Antiviral antibody responses: the two extremes of a wide spectrum

Viruses elicit a diverse spectrum of antiviral antibody responses. In this review, we discuss two widely used experimental model systems for viral infections - non-cytopathic lymphocytic choriomeningitis virus (LCMV) and acutely cytopathic vesicular stomatitis virus (VSV) - to analyse two fundamentally different types of antiviral antibody response. The basic principles found in these model infections are discussed in the context of other viral infections, and with regard to protective neutralizing versus non-protective enzyme-linked immunosorbent assay (ELISA)-detected antibody responses. Issues of antibody specificity, affinity and avidity, maturation and escape are discussed in the context of co-evolution of the host and viruses.     

Relation between Enhanced Antibody Responses Elicited by Adjuvant Injection and Those Elicited by Secondary Antigenic Stimulation

An attempt was made to determine if there is any common mechanism in the enhanced antibody response caused either by injection of adjuvant, such as bacterial endotoxin (LPS) and complexed polynucleotides, or by secondary antigenic stimulation. LPS inoculated in mice 4 days before injection of sheep red blood cells (SRBC) and polyA:U invalidated the adjuvant effect of polyA:U injected together with SRBC, and the hemolysin plaque-forming cell (PFC) response of such mice was similar to that of the mice which received SRBC alone. When mice primed with SRBC 24 days in advance were injected with LPS and 4 days later re-stimulated with SRBC, their PFC response to the secondary stimulation was suppressed to less than one tenth of the normal secondary PFC response. The suppressive effect of LPS on the secondary antibody response was abolished if the serum collected from mice injected with LPS was given to the primed and LPS-injected mice at the time of the secondary antigenic stimulation. From these results we discussed the possibility that some common mediator might play a role in the enhanced antibody response elicited by either adjuvant injection or secondary injection of antigen.     

Using peptide mimetopes to elucidate anti-polysaccharide and anti-nucleic acid humoral responses.

Humoral responses against polysaccharide or nucleic acid antigens are often difficult to characterize and to induce. For example, the eliciting antigen for the development of anti-double-stranded(ds)DNA antibodies is unclear. dsDNA is a poor immunogen, yet antibodies to it bear the hallmark of a T cell dependent response. The microbial origin of polysaccharide antigens is, in general, readily known, but these antigens often do not elicit B cell memory responses, which are crucial for vaccine development. This review focuses on the use of peptide mimetopes to better understand humoral responses against non-protein antigens. First we describe a mimetope for dsDNA that was derived by probing a peptide phage library with an anti-dsDNA antibody. We discuss the usefulness of this mimetope in a search for candidate protein antigens and for examining the phenotype of antigen-specific B cells. Next, we discuss two mimetopes for phosphorylcholine (PC), a component of S. pneumoniae C polysaccharide. One was derived through mapping an anti-idiotype epitope and the other by probing a phagodisplay peptide library with an anti-PC antibody. Both of these peptide mimetopes for PC provide useful information regarding the requirements of a protective antibody response against pneumococcal infection, and define a critical role for adjuvant and carrier as well as mimetope.     

Antibody Engineering and Therapeutics Conference

The Antibody Engineering and Therapeutics conference, which serves as the annual meeting of The Antibody Society, will be held in Huntington Beach, CA from Sunday December 8 through Thursday December 12, 2013. The scientific program will cover the full spectrum of challenges in antibody research and development, and provide updates on recent progress in areas from basic science through approval of antibody therapeutics. Keynote presentations will be given by Leroy Hood (Institute of System Biology), who will discuss a systems approach for studying disease that is enabled by emerging technology; Douglas Lauffenburger (Massachusetts Institute of Technology), who will discuss systems analysis of cell communication network dynamics for therapeutic biologics design; David Baker (University of Washington), who will describe computer-based design of smart protein therapeutics; and William Schief (The Scripps Research Institute), who will discuss epitope-focused immunogen design.

In this preview of the conference, the workshop and session chairs share their thoughts on what conference participants may learn in sessions on: (1) three-dimensional structure antibody modeling; (2) identifying clonal lineages from next-generation data sets of expressed V_H gene sequences; (3) antibodies in cardiometabolic medicine; (4) the effects of antibody gene variation and usage on the antibody response; (5) directed evolution; (6) antibody pharmacokinetics, distribution and off-target toxicity; (7) use of knowledge-based design to guide development of complementarity-determining regions and epitopes to engineer or elicit the desired antibody; (8) optimizing antibody formats for immunotherapy; (9) antibodies in a complex environment; (10) polyclonal, oligoclonal and bispecific antibodies; (11) antibodies to watch in 2014; and (12) polyreactive antibodies and polyspecificity.     

Predicting antigenic sites on proteins.

The ability to predict antigenic sites on proteins is of major importance for the production of synthetic peptide vaccines and synthetic peptide probes of antibody structure. Many predictive methods, based on various assumptions about the nature of the antigenic response have been proposed and tested. This review will discuss the principles underlying the various approaches to predicting antigenic sites and will attempt to answer the question of how well they work.     

Assessment of the humoral immune response to cancer

One of the deadly hallmarks of cancer is its ability to prosper within the constraints of the host immune system. Recent advances in immunoproteomics and high-throughput technologies have lead to profiling of the antibody repertoire in cancer patients. This in turn has lead to the identification of tumour associated antigens/autoantibodies. Autoantibodies are extremely attractive and promising biomarker entities, however there has been relatively little discussion on how to interpret the humoral immune response. It may be that autoantibody profiles hold the key to ultimately uncovering neoplastic associated pathways and through the process of immunosculpting the tumour may have yielded an immune response in the early stages of malignant tumour development. The aim of this review is to discuss the utility of the autoantibody response that is elicited as a result of malignancy and discuss the advantages and limitations of autoantibody profiling. This article is part of a Special Issue entitled: Translational Proteomics.     

抗人类免疫缺陷病毒广谱中和抗体与疫苗设计

自发现人类免疫缺陷病毒1型（HIV-1）30年来,科学家们不断探索有效的HIV-1疫苗,但至今效果不理想。由于“精英患者”的广谱中和血清能起到有效的抗病毒作用,研究人员希望通过对体液保护免疫机制的研究,推动疫苗的设计和优化,为尽早研发成功HIV疫苗提供关键理论和技术支撑。近几年来,由于技术的突破和改进,从HIV感染者中分离获得广谱中和抗体的概率和数量大大提高。本文针对近几年来分离的有代表性的广谱中和抗体,根据其不同的识别位点分为四大类进行详细介绍,并总结了从研究广谱中和抗体中所获得的疫苗设计创新思路与启示。     

Antibody-antigen pair probed by combinatorial approach and rational design: Bringing together structural insights, directed evolution, and novel functionality

The unique hypervariability of the immunoglobulin (Ig) superfamily provides a means to create both binding and catalytic antibodies with almost any desired specificity and activity. The diversity of antigens and concept of adaptive response suggest that it is possible to find an antigen pair to any raised Ig. In the current review we discuss combinatorial approaches, which makes it possible to obtain an antibody with predefined properties, followed by 3D structure-based rational design to enhance or dramatically change its characteristics. A similar strategy, but applied to the second partner of the antibody-antigen pair, may result in selection of complementary substrates to the chosen Ig. Finally, 2D screening may be performed solving the "Chicken and Egg" problem when neither antibody nor antigen is known.     

Intracellular antibody-mediated immunity and the role of TRIM21

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.     

No receptor stands alone: IgG B-cell receptor intrinsic and extrinsic mechanisms contribute to antibody memory

Acquired immunological memory is a striking phenomenon. A lethal epidemic sweeps through a naïve population, many die but those who survive are never “attacked twice ― never at least fatally”, as the historian Thucydides observed in 430 BCE. Antibody memory is critical for protection against many human infectious diseases and is the basis for nearly all current human vaccines. Antibody memory is encoded, in part, in isotype-switched immunoglobulin (Ig)G-expressing memory B cells that are generated in the primary response to antigen and give rise to rapid, high-affinity and high-titered antibody responses upon challenge with the same antigen. How IgG-B-cell receptors (BCRs) and antigen-induced IgG-BCR signaling contribute to memory antibody responses are not fully understood. In this review, we summarize exciting new advances that are revealing the cellular and molecular mechanisms at play in antibody memory and discuss how studies using different experimental approaches will help elucidate the complex phenomenon of B-cell memory.     

Differential regulation of the antibody responses to Gag and Env proteins of human immunodeficiency virus type 1.

We have studied the antibody responses to Env and Gag antigens of human immunodeficiency virus type 1 (HIV-1) in several cohorts of HIV-1-infected individuals: long-term nonprogressors, progressors to disease, acute seroconvertors, and recipients of HIV-1 protease inhibitors. We conclude that the antibody responses to Env and Gag antigens are differentially regulated and that changes in the plasma viral load in the measurable range (500 to 10(8) RNA copies per ml) do not directly affect the antibody responses to these HIV-1 proteins. We provide quantitative estimates of HIV-1-specific immunoglobulin G concentrations in plasma, which can be in excess of 1 mg/ml for both anti-gp120 and anti-p24 once the immune response to HIV-1 has stabilized after seroconversion. We discuss the apparent paradox that the absence of anti-Gag antibodies (which have, at best, limited antiviral activity) is indicative of disease progression, while the retention of anti-Env antibodies (which do have antiviral activity) is of limited (or no) prognostic value. We show that the disappearance of anti-Gag antibodies during disease progression is highly unlikely to be due to immune complexing; instead, we believe that it reflects the loss of T-cell help that is more necessary for the anti-Gag than the anti-Env response.     

Naturally occurring subclinical Corynebacterium kutscheri infection in laboratory rats: strain and age related antibody response

Naturally occurring subclinical Corynebacterium kutscheri infection was analyzed by antibody response related to the strain of rats. Wistar-Lewis, Wistar and Spraque-Dawley rats were high responders in seroconversion rates and antibody titers, while Brown Norway and Fischer rats were low responders. The antibody response was related to age also. Some young rats had maternal antibody to C. kutscheri, but antibody disappeared before 8 weeks of age. Rats were antibody-negative for several months thereafter and became antibody-positive after 6 months of age. The antibody response was highest at 8 to 9 months of age in subclinical C. kutscheri infection. This antibody response was very late, compared to the antibody response to Sendai virus and Mycoplasma infections.     

Immunocontraception for population control: will resistance evolve?

The prospect for successful biocontrol using immunocontraception is threatened if there is adaptation to the vaccine through natural selection of individuals that are genetically resistant to the contraceptive agent. To assess this possibility we examined the literature and found that little relevant data are available for any species on the appropriate trait, fertility variation among immunized individuals, or about appropriate population and genetic parameters influencing the likelihood of a selection response. Some data are available on variation in antibody response to immunocontraceptives, but the relationship between antibody response and fertility levels is poorly documented. The antibody response data indicate low heritability for this trait suggesting that fertility levels of contraceptive-resistant individuals will also have a low heritability. Slow evolution of contraception resistance might therefore be anticipated. The absence of information about relevant parameters makes the construction of quantitative models premature. We discuss factors in particular need of investigation if predictions about resistance evolution are to be made. These include: 1. the genetic basis of fertility retention, 2. the proportion of the population resistant to the contraceptive agent and how this is affected by gene flow from refuge populations, 3. the genetically-based fitness tradeoffs of resistant individuals that often accompany selection, 4. cross-generation effects that can thwart the effects of selection, and 5. the efficiency of delivery of the contraceptive agent. An understanding of the above for particular species, and the development of appropriate divergently acting multiple vaccines that can be used in temporal rotation or in mixtures, should facilitate the development of management options to minimize resistance evolution.     

Trypanosoma gambiense: immunosuppression and polyclonal B-cell activation in mice

The relationship between the suppression of antibody response and polyclonal B-cell activation was studied in mice treated with a cell homogenate of Trypanosoma gambiense. The cell homogenate injection in mice caused a progressive increase in splenic background plaque-forming cell response to sheep erythrocyte. In the mice with markedly increased background plaque-forming cell response, the different reactivity in the primary antibody response to sheep erythrocytes was observed between the intraperitoneal and intravenous immunization with sheep erythrocytes. The intraperitoneal immunization of mice with sheep erythrocytes strongly suppressed the antibody response, while the intravenous immunization with sheep erythrocytes led to an enhancement of the antibody response. The intraperitoneal injection of silica particles, a toxic agent to macrophages, 30 min before intraperitoneal immunization with sheep erythrocytes abolished the suppression of the antibody response completely. In addition, restoration of the suppressed antibody response was found in mice immunized intraperitoneally with a high dose of sheep erythrocytes. It appears that the suppression of antibody response is not attributable to polyclonal B-cell activation, and is associated with the elevation of the phagocytic activity of peritoneal macrophages.     

A new approach for drug discovery from glycobiology and phage-displayed peptide library technology

Peptides which mimic functional activities of glycosphingolipids were prepared by a technology of phage-displayed peptide library using monoclonal antibodies against glycosphingolipids. These peptides were named glyco-replica peptides. Peptides prepared with anti-GD1alpha antibody by this technology were found to contain WHW as common motif, and they showed suppressive activity not only on adhesion between hepatic sinusoidal endothelial cells and lymphosarcoma RAW117-H10 cells, but also on metastasis of the tumor cell to the liver and lung. The WHW motif seems to be important to mimic the functional activity of the ganglioside GD1alpha. Next, we prepared GD3-replica peptides using a monoclonal antibody against GD3 (4F6). A peptide, GD3-P4 with highest affinity to 4F6 was used to immunize mice to examine if the mice show their immune response to raise antibodies against GD3. We confirmed the immune response and succeeded in the production of a monoclonal antibody (3D2) against GD3. The monoclonal antibody 3D2 showed specific binding to GD3 on a thin-layer chromatography plate and also melanoma tissues. Interestingly, the amino acid sequence of the CDR regions of light and heavy chains showed high similarity with those of the original GD3 monoclonal antibody (4F6) used for the preparation of GD3-replica peptide. The technology of the phage-displayed peptide library was applied to in vivo bio-panning study using an angiogenesis experimental model. The obtained peptides were found to show strong binding property to the neo-vasculature system and to be quite useful to carry an anti-tumor drug to the tumor tissue. Based on these experimental results, we discuss about some applications of this method to drug discovery.     

B cells--masters of the immunoverse

The immune system involves the complex interplay between many different cell types. Over the last decade, T cells, dendritic cells (DC) and macrophages have all been implicated as the key regulator cells of the immunological response, linking innate and adaptive immunity. The forgotten cell in this discourse has been the B-cell. Long considered as simple antibody production units dictated to by T-cells, recent years have begun to shift this assumption. The discovery that numerous B-cell subsets exist, with specific regulatory functions capable of modulating T-cell and chronic inflammatory responses has revealed a hitherto unappreciated role of B-cells. In particular, these ideas have been developed in light of the surprisingly successful responses delivered in autoimmune settings following depletion of B-cells with the anti-CD20 antibody rituximab. Here we summarise the history of the humble B-cell and discuss some of the key recent findings that lead us to propose it as an important regulator of ongoing immune responses and as such, one of the masters of the immunoverse.     

Adjuvant Action of Capsular Polysaccharide of Klebsiella pneumoniae on Antibody Response

A study was performed to clarify the roles of primary and secondary injections of antigen and adjuvant (capsular polysaccharide of Klebsiella pneumoniae, CPS-K) in induction of antibody responses and in development of immunological memory in mice to bovine serum albumin (BSA). A primary injecion of BSA alone neither induced significant primary antibody response nor increased immunological memory for a secondary antibody response but, if primary injections of BSA and CPS-K were performed simultaneously, high antibody responses were induced. Moreover, a prior injection of BSA alone or CPS-K alone decreased the level of primary antibody response and the degree of increase in memory following the subsequent injection of BSA mixed with CPS-K. In contrast, a secondary injection of BSA alone into mice once primed with a mixture of BSA and CPS-K elicited very high secondary type antibody response and increased secondarily the memory for a tertiary antibody response. Injection of CPS-K simultaneously with or shortly before or after the secondary injection of BSA did not increase the level of the secondary antibody response and the degree of the secondary increase in memory. Augmentation of the secondary antibody response was elicited by simultaneous injection of CPS-K only when the secondary response was induced inadequately by a suboptimum or supraoptimum dose of antigen.     

Immunogenicity of lysozyme derivatives lipid-conjugated to various degrees in mice treated with and without cyclophosphamide: dissociation of delayed-type hypersensitivity and helper function.

Lysozyme and a series of its lipid-conjugated derivatives without adjuvant were examined in mice for their abilities to induce delayed-type hypersensitivity (DTH), helper T-cell activity, and antibody formation. In addition, the effect of cyclophosphamide (CY) on the immune responses was assessed in mice immunized with these lysozyme derivatives. Precipitated lysozyme without lipid conjugation was a good inducer of both antibody and DTH responses. Lipid conjugation to lysozyme to intermediate degrees readily caused the failure only in inducing the antibody response. As lysozyme was lipid-conjugated more heavily, DTH response was also reduced and finally abolished. In contrast, the helper activity was little affected by any degree of lipid conjugation. These results indicate that the helper T-cell activity was dissociated from the both DTH response and the antibody production. CY pretreatment extensively enhanced DTH response induced by such lipid-conjugated derivatives that failed to induce antibody response. Furthermore, CY pretreatment in doses in a wide range enhanced not only DTH response but also antibody formation. It is, therefore, concluded that the enhancement of DTH response by CY does not necessarily entail suppression of antibody formation.     

Transition in the Character of Immunological Memory in Mice after Immunization

The immunological memory in antibody response of mice to bovine serum albumin was investigated at the level of IgM and IgG antibody-forming cells. The antigen at a dose much lower than required for eliciting a detectable level of the primary antibody response could latently activate the immune machinery to an extent adequate for specific recall, whereas higher doses of antigen were effective in evoking strong anamnestic response. The potentiality to develop the anamnestic response was found even in the latent phase of the primary antibody response and was maintained for more than 2 months. The immunological memory acquired in an early phase after the primary immunization mainly involved IgM antibody response and late memory concerned IgG response.