimicrobial activities and multifaceted immunomodulatory functions have been extensively studied, cementing their role in innate immunity as a core host-protective component against bacterial, viral and fungal infections. More recent studies, however, paint defensins in a bad light such that they are "alleged" to promote viral and bacterial infections in certain biological settings. This mini review summarizes the latest findings on the potential pathogenic properties of defensins against the backdrop of their protective roles in antiviral and antibacterial immunity. Further, a succinct description of both tumor-proliferative and -suppressive activities of defensins is also given to highlight their functional and mechanistic complexity in antitumor immunity. We posit that given an enabling environment defensins, widely heralded as the "Swiss army knife," can function as a "double-edged sword" in host immunity.
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Affiliation(s)
- Dan Xu
- Institute of Mitochondrial Biology and Medicine, Key Laboratory of Biomedical Information Engineering of the Ministry of Education, School of Life Sciences and Technology, Xi’an Jiaotong University, Xi’an, China
| | - Wuyuan Lu
- Institute of Human Virology and Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD, United States
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Kane JR, Fong S, Shaul J, Frommlet A, Frank AO, Knapp M, Bussiere DE, Kim P, Ornelas E, Cuellar C, Hyrina A, Abend JR, Wartchow CA. A polyomavirus peptide binds to the capsid VP1 pore and has potent antiviral activity against BK and JC polyomaviruses. eLife 2020; 9:50722. [PMID: 31960795 PMCID: PMC6974358 DOI: 10.7554/elife.50722] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 12/30/2019] [Indexed: 12/18/2022] Open
Abstract
In pursuit of therapeutics for human polyomaviruses, we identified a peptide derived from the BK polyomavirus (BKV) minor structural proteins VP2/3 that is a potent inhibitor of BKV infection with no observable cellular toxicity. The thirteen-residue peptide binds to major structural protein VP1 with single-digit nanomolar affinity. Alanine-scanning of the peptide identified three key residues, substitution of each of which results in ~1000 fold loss of binding affinity with a concomitant reduction in antiviral activity. Structural studies demonstrate specific binding of the peptide to the pore of pentameric VP1. Cell-based assays demonstrate nanomolar inhibition (EC50) of BKV infection and suggest that the peptide acts early in the viral entry pathway. Homologous peptide exhibits similar binding to JC polyomavirus VP1 and inhibits infection with similar potency to BKV in a model cell line. Lastly, these studies validate targeting the VP1 pore as a novel strategy for the development of anti-polyomavirus agents.
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Affiliation(s)
- Joshua R Kane
- Infectious Diseases, Novartis Institutes for BioMedical Research, Emeryville, United States.,Global Discovery Chemistry, Novartis Institutes for BioMedical Research, Emeryville, United States
| | - Susan Fong
- Infectious Diseases, Novartis Institutes for BioMedical Research, Emeryville, United States
| | - Jacob Shaul
- Chemical Biology and Therapeutics, Novartis Institutes for BioMedical Research, Emeryville, United States
| | - Alexandra Frommlet
- Global Discovery Chemistry, Novartis Institutes for BioMedical Research, Emeryville, United States
| | - Andreas O Frank
- Global Discovery Chemistry, Novartis Institutes for BioMedical Research, Emeryville, United States
| | - Mark Knapp
- Global Discovery Chemistry, Novartis Institutes for BioMedical Research, Emeryville, United States
| | - Dirksen E Bussiere
- Global Discovery Chemistry, Novartis Institutes for BioMedical Research, Emeryville, United States
| | - Peter Kim
- Infectious Diseases, Novartis Institutes for BioMedical Research, Emeryville, United States
| | - Elizabeth Ornelas
- Global Discovery Chemistry, Novartis Institutes for BioMedical Research, Emeryville, United States
| | - Carlos Cuellar
- Global Discovery Chemistry, Novartis Institutes for BioMedical Research, Emeryville, United States
| | - Anastasia Hyrina
- Chemical Biology and Therapeutics, Novartis Institutes for BioMedical Research, Emeryville, United States
| | - Johanna R Abend
- Infectious Diseases, Novartis Institutes for BioMedical Research, Emeryville, United States
| | - Charles A Wartchow
- Global Discovery Chemistry, Novartis Institutes for BioMedical Research, Emeryville, United States
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8
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Brice DC, Diamond G. Antiviral Activities of Human Host Defense Peptides. Curr Med Chem 2020; 27:1420-1443. [PMID: 31385762 PMCID: PMC9008596 DOI: 10.2174/0929867326666190805151654] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 07/17/2019] [Accepted: 07/22/2019] [Indexed: 01/05/2023]
Abstract
Peptides with broad-spectrum antimicrobial activity are found widely expressed throughout nature. As they participate in a number of different aspects of innate immunity in mammals, they have been termed Host Defense Peptides (HDPs). Due to their common structural features, including an amphipathic structure and cationic charge, they have been widely shown to interact with and disrupt microbial membranes. Thus, it is not surprising that human HDPs have activity against enveloped viruses as well as bacteria and fungi. However, these peptides also exhibit activity against a wide range of non-enveloped viruses as well, acting at a number of different steps in viral infection. This review focuses on the activity of human host defense peptides, including alpha- and beta-defensins and the sole human cathelicidin, LL-37, against both enveloped and non-enveloped viruses. The broad spectrum of antiviral activity of these peptides, both in vitro and in vivo suggest that they play an important role in the innate antiviral defense against viral infections. Furthermore, the literature suggests that they may be developed into antiviral therapeutic agents.
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Affiliation(s)
- David C. Brice
- Department of Oral Biology, University of Florida, Box 100424, Gainesville, Florida 32610, USA
| | - Gill Diamond
- Department of Oral Biology, University of Florida, Box 100424, Gainesville, Florida 32610, USA
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9
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Gulati NM, Miyagi M, Wiens ME, Smith JG, Stewart PL. α-Defensin HD5 Stabilizes Human Papillomavirus 16 Capsid/Core Interactions. Pathog Immun 2019; 4:196-234. [PMID: 31583330 PMCID: PMC6755940 DOI: 10.20411/pai.v4i2.314] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2019] [Accepted: 08/17/2019] [Indexed: 12/17/2022] Open
Abstract
Background: Human papillomavirus (HPV) is linked to nearly all cases of cervical cancer. Despite available vaccines, a deeper understanding of the immune response to HPV is needed. Human α-defensin 5 (HD5), an innate immune effector peptide, blocks infection of multiple sero-types of HPV, including high-risk HPV16. While a common mechanism of α-defensin anti-viral activity against nonenveloped viruses such as HPV has emerged, there is limited understanding of how α-defensins bind to viral capsids to block infection. Methods: We have used cryo-electron microscopy (cryoEM), mass spectrometry (MS) crosslinking and differential lysine modification studies, and molecular dynamics (MD) simulations to probe the interaction of HPV16 pseudovirions (PsVs) with HD5. Results: CryoEM single particle reconstruction did not reveal HD5 density on the capsid surface. Rather, increased density was observed under the capsid shell in the presence of HD5. MS studies indicate that HD5 binds near the L1 and L2 capsid proteins and specifically near the C-terminal region of L1. MD simulations indicate that favorable electrostatic interactions can be formed between HD5 and the L1 C-terminal tail. Conclusions: A model is presented for how HD5 affects HPV16 structure and cell entry. In this model, HD5 binds to disordered regions of L1 and L2 protruding from the icosahedrally ordered capsid. HD5 acts to cement interactions between L1 and L2 and leads to a closer association of the L2/genome core with the L1 capsid. This model provides a structural rationale for our prior observation that HD5 interferes with the separation of L1 from the L2/genome complex during cell entry. Graphical Abstract
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Affiliation(s)
- Neetu M Gulati
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio.,Cleveland Center for Membrane and Structural Biology, Case Western Reserve University, Cleveland, Ohio
| | - Masaru Miyagi
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio
| | - Mayim E Wiens
- Department of Microbiology, University of Washington, Seattle, Washington
| | - Jason G Smith
- Department of Microbiology, University of Washington, Seattle, Washington
| | - Phoebe L Stewart
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio.,Cleveland Center for Membrane and Structural Biology, Case Western Reserve University, Cleveland, Ohio
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10
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Abstract
α, β, and θ defensins are effectors of the innate immune system with potent antibacterial, antiviral, and antifungal activity. Defensins have direct antiviral activity in cell culture, with varied mechanisms for individual viruses, although some common themes have emerged. In addition, defensins have potent immunomodulatory activity that can alter innate and adaptive immune responses to viral infection. In some cases, there is evidence for paradoxical escape from defensin neutralization or enhancement of viral infection. The direct and indirect activities of defensins have led to their development as therapeutics and vaccine components. The major area of investigation that continues to lag is the connection between the effects of defensins in cell culture models and viral pathogenesis in vivo. Model systems to study defensin biology, including more physiologic models designed to bridge this gap, are also discussed.
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Affiliation(s)
- Mayumi K Holly
- Department of Microbiology, University of Washington, Seattle, Washington 98195;
| | - Karina Diaz
- Department of Microbiology, University of Washington, Seattle, Washington 98195;
| | - Jason G Smith
- Department of Microbiology, University of Washington, Seattle, Washington 98195;
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11
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Abstract
The small intestinal epithelium produces numerous antimicrobial peptides and proteins, including abundant enteric α-defensins. Although they most commonly function as potent antivirals in cell culture, enteric α-defensins have also been shown to enhance some viral infections in vitro. Efforts to determine the physiologic relevance of enhanced infection have been limited by the absence of a suitable cell culture system. To address this issue, here we use primary stem cell-derived small intestinal enteroids to examine the impact of naturally secreted α-defensins on infection by the enteric mouse pathogen, mouse adenovirus 2 (MAdV-2). MAdV-2 infection was increased when enteroids were inoculated across an α-defensin gradient in a manner that mimics oral infection but not when α-defensin levels were absent or bypassed through other routes of inoculation. This increased infection was a result of receptor-independent binding of virus to the cell surface. The enteroid experiments accurately predicted increased MAdV-2 shedding in the feces of wild type mice compared to mice lacking functional α-defensins. Thus, our studies have shown that viral infection enhanced by enteric α-defensins may reflect the evolution of some viruses to utilize these host proteins to promote their own infection. Enteric α-defensins are an ancient form of host defense against pathogens, but until recently there was no robust in vitro system available to study their functions upon secretion from the cells that produce them naturally in vivo. Here, using small intestinal enteroids as a source of naturally secreted α-defensins, we show that enteric viral infection is increased in the presence of these peptides. We then show that α-defensins also enhance infection in vivo, as predicted by the results of the enteroid model. This study points to a new role for enteric α-defensins in promoting viral infection and has implications for the ability of these peptides to dictate viral tropism in the gastrointestinal tract.
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12
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Herfs M, Soong TR, Delvenne P, Crum CP. Deciphering the Multifactorial Susceptibility of Mucosal Junction Cells to HPV Infection and Related Carcinogenesis. Viruses 2017; 9:v9040085. [PMID: 28425968 PMCID: PMC5408691 DOI: 10.3390/v9040085] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Revised: 04/13/2017] [Accepted: 04/18/2017] [Indexed: 12/13/2022] Open
Abstract
Human papillomavirus (HPV)-induced neoplasms have long been considered to originate from viral infection of the basal cell layer of the squamous mucosa. However, this paradigm has been recently undermined by accumulating data supporting the critical role of a discrete population of squamo-columnar (SC) junction cells in the pathogenesis of cervical (pre)cancers. The present review summarizes the current knowledge on junctional cells, discusses their high vulnerability to HPV infection, and stresses the potential clinical/translational value of the novel dualistic model of HPV-related carcinogenesis.
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Affiliation(s)
- Michael Herfs
- Laboratory of Experimental Pathology, GIGA-Cancer, University of Liege, 4000 Liege, Belgium.
| | - Thing R Soong
- Division of Women's and Perinatal Pathology, Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
| | - Philippe Delvenne
- Laboratory of Experimental Pathology, GIGA-Cancer, University of Liege, 4000 Liege, Belgium.
| | - Christopher P Crum
- Division of Women's and Perinatal Pathology, Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
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13
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Sankaran-Walters S, Hart R, Dills C. Guardians of the Gut: Enteric Defensins. Front Microbiol 2017; 8:647. [PMID: 28469609 PMCID: PMC5395650 DOI: 10.3389/fmicb.2017.00647] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 03/29/2017] [Indexed: 01/01/2023] Open
Abstract
Enteric defensins likely play a key role in the management of the human microbiome throughout development. The functional and mechanistic diversity of defensins is much greater than was initially thought. Defensin expression and overall Paneth cell physiology likely plays a key role in the development of colitis and other inflammatory or dysbiotic diseases of the gut. As our understanding of enteric defensins grows, their potential as tools of clinical intervention becomes more apparent. In this review, we focus on the function and activity of Paneth Cell defensins and highlight their role in disease.
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14
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α-Defensin HD5 Inhibits Human Papillomavirus 16 Infection via Capsid Stabilization and Redirection to the Lysosome. mBio 2017; 8:mBio.02304-16. [PMID: 28119475 PMCID: PMC5263252 DOI: 10.1128/mbio.02304-16] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
α-Defensins are an important class of abundant innate immune effectors that are potently antiviral against a number of nonenveloped viral pathogens; however, a common mechanism to explain their ability to block infection by these unrelated viruses is lacking. We previously found that human defensin 5 (HD5) blocks a critical host-mediated proteolytic processing step required for human papillomavirus (HPV) infection. Here, we show that bypassing the requirement for this cleavage failed to abrogate HD5 inhibition. Instead, HD5 altered HPV trafficking in the cell. In the presence of an inhibitory concentration of HD5, HPV was internalized and reached the early endosome. The internalized capsid became permeable to antibodies and proteases; however, HD5 prevented dissociation of the viral capsid from the genome, reduced viral trafficking to the trans-Golgi network, redirected the incoming viral particle to the lysosome, and accelerated the degradation of internalized capsid proteins. This mechanism is equivalent to the mechanism by which HD5 inhibits human adenovirus. Thus, our data support capsid stabilization and redirection to the lysosome during infection as a general antiviral mechanism of α-defensins against nonenveloped viruses. IMPORTANCE Although the antiviral activity of α-defensins against enveloped viruses can be largely explained by interference with receptor binding and fusion, a common mechanism for inhibition of nonenveloped viruses remains elusive. In studies of a prominent human α-defensin that is expressed in the gut and in the male and female genitourinary tract, we discovered striking parallels between the mechanisms of inhibition of HPV and human adenovirus infection. Thus, detailed studies of the impact of α-defensins on the intracellular trafficking of two disparate viruses support a general mechanism of α-defensin antiviral activity against nonenveloped viruses.
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Thermodynamic instability of viral proteins is a pathogen-associated molecular pattern targeted by human defensins. Sci Rep 2016; 6:32499. [PMID: 27581352 PMCID: PMC5007486 DOI: 10.1038/srep32499] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2016] [Accepted: 08/08/2016] [Indexed: 11/21/2022] Open
Abstract
Human defensins are innate immune defense peptides with a remarkably broad repertoire of anti-pathogen activities. In addition to modulating immune response, inflammation, and angiogenesis, disintegrating bacterial membranes, and inactivating bacterial toxins, defensins are known to intercept various viruses at different stages of their life cycles, while remaining relatively benign towards human cells and proteins. Recently we have found that human defensins inactivate proteinaceous bacterial toxins by taking advantage of their low thermodynamic stability and acting as natural “anti-chaperones”, i.e. destabilizing the native conformation of the toxins. In the present study we tested various proteins produced by several viruses (HIV-1, PFV, and TEV) and found them to be susceptible to destabilizing effects of human α-defensins HNP-1 and HD-5 and the synthetic θ-defensin RC-101, but not β-defensins hBD-1 and hBD-2 or structurally related plant-derived peptides. Defensin-induced unfolding promoted exposure of hydrophobic groups otherwise confined to the core of the viral proteins. This resulted in precipitation, an enhanced susceptibility to proteolytic cleavage, and a loss of viral protein activities. We propose, that defensins recognize and target a common and essential physico-chemical property shared by many bacterial toxins and viral proteins – the intrinsically low thermodynamic protein stability.
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Defensins at the Mucosal Surface: Latest Insights into Defensin-Virus Interactions. J Virol 2016; 90:5216-5218. [PMID: 27009960 DOI: 10.1128/jvi.00904-15] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Defensins are innate immune effector peptides expressed at mucosal surfaces throughout the human body and are potently antiviral in vitro The role of defensins in viral pathogenesis in vivo is poorly understood; however, recent studies have revealed that defensin-virus interactions in vivo are complicated and distinct from their proposed antiviral mechanisms in vitro These findings highlight the need for additional research that connects defensin neutralization of viruses in cell culture to in vivo antiviral mechanisms.
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Loignon M, Toma E. Treatment options for progressive multifocal leukoencephalopathy in HIV-infected persons: current status and future directions. Expert Rev Anti Infect Ther 2016; 14:177-91. [PMID: 26655489 DOI: 10.1586/14787210.2016.1132162] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Progressive multifocal encephalopathy (PML) caused by JC virus was frequently encountered in AIDS patients before combination antiretroviral therapy (cART). Incidence decreased and the outcome improved with cART. The immune reconstitution with cART is beneficial for HIV-infected patients and is an effective treatment for PML. However, when it is excessive an inflammatory response immune syndrome might occur with deterioration of PML. So far, no specific therapy has proven efficacious in small clinical trials in spite of some optimistic case reports. Combination of drugs targeted at different stages of JC virus life cycle seems to have a better effect. Passive and active immune therapies, immune competence "boosters" appear promising. New future approaches such as gene editing are not far away.
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Affiliation(s)
- Maude Loignon
- a Department of Microbiology, Immunology and Infectious Diseases , University of Montreal, Succursale Centre Ville , Montreal , Quebec , Canada
| | - Emil Toma
- a Department of Microbiology, Immunology and Infectious Diseases , University of Montreal, Succursale Centre Ville , Montreal , Quebec , Canada.,b Département de microbiologie et maladies infectieuses , Hôtel-Dieu Hospital du Centre Hospitalier de l'Université de Montréal (CHUM) , Montreal , Quebec , Canada
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Reiss CS. Innate Immunity in Viral Encephalitis. NEUROTROPIC VIRAL INFECTIONS 2016. [PMCID: PMC7153449 DOI: 10.1007/978-3-319-33189-8_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Carol Shoshkes Reiss
- Departments of Biology and Neural Science, New York University, New York, New York USA
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Epand RM. Antiviral Host Defence Peptides. HOST DEFENSE PEPTIDES AND THEIR POTENTIAL AS THERAPEUTIC AGENTS 2016. [PMCID: PMC7123656 DOI: 10.1007/978-3-319-32949-9_3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The ongoing global mortality and morbidity associated with viral pathogens highlights the need for the continued development of effective, novel antiviral molecules. The antiviral activity of cationic host defence peptides is of significant interest as novel therapeutics for treating viral infection and predominantly due to their broad spectrum antiviral activity. These peptides also display powerful immunomodulatory activity and are key mediators of inflammation. Therefore, they offer a significant opportunity to inform the development of novel therapeutics for treating viral infections by either directly targeting the pathogen or by enhancing the innate immune response. In this chapter, we review the antiviral activity of cathelicidins and defensins, and examine the potential for these peptides to be used as novel antiviral agents.
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Affiliation(s)
- Richard M. Epand
- Health Sciences Centre, McMaster University, Hamilton, Ontario Canada
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Shan Y, Dong Y, Jiang D. Recombinant expression of a novel antimicrobial peptide consisting of human α-defensin 5 and Mytilus coruscus mytilin-1 in Escherichia coli. ACTA ACUST UNITED AC 2015. [DOI: 10.1007/s13765-015-0109-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Alpha-defensin HD5 inhibits furin cleavage of human papillomavirus 16 L2 to block infection. J Virol 2014; 89:2866-74. [PMID: 25540379 DOI: 10.1128/jvi.02901-14] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Human papillomavirus (HPV) is a significant oncogenic virus, but the innate immune response to HPV is poorly understood. Human α-defensin 5 (HD5) is an innate immune effector peptide secreted by epithelial cells in the genitourinary tract. HD5 is broadly antimicrobial, exhibiting potent antiviral activity against HPV at physiologic concentrations; however, the specific mechanism of HD5-mediated inhibition against HPV is unknown. During infection, the HPV capsid undergoes several critical cell-mediated viral protein processing steps, including unfolding and cleavage of the minor capsid protein L2 by host cyclophilin B and furin. Using HPV16 pseudovirus, we show that HD5 interacts directly with the virus and inhibits the furin-mediated cleavage of L2 at the cell surface during infection at a step downstream of the cyclophilin B-mediated unfolding of L2. Importantly, HD5 does not affect the enzymatic activity of furin directly. Thus, our data support a model in which HD5 prevents furin from accessing L2 by occluding the furin cleavage site via direct binding to the viral capsid. IMPORTANCE Our study elucidates a new antiviral action for α-defensins against nonenveloped viruses in which HD5 directly interferes with a critical host-mediated viral processing step, furin cleavage of L2, at the cell surface. Blocking this key event has deleterious effects on the intracellular steps of virus infection. Thus, in addition to informing the antiviral mechanisms of α-defensins, our studies highlight the critical role of furin cleavage in HPV entry. Innate immune control, mediated in part by α-defensins expressed in the genital mucosa, may influence susceptibility to HPV infections that lead to cervical cancer. Moreover, understanding the mechanism of these natural antivirals may inform the design of therapeutics to limit HPV infection.
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Delineation of interfaces on human alpha-defensins critical for human adenovirus and human papillomavirus inhibition. PLoS Pathog 2014; 10:e1004360. [PMID: 25188351 PMCID: PMC4154873 DOI: 10.1371/journal.ppat.1004360] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Accepted: 07/26/2014] [Indexed: 12/18/2022] Open
Abstract
Human α-defensins are potent anti-microbial peptides with the ability to neutralize bacterial and viral targets. Single alanine mutagenesis has been used to identify determinants of anti-bacterial activity and binding to bacterial proteins such as anthrax lethal factor. Similar analyses of α-defensin interactions with non-enveloped viruses are limited. We used a comprehensive set of human α-defensin 5 (HD5) and human neutrophil peptide 1 (HNP1) alanine scan mutants in a combination of binding and neutralization assays with human adenovirus (AdV) and human papillomavirus (HPV). We have identified a core of critical hydrophobic residues that are common determinants for all of the virus-defensin interactions that were analyzed, while specificity in viral recognition is conferred by specific surface-exposed charged residues. The hydrophobic residues serve multiple roles in maintaining the tertiary and quaternary structure of the defensins as well as forming an interface for virus binding. Many of the important solvent-exposed residues of HD5 group together to form a critical surface. However, a single discrete binding face was not identified for HNP1. In lieu of whole AdV, we used a recombinant capsid subunit comprised of penton base and fiber in quantitative binding studies and determined that the anti-viral potency of HD5 was a function of stoichiometry rather than affinity. Our studies support a mechanism in which α-defensins depend on hydrophobic and charge-charge interactions to bind at high copy number to these non-enveloped viruses to neutralize infection and provide insight into properties that guide α-defensin anti-viral activity. Human α-defensins are an important component of the innate immune response and provide an initial block against a broad number of infectious agents, including viruses and bacteria. Characteristics of α-defensins that are necessary for their anti-bacterial activity have been identified, but our understanding of determinants required for activity against non-enveloped viruses is limited. In this work, we utilized alanine scan mutagenesis to systematically and comprehensively investigate the role of hydrophobic and charged residues of two α-defensins in binding to and/or neutralization of human adenovirus and human papillomavirus. Our results implicate common core hydrophobic residues as critical for inhibition of these non-enveloped viruses by the two α-defensins, with specificity provided by charged residues unique to each interaction. We also found that the number of α-defensin molecules bound to the virus was a stronger correlate of the anti-viral potency of the α-defensin mutants than their absolute affinity for the viral capsid. Understanding common characteristics of α-defensins important for non-enveloped virus binding will inform rules that govern the function of these abundant and multifaceted peptides in host defense.
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Abstract
UNLABELLED The human fetal glial cell line SVG was generated in 1985 by transfecting primary fetal brain cells with a plasmid containing an origin-defective mutant of simian virus 40 (SV40). The cells, which express SV40 large T-antigen, support the replication of human JC polyomavirus (JCPyV) and have been used for JCPyV studies but also for other studies in which cells of neural origin were desirable. We intended to use the SVG p12 cells from ATCC for antiviral drug studies with JCPyV. However, during initial experiments, immunofluorescence microscopy controls unexpectedly revealed cells expressing the late viral proteins VP1, VP2/VP3, and agno. This was confirmed by Western blotting. Since our agnoprotein antiserum is specific for BKPyV agnoprotein, infection with BKPyV was suspected. Indeed, specific BKPyV PCR of SVG p12 supernatants revealed a viral load of >1 × 10(10) genomic equivalents/ml. Negative-staining electron microscopy showed characteristic polyomavirus virions, and infectious BKPyV was transmitted from SVG p12 supernatant to other cells. Long-range PCR covering the viral genome, followed by DNA sequencing, identified BKPyV strain UT as well as deletion derivatives. This was confirmed by next-generation sequencing. JCPyV (MAD-4) was found to infect apparently uninfected and BKPyV-infected SVG p12 cells. In total, 4 vials from 2 different ATCC lots of SVG p12 cells dating back to 2006 contained BKPyV, whereas the subclone SVG-A was negative. In conclusion, SVG p12 cells from ATCC contain infectious BKPyV. This may have affected results and interpretations of previous studies, and caution should be taken in future experiments. IMPORTANCE This work reveals that one of the most frequently used cell lines for JC polyomavirus (JCPyV) research, the SV40-immortalized human fetal glial cell line SVG p12 obtained directly from ATCC, contains infectious BK polyomavirus (BKPyV) of strain UT and a spectrum of defective mutants. Strain UT has been previously found in urine and in tumors of different patients but is also frequently used for research. It is therefore not clear if BKPyV was present in the brain tissue used to generate the cell line or if this is a contamination. Although productive JCPyV infection of SVG cells was not dependent on prior BKPyV infection, the unnoticed presence of BKPyV may have influenced the results of studies using these cells. The interpretation of past results should therefore be reconsidered and cells tested for BKPyV before new studies are initiated. The frequently used subclone SVG-A did not contain BKPyV and could be a useful substitute.
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