Antibody to the ligand for CD40 (gp39) inhibits murine AIDS-associated splenomegaly, hypergammaglobulinemia, and immunodeficiency in disease-susceptible C57BL/6 mice.

Infection of genetically susceptible C57BL/6 mice with the LP-BM5 isolate of murine retroviruses cause profound splenomegaly, hypergammaglobulinemia, lymphadenopathy, and an immunodeficiency syndrome which includes the development of terminal B-cell lymphomas. Because many of these and the other manifestations of LP-BM5 virus-induced disease are similar to those seen in AIDS, this syndrome has been named murine AIDS, or MAIDS. Previous reports have shown that the onset of MAIDS depends on the presence of both CD4+ T cells and B cells and have suggested that CD4+ T-cell-B-cell interactions are important to disease pathogenesis.

CD40-CD40 ligand interactions in experimental allergic encephalomyelitis and multiple sclerosis.

We investigated the role of CD40-CD40 ligand (CD40L) interactions in multiple sclerosis (MS) and experimental allergic encephalomyelitis (EAE). Activated helper T cells expressing CD40L (gp39) surface protein were found in MS patient brain sections, but not in brain tissue sections of normal controls or patients with other neurological disease. CD40L-positive cells were co-localized with CD40-bearing cells in active lesions (perivascular infiltrates).

Functions of CD40 and its ligand, gp39 (CD40L).

Initially, a role for the interaction between CD40, expressed on B cells, and gp39 (CD40L), expressed on activated T cells, has been defined in humoral immunity. CD40-CD40L interaction is an essential signal for B cell proliferation, expression of activation markers, immunoglobulin production, and isotype switching. CD40-CD40L interaction is also required for formation of B memory cells and germinal centers, and signaling through CD40 prevents apoptosis of germinal center B cells.

Protection from HIV-1 envelope-bearing chimeric simian immunodeficiency virus (SHIV) in rhesus macaques infected with attenuated SIV: consequences of challenge.

Objectives: To determine whether prior infection with simian immunodeficiency virus (SIV)BK28 protects macaques from subsequent exposure to an HIV-1 envelope chimeric SIV (SHIV). Also, to determine the consequences of viral challenge on CD4 numbers and virus load on the current SIV infection.

Design And Methods: A total of 12 mature outbred Macacca mulatta were studied.

An essential role for gp39, the ligand for CD40, in thymic selection.

The interactions between CD40 on B cells and its ligand gp39 on activated T helper cells are known to be essential for the development of thymus-dependent humoral immunity. However, CD40 is also functionally expressed on thymic epithelial cells and dendritic cells, suggesting that gp39-CD40 interactions may also play a role in thymic education, the process by which self-reactive cells are deleted from the T cell repertoire. Six systems of negative selection were studied for their reliance on gp39-CD40 interactions to mediate negative selection.

Interaction between CD40 and its ligand gp39 in the development of murine lupus nephritis.

We investigated the role of gp39-CD40 interaction in the development of glomerulonephritis in lupus mice. In contrast to normal mice, lupus mice had much higher percentages of intensely gp39+ T cells in their spleens even at the preautoimmune age of 1 mo, and the further increase in gp39 expression by anti-CD3 Ab stimulation was markedly greater in lupus T cells. The pathogenic autoantibody-inducing ability of Th clones and splenic Th cells from lupus mice could be blocked in vitro by anti-gp39 Ab.

In vivo T-B cell interactions and cytokine-production in the spleen.

T-B cell interactions have a central role in the development of humoral immunity. The binding of a 39 kDa protein (gp39), selectively expressed on activated Th cells, to its receptor CD40, on B cells, results in the initial B cell activation. Thereafter, Th cell derived cytokines regulate the differentiation of B cells into antibody-forming cells.

Enhanced activation of human T cell clones specific for virus-like particles expressing the HIV V3 loop in the presence of HIV V3 loop-specific polyclonal antibodies.

Recombinant virus-like particles (VLP), formed by the yeast Ty p1 protein, carrying the HIV gp120 V3 loop on their surface (V3-VLP) have been tested in vitro for immunogenicity and antigenicity by using VLP p1-specific human CD4+ T cell lines and clones. VLP-specific human T cell lines and clones were generated from normal individuals, indicating that VLP-specific precursor cells present in the peripheral lymphocyte pool can be induced to expand clonally upon antigen challenge in vitro, in the absence of previous immunization. It was also shown that V3-specific polyclonal antibodies enhance V3-VLP-induced activation of VLP-specific T cell clones.

The role of CD40 in the regulation of humoral and cell-mediated immunity.

The dynamic and reciprocal communication between T helper (Th) cells and B cells appears to rely on the provision of multiple signals. The first is antigen specific and is mediated by the interaction between the T-cell receptor (TCR) and antigen bound to the major histocompatibility complex (MHC). The subsequent signals are provided by the binding of accessory molecules such as CD28 and CD40 to their respective ligands.

Mice deficient for the CD40 ligand.

To study the potential roles of CD40L in immune responses, we generated CD40L-deficient mice by gene targeting. Similar to the effects of CD40L mutations in humans (hyper-IgM syndrome), CD40L-deficient mice have a decreased IgM response to thymus-dependent antigens, fail altogether to produce an antigen-specific IgG1 response following immunization, yet respond normally to a T-independent antigen, TNP-Ficoll. Moreover, these mice do not develop germinal centers in response to thymus-dependent antigens, suggesting an inability to develop memory B cell responses.

Immunodeficiency due to a faulty interaction between T cells and B cells.

The identification of the ligand for CD40, gp39, which is expressed on the membrane of activated CD4+ T-helper cells, has sparked intense investigation into the roles of this molecule in physiological B-cell activation. Recently, it has become clear that some human immunodeficiencies, such as X-linked hyper IgM syndrome and common variable immunodeficiency are linked to mutations in the gp39 gene or are a result of defective expression of gp39, leading to suboptimal, or a lack of, B-cell activation by T-helper cells.

gp39-CD40 interactions are essential for germinal center formation and the development of B cell memory.

gp39, the ligand for CD40 expressed on activated CD4+ T helper cells, is required for the generation of antibody responses to T-dependent (TD) antigens. Treatment of mice with anti-gp39 in vivo inhibits both primary and secondary antibody formation to TD, but not T-independent antigens. However, the role of this receptor-ligand pair in the development of germinal centers and the generation of B cell memory is as yet undefined.

Epitope mapping and topology of baculovirus-expressed HIV-1 gp160 determined with a panel of murine monoclonal antibodies.

To define protein folding patterns of HIV-1 Env subunit vaccines, we have isolated a set of 30 monoclonal antibodies (MAbs) from BALB/c mice immunized with a recombinant gp160 vaccine (rgp160) expressed in a baculovirus system. This article describes epitope mapping for the MAb panel and topology of the epitopes for rgp160 and a recombinant gp120 (rgp120) also expressed in a baculovirus system. The following results are reported: (1) rgp160 harbors a minimum of 4 antigenic domains, 3 mapping to the C1, C2, and C3/V4 regions of gp120 and 1 mapping to the cytoplasmic tail of gp41; (2) there are at least 3 adjacent or overlapping epitopes in each antigenic domain; (3) a minimum of 14 independent epitopes were mapped, all of which are continuous sites; (4) each of the epitopes is exposed on rgp160 without prior manipulation of the protein; and (5) by contrast, 6 of the 8 epitopes mapping to the C1, C2, and C3/V4 regions are not exposed on rgp120, but become exposed when the protein is denatured.

A hidden region in the third variable domain of HIV-1 IIIB gp120 identified by a monoclonal antibody.

The third variable domain (V3 domain) of HIV-1 gp120 is involved in virus neutralization by antibody, in determination of cell tropism, and in syncytium-inducing/non-syncytium-inducing capacity. Antibodies are highly specific tools to delineate the role of different V3 amino acid sequences in these processes, and to dissect events occurring during synthesis of gp120/160, gp120-CD4 interaction, cellular infection, and syncytium formation. We describe here an IgG1 murine monoclonal antibody (MAb), coded IIIB-V3-01, that was raised with a synthetic peptide (FVTIGKIGNMRQAHC) derived from the carboxy-terminal flank of the HIV-1 IIIB V3 domain.

Variant-specific monoclonal and group-specific polyclonal human immunodeficiency virus type 1 neutralizing antibodies raised with synthetic peptides from the gp120 third variable domain.

The third variable (V3) domain of the human immunodeficiency virus type 1 (HIV-1) external membrane glycoprotein gp120 is of crucial importance in eliciting neutralizing antibodies in infected persons. Polyclonal (PAb) and monoclonal (MAb) antibodies directed against selected epitopes in the V3 domain are valuable tools for analysis of the involvement of such sequences in neutralization and for definition of the relation between amino acid variability and immunological cross-reactions. The aim of this study was to obtain such site-specific antibodies.

Complement-mediated follicular localization of T-independent type-2 antigens: the role of marginal zone macrophages revisited.

In this study we demonstrate a hitherto undescribed phenomenon, namely that thymus-independent type-2 antigens (TI-2 Ag) localize in splenic follicles within 1 h after administration. The follicular localization of 2,4,6-trinitrophenyl (TNP)-Ficoll was not antibody mediated. In addition in case of high-dose administration we observed a relatively large amount of TI-2 Ag in marginal zone macrophages.

Production of monomeric antigen-enzyme conjugate to study requirements for follicular immune complex trapping.

Studies concerning the localization of immune complexes in lymphoid follicles and the involvement of these trapped immune complexes in the regulation of the immune response have thus far been performed with poorly defined complexes in terms of size and composition. For that reason, the minimum requirements for trapping in terms of number of antigen- and antibody molecules present in immune complexes could not be determined. We here describe the production and in vivo use of a monomeric HSA-HRP antigen-enzyme conjugate, readily demonstrable in cryostat sections and ELISA.

Synthetic peptide conjugates with horseradish peroxidase and beta-galactosidase for use in epitope-specific immunocytochemistry and ELISA.

Synthetic peptide-alkaline phosphatase conjugates can be used to detect the epitope specificity of (i) antibody-forming cells in vivo by immunocytochemistry; (ii) of antibody secreting cells in vitro by spot-ELISA; and (iii) antibodies in solution by capture ELISA. The availability of synthetic peptide-enzyme conjugates using detector enzymes other than alkaline phosphatase would offer several important advantages, for example in double staining approaches. This paper reports the production of synthetic peptide-horseradish peroxidase conjugates and synthetic peptide-beta-galactosidase conjugates.