Recognition of a leukemia-related antigen by an antiidiotypic antiserum to an anti-gp70 monoclonal antibody

Animal virus receptors

The term 'receptor' is generally accepted as the cell-surface component that participates in virus binding and facilitates subsequent viral infection. Recent advances in technology have permitted the identification of several virus receptors, increasing our understanding of the significance of this initial virus-cell and virus-host interaction. Virus binding was previously considered to involve simple recognition and attachment to a single cell surface molecule by virus attachment proteins. The classical concept of these as single entities that participate in a lock-and-key-type process has been superseded by new data indicating that binding can be a multistep process, often involving different virus-attachment proteins and more than one host-cell receptor.

Anti-idiotype vaccines in toxicology

The majority of naturally occurring biological and chemical toxins are highly lethal, nonproteinaceous, low molecular weight substances which exert their toxicity through a variety of mechanisms. Their relative small size and extreme in vivo toxicity have hampered the development of protective vaccines. We have investigated the feasibility of anti-idiotype-based vaccines which utilize antibodies for inducing a systemic and protective immunity against the in vivo toxicity of some of these toxic substances. A murine IgG1 monoclonal anti-T-2 mycotoxin antibody protective against mycotoxin toxicity was generated. This antibody was used to produce a second generation monoclonal anti-idiotype antibody which was capable of serologically mimicking the tertiary conformation of the nominal antigen, i.e., T-2 mycotoxin. Administration of the monoclonal anti-idiotype antibody to mice induced a circulating and protective antibody response against the in vitro and in vivo toxicity of T-2 mycotoxin. Antibody-based vaccines may represent the only safe and effective strategy for the design of protective vaccines against small nonproteinaceous toxic compounds whose extreme toxicity prevents their use as safe immunogens. The potential of antibody-based vaccines for producing protective immunity against low molecular weight chemical and biological toxins is discussed.

Identification of a putative alphavirus receptor on mouse neural cells

Alphaviruses replicate in a wide variety of cells in vitro. The prototype alphavirus, Sindbis virus, causes an age-dependent encephalitis in mice and serves as an important model system for the study of alphavirus neurovirulence. To begin to understand the role of cellular virus receptors in the pathogenesis of Sindbis virus infection, we developed an anti-idiotypic antibody made in rabbits against a neutralizing monoclonal antibody specific for the E2 surface glycoprotein. The anti-idiotypic antibody (anti-Id 209) bound to N18 mouse neuroblastoma cells and inhibited adsorption of 35S-labeled virus by 50%. Binding of anti-Id 209 was inhibited by pretreatment of N18 cells with various proteases but not with neuraminidase or phospholipase, while virus binding was inhibited by pretreatment with phospholipase as well as protease. Anti-Id 209 precipitated proteins of 110 and 74 kDa from N18 cells intrinsically labeled with [35S]methionine. N18 cells grow with two phenotypes in culture, and immunoprecipitation of 125I-surface-labeled cells showed that the 74-kDa protein was present on loosely adherent cells growing in aggregates, while the 110-kDa protein was present in smaller amounts on firmly adherent cells growing as a monolayer. Analysis of brain cells from newborn mice by flow cytometry showed that all cells expressed the receptor protein at birth, but by 4 days after birth half of the cells had ceased receptor expression. A survey of other cell lines showed the protein to be present on murine fibroblastic and other rodent neuroblastoma cell lines but rarely on human neural or nonneural cell lines. These studies suggest that one of the receptors for Sindbis virus on mouse neural cells is a protein that is regulated during development of the nervous system. Developmental down-regulation of receptor protein expression may contribute to the age-dependent nature of susceptibility of mice to fatal alphavirus encephalitis.

Current approaches to vaccine preparation

Numerous conventional vaccines for animal use are currently available, and many of these vaccines have been instrumental in the control of infectious diseases of major economic importance. A vaccine has even been instrumental in global eradication of smallpox, an important human disease. However, many of the current vaccines are deficient in efficiency, potency, or safety. It has been recognized that the conventional methodologies are a limitation to further vaccine development. Introduction of monoclonal antibodies, recombinant DNA, and protein engineering techniques has facilitated a rather rapid increase in the knowledge of pathogenetic mechanisms, as well as of protective antigens at the molecular level. This knowledge provides the basis for development of a new generation of vaccines. As a rule, these vaccines contain purified immunogens, or even isolated epitopes, identified and prepared by molecular biological techniques. The efforts to find better delivery systems and better adjuvants accompany the research on vaccines.

Idiotypic cascades associated with the CD4-HIV gp120 interaction: principles for idiotype-based vaccines

Idiotypes (Id) are antigenic determinants expressed on the variable (V) region of the immunoglobulin molecule. Id-bearing antibodies, or Ab-1, are produced upon stimulation with a given antigen. Ab-1 may elicit the production of anti-idiotypic antibodies (anti-Id) or Ab-2. The anti-Id also expresses Id determinants and may in turn elicit the production of anti-anti-Id or Ab-3. The production of Ab-1, Ab-2, and Ab-3 responses resulting from stimulation with the antigen is representative of components within an Id cascade. The existence of this Id cascade is the basis for the development of Id based strategies for controlling the immune response to infectious agents and tumors. In this review we will focus on several aspects regarding the Id cascades that may be operational during the immune response to the human immunodeficiency virus (HIV). In light of several studies which suggest the existence of Id-anti-Id interactions operating during the course of HIV infection, we will discuss the potential applications of Id based strategies in manipulating the immune response to HIV.

Influenza viruses induce autoantibodies to a brain-specific 37-kDa protein in rabbit

Immunization of rabbits with certain H1N1 influenza viruses, including the neurotropic strains NWS/33 and WSN/33 and the New Jersey/76 strain, resulted in the production of autoantibodies to a brain-specific protein of 37 kDa that is present in various species, including humans. Autoantibodies were produced to brain only; various other tissues tested were negative. These antibodies were not elicited by other influenza A or B viruses, including closely related recombinant strains, but were elicited by the isolated hemagglutinin of A/Bellamy/42 strain and by formaldehyde-fixed WSN virus--demonstrating that infection was not essential for the induction of autoantibodies. In histological studies, reaction with anti-viral antisera was specific to gray matter and was confined to sera that recognized the 37-kDa protein. Antibody binding was prominent in regions comprised of neuronal cell bodies in cellular layers of the dentate gyrus, hippocampus, cerebral cortex, and cerebellum and was undetectable in myelin-rich regions, such as the corpus callosum. The 37-kDa protein, therefore, appears to be a neuronal antigen. Antibodies directed against this protein may be involved in the pathogenesis of one or more of the neuropsychiatric disorders that occur after infection with influenza.

Spike--nucleocapsid interaction in Semliki Forest virus reconstructed using network antibodies

Using in vitro immunization, we have reconstructed three consecutive steps of an idiotype network to show that the nucleocapsid of Semliki Forest virus contains a specific 'receptor' for the cytoplasmic tail of the E2 spike glycoprotein. This interaction could be the basis for the highly selective inclusion of viral glycoproteins--and exclusion of host cell surface proteins--during virus budding.

Mice immunized with measles virus develop antibodies to a cell surface receptor for binding virus

Mice were immunized with measles virus to determine whether an auto-anti-idiotypic antireceptor response could be generated as a probe for measles virus receptors. Mice initially responded to viral antigens (days 11 to 18) and subsequently developed antibodies to a putative measles virus receptor (peak at day 30 to 35) by three criteria: the sera (1) agglutinated erythrocytes which virus agglutinates, (2) reacted with Vero cells, and (3) inhibited virus attachment to Vero cells. Additionally, select sera inhibited virus infection of Vero cells. The cell-reactive activity was identified as immunoglobulin G antibody and was neutralized by sera reacting with virus (idiotype). The application of this anti-idiotypic antibody to identify measles virus-binding sites on Vero cells was revealed by the ability of sera to immunoprecipitate 20- and 30.5-kilodalton proteins from metabolically labeled ([35S]methionine) Vero cells.

Monoclonal anti-idiotypic antibody mimics the CD4 receptor and binds human immunodeficiency virus

A monoclonal anti-idiotypic (anti-Id) antibody, HF1.7, was generated against anti-Leu-3a, a mouse monoclonal antibody (mAb) specific for the CD4 molecule on human helper/inducer T lymphocytes. The anti-Id nature of HF1.7 was demonstrated by the following properties. (i) It reacted in a solid-phase immunoassay with anti-Leu-3a and not with a panel of irrelevant mouse mAbs. (ii) It partially inhibited the binding of anti-Leu-3a to CD4+ T cells. (iii) It detected a common idiotype present on various anti-CD4 mAbs. Because the CD4 molecule represents the receptor site for human immunodeficiency virus (HIV), the etiologic viral agent of acquired immunodeficiency syndrome, we examined the ability of the anti-mAb HF1.7 to mimic CD4 and bind HIV. This anti-Id mAb reacted with HIV antigens in commercial HIV ELISAs and recognized HIV-infected human T cells but not uninfected cells when analyzed by flow cytofluorometry. Attesting further to the HIV specificity, the anti-Id mAb reacted with a recombinant gp160 peptide and a molecule of Mr 110,000-120,000 in immunoblot analysis of HIV-infected cell lysates. The anti-Id mAb also partially neutralized HIV infection of human T cells in vitro. These results strongly suggest that this anti-Id mAb mimics the CD4 antigenic determinants involved in binding to HIV.

Parallel sets of autoantibodies in MRL-lpr/lpr mice. An anti-DNA, anti-SmRNP, anti-gp70 network

The public idiotype Id-H130 occurs in MRL-lpr/lpr serum both on a high proportion of anti-DNA autoantibodies as well as on antibodies that do not bind to DNA. To define members of the latter population, we prepared hybridomas and selected Id-H130+ mAbs that did not bind to DNA. One such antibody, mAb 28/12, was found to be an anti-SmRNP antibody. To determine whether mAb 28/12 had rheumatoid factor activity, we tested its ability to bind, in a solid-phase assay, to 16 mouse IgM mAbs. mAb 28/12 bound to only four of the panel, two anti-DNA antibodies (mAbs 512 and 319) and two anti-gp70 antibodies (mAbs 514 and 1417). In a liquid-phase competition assay with a panel of 32 monoclonal IgM and IgG antibodies, including allotype-matched Igs, mAb 28/12 reacted only with mAbs 512, 319, 514, and 1417. The binding of mAb 28/12 to mAbs 512 and 319 was displaced by DNA, but not by RNA, indicating that the idiotype it defines (Id-28/12) is in the antigen-binding region of the two anti-DNA antibodies. In the two anti-gp70 antibodies (mAbs 514 and 1417), Id-28/12 seems to occur in the framework region. To determine if all four Id-28/12+ antibodies shared a common antigen-binding property, they were tested for their ability to react with DNA and gp70. The two anti-gp70 antibodies did not bind to DNA. However, the two anti-DNA antibodies were found to immunoprecipitate viral proteins from retrovirus-infected cells. mAb 512 reacted with gp70, both in cell membrane lysates and in purified form; mAb 319 reacted with gp85, which contains both gp70 and the retroviral protein p15. Antibodies with properties similar to those of mAb 28/12 were found in MRL-lpr/lpr serum. It was possible, by affinity chromatography on an anti-gp70 antibody column, to isolate from serum those anti-(anti-gp70) antibodies with anti-SmRNP activity. These results show that parallel sets of autoantibodies, which share a common idiotype, but which bind to different autoantigens, occur in MRL-lpr/lpr mice. Some populations of anti-DNA, anti-SmRNP, and anti-gp70 antibodies appear to constitute a network of autoantibodies in that strain. We speculate that part of the anti-SmRNP population of autoantibodies can arise by mutation of germline-encoded anti-DNA antibodies.