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A VP26-mNeonGreen Capsid Fusion HSV-2 Mutant Reactivates from Viral Latency in the Guinea Pig Genital Model with Normal Kinetics. Viruses 2018; 10:v10050246. [PMID: 29738431 PMCID: PMC5977239 DOI: 10.3390/v10050246] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 05/01/2018] [Accepted: 05/03/2018] [Indexed: 12/27/2022] Open
Abstract
Fluorescent herpes simplex viruses (HSV) are invaluable tools for localizing virus in cells, permitting visualization of capsid trafficking and enhancing neuroanatomical research. Fluorescent viruses can also be used to study virus kinetics and reactivation in vivo. Such studies would be facilitated by fluorescent herpes simplex virus recombinants that exhibit wild-type kinetics of replication and reactivation and that are genetically stable. We engineered an HSV-2 strain expressing the fluorescent mNeonGreen protein as a fusion with the VP26 capsid protein. This virus has normal replication and in vivo recurrence phenotypes, providing an essential improved tool for further study of HSV-2 infection.
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Grzesik P, MacMath D, Henson B, Prasad S, Joshi P, Desai PJ. Incorporation of the Kaposi's sarcoma-associated herpesvirus capsid vertex-specific component (CVSC) into self-assembled capsids. Virus Res 2017; 236:9-13. [PMID: 28456575 DOI: 10.1016/j.virusres.2017.04.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 03/30/2017] [Accepted: 04/21/2017] [Indexed: 11/18/2022]
Abstract
Self-assembly of herpesvirus capsids can be accomplished in heterologous expression systems provided all six capsid proteins are present. We have demonstrated the assembly of icosahedral Kaposi's sarcoma-associated herpesvirus (KSHV) capsids in insect cells using the baculovirus expression system. Using this self-assembly system we investigated whether we could add additional capsid associated proteins and determine their incorporation into the assembled capsid. We chose the capsid vertex-specific component (CVSC) proteins encoded by open reading frames (ORFs) 19 and 32 to test this. This complex sits on the capsid vertex and is important for capsid maturation in herpesvirus-infected cells. Co-immunoprecipitation assays were used to initially confirm a bi-molecular interaction between ORF19 and ORF32. Both proteins also precipitated the triplex proteins of the capsid shell (ORF26 and ORF62) as well as the major capsid protein (ORF25). Capsid immunoprecipitation assays revealed the incorporation of ORF19 as well as ORF32 into assembled capsids. Similar experiments also showed that the incorporation of each protein occurred independent of the other. These studies reveal biochemically how the KSHV CVSC interacts with the capsid shell.
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Affiliation(s)
- Peter Grzesik
- Department of Oncology, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, The Johns Hopkins University, Baltimore, MD, USA
| | - Derek MacMath
- Department of Oncology, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, The Johns Hopkins University, Baltimore, MD, USA
| | - Brandon Henson
- Department of Oncology, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, The Johns Hopkins University, Baltimore, MD, USA
| | - Sanjana Prasad
- Department of Oncology, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, The Johns Hopkins University, Baltimore, MD, USA
| | - Poorval Joshi
- Department of Oncology, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, The Johns Hopkins University, Baltimore, MD, USA
| | - Prashant J Desai
- Department of Oncology, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, The Johns Hopkins University, Baltimore, MD, USA.
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3
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Li S, Bai L, Dong J, Sun R, Lan K. Kaposi's Sarcoma-Associated Herpesvirus: Epidemiology and Molecular Biology. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1018:91-127. [PMID: 29052134 DOI: 10.1007/978-981-10-5765-6_7] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV), also known as Human herpesvirus 8 (HHV-8), is a member of the lymphotropic gammaherpesvirus subfamily and a human oncogenic virus. Since its discovery in AIDS-associated KS tissues by Drs. Yuan Chang and Patrick Moore, much progress has been made in the past two decades. There are four types of KS including classic KS, endemic KS, immunosuppressive therapy-related KS, and AIDS-associated KS. In addition to KS, KSHV is also involved in the development of primary effusion lymphoma (PEL) and certain types of multicentric Castleman's disease. KSHV manipulates numerous viral proteins to promote the progression of angiogenesis and tumorigenesis. In this chapter, we review the epidemiology and molecular biology of KSHV and the mechanisms underlying KSHV-induced diseases.
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Affiliation(s)
- Shasha Li
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, 430072, People's Republic of China
| | - Lei Bai
- Key Laboratory of Molecular Virology and Immunology, Institute Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, 200031, People's Republic of China
| | - Jiazhen Dong
- Key Laboratory of Molecular Virology and Immunology, Institute Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, 200031, People's Republic of China
| | - Rui Sun
- Key Laboratory of Molecular Virology and Immunology, Institute Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, 200031, People's Republic of China
| | - Ke Lan
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, 430072, People's Republic of China.
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4
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CryoEM and mutagenesis reveal that the smallest capsid protein cements and stabilizes Kaposi's sarcoma-associated herpesvirus capsid. Proc Natl Acad Sci U S A 2015; 112:E649-56. [PMID: 25646489 DOI: 10.1073/pnas.1420317112] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
With just one eighth the size of the major capsid protein (MCP), the smallest capsid protein (SCP) of human tumor herpesviruses--Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV)--is vital to capsid assembly, yet its mechanism of action is unknown. Here, by cryoEM of KSHV at 6-Å resolution, we show that SCP forms a crown on each hexon and uses a kinked helix to cross-link neighboring MCP subunits. SCP-null mutation decreased viral titer by 1,000 times and impaired but did not fully abolish capsid assembly, indicating an important but nonessential role of SCP. By truncating the C-terminal half of SCP and performing cryoEM reconstruction, we demonstrate that SCP's N-terminal half is responsible for the observed structure and function whereas the C-terminal half is flexible and dispensable. Serial truncations further highlight the critical importance of the N-terminal 10 aa, and cryoEM reconstruction of the one with six residues truncated localizes the N terminus of SCP in the cryoEM density map and enables us to construct a pseudoatomic model of SCP. Fitting of this SCP model and a homology model for the MCP upper domain into the cryoEM map reveals that SCP binds MCP largely via hydrophobic interactions and the kinked helix of SCP bridges over neighboring MCPs to form noncovalent cross-links. These data support a mechanistic model that tumor herpesvirus SCP reinforces the capsid for genome packaging, thus acting as a cementing protein similar to those found in many bacteriophages.
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5
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Capuano CM, Grzesik P, Kreitler D, Pryce EN, Desai KV, Coombs G, McCaffery JM, Desai PJ. A hydrophobic domain within the small capsid protein of Kaposi's sarcoma-associated herpesvirus is required for assembly. J Gen Virol 2014; 95:1755-1769. [PMID: 24824860 DOI: 10.1099/vir.0.064303-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV) capsids can be produced in insect cells using recombinant baculoviruses for protein expression. All six capsid proteins are required for this process to occur and, unlike for alphaherpesviruses, the small capsid protein (SCP) ORF65 is essential for this process. This protein decorates the capsid shell by virtue of its interaction with the capsomeres. In this study, we have explored the SCP interaction with the major capsid protein (MCP) using GFP fusions. The assembly site within the nucleus of infected cells was visualized by light microscopy using fluorescence produced by the SCP-GFP polypeptide, and the relocalization of the SCP to these sites was evident only when the MCP and the scaffold protein were also present - indicative of an interaction between these proteins that ensures delivery of the SCP to assembly sites. Biochemical assays demonstrated a physical interaction between the SCP and MCP, and also between this complex and the scaffold protein. Self-assembly of capsids with the SCP-GFP polypeptide was evident. Potentially, this result can be used to engineer fluorescent KSHV particles. A similar SCP-His6 polypeptide was used to purify capsids from infected cell lysates using immobilized affinity chromatography and to directly label this protein in capsids using chemically derivatized gold particles. Additional studies with SCP-GFP polypeptide truncation mutants identified a domain residing between aa 50 and 60 of ORF65 that was required for the relocalization of SCP-GFP to nuclear assembly sites. Substitution of residues in this region and specifically at residue 54 with a polar amino acid (lysine) disrupted or abolished this localization as well as capsid assembly, whereas substitution with non-polar residues did not affect the interaction. Thus, this study identified a small conserved hydrophobic domain that is important for the SCP-MCP interaction.
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Affiliation(s)
- Christopher M Capuano
- Viral Oncology Program, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD, USA
| | - Peter Grzesik
- Viral Oncology Program, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD, USA
| | - Dale Kreitler
- Viral Oncology Program, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD, USA
| | - Erin N Pryce
- Integrated Imaging Center, Department of Biology, Johns Hopkins University, Baltimore, MD, USA
| | - Keshal V Desai
- Viral Oncology Program, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD, USA
| | - Gavin Coombs
- Integrated Imaging Center, Department of Biology, Johns Hopkins University, Baltimore, MD, USA
| | - J Michael McCaffery
- Integrated Imaging Center, Department of Biology, Johns Hopkins University, Baltimore, MD, USA
| | - Prashant J Desai
- Viral Oncology Program, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD, USA
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6
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Nagel CH, Döhner K, Binz A, Bauerfeind R, Sodeik B. Improper tagging of the non-essential small capsid protein VP26 impairs nuclear capsid egress of herpes simplex virus. PLoS One 2012; 7:e44177. [PMID: 22952920 PMCID: PMC3432071 DOI: 10.1371/journal.pone.0044177] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Accepted: 07/30/2012] [Indexed: 01/10/2023] Open
Abstract
To analyze the subcellular trafficking of herpesvirus capsids, the small capsid protein has been labeled with different fluorescent proteins. Here, we analyzed the infectivity of several HSV1(17(+)) strains in which the N-terminal region of the non-essential small capsid protein VP26 had been tagged at different positions. While some variants replicated with similar kinetics as their parental wild type strain, others were not infectious at all. Improper tagging resulted in the aggregation of VP26 in the nucleus, prevented efficient nuclear egress of viral capsids, and thus virion formation. Correlative fluorescence and electron microscopy showed that these aggregates had sequestered several other viral proteins, but often did not contain viral capsids. The propensity for aggregate formation was influenced by the type of the fluorescent protein domain, the position of the inserted tag, the cell type, and the progression of infection. Among the tags that we have tested, mRFPVP26 had the lowest tendency to induce nuclear aggregates, and showed the least reduction in replication when compared to wild type. Our data suggest that bona fide monomeric fluorescent protein tags have less impact on proper assembly of HSV1 capsids and nuclear capsid egress than tags that tend to dimerize. Small chemical compounds capable of inducing aggregate formation of VP26 may lead to new antiviral drugs against HSV infections.
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Affiliation(s)
| | - Katinka Döhner
- Institute of Virology, Hanover Medical School, Hanover, Germany
| | - Anne Binz
- Institute of Virology, Hanover Medical School, Hanover, Germany
| | | | - Beate Sodeik
- Institute of Virology, Hanover Medical School, Hanover, Germany
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7
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Yu X, Shah S, Lee M, Dai W, Lo P, Britt W, Zhu H, Liu F, Zhou ZH. Biochemical and structural characterization of the capsid-bound tegument proteins of human cytomegalovirus. J Struct Biol 2011; 174:451-60. [PMID: 21459145 DOI: 10.1016/j.jsb.2011.03.006] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Revised: 02/24/2011] [Accepted: 03/11/2011] [Indexed: 01/25/2023]
Abstract
Human cytomegalovirus (HCMV) is the most genetically and structurally complex human herpesvirus and is composed of an envelope, a tegument, and a dsDNA-containing capsid. HCMV tegument plays essential roles in HCMV infection and assembly. Using cryo electron tomography (cryoET), here we show that HCMV tegument compartment can be divided into two sub-compartments: an inner and an outer tegument. The inner tegument consists of densely-packed proteins surrounding the capsid. The outer tegument contains those components that are loosely packed in the space between the inner tegument and the pleomorphic glycoprotein-containing envelope. To systematically characterize the inner tegument proteins interacting with the capsid, we used chemical treatment to strip off the entire envelope and most tegument proteins to obtain a tegumented capsid with inner tegument proteins. SDS-polyacrylamide gel electrophoresis analyses show that only two tegument proteins, UL32-encoded pp150 and UL48-encoded high molecular weight protein (HMWP), remains unchanged in their abundance in the tegumented capsids as compared to their abundance in the intact particles. Three-dimensional reconstructions by single particle cryo electron microscopy (cryoEM) reveal that the net-like layer of icosahedrally-ordered tegument densities are also the same in the tegumented capsid and in the intact particles. CryoET reconstruction of the tegumented capsid labeled with an anti-pp150 antibody is consistent with the biochemical and cryoEM data in localizing pp150 within the ordered tegument. Taken together, these results suggest that pp150, a betaherpesvirus-specific tegument protein, is a constituent of the net-like layer of icosahedrally-ordered capsid-bound tegument densities, a structure lacking similarities in alpha and gammaherpesviruses.
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Affiliation(s)
- Xuekui Yu
- Department of Microbiology, Immunology and Molecular Genetics, University of California at Los Angeles, USA
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8
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Functional characterization of Kaposi's sarcoma-associated herpesvirus small capsid protein by bacterial artificial chromosome-based mutagenesis. Virology 2010; 407:306-18. [PMID: 20850163 DOI: 10.1016/j.virol.2010.08.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2010] [Revised: 07/16/2010] [Accepted: 08/17/2010] [Indexed: 11/20/2022]
Abstract
A systematic investigation of interactions amongst KSHV capsid proteins was undertaken in this study to comprehend lesser known KSHV capsid assembly mechanisms. Interestingly the interaction patterns of the KSHV small capsid protein, ORF65 suggested its plausible role in viral capsid assembly pathways. Towards further understanding this, ORF65-null recombinant mutants (BAC-∆65 and BAC-stop65) employing a bacterial artificial chromosome (BAC) system were generated. No significant difference was found in both overall viral gene expression and lytic DNA replication between stable monolayers of 293T-BAC36 (wild-type) and 293T-BAC-ORF65-null upon induction with 12-O-tetradecanoylphorbol-13-acetate, though the latter released 30-fold fewer virions to the medium than 293T-BAC36 cells. Sedimentation profiles of capsid proteins of ORF65-null recombinant mutants were non-reflective of their organization into the KSHV capsids and were also undetectable in cytoplasmic extracts compared to noticeable levels in nuclear extracts. These observations collectively suggested the pivotal role of ORF65 in the KSHV capsid assembly processes.
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9
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Wan QJ, Gong J, Huang XH, Huang YH, Zhou S, Ou-Yang ZL, Cao JH, Ye LL, Qin QW. Identification and characterization of a novel capsid protein encoded by Singapore grouper iridovirus ORF038L. Arch Virol 2010; 155:351-9. [PMID: 20130938 DOI: 10.1007/s00705-010-0594-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2009] [Accepted: 12/16/2009] [Indexed: 11/26/2022]
Abstract
Singapore grouper iridovirus (SGIV) is an important pathogen isolated from grouper, Epinephelus tauvina, and characterized as a novel ranavirus. To better understand the function of viral structural genes involved in SGIV infection and virus-host interactions, a candidate gene, VP38 (ORF038L), was investigated in this study. SGIV VP38 was found to encode a 170-aa peptide containing an RGD motif, and it showed significant identity only to members of the genus Iridovirus, family Iridoviridae, except megalocytivirus. The VP38 gene was identified by temporal expression pattern analysis and drug inhibition assay as a late (L) gene. Immunofluorescence localization revealed that P38 was distributed predominately in the cytoplasm and that association of VP38 with viral factories increased at the late stage of SGIV infection. Consistent results from immunoelectron microscopy (IEM) and western blot analysis revealed that SGIV VP38 is a viral capsid protein. Furthermore, antibodies specific for SGIV VP38 exhibited substantial SGIV-neutralizing activity in vitro, suggesting that VP38 might play an important role in SGIV infectivity.
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Affiliation(s)
- Qing Jiao Wan
- State Key Laboratory of Biocontrol, School of Life Science, Sun Yat-sen University, 135 West Xingang Road, Guangzhou, China
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10
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Small capsid protein pORF65 is essential for assembly of Kaposi's sarcoma-associated herpesvirus capsids. J Virol 2008; 82:7201-11. [PMID: 18463150 DOI: 10.1128/jvi.00423-08] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiologic agent for KS tumors, multicentric Castleman's disease, and primary effusion lymphomas. Like other herpesvirus capsids, the KSHV capsid is an icosahedral structure composed of six proteins. The capsid shell is made up of the major capsid protein, two triplex proteins, and the small capsid protein. The scaffold protein and the protease occupy the internal space. The assembly of KSHV capsids is thought to occur in a manner similar to that determined for herpes simplex virus type 1 (HSV-1). Our goal was to assemble KSHV capsids in insect cells using the baculovirus expression vector system. Six KSHV capsid open reading frames were cloned and the proteins expressed in Sf9 cells: pORF25 (major capsid protein), pORF62 (triplex 1), pORF26 (triplex 2), pORF17 (protease), pORF17.5 (scaffold protein), and also pORF65 (small capsid protein). When insect cells were coinfected with these baculoviruses, angular capsids that contained internal core structures were readily observed by conventional electron microscopy of the infected cells. Capsids were also readily isolated from infected cells by using rate velocity sedimentation. With immuno-electron microscopy methods, these capsids were seen to be reactive to antisera to pORF65 as well as to KSHV-positive human sera, indicating the correct conformation of pORF65 in these capsids. When either virus expressing the triplex proteins was omitted from the coinfection, capsids did not assemble; similar to observations made in HSV-1-infected cells. If the virus expressing the scaffold protein was excluded, large open shells that did not attain icosahedral structure were seen in the nuclei of infected cells. The presence of pORF65 was required for capsid assembly, in that capsids did not form if this protein was absent as judged by both by ultrastructural analysis of infected cells and rate velocity sedimentation experiments. Thus, a novel outcome of this study is the finding that the small capsid protein of KSHV, like the major capsid and triplex proteins, is essential for capsid shell assembly.
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Abstract
The gammaherpesvirus alcelaphine herpesvirus 1 (AlHV-1) causes malignant catarrhal fever in susceptible ungulates but infects its natural host, wildebeest, without obvious clinical signs. In tissue culture, AlHV-1 is initially predominantly cell associated and virulent but on extended culture becomes cell-free and attenuated. We wanted to determine what changes in protein composition had taken place during the transition from virulent to attenuated virus in culture. Purified virus preparations were fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and proteins were analyzed by liquid chromatography-electrospray ionization-tandem mass spectrometry. Peptides were identified in serial gel slices by using MASCOT software to interrogate virus-specific and nonredundant sequence databases. Twenty-three AlHV-1-encoded proteins and six cellular proteins were identified in the attenuated and virulent viruses. Two polypeptides were detected in only the virulent virus preparations, while one other protein was found in only the attenuated virus. Two of these virus-specific proteins were identified by a single peptide, suggesting that these may be low-abundance virion proteins rather than markers of attenuation or pathogenesis. The results suggest that attenuation of AlHV-1 is not the result of gross changes in the composition of the virus particle but probably due to altered viral gene expression in the infected cell.
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Dai W, Jia Q, Bortz E, Shah S, Liu J, Atanasov I, Li X, Taylor KA, Sun R, Zhou ZH. Unique structures in a tumor herpesvirus revealed by cryo-electron tomography and microscopy. J Struct Biol 2007; 161:428-38. [PMID: 18096403 DOI: 10.1016/j.jsb.2007.10.010] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2007] [Revised: 10/12/2007] [Accepted: 10/13/2007] [Indexed: 11/17/2022]
Abstract
Gammaherpesviruses, including the human pathogens Epstein-Barr virus and Kaposi's sarcoma-associated herpesvirus, are causative agents of lymphomas and other malignancies. The structural characterization of these viruses has been limited due to difficulties in obtaining adequate amount of virion particles. Here we report the first three-dimensional structural characterization of a whole gammaherpesvirus virion by an emerging integrated approach of cryo-electron tomography combined with single-particle cryo-electron microscopy, using murine gammaherpesvirus-68 (MHV-68) as a model system. We found that the MHV-68 virion consists of distinctive envelope and tegument compartments, and a highly conserved nucleocapsid. Two layers of tegument are identified: an inner tegument layer tethered to the underlying capsid and an outer, flexible tegument layer conforming to the overlying, pleomorphic envelope, consistent with the sequential viral tegumentation process inside host cells. Surprisingly, comparison of the MHV-68 virion and capsid reconstructions shows that the interactions between the capsid and inner tegument proteins are completely different from those observed in alpha and betaherpesviruses. These observations support the notion that the inner layer tegument across different subfamilies of herpesviruses has evolved significantly to confer specific characteristics related to viral-host interactions, in contrast to a highly conserved capsid for genome encapsidation and protection.
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Affiliation(s)
- Wei Dai
- Department of Pathology and Laboratory Medicine, University of Texas Medical School at Houston, Houston, TX 77030, USA
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Bortz E, Wang L, Jia Q, Wu TT, Whitelegge JP, Deng H, Zhou ZH, Sun R. Murine gammaherpesvirus 68 ORF52 encodes a tegument protein required for virion morphogenesis in the cytoplasm. J Virol 2007; 81:10137-50. [PMID: 17634243 PMCID: PMC2045416 DOI: 10.1128/jvi.01233-06] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The tegument, a semiordered matrix of proteins overlying the nucleocapsid and underlying the virion envelope, in viruses in the gamma subfamily of Herpesviridae is poorly understood. Murine gammaherpesvirus 68 (MHV-68) is a robust model for studying gammaherpesvirus virion structure, assembly, and composition, as MHV-68 efficiently completes the lytic phase and productively infects cultured cells. We have found that MHV-68 ORF52 encodes an abundant tegument protein conserved among gammaherpesviruses. Detergent sensitivity experiments revealed that the MHV-68 ORF52 protein is more tightly bound to the virion nucleocapsid than the ORF45 tegument protein but could be dissociated from particles that retained the ORF65 small capsomer protein. ORF52, tagged with enhanced green fluorescent protein or FLAG epitope, localized to the cytoplasm. A recombinant MHV-68 bacterial artificial chromosome mutant with a nonsense mutation incorporated into ORF52 exhibited viral DNA replication, expression of late lytic genes, and capsid assembly and packaging at levels near those of the wild type. However, the MHV-68 ORF52-null virus was deficient in the assembly and release of infectious virion particles. Instead, partially tegumented capsids produced by the ORF52-null mutant accumulated in the cytoplasm, containing conserved capsid proteins, the ORF64 and ORF67 tegument proteins, but virtually no ORF45 tegument protein. Thus, ORF52 is essential for the tegumentation and egress of infectious MHV-68 particles in the cytoplasm, suggesting an important conserved function in gammaherpesvirus virion morphogenesis.
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Affiliation(s)
- Eric Bortz
- Molecular Biology IDP, University of California at Los Angeles, Los Angeles, CA 90095, USA
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14
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Raghu H, Sharma-Walia N, Veettil MV, Sadagopan S, Caballero A, Sivakumar R, Varga L, Bottero V, Chandran B. Lipid rafts of primary endothelial cells are essential for Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8-induced phosphatidylinositol 3-kinase and RhoA-GTPases critical for microtubule dynamics and nuclear delivery of viral DNA but dispensable for binding and entry. J Virol 2007; 81:7941-59. [PMID: 17507466 PMCID: PMC1951274 DOI: 10.1128/jvi.02848-06] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Early during de novo infection of human microvascular dermal endothelial (HMVEC-d) cells, Kaposi's sarcoma-associated herpesvirus (KSHV) (human herpesvirus 8 [HHV-8]) induces the host cell's preexisting FAK, Src, phosphatidylinositol 3-kinase (PI3-K), Rho-GTPases, Diaphanous-2 (Dia-2), Ezrin, protein kinase C-zeta, extracellular signal-regulated kinase 1/2 (ERK1/2), and NF-kappaB signal pathways that are critical for virus entry, nuclear delivery of viral DNA, and initiation of viral gene expression. Since several of these signal molecules are known to be associated with lipid raft (LR) domains, we investigated the role of LR during KSHV infection of HMVEC-d cells. Pretreatment of cells with LR-disrupting agents methyl beta-cyclo dextrin (MbetaCD) or nystatin significantly inhibited the expression of viral latent (ORF73) and lytic (ORF50) genes. LR disruption did not affect KSHV binding but increased viral DNA internalization. In contrast, association of internalized viral capsids with microtubules (MTs) and the quantity of infected nucleus-associated viral DNA were significantly reduced. Disorganized and disrupted MTs and thick rounded plasma membranes were observed in MbetaCD-treated cells. LR disruption did not affect KSHV-induced FAK and ERK1/2 phosphorylation; in contrast, it increased the phosphorylation of Src, significantly reduced the KSHV-induced PI3-K and RhoA-GTPase and NF-kappaB activation, and reduced the colocalizations of PI3-K and RhoA-GTPase with LRs. Biochemical characterization demonstrated the association of activated PI3-K with LR fractions which was inhibited by MbetaCD treatment. RhoA-GTPase activation was inhibited by PI3-K inhibitors, demonstrating that PI3-K is upstream to RhoA-GTPase. In addition, colocalization of Dia-2, a RhoA-GTPase activated molecule involved in MT activation, with LR was reduced. KSHV-RhoA-GTPase mediated acetylation and aggregation of MTs were also reduced. Taken together, these studies suggest that LRs of endothelial cells play critical roles in KSHV infection and gene expression, probably due to their roles in modulating KSHV-induced PI3-K, RhoA-GTPase, and Dia-2 molecules essential for postbinding and entry stages of infection such as modulation of microtubular dynamics, movement of virus in the cytoplasm, and nuclear delivery of viral DNA.
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Affiliation(s)
- Hari Raghu
- Department of Microbiology and Immunology, Chicago Medical School, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064, USA
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Parsons CH, Adang LA, Overdevest J, O’Connor CM, Taylor JR, Camerini D, Kedes DH. KSHV targets multiple leukocyte lineages during long-term productive infection in NOD/SCID mice. J Clin Invest 2006; 116:1963-73. [PMID: 16794734 PMCID: PMC1481659 DOI: 10.1172/jci27249] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2005] [Accepted: 05/09/2006] [Indexed: 12/31/2022] Open
Abstract
To develop an animal model of Kaposi sarcoma-associated herpesvirus (KSHV) infection uniquely suited to evaluate longitudinal patterns of viral gene expression, cell tropism, and immune responses, we injected NOD/SCID mice intravenously with purified virus and measured latent and lytic viral transcripts in distal organs over the subsequent 4 months. We observed sequential escalation of first latent and then lytic KSHV gene expression coupled with electron micrographic evidence of virion production within the murine spleen. Using novel technology that integrates flow cytometry with immunofluorescence microscopy, we found that the virus establishes infection in murine B cells, macrophages, NK cells, and, to a lesser extent, dendritic cells. To investigate the potential for human KSHV-specific immune responses within this immunocompromised host, we implanted NOD/SCID mice with functional human hematopoietic tissue grafts (NOD/SCID-hu mice) and observed that a subset of animals produced human KSHV-specific antibodies. Furthermore, treatment of these chimeric mice with ganciclovir at the time of inoculation led to prolonged but reversible suppression of KSHV DNA and RNA levels, suggesting that KSHV can establish latent infection in vivo despite ongoing suppression of lytic replication.
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Affiliation(s)
- Christopher H. Parsons
- Myles H. Thaler Center for AIDS and Human Retrovirus Research, Departments of Microbiology and Internal Medicine, University of Virginia Health Systems, Charlottesville, Virginia, USA.
Department of Molecular Biology & Biochemistry, Center for Immunology, and Center for Virus Research, School of Biological Sciences, University of California, Irvine, California, USA
| | - Laura A. Adang
- Myles H. Thaler Center for AIDS and Human Retrovirus Research, Departments of Microbiology and Internal Medicine, University of Virginia Health Systems, Charlottesville, Virginia, USA.
Department of Molecular Biology & Biochemistry, Center for Immunology, and Center for Virus Research, School of Biological Sciences, University of California, Irvine, California, USA
| | - Jon Overdevest
- Myles H. Thaler Center for AIDS and Human Retrovirus Research, Departments of Microbiology and Internal Medicine, University of Virginia Health Systems, Charlottesville, Virginia, USA.
Department of Molecular Biology & Biochemistry, Center for Immunology, and Center for Virus Research, School of Biological Sciences, University of California, Irvine, California, USA
| | - Christine M. O’Connor
- Myles H. Thaler Center for AIDS and Human Retrovirus Research, Departments of Microbiology and Internal Medicine, University of Virginia Health Systems, Charlottesville, Virginia, USA.
Department of Molecular Biology & Biochemistry, Center for Immunology, and Center for Virus Research, School of Biological Sciences, University of California, Irvine, California, USA
| | - J. Robert Taylor
- Myles H. Thaler Center for AIDS and Human Retrovirus Research, Departments of Microbiology and Internal Medicine, University of Virginia Health Systems, Charlottesville, Virginia, USA.
Department of Molecular Biology & Biochemistry, Center for Immunology, and Center for Virus Research, School of Biological Sciences, University of California, Irvine, California, USA
| | - David Camerini
- Myles H. Thaler Center for AIDS and Human Retrovirus Research, Departments of Microbiology and Internal Medicine, University of Virginia Health Systems, Charlottesville, Virginia, USA.
Department of Molecular Biology & Biochemistry, Center for Immunology, and Center for Virus Research, School of Biological Sciences, University of California, Irvine, California, USA
| | - Dean H. Kedes
- Myles H. Thaler Center for AIDS and Human Retrovirus Research, Departments of Microbiology and Internal Medicine, University of Virginia Health Systems, Charlottesville, Virginia, USA.
Department of Molecular Biology & Biochemistry, Center for Immunology, and Center for Virus Research, School of Biological Sciences, University of California, Irvine, California, USA
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16
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O'Connor CM, Kedes DH. Mass spectrometric analyses of purified rhesus monkey rhadinovirus reveal 33 virion-associated proteins. J Virol 2006; 80:1574-83. [PMID: 16415032 PMCID: PMC1346966 DOI: 10.1128/jvi.80.3.1574-1583.2006] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The repertoire of proteins that comprise intact gammaherpesviruses, including the human pathogen Kaposi's sarcoma-associated herpesvirus (KSHV), is likely to have critical functions not only in viral structure and assembly but also in the early stages of infection and evasion of the host's rapidly deployed antiviral defenses. To develop a better understanding of these proteins, we analyzed the composition of rhesus monkey rhadinovirus (RRV), a close phylogenetic relative of KSHV. Unlike KSHV, RRV replicates to high titer in cell culture and thus serves as an effective model for studying primate gammaherpesvirus structure and virion proteomics. We employed two complementary mass spectrometric approaches and found that RRV contains at least 33 distinct virally encoded proteins. We have assigned 7 of these proteins to the capsid, 17 to the tegument, and 9 to the envelope. Of the five gammaherpesvirus-specific tegument proteins, three have no known function. We also found three proteins not previously associated with a purified herpesvirus and an additional seven that represent new findings for a member of the gamma-2 herpesviruses. Detergent extraction resulted in particles that contained six distinct tegument proteins in addition to the expected capsid structural proteins, suggesting that this subset of tegument components may interact more directly with or with higher affinity for the underlying capsid and, in turn, may play a role in assembly or transport of viral or subviral particles during entry or egress.
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Affiliation(s)
- Christine M O'Connor
- Myles H. Thaler Center for AIDS and Human Retrovirus Research, Box 800734, University of Virginia Health Systems, Charlottesville, VA 22908, USA
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Abstract
In 1994, Chang and Moore reported on the latest of the gammaherpesviruses to infect humans, human herpesvirus 8 (HHV-8) [1]. This novel herpesvirus has and continues to present challenges to define its scope of involvement in human disease. In this review, aspects of HHV-8 infection are discussed, such as, the human immune response, viral pathogenesis and transmission, viral disease entities, and the virus's epidemiology with an emphasis on HHV-8 diagnostics.
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Affiliation(s)
- Daniel C Edelman
- Department of Pathology, University of Maryland Baltimore, School of Medicine, Baltimore, Maryland 21201, USA.
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18
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Grange PA, Marcelin AG, Calvez V, Chauvel C, Escande JP, Dupin N. Salivary lactoferrin is recognized by the human herpesvirus-8. J Invest Dermatol 2005; 124:1249-58. [PMID: 15955101 DOI: 10.1111/j.0022-202x.2005.23756.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Human herpesvirus-8 (HHV-8) is commonly detected in all epidemiologic forms of Kaposi's sarcoma. Despite the broad cellular tropism of HHV-8, studies on mucosal shedding of HHV-8 have shown that infectious particles are restricted to saliva isolated from the oropharynx. We used biotinylated purified HHV-8 particles in a direct binding assay to whole clarified human salivary samples isolated from HHV-8-infected and uninfected individuals. We found that the major binding activity was carried out by a protein of 78-kDa size, which was further characterized as human lactoferrin (hLf) using 2-D electrophoresis and MALDI-ToF analysis. Preliminary comparison of HHV-8 binding activity of 76 salivary samples from HHV-8-infected and uninfected individuals showed that 7.8% of the uninfected population exhibited a form of Lf not recognized by HHV-8. Deglycosylation of hLf by PNGase F did not reduce HHV-8 binding activity, whereas endoproteinase cleavage of native hLf generated a non-glycosylated 8-kDa peptide recognized by HHV-8 particles and was located at the position Ala606-Tyr679 in the native hLf amino acid sequence, corresponding to the C-terminal region of the glycoprotein. This work identify the lactoferrin in saliva as a ligand for HHV-8 and suggests that this glycoprotein could be used as a carrier for the viral particles.
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Affiliation(s)
- Philippe A Grange
- Laboratoire de Microbiologie Cutanée, Pavillon Tarnier, Groupe Hospitalier Cochin-Port Royal, Université Paris V, Paris, France.
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19
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Naranatt PP, Krishnan HH, Smith MS, Chandran B. Kaposi's sarcoma-associated herpesvirus modulates microtubule dynamics via RhoA-GTP-diaphanous 2 signaling and utilizes the dynein motors to deliver its DNA to the nucleus. J Virol 2005; 79:1191-206. [PMID: 15613346 PMCID: PMC538527 DOI: 10.1128/jvi.79.2.1191-1206.2005] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Human herpesvirus 8 (HHV-8; also called Kaposi's sarcoma-associated herpesvirus), which is implicated in the pathogenesis of Kaposi's sarcoma (KS) and lymphoproliferative disorders, infects a variety of target cells both in vivo and in vitro. HHV-8 binds to several in vitro target cells via cell surface heparan sulfate and utilizes the alpha3beta1 integrin as one of its entry receptors. Interactions with cell surface molecules induce the activation of host cell signaling cascades and cytoskeletal changes (P. P. Naranatt, S. M. Akula, C. A. Zien, H. H. Krishnan, and B. Chandran, J. Virol. 77:1524-1539, 2003). However, the mechanism by which the HHV-8-induced signaling pathway facilitates the complex events associated with the internalization and nuclear trafficking of internalized viral DNA is as yet undefined. Here we examined the role of HHV-8-induced cytoskeletal dynamics in the infectious process and their interlinkage with signaling pathways. The depolymerization of microtubules did not affect HHV-8 binding and internalization, but it inhibited the nuclear delivery of viral DNA and infection. In contrast, the depolymerization of actin microfilaments did not have any effect on virus binding, entry, nuclear delivery, or infection. Early during infection, HHV-8 induced the acetylation of microtubules and the activation of the RhoA and Rac1 GTPases. The inactivation of Rho GTPases by Clostridium difficile toxin B significantly reduced microtubular acetylation and the delivery of viral DNA to the nucleus. In contrast, the activation of Rho GTPases by Escherichia coli cytotoxic necrotizing factor significantly augmented the nuclear delivery of viral DNA. Among the Rho GTPase-induced downstream effector molecules known to stabilize the microtubules, the activation of RhoA-GTP-dependent diaphanous 2 was observed, with no significant activation in the Rac- and Cdc42-dependent PAK1/2 and stathmin molecules. The nuclear delivery of viral DNA increased in cells expressing a constitutively active RhoA mutant and decreased in cells expressing a dominant-negative mutant of RhoA. HHV-8 capsids colocalized with the microtubules, as observed by confocal microscopic examination, and the colocalization was abolished by the destabilization of microtubules with nocodazole and by the phosphatidylinositol 3-kinase inhibitor affecting the Rho GTPases. These results suggest that HHV-8 induces Rho GTPases, and in doing so, modulates microtubules and promotes the trafficking of viral capsids and the establishment of infection. This is the first demonstration of virus-induced host cell signaling pathways in the modulation of microtubule dynamics and in the trafficking of viral DNA to the infected cell nucleus. These results further support our hypothesis that HHV-8 manipulates the host cell signaling pathway to create an appropriate intracellular environment that is conducive to the establishment of a successful infection.
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Affiliation(s)
- Pramod P Naranatt
- Department of Microbiology, Molecular Genetics and Immunology, Mail Stop 3029, The University of Kansas Medical Center, 3901 Rainbow Blvd., Kansas City, KS 66160, USA
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20
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Yu X, Shah S, Atanasov I, Lo P, Liu F, Britt WJ, Zhou ZH. Three-dimensional localization of the smallest capsid protein in the human cytomegalovirus capsid. J Virol 2005; 79:1327-32. [PMID: 15613360 PMCID: PMC538561 DOI: 10.1128/jvi.79.2.1327-1332.2005] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The smallest capsid proteins (SCPs) of the human herpesviruses differ substantially in size and sequence and are thought to impart some unique aspects of infection to their respective viruses. We used electron cryomicroscopy and antibody labeling to show that the 8-kDa SCP of human cytomegalovirus is attached only to major capsid protein subunits of the hexons, not the pentons. Thus, the SCPs of different herpesviruses illustrate that a protein can evolve significantly in sequence, structure, and function, while preserving its role in the architecture of the virus by binding to a specific partner in a specific oligomeric state.
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Affiliation(s)
- Xuekui Yu
- Department of Pathology and Laboratory Medicine, University of Texas Medical School at Houston, 6431 Fannin St., MSB 2.280, Houston, TX 77030, USA
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21
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Kaposi's sarcoma-associated herpesvirus modulates microtubule dynamics via RhoA-GTP-diaphanous 2 signaling and utilizes the dynein motors to deliver its DNA to the nucleus. J Virol 2004. [PMID: 15613346 DOI: 10.1128/jvi.79.2.1191–1206.2005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human herpesvirus 8 (HHV-8; also called Kaposi's sarcoma-associated herpesvirus), which is implicated in the pathogenesis of Kaposi's sarcoma (KS) and lymphoproliferative disorders, infects a variety of target cells both in vivo and in vitro. HHV-8 binds to several in vitro target cells via cell surface heparan sulfate and utilizes the alpha3beta1 integrin as one of its entry receptors. Interactions with cell surface molecules induce the activation of host cell signaling cascades and cytoskeletal changes (P. P. Naranatt, S. M. Akula, C. A. Zien, H. H. Krishnan, and B. Chandran, J. Virol. 77:1524-1539, 2003). However, the mechanism by which the HHV-8-induced signaling pathway facilitates the complex events associated with the internalization and nuclear trafficking of internalized viral DNA is as yet undefined. Here we examined the role of HHV-8-induced cytoskeletal dynamics in the infectious process and their interlinkage with signaling pathways. The depolymerization of microtubules did not affect HHV-8 binding and internalization, but it inhibited the nuclear delivery of viral DNA and infection. In contrast, the depolymerization of actin microfilaments did not have any effect on virus binding, entry, nuclear delivery, or infection. Early during infection, HHV-8 induced the acetylation of microtubules and the activation of the RhoA and Rac1 GTPases. The inactivation of Rho GTPases by Clostridium difficile toxin B significantly reduced microtubular acetylation and the delivery of viral DNA to the nucleus. In contrast, the activation of Rho GTPases by Escherichia coli cytotoxic necrotizing factor significantly augmented the nuclear delivery of viral DNA. Among the Rho GTPase-induced downstream effector molecules known to stabilize the microtubules, the activation of RhoA-GTP-dependent diaphanous 2 was observed, with no significant activation in the Rac- and Cdc42-dependent PAK1/2 and stathmin molecules. The nuclear delivery of viral DNA increased in cells expressing a constitutively active RhoA mutant and decreased in cells expressing a dominant-negative mutant of RhoA. HHV-8 capsids colocalized with the microtubules, as observed by confocal microscopic examination, and the colocalization was abolished by the destabilization of microtubules with nocodazole and by the phosphatidylinositol 3-kinase inhibitor affecting the Rho GTPases. These results suggest that HHV-8 induces Rho GTPases, and in doing so, modulates microtubules and promotes the trafficking of viral capsids and the establishment of infection. This is the first demonstration of virus-induced host cell signaling pathways in the modulation of microtubule dynamics and in the trafficking of viral DNA to the infected cell nucleus. These results further support our hypothesis that HHV-8 manipulates the host cell signaling pathway to create an appropriate intracellular environment that is conducive to the establishment of a successful infection.
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22
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Yu XK, O'Connor CM, Atanasov I, Damania B, Kedes DH, Zhou ZH. Three-dimensional structures of the A, B, and C capsids of rhesus monkey rhadinovirus: insights into gammaherpesvirus capsid assembly, maturation, and DNA packaging. J Virol 2004; 77:13182-93. [PMID: 14645575 PMCID: PMC296048 DOI: 10.1128/jvi.77.24.13182-13193.2003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rhesus monkey rhadinovirus (RRV) exhibits high levels of sequence homology to human gammaherpesviruses, such as Kaposi's sarcoma-associated herpesvirus, and grows to high titers in cell cultures, making it a good model system for studying gammaherpesvirus capsid structure and assembly. We have purified RRV A, B, and C capsids, thus for the first time allowing direct structure comparisons by electron cryomicroscopy and three-dimensional reconstruction. The results show that the shells of these capsids are identical and are each composed of 12 pentons, 150 hexons, and 320 triplexes. Structural differences were apparent inside the shells and through the penton channels. The A capsid is empty, and its penton channels are open. The B capsid contains a scaffolding core, and its penton channels are closed. The C capsid contains a DNA genome, which is closely packaged into regularly spaced density shells (25 A apart), and its penton channels are open. The different statuses of the penton channels suggest a functional role of the channels during capsid maturation, and the overall structural similarities of RRV capsids to alphaherpesvirus capsids suggest a common assembly and maturation pathway. The RRV A capsid reconstruction at a 15-A resolution, the best achieved for gammaherpesvirus particles, reveals overall structural similarities to alpha- and betaherpesvirus capsids. However, the outer regions of the capsid, including densities attributed to the Ta triplex and the small capsomer-interacting protein (SCIP or ORF65), exhibit prominent differences from their structural counterparts in alphaherpesviruses. This structural disparity suggests that SCIP and the triplex, together with tegument and envelope proteins, confer structural and potentially functional specificities to alpha-, beta-, and gammaherpesviruses.
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Affiliation(s)
- Xue-Kui Yu
- Department of PathologyLaboratory Medicine, University of Texas at Houston Medical School, Houston, Texas 77030, USA
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