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Selvaraj C, Shri GR, Vijayakumar R, Alothaim AS, Ramya S, Singh SK. Viral hijacking mechanism in humans through protein-protein interactions. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2022; 131:261-276. [PMID: 35871893 DOI: 10.1016/bs.apcsb.2022.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Numerous viruses have evolved mechanisms to inhibit or alter the host cell's apoptotic response as part of their coevolution with their hosts. The analysis of virus-host protein interactions require an in-depth understanding of both the viral and host protein structures and repertoires, as well as evolutionary mechanisms and pertinent biological facts. Throughout the course of a viral infection, there is constant battle for binding between virus and cellular proteins. Exogenous interfaces facilitating viral-host interactions are well known for constantly targeting and suppressing endogenous interfaces mediating intraspecific interactions, such as viral-viral and host-host connections. In these interactions, the protein-protein interactions (PPIs), are mostly shown as networks (protein interaction networks, PINs), with proteins represented as nodes and their interactions represented as edges. Host proteins with a higher degree of connectivity are more likely to interact with viral proteins. Due to technical advancements, three-dimensional interactions may now be visualized computationally utilizing molecular modeling and cryo-EM approaches. The uniqueness of viral domain repertoires, their evolution, and their activities during viral infection make viruses fascinating models for research. This chapter aims to provide readers a complete picture of the viral hijacking mechanism in protein-protein interactions.
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Affiliation(s)
- Chandrabose Selvaraj
- Computer Aided Drug Design and Molecular Modeling Lab, Department of Bioinformatics, Science Block, Alagappa University, Karaikudi, Tamil Nadu, India.
| | - Gurunathan Rubha Shri
- Computer Aided Drug Design and Molecular Modeling Lab, Department of Bioinformatics, Science Block, Alagappa University, Karaikudi, Tamil Nadu, India
| | - Rajendran Vijayakumar
- Department of Biology, College of Science in Zulfi, Majmaah University, Majmaah, Saudi Arabia
| | - Abdulaziz S Alothaim
- Department of Biology, College of Science in Zulfi, Majmaah University, Majmaah, Saudi Arabia
| | - Saravanan Ramya
- Computer Aided Drug Design and Molecular Modeling Lab, Department of Bioinformatics, Science Block, Alagappa University, Karaikudi, Tamil Nadu, India
| | - Sanjeev Kumar Singh
- Computer Aided Drug Design and Molecular Modeling Lab, Department of Bioinformatics, Science Block, Alagappa University, Karaikudi, Tamil Nadu, India.
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Baba H, Kettani A, Bouqdayr M, Ouladlahsen A, Bensghir R, Marih L, Sodqi M, Benjelloun S, Ezzikouri S, Zaidane I, Jadid FZ, Filali KME, Wakrim L. Programmed cell death-1 single-nucleotide polymorphism rs10204525 is associated with human immunodeficiency virus type 1 RNA viral load in HIV-1-infected Moroccan subjects. Med Microbiol Immunol 2021; 210:187-196. [PMID: 34031715 DOI: 10.1007/s00430-021-00712-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2020] [Accepted: 05/15/2021] [Indexed: 10/21/2022]
Abstract
Human Immunodeficiency Virus (HIV-1) infections are characterized by dysfunctional cellular and humoral antiviral immune responses. The progressive loss of effector functions in chronic viral infection has been associated with the up-regulation of programmed death-1 (PD-1), a negative regulator of activated T cells and Natural Killer cells. In HIV-1 infection, increased levels of PD-1 expression correlate with CD8 + T-cell exhaustion. In vitro, PD-1 blockade using PD-1 antibodies led to an increase in HIV-1 specific CD8 + T and memory B cell proliferation. We aimed to investigate the impact of PDCD1 rs10204525 polymorphism on HIV-1 susceptibility, AIDS development, and treatment response outcomes in HIV-1 infection in a Moroccan population. A total of 214 HIV-1 seropositive and 250 seronegative subjects were enrolled to investigate the association between the between the single-nucleotide polymorphism (SNP) rs10204525 of PDCD1 gene and HIV-1 pathogenesis using a predesigned TaqMan SNP genotyping assay. No significant association was found between rs10204525 and susceptibility to HIV-1 infection and AIDS development (p > 0.05). Genotype frequencies were significantly associated with the viral load before ART (p = 0.0105). HIV-1 viral load was significantly higher among subjects with the CC compared to TT genotype (p = 0.0043). In treated subjects, the median of viral load levels was significantly higher in CC and CT groups than TT subjects (p < 0.005). However, analysis of the correlation between CD4 + T-cell levels and PDCD1 polymorphism before and after ART showed no significant difference (p > 0.05). Our results demonstrated that rs10204525 polymorphism does not affect HIV-1 infection. However, this polymorphism may affect the response to treatment as measured by RNA viral load levels.
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Affiliation(s)
- Hanâ Baba
- Virology Unit, Immuno-Virology Laboratory, Institut Pasteur du Maroc, Casablanca, Morocco.
- Laboratory of Biology and Health, URAC 34, Faculty of Sciences Ben M'Sik, Hassan II University-Casablanca, Casablanca, Morocco.
| | - Anass Kettani
- Laboratory of Biology and Health, URAC 34, Faculty of Sciences Ben M'Sik, Hassan II University-Casablanca, Casablanca, Morocco
| | - Meryem Bouqdayr
- Virology Unit, Immuno-Virology Laboratory, Institut Pasteur du Maroc, Casablanca, Morocco
- Laboratory of Biology and Health, URAC 34, Faculty of Sciences Ben M'Sik, Hassan II University-Casablanca, Casablanca, Morocco
| | - Ahd Ouladlahsen
- Service Des Maladies Infectieuses, CHU Ibn Rochd, Casablanca, Morocco
| | - Rajaa Bensghir
- Service Des Maladies Infectieuses, CHU Ibn Rochd, Casablanca, Morocco
| | - Latifa Marih
- Service Des Maladies Infectieuses, CHU Ibn Rochd, Casablanca, Morocco
| | - Mustapha Sodqi
- Service Des Maladies Infectieuses, CHU Ibn Rochd, Casablanca, Morocco
| | - Soumaya Benjelloun
- Virology Unit, Viral Hepatitis Laboratory, Institut Pasteur du Maroc, Casablanca, Morocco
| | - Sayeh Ezzikouri
- Virology Unit, Viral Hepatitis Laboratory, Institut Pasteur du Maroc, Casablanca, Morocco
| | - Imane Zaidane
- Virology Unit, Viral Hepatitis Laboratory, Institut Pasteur du Maroc, Casablanca, Morocco
| | - Fatima-Zahra Jadid
- Virology Unit, Viral Hepatitis Laboratory, Institut Pasteur du Maroc, Casablanca, Morocco
| | | | - Lahcen Wakrim
- Virology Unit, Immuno-Virology Laboratory, Institut Pasteur du Maroc, Casablanca, Morocco
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Yee PTI, Tan SH, Ong KC, Tan KO, Wong KT, Hassan SS, Poh CL. Development of live attenuated Enterovirus 71 vaccine strains that confer protection against lethal challenge in mice. Sci Rep 2019; 9:4805. [PMID: 30886246 PMCID: PMC6423319 DOI: 10.1038/s41598-019-41285-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Accepted: 02/27/2019] [Indexed: 12/12/2022] Open
Abstract
Besides causing mild hand, foot and mouth infections, Enterovirus A71 (EV-A71) is associated with neurological complications and fatality. With concerns about rising EV-A71 virulence, there is an urgency for more effective vaccines. The live attenuated vaccine (LAV) is a more valuable vaccine as it can elicit both humoral and cellular immune responses. A miRNA-based vaccine strain (pIY) carrying let-7a and miR-124a target genes in the EV-A71 genome which has a partial deletion in the 5′NTR (∆11 bp) and G64R mutation (3Dp°l) was designed. The viral RNA copy number and viral titers of the pIY strain were significantly lower in SHSY-5Y cells that expressed both let-7a and miR-124a. Inhibition of the cognate miRNAs expressed in RD and SHSY-5Y cells demonstrated de-repression of viral mRNA translation. A previously constructed multiply mutated strain, MMS and the pIY vaccine strain were assessed in their ability to protect 4-week old mice from hind limb paralysis. The MMS showed higher amounts of IFN-γ ex vivo than the pIY vaccine strain. There was absence of EV-A71 antigen in the skeletal muscles and spinal cord micrographs of mice vaccinated with the MMS and pIY strains. The MMS and pIY strains are promising LAV candidates developed against severe EV-A71 infections.
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Affiliation(s)
- Pinn Tsin Isabel Yee
- Centre for Virus and Vaccine Research, School of Science and Technology, Sunway University, Bandar Sunway, Selangor, 47500, Malaysia
| | - Soon Hao Tan
- Department of Biomedical Science, Faculty of Medicine, University of Malaya, Jalan University, 50603, Kuala Lumpur, Selangor, Malaysia
| | - Kien Chai Ong
- Department of Biomedical Science, Faculty of Medicine, University of Malaya, Jalan University, 50603, Kuala Lumpur, Selangor, Malaysia
| | - Kuan Onn Tan
- Department of Biological Sciences, School of Science and Technology, Sunway University, Kuala Lumpur, Selangor, 47500, Malaysia
| | - Kum Thong Wong
- Department of Pathology, Faculty of Medicine, University of Malaya, Jalan University, 50603, Kuala Lumpur, Selangor, Malaysia
| | - Sharifah Syed Hassan
- Jeffrey Cheah School of Medicine and Health Sciences, Monash University, Jalan Lagoon Selatan, Bandar Sunway, 47500, Subang Jaya, Malaysia
| | - Chit Laa Poh
- Centre for Virus and Vaccine Research, School of Science and Technology, Sunway University, Bandar Sunway, Selangor, 47500, Malaysia.
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Tang M, Liu Y, Zhang QC, Zhang P, Wu JK, Wang JN, Ruan Y, Huang Y. Antitumor efficacy of the Runx2-dendritic cell vaccine in triple-negative breast cancer in vitro. Oncol Lett 2018; 16:2813-2822. [PMID: 30127867 PMCID: PMC6096217 DOI: 10.3892/ol.2018.9001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2017] [Accepted: 04/05/2018] [Indexed: 12/13/2022] Open
Abstract
Triple-negative breast cancer (TNBC) is a subtype of breast cancer with a poor prognosis and limited effective treatment. The rise in immunotherapeutic strategies prompted the establishment of a genetic vaccine against TNBC in vitro using a possible biological marker of TNBC. In the present study, different detection methods were used to evaluate the distribution and expression of runt-associated transcription factor 2 (Runx2) in various breast cancer cell lines. Following the development of the Runx2-dendritic cell (DC) vaccine using a lentivirus, the transfection efficacy was recorded. The T lymphocytes co-cultured with the vaccine were collected to assess the antitumor potency. Increased levels of Runx2 were expressed in breast cancer cells; however, different breast cancer cell lines expressed various levels of Runx2. Runx2 demonstrated particularly high expression in TNBC cells, compared with non-TNBC cells. A Runx2 lentivirus transfection system was successfully engineered, and Runx2 was transduced into dendritic cells whilst maintaining stable expression. The sustained and stable cytotoxic T cells induced in the transfected group had higher and more specific antitumor efficacy against TNBC, compared with the other cell lines. Runx2 may be a novel target for TNBC treatment. The Runx2-DC vaccine may induce specific and efficient antitumor effects in TNBC in vitro.
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Affiliation(s)
- Mi Tang
- Department of General Surgery, Chongqing General Hospital, Chongqing 400010, P.R. China
| | - Yu Liu
- Department of Thyroid and Breast Surgery, Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong 510000, P.R. China
| | - Qiao-Chu Zhang
- Department of VIP, Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong 510000, P.R. China
| | - Peng Zhang
- Department of General Surgery, Lingnan Hospital, Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong 510000, P.R. China
| | - Jue-Kun Wu
- Department of Thyroid and Breast Surgery, Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong 510000, P.R. China
| | - Jia-Ni Wang
- Department of Thyroid and Breast Surgery, Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong 510000, P.R. China
| | - Ying Ruan
- Department of Thyroid and Breast Surgery, Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong 510000, P.R. China
| | - Yong Huang
- Department of Thyroid and Breast Surgery, Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong 510000, P.R. China
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A Biomolecular Network Driven Proteinic Interaction in HCV Clearance. Cell Biochem Biophys 2018; 76:161-172. [PMID: 29313175 DOI: 10.1007/s12013-017-0837-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 12/26/2017] [Indexed: 12/20/2022]
Abstract
Hepatitis C virus infection causes chronic liver disease that leads to cancer-related mortality. Presently around 30% of the HCV (infected) affected population get rid of the infection through spontaneous disease clearance. This phenomenon is conducted by a set of reported immune candidate genes. Hence, this study focuses only on these immune-response related genes with aid of network approach, where the idea is to disseminate the network for better understanding of key functional genes and their transcription control activity. Based on the network analysis the IFNG, TNF, IFNB1, STAT1, NFKB1, STAT3, SOCS1, and MYD88 genes are prioritized as hub genes along with their common transcription factors (TFs), IRF9, NFKB1, and STAT1. The dinucleotide frequency of TF binding elements indicated GG-rich motifs in these regulatory elements. On the other hand, gene enrichment report suggests the regulation of response to interferon gamma signaling pathway, which plays central role in the spontaneous HCV clearance. Therefore, our study tends to prioritize the genes, TFs, and their regulatory pathway towards HCV clearance. Even so, the resultant hub genes and their TFs and TF binding elements could be crucial in underscoring the clearance activity in specific populations.
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Górski A, Dąbrowska K, Międzybrodzki R, Weber-Dąbrowska B, Łusiak-Szelachowska M, Jończyk-Matysiak E, Borysowski J. Phages and immunomodulation. Future Microbiol 2017; 12:905-914. [PMID: 28434234 DOI: 10.2217/fmb-2017-0049] [Citation(s) in RCA: 95] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
In the past years, the microbiome and its role in the pathophysiology of diseases have gained great interest. The progress of our knowledge in this field opens completely novel prospects for treating disorders, including those which are most challenging to medicine today. Of special interest are studies on the interactions of the microbiome with the immune system. Only recently has the presence of bacteriophages in the microbiome been highlighted, and their potential role in maintaining normal immunity has gained increasing attention. We summarize the available data pointing to the potential impact of phages in maintaining immunological homeostasis.
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Affiliation(s)
- Andrzej Górski
- Bacteriophage Laboratory, Ludwik Hirszfeld Institute of Immunology & Experimental Therapy, Polish Academy of Sciences (HIIET PAS), Wrocław, Poland.,Phage Therapy Unit, Ludwik Hirszfeld Institute of Immunology & Experimental Therapy, Polish Academy of Sciences, Wrocław, Poland.,Department of Clinical Immunology, Transplantation Institute, The Medical University of Warsaw, Warsaw, Poland
| | - Krystyna Dąbrowska
- Bacteriophage Laboratory, Ludwik Hirszfeld Institute of Immunology & Experimental Therapy, Polish Academy of Sciences (HIIET PAS), Wrocław, Poland
| | - Ryszard Międzybrodzki
- Bacteriophage Laboratory, Ludwik Hirszfeld Institute of Immunology & Experimental Therapy, Polish Academy of Sciences (HIIET PAS), Wrocław, Poland.,Phage Therapy Unit, Ludwik Hirszfeld Institute of Immunology & Experimental Therapy, Polish Academy of Sciences, Wrocław, Poland.,Department of Clinical Immunology, Transplantation Institute, The Medical University of Warsaw, Warsaw, Poland
| | - Beata Weber-Dąbrowska
- Bacteriophage Laboratory, Ludwik Hirszfeld Institute of Immunology & Experimental Therapy, Polish Academy of Sciences (HIIET PAS), Wrocław, Poland.,Phage Therapy Unit, Ludwik Hirszfeld Institute of Immunology & Experimental Therapy, Polish Academy of Sciences, Wrocław, Poland
| | - Marzanna Łusiak-Szelachowska
- Bacteriophage Laboratory, Ludwik Hirszfeld Institute of Immunology & Experimental Therapy, Polish Academy of Sciences (HIIET PAS), Wrocław, Poland
| | - Ewa Jończyk-Matysiak
- Bacteriophage Laboratory, Ludwik Hirszfeld Institute of Immunology & Experimental Therapy, Polish Academy of Sciences (HIIET PAS), Wrocław, Poland
| | - Jan Borysowski
- Department of Clinical Immunology, Transplantation Institute, The Medical University of Warsaw, Warsaw, Poland
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He Y, Zhang J, Mi Z, Robbins P, Falo LD. Immunization with lentiviral vector-transduced dendritic cells induces strong and long-lasting T cell responses and therapeutic immunity. THE JOURNAL OF IMMUNOLOGY 2005; 174:3808-17. [PMID: 15749922 DOI: 10.4049/jimmunol.174.6.3808] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Dendritic cell (DC) therapies are currently being evaluated for the treatment of cancer. The majority of ongoing clinical trials use DCs loaded with defined antigenic peptides or proteins, or tumor-derived products, such as lysates or apoptotic cells, as sources of Ag. Although several theoretical considerations suggest that DCs expressing transgenic protein Ags may be more effective immunogens than protein-loaded cells, methods for efficiently transfecting DCs are only now being developed. In this study we directly compare the immunogenicity of peptide/protein-pulsed DCs with lentiviral vector-transduced DCs, and their comparative efficacy in tumor immunotherapy. Maturing, bone marrow-derived DCs can be efficiently transduced with lentiviral vectors, and transduction does not affect DC maturation, plasticity, or Ag presentation function. Transduced DCs efficiently process and present both MHC class I- and II-restricted epitopes from the expressed transgenic Ag OVA. Compared with peptide- or protein-pulsed DCs, lentiviral vector-transduced DCs elicit stronger and longer-lasting T cell responses in vivo, as measured by both in vivo killing assays and intracellular production of IFN-gamma by Ag-specific T cells. In the B16-OVA tumor therapy model, the growth of established tumors was significantly inhibited by a single immunization using lentiviral vector-transduced DCs, resulting in significantly longer survival of immunized animals. These results suggest that compared with Ag-pulsed DCs, vaccination with lentiviral vector-transduced DCs may achieve more potent antitumor immunity. These data support the further development of lentiviral vectors to transduce DCs with genes encoding Ags or immunomodulatory adjuvants to generate and control systemic immune responses.
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Affiliation(s)
- Yukai He
- Department of Dermatology, University of Pittsburgh Cancer Institute, Pittsburgh, PA 15261, USA.
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Asojo OA, Goud G, Dhar K, Loukas A, Zhan B, Deumic V, Liu S, Borgstahl GEO, Hotez PJ. X-ray structure of Na-ASP-2, a pathogenesis-related-1 protein from the nematode parasite, Necator americanus, and a vaccine antigen for human hookworm infection. J Mol Biol 2005; 346:801-14. [PMID: 15713464 DOI: 10.1016/j.jmb.2004.12.023] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2004] [Revised: 12/08/2004] [Accepted: 12/09/2004] [Indexed: 11/15/2022]
Abstract
Human hookworm infection is a major cause of anemia and malnutrition of adults and children in the developing world. As part of on-going efforts to control hookworm infection, The Human Hookworm Vaccine Initiative has identified candidate vaccine antigens from the infective L3 larval stages of the parasite, including a family of pathogenesis-related (PR) proteins known as the Ancylostoma-secreted proteins (ASPs). A novel crystal structure of Na-ASP-2, a PR-1 protein secreted by infective larvae of the human hookworm Necator americanus, has been solved to resolution limits of 1.68 A and to an R-factor of 17% using the recombinant protein expressed in and secreted by Pichia pastoris. The overall fold of Na-ASP-2 is a three-layer alphabetaalpha sandwich flanked by an N-terminal loop and a short, cysteine-rich C terminus. Our structure reveals a large central cavity that is flanked by His129 and Glu106, two residues that are well conserved in all parasitic nematode L3 ASPs. Na-ASP-2 has structural and charge similarities to chemokines, which suggests that Na-ASP-2 may be an extra-cellular ligand of an unknown receptor. Na-ASP-2 is a useful homology model for NIF, a natural antagonistic ligand of CR3 receptor. From these modeling studies, possible binding modes were predicted. In addition, this first structure of a PR-1 protein from parasitic helminths may shed light on the molecular basis of host-parasite interactions.
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Affiliation(s)
- Oluwatoyin A Asojo
- Eppley Institute for Research in Cancer and Allied Diseases, 987696 Nebraska Medical Center, Omaha, NE 68198-7696, USA.
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Abstract
Gene delivery has the potential to offer effective treatment to patients with life-threatening lung diseases such as cystic fibrosis, alpha1-antitrypsin deficiency and lung cancer. Phase I/II clinical trials have shown that, in principle, gene transfer to the lung is feasible and safe. However, gene expression from both viral and non-viral gene delivery systems has been inefficient. In addition to extra- and intracellular barriers, the host innate and acquired immune system represents a major barrier to successful gene transfer to the lung. Results from studies in experimental animals and clinical trials have shown that inflammatory, antibody and T cell responses can limit transgene expression duration and readministration of the gene transfer vector. We will review here how the development of pharmacological and/or immunological agents can modulate the host immune system and the limitations of these strategies. A better understanding of the immunological barriers which exist in the lung might allow for a more sustained expression of the transgene and importantly help overcome the problem of readministration of viral vectors.
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Affiliation(s)
- S Ferrari
- Department of Gene Therapy, National Heart and Lung Institute, Imperial College Faculty of Medicine, London, UK.
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Xue SA, Jones MD, Lu QL, Middeldorp JM, Griffin BE. Genetic diversity: frameshift mechanisms alter coding of a gene (Epstein-Barr virus LF3 gene) that contains multiple 102-base-pair direct sequence repeats. Mol Cell Biol 2003; 23:2192-201. [PMID: 12612089 PMCID: PMC149476 DOI: 10.1128/mcb.23.6.2192-2201.2003] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Frameshift mutations provide recognized mechanisms for changing the coding potential of an organism. Here, multiple frameshifts are identified in repetitive sequences within an Epstein-Barr virus unspliced early gene, LF3, which is associated with the viral replicative cycle and also transcriptionally expressed in many virally associated tumors. On the DNA strand encoding LF3, there are three open reading frames, only one of which contains an initiation codon. Most (>95%) of the gene consists of numerous (>20, varying with cell source) GC-rich copies of a 102-bp direct repeat (called IR 4) flanked by small unique sequences. LF3 may express a protein if its initiation and termination codons reside in the same reading frame, but this is not always the case. Frameshifting events, occurring in short runs of pyrimidines (mainly C residues) in the repeats, give rise to mutations which may provide a mechanism for escape of an LF3 function from host surveillance. Sequence studies link these frameshifts to DNA replication errors. Notably, the number of sites in LF3 at which such mutations can occur permits a very large amount of diversity in this gene. Our data also suggest a second degeneracy mechanism within the protein itself, which influences its stability and may reflect a host defense mechanism. LF3 thus provides a potentially important model for studying the quest for supremacy between a virus and its host.
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Affiliation(s)
- Shao-An Xue
- Viral Oncology Unit, Division of Medicine, Wright-Fleming Institute, Imperial College of Science, Technology and Medicine at St. Mary's, Norfolk Place, London W2 1PG, UK
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