101
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Ivanov AP, Dragunsky EM. ELISA as a possible alternative to the neutralization test for evaluating the immune response to poliovirus vaccines. Expert Rev Vaccines 2014; 4:167-72. [PMID: 15889990 DOI: 10.1586/14760584.4.2.167] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This review describes several enzyme-linked immunosorbent assay (ELISA) techniques proposed to replace the neutralization test for detecting neutralization-relevant antibodies to polioviruses in recipients of inactivated poliovirus vaccine and oral poliovirus vaccine, and for seroepidemiologic studies. Comparisons of results from ELISA and the neutralization test suggest that ELISA variants, based on the principle of blocking or binding inhibition that emulate the neutralization test, might offer an alternative to the neutralization test. However, to replace the neutralization test with ELISA would first require extensive studies with very large numbers of serum samples, including sera having low titers of neutralizing antibodies, in order to obtain reliable and statistically sound validation.
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Affiliation(s)
- Alexander P Ivanov
- United States Food and Drug Administration, Center for Biologics Evaluation and Research, 1401 Rockville Pike, Rockville, MD 20852, USA.
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102
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Optimization of fixed-permeabilized cell monolayers for high throughput micro-neutralizing antibody assays: Application to the zebrafish/viral hemorrhagic septicemia virus (vhsv) model. J Virol Methods 2013; 193:627-32. [DOI: 10.1016/j.jviromet.2013.07.049] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Revised: 07/24/2013] [Accepted: 07/26/2013] [Indexed: 11/24/2022]
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103
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Abstract
Adeno-associated virus (AAV) is a member of the family Parvoviridae that has been widely used as a vector for gene therapy because of its safety profile, its ability to transduce both dividing and non-dividing cells, and its low immunogenicity. AAV has been detected in many different tissues of several animal species but has not been associated with any disease. As a result of natural infections, antibodies to AAV can be found in many animals including humans. It has been shown that pre-existing AAV antibodies can modulate the safety and efficacy of AAV vector-mediated gene therapy by blocking vector transduction or by redirecting distribution of AAV vectors to tissues other than the target organ. This review will summarize antibody responses against natural AAV infections, as well as AAV gene therapy vectors and their impact in the clinical development of AAV vectors for gene therapy. We will also review and discuss the various methods used for AAV antibody detection and strategies to overcome neutralizing antibodies in AAV-mediated gene therapy.
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Affiliation(s)
- Roberto Calcedo
- Gene Therapy Program, Department of Pathology and Laboratory Medicine, University of Pennsylvania , Philadelphia, PA , USA
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104
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The Fc region of an antibody impacts the neutralization of West Nile viruses in different maturation states. J Virol 2013; 87:13729-40. [PMID: 24109224 DOI: 10.1128/jvi.02340-13] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Flavivirus-infected cells secrete a structurally heterogeneous population of viruses because of an inefficient virion maturation process. Flaviviruses assemble as noninfectious, immature virions composed of trimers of envelope (E) and precursor membrane (prM) protein heterodimers. Cleavage of prM is a required process during virion maturation, although this often remains incomplete for infectious virus particles. Previous work demonstrated that the efficiency of virion maturation could impact antibody neutralization through changes in the accessibility of otherwise cryptic epitopes on the virion. In this study, we show that the neutralization potency of monoclonal antibody (MAb) E33 is sensitive to the maturation state of West Nile virus (WNV), despite its recognition of an accessible epitope, the domain III lateral ridge (DIII-LR). Comprehensive epitope mapping studies with 166 E protein DIII-LR variants revealed that the functional footprint of MAb E33 on the E protein differs subtly from that of the well-characterized DIII-LR MAb E16. Remarkably, aromatic substitutions at E protein residue 306 ablated the maturation state sensitivity of E33 IgG, and the neutralization efficacy of E33 Fab fragments was not affected by changes in the virion maturation state. We propose that E33 IgG binding on mature virions orients the Fc region in a manner that impacts subsequent antibody binding to nearby sites. This Fc-mediated steric constraint is a novel mechanism by which the maturation state of a virion modulates the efficacy of the humoral immune response to flavivirus infection.
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105
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Tu C, Lu YP, Hsieh CY, Huang SM, Chang SK, Chen MM. Production of monoclonal antibody against ORF72 of koi herpesvirus isolated in Taiwan. Folia Microbiol (Praha) 2013; 59:159-65. [DOI: 10.1007/s12223-013-0261-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2012] [Accepted: 05/27/2013] [Indexed: 11/24/2022]
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106
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A next-generation cleaved, soluble HIV-1 Env trimer, BG505 SOSIP.664 gp140, expresses multiple epitopes for broadly neutralizing but not non-neutralizing antibodies. PLoS Pathog 2013; 9:e1003618. [PMID: 24068931 PMCID: PMC3777863 DOI: 10.1371/journal.ppat.1003618] [Citation(s) in RCA: 740] [Impact Index Per Article: 67.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 07/30/2013] [Indexed: 01/17/2023] Open
Abstract
A desirable but as yet unachieved property of a human immunodeficiency virus type 1 (HIV-1) vaccine candidate is the ability to induce broadly neutralizing antibodies (bNAbs). One approach to the problem is to create trimeric mimics of the native envelope glycoprotein (Env) spike that expose as many bNAb epitopes as possible, while occluding those for non-neutralizing antibodies (non-NAbs). Here, we describe the design and properties of soluble, cleaved SOSIP.664 gp140 trimers based on the subtype A transmitted/founder strain, BG505. These trimers are highly stable, more so even than the corresponding gp120 monomer, as judged by differential scanning calorimetry. They are also homogenous and closely resemble native virus spikes when visualized by negative stain electron microscopy (EM). We used several techniques, including ELISA and surface plasmon resonance (SPR), to determine the relationship between the ability of monoclonal antibodies (MAbs) to bind the soluble trimers and neutralize the corresponding virus. In general, the concordance was excellent, in that virtually all bNAbs against multiple neutralizing epitopes on HIV-1 Env were highly reactive with the BG505 SOSIP.664 gp140 trimers, including quaternary epitopes (CH01, PG9, PG16 and PGT145). Conversely, non-NAbs to the CD4-binding site, CD4-induced epitopes or gp41ECTO did not react with the trimers, even when their epitopes were present on simpler forms of Env (e.g. gp120 monomers or dissociated gp41 subunits). Three non-neutralizing MAbs to V3 epitopes did, however, react strongly with the trimers but only by ELISA, and not at all by SPR and to only a limited extent by EM. These new soluble trimers are useful for structural studies and are being assessed for their performance as immunogens.
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107
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Mathematical models: a key to understanding HIV envelope interactions? J Immunol Methods 2013; 398-399:1-18. [PMID: 24041473 DOI: 10.1016/j.jim.2013.09.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 07/17/2013] [Accepted: 09/02/2013] [Indexed: 11/23/2022]
Abstract
The spikes of the human immunodeficiency virus (HIV) mediate viral entry and are the most important targets for neutralizing antibodies. Each spike consists of three identical subunits. The role of the spike's subunits in antibody binding is not fully understood. One experimental approach to analyze trimer function uses assays with mixed envelope trimer expressing cells or viruses. As these experiments do not allow direct observation of subunit functions, mathematical models are required to interpret them. Here we describe a modeling framework to study (i) the interaction of the V1V2 loop with epitopes on the V3 loop and (ii) the composition of quaternary epitopes. In a first step we identify which trimers can form in these assays and how they function under antibody binding. We then derive the behavior of an average trimer. We contrast two experimental reporting systems and list their advantages and disadvantages. In these experiments trimer formation might not be perfectly random and we show how these effects can be tested. As we still lack a potent vaccine against HIV, and this vaccine surely has to stimulate the production of neutralizing antibodies, mixed trimer approaches in combination with mathematical models will help to identify vulnerable sites of the HIV spike.
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108
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Tedcastle A, Fenwick F, Robinson M, Toms G. Immunogenicity in mice of human metapneumovirus with a truncated SH glycoprotein. J Med Virol 2013; 86:547-57. [DOI: 10.1002/jmv.23731] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/12/2013] [Indexed: 11/12/2022]
Affiliation(s)
- A.B. Tedcastle
- The Institute of Cellular Medicine; The University of Newcastle upon Tyne; Newcastle upon Tyne United Kingdom
| | - F. Fenwick
- The Institute of Cellular Medicine; The University of Newcastle upon Tyne; Newcastle upon Tyne United Kingdom
| | - M.J. Robinson
- The Institute of Cellular Medicine; The University of Newcastle upon Tyne; Newcastle upon Tyne United Kingdom
| | - G.L. Toms
- The Institute of Cellular Medicine; The University of Newcastle upon Tyne; Newcastle upon Tyne United Kingdom
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109
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Monoclonal antibodies for prophylactic and therapeutic use against viral infections. ACTA ACUST UNITED AC 2013; 88:T15-T23. [PMID: 32287402 PMCID: PMC7111719 DOI: 10.1016/j.pepo.2013.08.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2012] [Accepted: 01/15/2013] [Indexed: 11/21/2022]
Abstract
Neutralizing antibodies play an essential part in antiviral immunity and are instrumental in preventing or modulating viral diseases. Polyclonal antibody preparations are increasingly being replaced by highly potent monoclonal antibodies (mAbs). Cocktails of mAbs and bispecific constructs can be used to simultaneously target multiple viral epitopes and to overcome issues of neutralization escape. Advances in antibody engineering have led to a large array of novel mAb formats, while deeper insight into the biology of several viruses and increasing knowledge of their neutralizing epitopes has extended the list of potential targets. In addition, progress in developing inexpensive production platforms will make antiviral mAbs more widely available and affordable.
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110
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Varada JC, Teferedegne B, Crim RL, Mdluli T, Audet S, Peden K, Beeler J, Murata H. A neutralization assay for respiratory syncytial virus using a quantitative PCR-based endpoint assessment. Virol J 2013; 10:195. [PMID: 23767960 PMCID: PMC3686610 DOI: 10.1186/1743-422x-10-195] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 06/11/2013] [Indexed: 11/22/2022] Open
Abstract
Background Few studies have used quantitative polymerase chain reaction (qPCR) as an approach to measure virus neutralization assay endpoints. Its lack of use may not be surprising considering that sample nucleic acid extraction and purification can be expensive, labor-intensive, and rate-limiting. Methods Virus/antibody mixtures were incubated for one hour at 37°C and then transferred to Vero cell monolayers in a 96-well plate format. At 24 (or 48) hours post-infection, we used a commercially available reagent to prepare cell lysates amenable to direct analysis by one-step SYBR Green quantitative reverse transcription PCR using primers specific for the RSV-N gene, thereby obviating the need for cumbersome RNA extraction and purification. The neutralization titer was defined as the reciprocal of the highest dilution needed to inhibit the PCR signal by 90% when compared with the mean value observed in virus control wells in the absence of neutralizing antibodies. Results We have developed a qPCR-based neutralization assay for human respiratory syncytial virus. Due to the sensitivity of qPCR in detecting virus replication, endpoints may be assessed as early as 24 hours post-infection. In addition, the dynamic range of qPCR provides a basis for the assay to be relatively robust to perturbations in input virus dose (i.e., the assay is in compliance with the Percentage Law). Conclusions This qPCR-based neutralization assay is suitable for automated high-throughput applications. In addition, our experimental approach may be generalizable for the rapid development of neutralization assays for other virus families.
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Affiliation(s)
- Jan C Varada
- Laboratory of DNA Viruses, Division of Viral Products, OVRR, CBER, FDA, Bethesda, MD 20892, USA
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111
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Magnus C. Virus neutralisation: new insights from kinetic neutralisation curves. PLoS Comput Biol 2013; 9:e1002900. [PMID: 23468602 PMCID: PMC3585397 DOI: 10.1371/journal.pcbi.1002900] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2012] [Accepted: 12/11/2012] [Indexed: 12/28/2022] Open
Abstract
Antibodies binding to the surface of virions can lead to virus neutralisation. Different theories have been proposed to determine the number of antibodies that must bind to a virion for neutralisation. Early models are based on chemical binding kinetics. Applying these models lead to very low estimates of the number of antibodies needed for neutralisation. In contrast, according to the more conceptual approach of stoichiometries in virology a much higher number of antibodies is required for virus neutralisation by antibodies. Here, we combine chemical binding kinetics with (virological) stoichiometries to better explain virus neutralisation by antibody binding. This framework is in agreement with published data on the neutralisation of the human immunodeficiency virus. Knowing antibody reaction constants, our model allows us to estimate stoichiometrical parameters from kinetic neutralisation curves. In addition, we can identify important parameters that will make further analysis of kinetic neutralisation curves more valuable in the context of estimating stoichiometries. Our model gives a more subtle explanation of kinetic neutralisation curves in terms of single-hit and multi-hit kinetics. How many antibodies have to bind to a virus particle such that it is prevented from infecting a cell? This seemingly simple question has not been answered yet. However, this number is crucial to determine whether a vaccine can stimulate the immune system to elicit enough antibodies to neutralise virus before starting an infection. Two different approaches have been applied to answer this question, leading to contradictory results. One approach is inspired by concepts from binding kinetics, the other approach is a more conceptual one. Here, I describe the advantages and disadvantages of either approaches and condense the advantages of both into one model framework. I show under which conditions the framework can be used to identify the number of neutralising antibodies. In addition, this model can explain why viruses might not completely loose their infection potential even when there is a huge excess of antibodies.
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Affiliation(s)
- Carsten Magnus
- Institute for Emerging Infections, Department of Zoology, University of Oxford, Oxford, United Kingdom.
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112
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Development of a neutralization assay for influenza virus using an endpoint assessment based on quantitative reverse-transcription PCR. PLoS One 2013; 8:e56023. [PMID: 23437084 PMCID: PMC3577804 DOI: 10.1371/journal.pone.0056023] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2012] [Accepted: 01/09/2013] [Indexed: 12/15/2022] Open
Abstract
A microneutralization assay using an ELISA-based endpoint assessment (ELISA-MN) is widely used to measure the serological response to influenza virus infection and vaccination. We have developed an alternative microneutralization assay for influenza virus using a quantitative reverse transcription PCR-based endpoint assessment (qPCR-MN) in order to improve upon technical limitations associated with ELISA-MN. For qPCR-MN, infected MDCK-London cells in 96-well cell-culture plates are processed with minimal steps such that resulting samples are amenable to high-throughput analysis by downstream one-step quantitative reverse transcription PCR (qRT-PCR; SYBR Green chemistry with primers targeting a conserved region of the M1 gene of influenza A viruses). The growth curves of three recent vaccine strains demonstrated that the qRT-PCR signal detected at 6 hours post-infection reflected an amplification of at least 100-fold over input. Using ferret antisera, we have established the feasibility of measuring virus neutralization at 6 hours post-infection, a duration likely confined to a single virus-replication cycle. The neutralization titer for qPCR-MN was defined as the highest reciprocal serum dilution necessary to achieve a 90% inhibition of the qRT-PCR signal; this endpoint was found to be in agreement with ELISA-MN using the same critical reagents in each assay. qPCR-MN was robust with respect to assay duration (6 hours vs. 12 hours). In addition, qPCR-MN appeared to be compliant with the Percentage Law (i.e., virus neutralization results appear to be consistent over an input virus dose ranging from 500 to 12,000 TCID50). Compared with ELISA-MN, qPCR-MN might have inherent properties conducive to reducing intra- and inter-laboratory variability while affording suitability for automation and high-throughput uses. Finally, our qRT-PCR-based approach may be broadly applicable to the development of neutralization assays for a wide variety of viruses.
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113
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Both L, Banyard AC, van Dolleweerd C, Wright E, Ma JKC, Fooks AR. Monoclonal antibodies for prophylactic and therapeutic use against viral infections. Vaccine 2013; 31:1553-9. [PMID: 23370150 PMCID: PMC7115371 DOI: 10.1016/j.vaccine.2013.01.025] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2012] [Revised: 01/01/2013] [Accepted: 01/15/2013] [Indexed: 12/27/2022]
Abstract
Neutralizing antibodies play an essential part in antiviral immunity and are instrumental in preventing or modulating viral diseases. Polyclonal antibody preparations are increasingly being replaced by highly potent monoclonal antibodies (mAbs). Cocktails of mAbs and bispecific constructs can be used to simultaneously target multiple viral epitopes and to overcome issues of neutralization escape. Advances in antibody engineering have led to a large array of novel mAb formats, while deeper insight into the biology of several viruses and increasing knowledge of their neutralizing epitopes has extended the list of potential targets. In addition, progress in developing inexpensive production platforms will make antiviral mAbs more widely available and affordable.
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Affiliation(s)
- Leonard Both
- The Hotung Molecular Immunology Unit, Division of Clinical Sciences, St George's, University of London, London, UK
- Animal Health and Veterinary Laboratories Agency (AHVLA), Wildlife Zoonoses and Vector-borne Diseases Research Group, Department of Virology, Weybridge, Surrey, UK
| | - Ashley C. Banyard
- Animal Health and Veterinary Laboratories Agency (AHVLA), Wildlife Zoonoses and Vector-borne Diseases Research Group, Department of Virology, Weybridge, Surrey, UK
| | - Craig van Dolleweerd
- The Hotung Molecular Immunology Unit, Division of Clinical Sciences, St George's, University of London, London, UK
| | - Edward Wright
- School of Life Sciences, University of Westminster, London, UK
| | - Julian K.-C. Ma
- The Hotung Molecular Immunology Unit, Division of Clinical Sciences, St George's, University of London, London, UK
| | - Anthony R. Fooks
- Animal Health and Veterinary Laboratories Agency (AHVLA), Wildlife Zoonoses and Vector-borne Diseases Research Group, Department of Virology, Weybridge, Surrey, UK
- National Consortium for Zoonosis Research, University of Liverpool, Leahurst, Neston, South Wirral CH64 7TE, UK
- Corresponding author at: Animal Health and Veterinary Laboratories Agency (AHVLA), Wildlife Zoonoses and Vector-borne Diseases Research Group, Department of Virology, Weybridge, Surrey KT15 3NB, UK. Tel.: +44 01932 357840; fax: +44 01932 357239.
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114
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Abstract
A fascinating aspect of viral evolution relates to the ability of viruses to escape the adaptive immune response. The widely held view has been that the great variability of viral glycoproteins would be an absolute obstacle to the development of antibody-based therapies or vaccines that could confer broad and long-lasting protection. In the past five years, new approaches have been developed to interrogate human memory B cells and plasma cells with high efficiency and to isolate several broadly neutralizing antiviral antibodies against highly variable pathogens such as HIV-1 and influenza virus. These antibodies not only provide new tools for prophylaxis and therapy for viral diseases but also identify conserved epitopes that may be used to design new vaccines capable of conferring broader protection.
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Affiliation(s)
- Davide Corti
- Institute for Research in Biomedicine IRB, 6500 Bellinzona, Switzerland.
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115
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IgG expression in human colorectal cancer and its relationship to cancer cell behaviors. PLoS One 2012; 7:e47362. [PMID: 23133595 PMCID: PMC3486799 DOI: 10.1371/journal.pone.0047362] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2012] [Accepted: 09/11/2012] [Indexed: 11/19/2022] Open
Abstract
Increasing evidence indicates that various cancer cell types are capable of producing IgG. The exact function of cancer-derived IgG has, however, not been elucidated. Here we demonstrated the expression of IgG genes with V(D)J recombination in 80 cases of colorectal cancers, 4 colon cancer cell lines and a tumor bearing immune deficient mouse model. IgG expression was associated with tumor differentiation, pTNM stage, lymph node involvement and inflammatory infiltration and positively correlated with the expressions of Cyclin D1, NF-κB and PCNA. Furthermore, we investigated the effect of cancer-derived IgG on the malignant behaviors of colorectal cancer cells and showed that blockage of IgG resulted in increased apoptosis and negatively affected the potential for anchor-independent colony formation and cancer cell invasion. These findings suggest that IgG synthesized by colorectal cancer cells is involved in the development and growth of colorectal cancer and blockage of IgG may be a potential therapy in treating this cancer.
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116
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Flipse J, Wilschut J, Smit JM. Molecular mechanisms involved in antibody-dependent enhancement of dengue virus infection in humans. Traffic 2012; 14:25-35. [PMID: 22998156 DOI: 10.1111/tra.12012] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Revised: 09/19/2012] [Accepted: 09/21/2012] [Indexed: 12/19/2022]
Abstract
Dengue is the most common arthropod-borne viral infection in humans with ∼50 million cases annually worldwide. In recent decades, a steady increase in the number of severe dengue cases has been seen. Severe dengue disease is most often observed in individuals that have pre-existing immunity against heterotypic dengue subtypes and in infants with low levels of maternal dengue antibodies. The generally accepted hypothesis explaining the immunopathogenesis of severe dengue is called antibody-dependent enhancement of dengue infection. Here, circulating antibodies bind to the newly infecting virus but do not neutralize infection. Rather, these antibodies increase the infected cell mass and virus production. Additionally, antiviral responses are diminished allowing massive virus particle production early in infection. The large infected cell mass and the high viral load are prelude for severe disease development. In this review, we discuss what is known about the trafficking of dengue virus in its human host cells, and the signalling pathways activated after virus detection, both in the absence and presence of antibodies against the virus. This review summarizes work that aims to better understand the complex immunopathogenesis of severe dengue disease.
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Affiliation(s)
- Jacky Flipse
- Department of Medical Microbiology, Molecular Virology Section, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
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117
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Assessment of a passive immunity mouse model to quantitatively analyze the impact of neutralizing antibodies on adeno-associated virus-mediated gene transfer. J Immunol Methods 2012; 387:114-20. [PMID: 23063691 DOI: 10.1016/j.jim.2012.10.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2012] [Revised: 10/04/2012] [Accepted: 10/05/2012] [Indexed: 02/05/2023]
Abstract
Adeno-associated viruses (AAVs) are common infective agents of primates. As such, healthy primates carry a large pool of AAV-specific neutralizing antibodies (NAbs), which inhibit AAV-mediated gene transfer therapeutic strategies. Thus, a clinical method to screen patient candidates for AAV-specific NAbs prior to treatment, especially with the frequently used AAV8 capsid component, will facilitate individualized treatment design and enhance therapeutic efficacy. In this study, we evaluated the efficacy and sensitivity of a passive immunity mouse model to quantitatively assess anti-AAV8 NAb titers, as compared to an in vitro immunoassay. The passive transfer model was established in C57BL/6 mice by tail vein injection of pre-defined sera from 23 male rhesus monkeys. The mice were then administered low dose (3e10 GC/mouse) self-complementary (sc) AAV8. The in vitro NAb assay indicated that 69.57% of the rhesus donors had pre-existing anti-AAV8 NAb. The in vivo NAb assay, however, was better able to detect low NAb titer (≤ 1:5), which can mediate neutralization in vivo. Indeed, 17 rhesus donors (74.0%) had pre-existing anti-AAV8 neutralization by in vivo NAb assay. Our findings indicated that the in vivo NAb assay is superior to the in vitro assay for detecting low NAb titers.
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118
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Klasse PJ, Moore JP. Good CoP, bad CoP? Interrogating the immune responses to primate lentiviral vaccines. Retrovirology 2012; 9:80. [PMID: 23025660 PMCID: PMC3484039 DOI: 10.1186/1742-4690-9-80] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Accepted: 09/14/2012] [Indexed: 11/17/2022] Open
Abstract
Correlates of protection (CoPs) against infection by primate lentiviruses remain undefined. Modest protection against HIV-1 was observed in one human vaccine trial, whereas previous trials and vaccine-challenge experiments in non-human primates have yielded inconsistent but intriguing results. Although high levels of neutralizing antibodies are known to protect macaques from mucosal and intravenous viral challenges, antibody or other adaptive immune responses associated with protection might also be mere markers of innate immunity or susceptibility. Specific strategies for augmenting the design of both human trials and animal experiments could help to identify mechanistic correlates of protection and clarify the influences of confounding factors. Robust protection may, however, require the combined actions of immune responses and other host factors, thereby limiting what inferences can be drawn from statistical associations. Here, we discuss how to analyze immune protection against primate lentiviruses, and how host factors could influence both the elicitation and effectiveness of vaccine-induced responses.
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Affiliation(s)
- Per Johan Klasse
- Department of Microbiology and Immunology, Weill Cornell Medical College, Cornel University, 1300 York Avenue, Box 62, New York, NY 10065-4896, USA.
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119
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Nicasio M, Sautto G, Clementi N, Diotti RA, Criscuolo E, Castelli M, Solforosi L, Clementi M, Burioni R. Neutralization interfering antibodies: a "novel" example of humoral immune dysfunction facilitating viral escape? Viruses 2012; 4:1731-52. [PMID: 23170181 PMCID: PMC3499828 DOI: 10.3390/v4091731] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Revised: 09/01/2012] [Accepted: 09/17/2012] [Indexed: 02/07/2023] Open
Abstract
The immune response against some viral pathogens, in particular those causing chronic infections, is often ineffective notwithstanding a robust humoral neutralizing response. Several evasion mechanisms capable of subverting the activity of neutralizing antibodies (nAbs) have been described. Among them, the elicitation of non-neutralizing and interfering Abs has been hypothesized. Recently, this evasion mechanism has acquired an increasing interest given its possible impact on novel nAb-based antiviral therapeutic and prophylactic approaches. In this review, we illustrate the mechanisms of Ab-mediated interference and the viral pathogens described in literature as able to adopt this "novel" evasion strategy.
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Affiliation(s)
- Mancini Nicasio
- Microbiology and Virology Unit, Vita-Salute San Raffaele University, via Olgettina 58, Milan 20132, Italy.
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120
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Klasse PJ. The molecular basis of HIV entry. Cell Microbiol 2012; 14:1183-92. [PMID: 22583677 PMCID: PMC3417324 DOI: 10.1111/j.1462-5822.2012.01812.x] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Revised: 04/30/2012] [Accepted: 05/02/2012] [Indexed: 11/30/2022]
Abstract
Infection by HIV starts when the virus attaches to a susceptible cell. For viral replication to continue, the viral envelope must fuse with a cellular membrane, thereby delivering the viral core to the cytoplasm, where the RNA genome is reverse-transcribed. The key players in this entry by fusion are the envelope glycoprotein, on the viral side, and CD4 and a co-receptor, CCR5 or CXCR4, on the cellular side. Here, the interplay of these molecules is reviewed from cell-biological, structural, mechanistic, and modelling-based perspectives. Hypotheses are evaluated regarding the cellular compartment for entry, the transfer of virus through direct cell-to-cell contact, the sequence of molecular events, and the number of molecules involved on each side of the virus-cell divide. An emerging theme is the heterogeneity among the entry mediators on both sides, a diversity that affects the efficacy of entry inhibitors, be they small-molecule ligands, peptides or neutralizing antibodies. These insights inform rational strategies for therapy as well as vaccination.
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Affiliation(s)
- Per Johan Klasse
- Department of Microbiology and Immunology, Cornell University, Weill Cornell Medical College, 1300 York Avenue, Box 62, New York, NY 10065-4896, USA.
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121
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Abstract
Despite a central role in immunity, antibody neutralization of virus infection is poorly understood. Here we show how the neutralization and persistence of adenovirus type 5, a prevalent nonenveloped human virus, are dependent upon the intracellular antibody receptor TRIM21. Cells with insufficient amounts of TRIM21 are readily infected, even at saturating concentrations of neutralizing antibody. Conversely, high TRIM21 expression levels decrease the persistent fraction of the infecting virus and allows neutralization by as few as 1.6 antibody molecules per virus. The direct interaction between TRIM21 and neutralizing antibody is essential, as single-point mutations within the TRIM21-binding site in the Fc region of a potently neutralizing antibody impair neutralization. However, infection at high multiplicity can saturate TRIM21 and overcome neutralization. These results provide insight into the mechanism and importance of a newly discovered, effector-driven process of antibody neutralization of nonenveloped viruses.
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122
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Kinetic mechanism for HIV-1 neutralization by antibody 2G12 entails reversible glycan binding that slows cell entry. Proc Natl Acad Sci U S A 2012; 109:7829-34. [PMID: 22547820 DOI: 10.1073/pnas.1109728109] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Despite structural knowledge of broadly neutralizing monoclonal antibodies (NMAbs) complexed to HIV-1 gp120 and gp41 envelope glycoproteins, virus inactivation mechanisms have been difficult to prove, in part because neutralization assays are complex and were previously not understood. Concordant with recent evidence that HIV-1 titers are determined by a race between entry of cell-attached virions and competing inactivation processes, we show that NMAb 2G12, which binds to gp120 N-glycans with α (1, 2)-linked mannose termini and inhibits replication after passive transfer into patients, neutralizes by slowing entry of adsorbed virions. Accordingly, apparent neutralization is attenuated when a kinetically competing virus inactivation pathway is blocked. Moreover, removing 2G12 from media causes its dissociation from virions coupled to accelerated entry and restored infectivity, demonstrating the reversibility of neutralization. A difference between 2G12 dissociation and infectivity recovery rates implies that the inhibited complexes at virus-cell junctions contain several 2G12's that must dissociate before entry commences. Quantitative microscopy of 2G12 binding and dissociation from single virions and studies using a split CCR5 coreceptor suggest that 2G12 competitively inhibits interactions between gp120's V3 loop and the tyrosine sulfate-containing CCR5 amino terminus, thereby reducing assembly of complexes that catalyze entry. These results reveal a unique reversible kinetic mechanism for neutralization by an antibody that binds near a critical V3 region in the glycan shield of gp120.
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123
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Stiasny K, Aberle JH, Keller M, Grubeck-Loebenstein B, Heinz FX. Age affects quantity but not quality of antibody responses after vaccination with an inactivated flavivirus vaccine against tick-borne encephalitis. PLoS One 2012; 7:e34145. [PMID: 22461903 PMCID: PMC3312914 DOI: 10.1371/journal.pone.0034145] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Accepted: 02/22/2012] [Indexed: 02/07/2023] Open
Abstract
The impairment of immune functions in the elderly (immunosenescence) results in post-vaccination antibody titers that are significantly lower than in young individuals. It is, however, a controversial question whether also the quality of antibodies declines with age. In this study, we have therefore investigated the age-dependence of functional characteristics of antibody responses induced by vaccination with an inactivated flavivirus vaccine against tick-borne encephalitis (TBE). For this purpose, we quantified TBE virus-specific IgG and neutralizing antibody titers in post-vaccination sera from groups of young and elderly healthy adults and determined antibody avidities and NT/ELISA titer ratios (functional activity). In contrast to the quantitative impairment of antibody production in the elderly, we found no age-related differences in the avidity and functional activity of antibodies induced by vaccination, which also appeared to be independent of the age at primary immunization. There was no correlation between antibody avidity and NT/ELISA ratios suggesting that additional factors affect the quality of polyclonal responses, independent of age. Our work indicates that healthy elderly people are able to produce antibodies in response to vaccination with similar avidity and functional activity as young individuals, albeit at lower titers.
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Affiliation(s)
- Karin Stiasny
- Department of Virology, Medical University of Vienna, Vienna, Austria.
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124
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PGV04, an HIV-1 gp120 CD4 binding site antibody, is broad and potent in neutralization but does not induce conformational changes characteristic of CD4. J Virol 2012; 86:4394-403. [PMID: 22345481 DOI: 10.1128/jvi.06973-11] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Recently, several broadly neutralizing monoclonal antibodies (bnMAbs) directed to the CD4-binding site (CD4bs) of gp120 have been isolated from HIV-1-positive donors. These include VRC01, 3BNC117, and NIH45-46, all of which are capable of neutralizing about 90% of circulating HIV-1 isolates and all of which induce conformational changes in the HIV-1 gp120 monomer similar to those induced by the CD4 receptor. In this study, we characterize PGV04 (also known as VRC-PG04), a MAb with potency and breadth that rivals those of the prototypic VRC01 and 3BNC117. When screened on a large panel of viruses, the neutralizing profile of PGV04 was distinct from those of CD4, b12, and VRC01. Furthermore, the ability of PGV04 to neutralize pseudovirus containing single alanine substitutions exhibited a pattern distinct from those of the other CD4bs MAbs. In particular, substitutions D279A, I420A, and I423A were found to abrogate PGV04 neutralization. In contrast to VRC01, PGV04 did not enhance the binding of 17b or X5 to their epitopes (the CD4-induced [CD4i] site) in the coreceptor region on the gp120 monomer. Furthermore, in contrast to CD4, none of the anti-CD4bs MAbs induced the expression of the 17b epitope on cell surface-expressed cleaved Env trimers. We conclude that potent CD4bs bnMAbs can display differences in the way they recognize and access the CD4bs and that mimicry of CD4, as assessed by inducing conformational changes in monomeric gp120 that lead to enhanced exposure of the CD4i site, is not uniquely correlated with effective neutralization at the site of CD4 binding on HIV-1.
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125
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Abstract
Hepatitis C virus (HCV) leads to progressive liver disease and hepatocellular carcinoma. Current treatments are only partially effective, and new therapies targeting viral and host pathways are required. Virus entry into a host cell provides a conserved target for therapeutic intervention. Tetraspanin CD81, scavenger receptor class B member I, and the tight-junction proteins claudin-1 and occludin have been identified as essential entry receptors. Limited information is available on the role of receptor trafficking in HCV entry. We demonstrate here that anti-CD81 antibodies inhibit HCV infection at late times after virus internalization, suggesting a role for intracellular CD81 in HCV infection. Several tetraspanins have been reported to internalize via motifs in their C-terminal cytoplasmic domains; however, CD81 lacks such motifs, leading several laboratories to suggest a limited role for CD81 endocytosis in HCV entry. We demonstrate CD81 internalization via a clathrin- and dynamin-dependent process, independent of its cytoplasmic domain, suggesting a role for associated partner proteins in regulating CD81 trafficking. Live cell imaging demonstrates CD81 and claudin-1 coendocytosis and fusion with Rab5 expressing endosomes, supporting a role for this receptor complex in HCV internalization. Receptor-specific antibodies and HCV particles increase CD81 and claudin-1 endocytosis, supporting a model wherein HCV stimulates receptor trafficking to promote particle internalization.
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126
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Klasse PJ, Sanders RW, Cerutti A, Moore JP. How can HIV-type-1-Env immunogenicity be improved to facilitate antibody-based vaccine development? AIDS Res Hum Retroviruses 2012; 28:1-15. [PMID: 21495876 DOI: 10.1089/aid.2011.0053] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
No vaccine candidate has induced antibodies (Abs) that efficiently neutralize multiple primary isolates of HIV-1. Preexisting high titers of neutralizing antibodies (NAbs) are essential, because the virus establishes infection before anamnestic responses could take effect. HIV-1 infection elicits Abs against Env, Gag, and other viral proteins, but of these only a subset of the anti-Env Abs can neutralize the virus. Whereas the corresponding proteins from other viruses form the basis of successful vaccines, multiple large doses of HIV-1 Env elicit low, transient titers of Abs that are not protective in humans. The inaccessibility of neutralization epitopes hinders NAb induction, but Env may also subvert the immune response by interacting with receptors on T cells, B cells, monocytes, macrophages, and dendritic cells. Here, we discuss evidence from immunizations of different species with various modified Env constructs. We also suggest how the divergent Ab responses to Gag and Env during infection may reflect differences in B cell regulation. Drawing on these analyses, we outline strategies for improving Env as a component of a vaccine aimed at inducing strong and sustained NAb responses.
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Affiliation(s)
- Per Johan Klasse
- Department of Microbiology and Immunology, Cornell University, Weill Cornell Medical College, New York, New York
| | - Rogier W. Sanders
- Department of Microbiology and Immunology, Cornell University, Weill Cornell Medical College, New York, New York
- Laboratory of Experimental Virology, Department of Medical Microbiology, Center for Infection and Immunity Amsterdam, Academic Medical Center of the University of Amsterdam, Amsterdam, The Netherlands
| | - Andrea Cerutti
- Immunology Institute, Department of Medicine, Mount Sinai School of Medicine, New York, New York
- Catalan Institute for Research and Advanced Studies, Barcelona Biomedical Research Park, IMIM-Hospital del Mar, Barcelona, Spain
| | - John P. Moore
- Department of Microbiology and Immunology, Cornell University, Weill Cornell Medical College, New York, New York
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127
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Sun P, Bauza K, Pal S, Liang Z, Wu SJ, Beckett C, Burgess T, Porter K. Infection and activation of human peripheral blood monocytes by dengue viruses through the mechanism of antibody-dependent enhancement. Virology 2011; 421:245-52. [DOI: 10.1016/j.virol.2011.08.026] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Revised: 08/29/2011] [Accepted: 08/31/2011] [Indexed: 11/29/2022]
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128
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Antibody-induced conformational changes in herpes simplex virus glycoprotein gD reveal new targets for virus neutralization. J Virol 2011; 86:1563-76. [PMID: 22130533 DOI: 10.1128/jvi.06480-11] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
As the receptor-binding protein of herpes simplex virus (HSV), gD plays an essential role in virus entry. In its native state, the last 56 amino acids of the ectodomain C terminus (C-term) occlude binding to its receptors, herpesvirus entry mediator (HVEM) and nectin-1. Although it is clear that movement of the C-term must occur to permit receptor binding, we believe that this conformational change is also a key event for triggering later steps leading to fusion. Specifically, gD mutants containing disulfide bonds that constrain the C-term are deficient in their ability to trigger fusion following receptor binding. In this report, we show that two newly made monoclonal antibodies (MAbs), MC2 and MC5, have virus-neutralizing activity but do not block binding of gD to either receptor. In contrast, all previously characterized neutralizing anti-gD MAbs block binding of gD to a receptor(s). Interestingly, instead of blocking receptor binding, MC2 significantly enhances the affinity of gD for both receptors. Several nonneutralizing MAbs (MC4, MC10, and MC14) also enhanced gD-receptor binding. While MC2 and MC5 recognized different epitopes on the core of gD, these nonneutralizing MAbs recognized the gD C-term. Both the neutralizing capacity and rate of neutralization of virus by MC2 are uniquely enhanced when MC2 is combined with MAb MC4, MC10, or MC14. We suggest that MC2 and MC5 prevent gD from performing a function that triggers later steps leading to fusion and that the epitope for MC2 is normally occluded by the C-term of the gD ectodomain.
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129
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Sabo MC, Luca VC, Ray SC, Bukh J, Fremont DH, Diamond MS. Hepatitis C virus epitope exposure and neutralization by antibodies is affected by time and temperature. Virology 2011; 422:174-84. [PMID: 22078164 DOI: 10.1016/j.virol.2011.10.023] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Revised: 10/14/2011] [Accepted: 10/22/2011] [Indexed: 01/22/2023]
Abstract
A recent study with flaviviruses suggested that structural dynamics of the virion impact antibody neutralization via exposure of ostensibly cryptic epitopes. To determine whether this holds true for the distantly related hepatitis C virus (HCV), whose neutralizing epitopes may be obscured by a glycan shield, apolipoprotein interactions, and the hypervariable region on the E2 envelope protein, we assessed how time and temperature of pre-incubation altered monoclonal antibody (MAb) neutralization of HCV. Notably, several MAbs showed increased inhibitory activity when pre-binding was performed at 37°C or after longer pre-incubation periods, and a corresponding loss-of-neutralization was observed when pre-binding was performed at 4°C. A similar profile of changes was observed with acute and chronic phase sera from HCV-infected patients. Our data suggest that time and temperature of incubation modulate epitope exposure on the conformational ensembles of HCV virions and thus, alter the potency of antibody neutralization.
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Affiliation(s)
- Michelle C Sabo
- Department of Pathology & Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
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130
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Harbison CE, Weichert WS, Gurda BL, Chiorini JA, Agbandje-McKenna M, Parrish CR. Examining the cross-reactivity and neutralization mechanisms of a panel of mAbs against adeno-associated virus serotypes 1 and 5. J Gen Virol 2011; 93:347-355. [PMID: 22071509 DOI: 10.1099/vir.0.035113-0] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Neutralizing antibodies play a central role in the prevention and clearance of viral infections, but can be detrimental to the use of viral capsids for gene delivery. Antibodies present a major hurdle for ongoing clinical trials using adeno-associated viruses (AAVs); however, relatively little is known about the antigenic epitopes of most AAV serotypes or the mechanism(s) of antibody-mediated neutralization. We developed panels of AAV mAbs by repeatedly immunizing mice with AAV serotype 1 (AAV1) capsids, or by sequentially immunizing with AAV1 followed by AAV5 capsids, in order to examine the efficiency and mechanisms of antibody-mediated neutralization. The antibodies were not cross-reactive between heterologous AAV serotypes except for a low level of recognition of AAV1 capsids by the AAV5 antibodies, probably due to the initial immunization with AAV1. The neutralization efficiency of different IgGs varied and Fab fragments derived from these antibodies were generally poorly neutralizing. The antibodies appeared to display various alternative mechanisms of neutralization, which included inhibition of receptor-binding and interference with a post-attachment step.
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Affiliation(s)
- Carole E Harbison
- Baker Institute for Animal Health, Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Wendy S Weichert
- Baker Institute for Animal Health, Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Brittney L Gurda
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32610, USA
| | - John A Chiorini
- Molecular Physiology and Therapeutics Branch, National Institute of Dental and Craniofacial Research, US National Institutes of Health (NIH), Bethesda, MD 20892, USA
| | - Mavis Agbandje-McKenna
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32610, USA
| | - Colin R Parrish
- Baker Institute for Animal Health, Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA
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131
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McEwan WA, Mallery DL, Rhodes DA, Trowsdale J, James LC. Intracellular antibody-mediated immunity and the role of TRIM21. Bioessays 2011; 33:803-9. [PMID: 22006823 DOI: 10.1002/bies.201100093] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Protection against bacterial and viral pathogens by antibodies has always been thought to end at the cell surface. Once inside the cell, a pathogen was understood to be safe from humoral immunity. However, it has now been found that antibodies can routinely enter cells attached to viral particles and mediate an intracellular immune response. Antibody-coated virions are detected inside the cell by means of an intracellular antibody receptor, TRIM21, which directs their degradation by recruitment of the ubiquitin-proteasome system. In this article we assess how this discovery alters our view of the way in which antibodies neutralise viral infection. We also consider the antiviral function of TRIM21 in the context of its other reported roles in immune signalling and autoimmunity. Finally, we discuss the conceptual implications of intracellular antibody immunity and how it alters our view of the discrete separation of extracellular and intracellular environments.
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Affiliation(s)
- William A McEwan
- MRC Laboratory of Molecular Biology, PNAC Division, Cambridge, UK
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132
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Ketas TJ, Holuigue S, Matthews K, Moore JP, Klasse PJ. Env-glycoprotein heterogeneity as a source of apparent synergy and enhanced cooperativity in inhibition of HIV-1 infection by neutralizing antibodies and entry inhibitors. Virology 2011; 422:22-36. [PMID: 22018634 DOI: 10.1016/j.virol.2011.09.019] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2011] [Revised: 08/19/2011] [Accepted: 09/17/2011] [Indexed: 10/16/2022]
Abstract
We measured the inhibition of infectivity of HIV-1 isolates and derivative clones by combinations of neutralizing antibodies (NAbs) and other entry inhibitors in a single-cycle-replication assay. Synergy was analyzed both by the current linear and a new non-linear method. The new method reduced spurious indications of synergy and antagonism. Synergy between NAbs was overall weaker than between other entry inhibitors, and no stronger where one ligand is known to enhance the binding of another. However, synergy was stronger for a genetically heterogeneous HIV-1 R5 isolate than for its derivative clones. Enhanced cooperativity in inhibition by combinations, compared with individual inhibitors, correlated with increased synergy at higher levels of inhibition, while being less variable. Again, cooperativity enhancement was stronger for isolates than clones. We hypothesize that genetic, post-translational or conformational heterogeneity of the Env protein and of other targets for inhibitors can yield apparent synergy and increased cooperativity between inhibitors.
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Affiliation(s)
- Thomas J Ketas
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, NY 10065-4896, USA
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133
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Jones JC, Settles EW, Brandt CR, Schultz-Cherry S. Virus aggregating peptide enhances the cell-mediated response to influenza virus vaccine. Vaccine 2011; 29:7696-703. [PMID: 21839131 PMCID: PMC3190079 DOI: 10.1016/j.vaccine.2011.07.133] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Revised: 07/22/2011] [Accepted: 07/29/2011] [Indexed: 10/17/2022]
Abstract
Given the poor immunogenicity of current H5N1 influenza vaccines, additives and adjuvants remain a viable solution for increasing efficacy. Here, we demonstrate that a 20-amino acid peptide (EB) possessing influenza antiviral activity also enhances the immune response to H5N1 vaccination in mice. The addition of EB to formalin-inactivated whole-virus vaccine induced virion aggregation and these aggregates were readily engulfed by phagocytic cells in vitro. In vivo, mice vaccinated with a suboptimal dose of inactivated vaccine containing EB peptide had reduced morbidity, improved viral clearance, and faster recovery than mice receiving vaccine alone. This phenomenon was not accompanied by an increase in virus-specific antibodies. Instead, cell-mediated immunity was enhanced as demonstrated by increased interferon-γ production from splenocytes. This data demonstrates that the EB peptide may a useful adjuvant for boosting the efficacy of poorly immunogenic influenza vaccines.
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Affiliation(s)
- Jeremy C. Jones
- St Jude Children’s Research Hospital, Department of Infectious Diseases, 262 Danny Thomas Place, Memphis, TN 38105
| | - Erik W. Settles
- University of Wisconsin-Madison, Department of Medical Microbiology & Immunology, 1556 Linden Dr, Madison, WI 53706
| | - Curtis R. Brandt
- University of Wisconsin-Madison, Department of Medical Microbiology & Immunology, 1556 Linden Dr, Madison, WI 53706
- University of Wisconsin-Madison, Department of Ophthalmology & Visual Sciences, 1300 University Ave, Madison, WI 53706
| | - Stacey Schultz-Cherry
- St Jude Children’s Research Hospital, Department of Infectious Diseases, 262 Danny Thomas Place, Memphis, TN 38105
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134
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Schepens B, Ibañez LI, De Baets S, Hultberg A, Bogaert P, De Bleser P, Vervalle F, Verrips T, Melero J, Vandevelde W, Vanlandschoot P, Saelens X. Nanobodies® specific for respiratory syncytial virus fusion protein protect against infection by inhibition of fusion. J Infect Dis 2011; 204:1692-701. [PMID: 21998474 DOI: 10.1093/infdis/jir622] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Despite the medical importance of respiratory syncytial virus (RSV) infections, there is no vaccine or therapeutic agent available. Prophylactic administration of palivizumab, a humanized monoclonal RSV fusion (F) protein-specific antibody, can protect high-risk children. Previously, we have demonstrated that RSV can be neutralized by picomolar concentrations of a camelid immunoglobulin single-variable domain that binds the RSV protein F (F-VHHb nanobodies). Here, we investigated the mechanism by which these nanobodies neutralize RSV and tested their antiviral activity in vivo. We demonstrate that bivalent RSV F-specific nanobodies neutralize RSV infection by inhibiting fusion without affecting viral attachment. The ability of RSV F-specific nanobodies to protect against RSV infection was investigated in vivo. Intranasal administration of bivalent RSV F-specific nanobodies protected BALB/c mice from RSV infection, and associated pulmonary inflammation. Moreover, therapeutic treatment with these nanobodies after RSV infection could reduce viral replication and reduced pulmonary inflammation. Thus, nanobodies are promising therapeutic molecules for treatment of RSV.
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Affiliation(s)
- Bert Schepens
- Department for Molecular Biomedical Research, VIB, Ghent University, Belgium
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135
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Oballah P, Flach B, Eller LA, Eller MA, Ouma B, de Souza M, Kibuuka HN, Wabwire-Mangen F, Brown BK, Michael NL, Robb ML, Montefiori D, Polonis VR. B cell depletion in HIV-1 subtype A infected Ugandan adults: relationship to CD4 T cell count, viral load and humoral immune responses. PLoS One 2011; 6:e22653. [PMID: 21886768 PMCID: PMC3160298 DOI: 10.1371/journal.pone.0022653] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Accepted: 06/27/2011] [Indexed: 11/19/2022] Open
Abstract
To better understand the nature of B cell dysfunctions in subjects infected with HIV-1 subtype A, a rural cohort of 50 treatment-naïve Ugandan patients chronically infected with HIV-1 subtype A was studied, and the relationship between B cell depletion and HIV disease was assessed. B cell absolute counts were found to be significantly lower in HIV-1+ patients, when compared to community matched negative controls (p<0.0001). HIV-1-infected patients displayed variable functional and binding antibody titers that showed no correlation with viral load or CD4+ T cell count. However, B cell absolute counts were found to correlate inversely with neutralizing antibody (NAb) titers against subtype A (p = 0.05) and subtype CRF02_AG (p = 0.02) viruses. A positive correlation was observed between subtype A gp120 binding antibody titers and NAb breadth (p = 0.02) and mean titer against the 10 viruses (p = 0.0002). In addition, HIV-1 subtype A sera showed preferential neutralization of the 5 subtype A or CRF02_AG pseudoviruses, as compared with 5 pseudoviruses from subtypes B, C or D (p<0.001). These data demonstrate that in patients with chronic HIV-1 subtype A infection, significant B cell depletion can be observed, the degree of which does not appear to be associated with a decrease in functional antibodies. These findings also highlight the potential importance of subtype in the specificity of cross-clade neutralization in HIV-1 infection.
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Affiliation(s)
- Peter Oballah
- Makerere University Walter Reed Project, Kampala, Uganda
| | - Britta Flach
- Makerere University Walter Reed Project, Kampala, Uganda
- Military HIV Research Program, Rockville, Maryland, United States of America
- The Henry M Jackson Foundation, Rockville, Maryland, United States of America
| | - Leigh A. Eller
- Military HIV Research Program, Rockville, Maryland, United States of America
- The Henry M Jackson Foundation, Rockville, Maryland, United States of America
| | - Michael A. Eller
- Military HIV Research Program, Rockville, Maryland, United States of America
- The Henry M Jackson Foundation, Rockville, Maryland, United States of America
| | - Benson Ouma
- Makerere University Walter Reed Project, Kampala, Uganda
| | - Mark de Souza
- Military HIV Research Program, Rockville, Maryland, United States of America
- The Henry M Jackson Foundation, Rockville, Maryland, United States of America
- Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | | | - Fred Wabwire-Mangen
- Makerere University Walter Reed Project, Kampala, Uganda
- Makerere University School of Public Health, Kampala, Uganda
| | - Bruce K. Brown
- Military HIV Research Program, Rockville, Maryland, United States of America
- The Henry M Jackson Foundation, Rockville, Maryland, United States of America
| | - Nelson L. Michael
- Military HIV Research Program, Rockville, Maryland, United States of America
- Walter Reed Army Institute of Research, Rockville, Maryland, United States of America
| | - Merlin L. Robb
- Military HIV Research Program, Rockville, Maryland, United States of America
- The Henry M Jackson Foundation, Rockville, Maryland, United States of America
| | - David Montefiori
- Duke University, Durham, North Carolina, United States of America
| | - Victoria R. Polonis
- Military HIV Research Program, Rockville, Maryland, United States of America
- Walter Reed Army Institute of Research, Rockville, Maryland, United States of America
- * E-mail:
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136
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Multiple CCR5 conformations on the cell surface are used differentially by human immunodeficiency viruses resistant or sensitive to CCR5 inhibitors. J Virol 2011; 85:8227-40. [PMID: 21680525 DOI: 10.1128/jvi.00767-11] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Resistance to small-molecule CCR5 inhibitors arises when HIV-1 variants acquire the ability to use inhibitor-bound CCR5 while still recognizing free CCR5. Two isolates, CC101.19 and D1/85.16, became resistant via four substitutions in the gp120 V3 region and three in the gp41 fusion peptide (FP), respectively. The binding characteristics of a panel of monoclonal antibodies (MAbs) imply that several antigenic forms of CCR5 are expressed at different levels on the surfaces of U87-CD4-CCR5 cells and primary CD4(+) T cells, in a cell-type-dependent manner. CCR5 binding and HIV-1 infection inhibition experiments suggest that the two CCR5 inhibitor-resistant viruses altered their interactions with CCR5 in different ways. As a result, both mutants became generally more sensitive to inhibition by CCR5 MAbs, and the FP mutant is specifically sensitive to a MAb that stains discrete cell surface clusters of CCR5 that may correspond to lipid rafts. We conclude that some MAbs detect different antigenic forms of CCR5 and that inhibitor-sensitive and -resistant viruses can use these CCR5 forms differently for entry in the presence or absence of CCR5 inhibitors.
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137
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Magnus C, Regoes RR. Restricted occupancy models for neutralization of HIV virions and populations. J Theor Biol 2011; 283:192-202. [PMID: 21683711 DOI: 10.1016/j.jtbi.2011.06.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2010] [Revised: 04/04/2011] [Accepted: 06/02/2011] [Indexed: 11/26/2022]
Abstract
HIV virions infect cells by attaching to target cell receptors, fusing membranes with the cell and by finally releasing their genetic material into the target cells. Antibodies can hinder the infection by attaching to the HIV envelope glycoprotein trimers before or during attachment. The exact mechanisms and the quantitative requirements of antibody neutralization are still debated. Recently, the number of antibodies rendering one trimer non-functional, called stoichiometry of (trimer) neutralization, was studied with mathematical models. Here we extend this theoretical framework to calculate the stoichiometries of neutralizing a single virion and a whole virion population. We derive mathematical equations for antibody neutralization based on restricted occupancy theory. Additionally we simulate these processes when a direct calculation is not possible. We find that the number of trimers needed for cell entry and the number of antibodies neutralizing one trimer strongly influence the mean number of antibodies needed for virion and population neutralization. Further we show that the mean number of antibodies needed to neutralize a virion population exceeds the product of the number of virions in the population and the mean number of antibodies needed to neutralize one virion.
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Affiliation(s)
- Carsten Magnus
- Institute of Integrative Biology, ETH Zurich, Switzerland.
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138
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Dowd KA, Pierson TC. Antibody-mediated neutralization of flaviviruses: a reductionist view. Virology 2011; 411:306-15. [PMID: 21255816 PMCID: PMC3100196 DOI: 10.1016/j.virol.2010.12.020] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Accepted: 12/11/2010] [Indexed: 12/28/2022]
Abstract
Flaviviruses are a group of ~70 small RNA viruses responsible for significant morbidity and mortality across the globe. Efforts to develop effective vaccines for several clinically important flaviviruses are underway. Antibodies are a significant component of the host's protective response against flavivirus infection with the potential to contribute to immunity via several distinct mechanisms, including an ability to directly neutralize virus infection. Conversely, virus-reactive antibodies have been implicated in the increased risk of severe clinical manifestations following secondary dengue virus infection. In this review, we will discuss recent progress toward understanding the molecular basis of antibody-mediated neutralization of flaviviruses. Neutralization requires engagement of the virion with a stoichiometry that exceeds a required threshold. From this perspective, we will discuss viral and host factors that impact the number of antibody molecules bound to the virus particle and significantly modulate the potency of neutralizing antibodies.
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Affiliation(s)
- Kimberly A. Dowd
- Viral Pathogenesis Section, Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Theodore C. Pierson
- Viral Pathogenesis Section, Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
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139
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Sistigu A, Bracci L, Valentini M, Proietti E, Bona R, Negri DRM, Ciccaglione AR, Tritarelli E, Nisini R, Equestre M, Costantino A, Marcantonio C, Santini SM, Lapenta C, Donati S, Tataseo P, Miceli M, Cara A, Federico M. Strong CD8+ T cell antigenicity and immunogenicity of large foreign proteins incorporated in HIV-1 VLPs able to induce a Nef-dependent activation/maturation of dendritic cells. Vaccine 2011; 29:3465-75. [PMID: 21382480 DOI: 10.1016/j.vaccine.2011.02.059] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2010] [Revised: 02/15/2011] [Accepted: 02/16/2011] [Indexed: 12/21/2022]
Abstract
Virus-like particles (VLPs) are excellent tools for vaccines against pathogens and tumors. They can accommodate foreign polypeptides whose incorporation efficiency and immunogenicity however decrease strongly with the increase of their size. We recently described the CD8(+) T cell immune response against a small foreign antigen (i.e., the 98 amino acid long human papilloma virus E7 protein) incorporated in human immunodeficiency virus (HIV)-1 based VLPs as product of fusion with an HIV-1 Nef mutant (Nef(mut)). Here, we extended our previous investigations by testing the antigenic/immunogenic properties of Nef(mut)-based VLPs incorporating much larger heterologous products, i.e., human hepatitis C virus (HCV) NS3 and influenza virus NP proteins, which are composed of 630 and 498 amino acids, respectively. We observed a remarkable cross-presentation of HCV NS3 in dendritic cells challenged with Nef(mut)-NS3 VLPs, as detected using a NS3 specific CD8(+) T cell clone as well as PBMCs from HCV infected patients. On the other hand, when injected in mice, Nef(mut)-NP VLPs elicited strong anti-NP CD8(+) T cell and CTL immune responses. In addition, we revealed the ability of Nef(mut) incorporated in VLPs to activate and mature primary human immature dendritic cells (iDCs). This phenomenon correlated with the activation of Src tyrosine kinase-related intracellular signaling, and can be transmitted from VLP-challenged to bystander iDCs. Overall, these results prove that Nef(mut)-based VLPs represent a rather flexible platform for the design of innovative CD8(+) T cell vaccines.
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Affiliation(s)
- A Sistigu
- Department of Cell Biology and Neurosciences, Istituto Superiore di Sanità, Rome, Italy
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140
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Vanhee M, Costers S, Van Breedam W, Geldhof MF, Van Doorsselaere J, Nauwynck HJ. A variable region in GP4 of European-type porcine reproductive and respiratory syndrome virus induces neutralizing antibodies against homologous but not heterologous virus strains. Viral Immunol 2011; 23:403-13. [PMID: 20712485 DOI: 10.1089/vim.2010.0025] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Porcine reproductive and respiratory syndrome virus (PRRSV) can induce severe reproductive failure in sows, and is involved in the porcine respiratory disease complex. The glycoprotein GP4 of the European prototype PRRSV strain Lelystad virus (LV) contains a linear neutralizing epitope that is located in a highly variable region. The current study aimed to evaluate the antibody response against this and other epitopes on GP4 to infection of pigs with European-type PRRSV. It was shown that three virus strains, differing in the region that corresponds to the neutralizing epitope on GP4 of LV, strongly induce antibodies against this area. Antibodies against the epitopes of the different virus strains were purified from polyclonal swine sera, and used in virus-neutralization tests on primary alveolar macrophages. This revealed that antibodies against the variable region in GP4 of different virus strains are able to neutralize infection with homologous but not heterologous virus strains.
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Affiliation(s)
- Merijn Vanhee
- Laboratory of Virology, Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
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141
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Pastrana DV, Pumphrey KA, Cuburu N, Schowalter RM, Buck CB. Characterization of monoclonal antibodies specific for the Merkel cell polyomavirus capsid. Virology 2010; 405:20-5. [PMID: 20598728 DOI: 10.1016/j.virol.2010.06.022] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2010] [Revised: 05/13/2010] [Accepted: 06/09/2010] [Indexed: 11/17/2022]
Abstract
Merkel cell polyomavirus (MCV) has been implicated as a causative agent in Merkel cell carcinoma. Robust polyclonal antibody responses against MCV have been documented in human subjects, but monoclonal antibodies (mAbs) specific for the VP1 capsid protein have not yet been characterized. We generated 12 mAbs capable of binding recombinant MCV virus-like particles. The use of a short immunogenic priming schedule was important for production of the mAbs. Ten of the 12 mAbs were highly effective for immunofluorescent staining of cells expressing capsid proteins. An overlapping set of 10 mAbs were able to neutralize the infectivity of MCV-based reporter vectors, with 50% effective doses in the low picomolar range. Three mAbs interfered with the binding of MCV virus-like particles to cells. This panel of anti-capsid antibodies should provide a useful set of tools for the study of MCV.
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Affiliation(s)
- Diana V Pastrana
- Laboratory of Cellular Oncology, National Cancer Institute, Bethesda, MD 20892-4263, USA
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142
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SHIBAGUCHI H, YAMAMOTO T, KUROKI M, FUTAGAMI K. Measurement and Assessment of Cytomegalovirus of Immunoglobulin (Ig) G Titer in Preparations. YAKUGAKU ZASSHI 2010; 130:977-82. [DOI: 10.1248/yakushi.130.977] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Hirotomo SHIBAGUCHI
- Department of Hospital Pharmacy, Fukuoka University Hospital
- Department of Biochemistry, Faculty of Medicine, Fukuoka University
| | - Tomoka YAMAMOTO
- Department of Hospital Pharmacy, Fukuoka University Hospital
- Department of Pharmaceutical and Health Care Management, Faculty of Pharmaceutical Science, Fukuoka University
| | - Masahide KUROKI
- Department of Biochemistry, Faculty of Medicine, Fukuoka University
| | - Koujiro FUTAGAMI
- Department of Hospital Pharmacy, Fukuoka University Hospital
- Department of Pharmaceutical and Health Care Management, Faculty of Pharmaceutical Science, Fukuoka University
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143
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Federico M. Virus-like particles show promise as candidates for new vaccine strategies. Future Virol 2010. [DOI: 10.2217/fvl.10.29] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- Maurizio Federico
- National AIDS Center, Division of Pathogenesis of Retroviruses, Istituto Superiore di Sanità, Viale Regina Elena, 299, 00161 Rome, Italy
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144
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Neutralization efficiency is greatly enhanced by bivalent binding of an antibody to epitopes in the V4 region and the membrane-proximal external region within one trimer of human immunodeficiency virus type 1 glycoproteins. J Virol 2010; 84:7114-23. [PMID: 20463081 DOI: 10.1128/jvi.00545-10] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Most antibodies are multivalent, with the potential to bind with high avidity. However, neutralizing antibodies commonly bind to virions monovalently. Bivalent binding of a monoclonal antibody (MAb) to a virion has been documented only in a single case. Thus, the role of high avidity in antibody-mediated neutralization of viruses has not been defined clearly. In this study, we demonstrated that when an artificial 2F5 epitope was inserted in the gp120 V4 region so that an HIV-1 envelope glycoprotein (Env) trimer contains a natural 2F5 epitope in the gp41 membrane-proximal envelope region (MPER) and an artificially engineered 2F5 epitope in the gp120 V4 region, bivalent 2F5 IgG achieved greatly enhanced neutralization efficiency, with a 50% inhibitory concentration (IC(50)) decrease over a 2-log scale. In contrast, the monovalent 2F5 Fab fragment did not exhibit any appreciable change in neutralization efficiency in the same context. These results demonstrate that bivalent binding of 2F5 IgG to a single HIV-1 Env trimer results in dramatic enhancement of neutralization, probably through an increase in binding avidity. Furthermore, we demonstrated that bivalent binding of MAb 2F5 to the V4 region and MPER of an HIV-1 Env trimer can be achieved only in a specific configuration, providing an important insight into the structure of a native/infectious HIV-1 Env trimer. This specific binding configuration also establishes a useful standard that can be applied to evaluate the biological relevance of structural information on the HIV-1 Env trimer.
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145
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Benchmarking B-cell epitope prediction for the design of peptide-based vaccines: problems and prospects. J Biomed Biotechnol 2010; 2010:910524. [PMID: 20368996 PMCID: PMC2847767 DOI: 10.1155/2010/910524] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2009] [Revised: 12/12/2009] [Accepted: 02/18/2010] [Indexed: 11/18/2022] Open
Abstract
To better support the design of peptide-based vaccines, refinement of methods to predict B-cell epitopes necessitates meaningful benchmarking against empirical data on the cross-reactivity of polyclonal antipeptide antibodies with proteins, such that the positive data reflect functionally relevant cross-reactivity (which is consistent with antibody-mediated change in protein function) and the negative data reflect genuine absence of cross-reactivity (rather than apparent absence of cross-reactivity due to artifactual masking of B-cell epitopes in immunoassays). These data are heterogeneous in view of multiple factors that complicate B-cell epitope prediction, notably physicochemical factors that define key structural differences between immunizing peptides and their cognate proteins (e.g., unmatched electrical charges along the peptide-protein sequence alignments). If the data are partitioned with respect to these factors, iterative parallel benchmarking against the resulting subsets of data provides a basis for systematically identifying and addressing the limitations of methods for B-cell epitope prediction as applied to vaccine design.
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146
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Abstract
PURPOSE OF REVIEW In this review we present current advances in our understanding of HIV-1 neutralization assays that employ primary cell types, as compared with those that utilize cell lines and the newer, more standardized pseudovirus assays. A commentary on the challenges of standardizing in-vitro neutralization assays using primary cells is included. RECENT FINDINGS The data from reporter cell line neutralization assays may agree with results observed in primary cells; however, exceptions have recently been reported. Multiple variables exist in primary cell assays using peripheral blood mononuclear cells from HIV-seronegative donors; in-vitro neutralization titers can vary significantly based on the donor cells used for assay targets and for virus propagation. Thus, more research is required to achieve validated primary cell neutralization assays. SUMMARY HIV-vaccine-induced antibody performance in the current neutralization assays may function as a 'gatekeeper' for HIV-1 subunit vaccine advancement. Development of standardized platforms for reproducible measurement of in-vitro neutralization is therefore a high priority. Given the considerable variation in results obtained from some widely applied HIV neutralization platforms, parallel evaluation of new antibodies using different host cells for assay targets, as well as virus propagation, is recommended until immune correlates of protection are identified.
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147
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Wang W, Xie H, Ye Z, Vassell R, Weiss CD. Characterization of lentiviral pseudotypes with influenza H5N1 hemagglutinin and their performance in neutralization assays. J Virol Methods 2010; 165:305-10. [PMID: 20153374 DOI: 10.1016/j.jviromet.2010.02.009] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2009] [Revised: 02/01/2010] [Accepted: 02/04/2010] [Indexed: 11/16/2022]
Abstract
Pseudotype reporter viruses are being used as safe, quantitative, and high-throughput tools for assessing antibody neutralization for many viruses, including influenza. However, characterization of pseudotypes containing influenza hemagglutinin (HA-pseudotypes) is needed before this system is widely adopted for evaluating neutralizing antibodies in sera following vaccination or infection. In this report HA-pseudotype stocks were analyzed for HA content, stability, and performance in neutralization assays under various conditions. HA-pseudotypes produced with HA genes of H5 strains representing clades 1, 2.2, and 2.3.4 consistently contain similar HA contents, and infectivity was not greatly affected by the purity of the HA-pseudotype preparations or variations in storage conditions. HA-pseudotype neutralization titers using a reference serum panel were also consistent across a wide range of dilutions of HA-pseudotype stocks and correlated well with results from microneutralization assays involving replicating influenza. Concentrated HA-pseudotypes were further shown to work well in hemagglutination inhibition assays. Finally, antisera elicited by genetically modified HA, with changes in the polybasic cleavage site that have been used in some H5 vaccines and reduce pathogenicity, gave identical neutralization titers against HA-pseudotypes with wild type or modified HA. These findings support continued development of HA-pseudotypes as a robust tool for analyzing sera in vaccine and serologic studies.
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Affiliation(s)
- Wei Wang
- Center for Biologics Evaluation and Research, US Food and Drug Administration, Bethesda, MD 20892, United States
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148
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Abstract
PURPOSE OF REVIEW The only unequivocal correlate of protection against primate immunodeficiency virus infection is the presence of neutralizing antibody at sufficient titre. This correlate has been determined experimentally using animal models, and the data are reproducible and robust. Recent advances have added further depth to this knowledge by moving us closer to understanding how antibodies neutralize HIV-1, and what effects they may have in vivo with regard to protection from infection and disease. RECENT FINDINGS This review will cover recent advances in our understanding of the structural basis of HIV-1 neutralization by antibody and how this understanding may relate to vaccine design, and incorporate this into the broader context of how antibodies may influence viral transmission, replication and disease. SUMMARY The sum of these findings provides a strong rationale for designing an HIV-1 vaccine on the principle of induction of neutralizing antibodies, although other effector functions of antibodies such as complement and antibody-mediated cellular immunity should also be borne in mind, as should CD4 and CD8 T cell responses.
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149
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Anti-tumor CD8+ T cell immunity elicited by HIV-1-based virus-like particles incorporating HPV-16 E7 protein. Virology 2009; 395:45-55. [DOI: 10.1016/j.virol.2009.09.012] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2009] [Revised: 07/13/2009] [Accepted: 09/10/2009] [Indexed: 11/23/2022]
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150
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Antibody-mediated synergy and interference in the neutralization of SARS-CoV at an epitope cluster on the spike protein. Biochem Biophys Res Commun 2009; 390:1056-60. [PMID: 19861118 PMCID: PMC7092930 DOI: 10.1016/j.bbrc.2009.10.115] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2009] [Accepted: 10/22/2009] [Indexed: 12/01/2022]
Abstract
Incomplete neutralization of virus, especially when it occurs in the presence of excess neutralizing antibody, represents a biological phenomenon that impacts greatly on antibody-mediated immune prophylaxis of viral infection and on successful vaccine design. To understand the mechanism by which a virus escapes from antibody-mediated neutralization, we have investigated the interactions of non-neutralizing and neutralizing antibodies at an epitope cluster on the spike protein of severe acute respiratory syndrome coronavirus (SARS-CoV). The epitope cluster was mapped at the C-terminus of the spike protein; it consists of structurally intertwined epitopes recognized by two neutralizing monoclonal antibodies (mAbs), 341C and 540C, and a non-neutralizing mAb, 240C. While mAb 341C binds to a mostly linear epitope composed of residues 507PAT509 and V349, mAb 240C binds to an epitope that partially overlaps the former by at least two residues (P507 and A508). The epitope corresponding to mAb 540C is a conformational one, involving residues L504 and N505. In neutralization assays, non-neutralizing 240C disrupted virus neutralization by mAb 341C and/or mAb 540C, whereas a combination of mAbs 341C and 540C blocked virus infectivity synergistically. These findings indicate that the epitope cluster on the spike protein may serve as an evolutionarily conserved platform at which a dynamic interplay between neutralizing and non-neutralizing antibodies occurs, thereby determining the outcome of SARS-CoV infection.
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