Inger Nordström

Differential expression of tissue-specific adhesion molecules on human circulating antibody-forming cells after systemic, enteric, and nasal immunizations. A molecular basis for the compartmentalization of effector B cell responses.

Expression of the adhesion molecules CD44, L-selectin (CD62L), and integrin alpha 4 beta 7 by antibody-secreting cells (ASC) was examined in human volunteers after oral, rectal, intranasal, or systemic immunization with cholera toxin B subunit. Almost all blood ASC, irrespective of immunization route, isotype (IgG and IgA), and immunogen, expressed CD44. On the other hand, marked differences were observed between systemically and intestinally induced ASC with respect to expression of integrin alpha 4 beta 7 and L-selectin, adhesion molecules conferring tissue specificity for mucosal tissues and peripheral lymph nodes, respectively. Thus, most ASC induced at systemic sites expressed L-selectin, whereas only a smaller proportion of ASC expressed alpha 4 beta 7. In contrast, virtually all IgA- and even IgG-ASC detected after peroral and rectal immunizations expressed alpha 4 beta 7, with only a minor fraction of these cells expressing L-selectin. Circulating ASC induced by intranasal immunization displayed a more promiscuous pattern of adhesion molecules, with a large majority of ASC coexpressing L-selectin and alpha 4 beta 7. These results demonstrate that circulating ASC induced by mucosal and systemic immunization express different sets of adhesion molecules. Furthermore, these findings provide for the first time evidence for differential expression of adhesion molecules on circulating ASC originating from different mucosal sites. Collectively, these results may explain the anatomical division of mucosal and systemic immune responses in humans as well as the compartmentalization of mucosal immune responses initiated in the upper vs. the lower aerodigestive tract.

Intestinal immune responses in humans. Oral cholera vaccination induces strong intestinal antibody responses and interferon-gamma production and evokes local immunological memory.

We have examined secretory antibody and cell-mediated immune responses to oral cholera vaccine in the human gastrointestinal mucosa. Freshly isolated peripheral blood lymphocytes and intestinal lymphocytes obtained by enzymatic dispersion of duodenal biopsies were assayed for numbers of total and vaccine specific immunoglobulin-secreting cells by enzyme-linked immunospot assay (ELISPOT) techniques; the frequency of cells secreting interferon-gamma (IFN-gamma) was also examined by a new modification of the ELISPOT technique. After booster immunizations with oral cholera vaccine, large numbers of cholera toxin-specific antibody-secreting cells (ASC) appeared in the small intestine. The responses were dominated by IgA ASC. A single immunization, performed 5 mo after the initial vaccinations, gave rise to an ASC response similar to that seen after the first booster immunization, with respect to both magnitude and isotype distribution. Each of the immunizations also evoked an ASC response in blood which was of lower magnitude than that seen in the small intestine, and comprised similar proportions of IgA and IgG ASC. A booster immunization also resulted in increased frequencies of IFN-gamma-secreting cells, but this increase was confined to the duodenal mucosa. This study establishes the feasibility of studying, at the single-cell level, intestinal immune reactivity in humans. Furthermore, it indicates that the small intestinal mucosa is an enriched source of IFN-gamma. It also demonstrates marked differences between intestinal and peripheral blood immune responses after enteric immunization, and confirms the notion that the mucosal immune system in humans displays immunological memory.

Cholera Toxin B Subunit as a Carrier Molecule Promotes Antigen Presentation and Increases CD40 and CD86 Expression on Antigen-Presenting Cells

ABSTRACT Cholera toxin B subunit (CTB) is an efficient mucosal carrier molecule for the generation of mucosal antibody responses and/or induction of systemic T-cell tolerance to linked antigens. CTB binds with high affinity to GM1 ganglioside cell surface receptors. In this study, we evaluated how conjugation of a peptide or protein antigen to CTB by chemical coupling or genetic fusion influences the T-cell-activating capacity of different antigen-presenting cell (APC) subsets. Using an in vitro system in which antigen-pulsed APCs were incubated with antigen-specific, T-cell receptor-transgenic T cells, we found that the dose of antigen required for T-cell activation could be decreased >10,000-fold using CTB-conjugated compared to free antigen. In contrast, no beneficial effects were observed when CTB was simply admixed with antigen. CTB conjugation enhanced the antigen-presenting capacity not only of dendritic cells and B cells but also of macrophages, which expressed low levels of cell surface major histocompatibility complex (MHC) class II and were normally poor activators of naive T cells. Enhanced antigen-presenting activity by CTB-linked antigen resulted in both increased T-cell proliferation and increased interleukin-12 and gamma interferon secretion and was associated with up-regulation of CD40 and CD86 on the APC surface. These results imply that conjugation to CTB dramatically lowers the threshold concentration of antigen required for immune cell activation and also permits low-MHC II-expressing APCs to prime for a specific immune response.

Reverse ELISPOT assay for clonal analysis of cytokine production. II. Enumeration of interleukin-1-secreting cells by amplified (avidin-biotin anti-peroxidase) assay.

Detection of cytokine-producing cells can be accomplished by reverse modifications of the ELISPOT assay using cytokine-specific unconjugated and enzyme-labelled antibodies as solid phase capture system and detecting reagents, respectively. However, in certain situations where the secreted cytokine is produced in minute amounts such as in the case of interleukin-1 (IL-1), the sensitivity of the indicator immunoenzyme system employed may be insufficient to permit detection of the corresponding secreting cells. We have developed a novel immunoenzyme amplification procedure that involves the use of a biotinylated secondary anti-enzyme antibody reagent to enhance the signal provided by the primary enzyme-labelled antibody conjugate. Following addition of enzyme-conjugated avidin, ELISPOT assay wells are developed with a suitable chromogen substrate yielding spots located at the former position of cells secreting the analyte under study. As a model system, the detection of IL-1 beta-secreting cells by human peripheral blood monocytes is described.

Cholera Toxin and Its B Subunit Promote Dendritic Cell Vaccination with Different Influences on Th1 and Th2 Development

ABSTRACT Cholera toxin (CT) is a strong mucosal adjuvant for codelivered antigens, whereas its nontoxic B subunit (CTB) is an efficient mucosal carrier molecule for the generation of immune responses to linked antigens. We investigated the effects of CT and CTB on the immunogenicity of in vitro-treated antigen-pulsed dendritic cells (DC) following intravenous injection into mice. Prior to infusion, DC were pulsed for 90 min with either free ovalbumin (OVA), OVA mixed with CT or CTB, or chemical conjugates of OVA with CT and CTB (OVA-CT and OVA-CTB). DC pulsed with OVA or with OVA and CTB gave rise to modest antibody and T-cell responses. Conjugation of OVA with CTB enhanced both the subsequent B-cell and T-cell responses to OVA and preferentially induced Th2 responses. CT was shown to be a strong adjuvant when it was coadministered to DC with OVA and was even stronger when it was coadministered with OVA-CTB and primed for a mixed Th1-Th2 response. The antibody and T-cell responses were further enhanced if OVA was coupled to CT, implying that CT can utilize a combined carrier and adjuvant function vis-a-vis linked antigens for DC vaccination. The immunopotentiating capacity of CT- and CTB-linked antigen was associated with both upregulated secretion of interleukin-1β by the pulsed DC and increased expression of CD80 and CD86 on the DC surface. These results imply that CT and CTB can be used to both markedly increase and partially direct the DC vaccine-induced immune response with respect to Th1 and Th2 responses, which has obvious implications for DC-based vaccine development.

Local and Systemic Immune Responses to Rectal Administration of Recombinant Cholera Toxin B Subunit in Humans

ABSTRACT The induction of immune responses to rectally administered recombinant cholera toxin B subunit (CTB) in humans was studied. Three immunizations induced high levels of CTB-specific antibody-secreting cells, particular of the immunoglobulin A isotype, in both rectum and peripheral blood. Antitoxin antibody responses in rectal secretions and serum were also found.

Th17 development and autoimmune arthritis in the absence of reactive oxygen species.

Dendritic cells (DC) express a functional NADPH oxidase and produce reactive oxygen species (ROS) upon interaction with microbes and T cells. Exposure to ROS leads to DC activation and maturation, as evidenced by phenotypic and functional changes. We have evaluated how endogenous ROS production affects the cytokine secretion pattern and T cell‐activating capacity of bone marrow‐derived murine DC. DC treated with ROS scavengers, as well as DC from mice that lack a functional NADPH oxidase (and thereby inherently deficient in ROS production) produced significantly increased levels of IL‐1β, IL‐6, TNF‐α and TGF‐β in response to microbial activation. DC deficient in ROS production induced high levels of IFN‐γ and IL‐17 in responding T cells after Ag‐specific or superantigen‐induced activation. Finally, we show that ROS deficiency affected the induction of a T cell‐dependent inflammatory condition, collagen‐induced arthritis (CIA). C57BL/6 mice that lack a functional NADPH oxidase developed a severe and erosive CD4‐dependent CIA, whereas the majority of the congenic wild‐type animals remained healthy. These data suggest that ROS act as immunomodulators in DC‐driven T cell activation and perhaps also in T cell‐dependent immunopathology.

High circulating immunoglobulin A levels in infants are associated with intestinal toxigenic Staphylococcus aureus and a lower frequency of eczema

Background Intestinal bacteria trigger IgA production and delayed maturation of mucosal IgA response is linked to allergy development.

Amplified ELISPOT assay for the detection of HIV-specific antibody-secreting cells in subhuman primates

A novel immunoenzyme amplification technique has been evaluated in an ELISPOT assay for the detection of antigen-specific antibody-secreting cells (ASC) in monkeys. In this assay, mononuclear cells containing putative ASC are incubated for a few hours in antigen-coated wells. Following removal of the cells, zones of solid phase bound antibodies secreted by individual ASC are visualized in four consecutive steps. First, a primary biotinylated anti-immunoglobulin (Ig) reagent is added followed by enzyme-labelled avidin. The amplification procedure comprises the addition of biotinylated anti-enzyme antibodies in the third stage, followed by enzyme-conjugated avidin and substrate. When evaluated in a modified ELISPOT assay for the detection of simian B cells secreting antibodies to the envelope glycoprotein gp120 of the human immunodeficiency virus type 1 (HIV-1), this amplification procedure proved to be suitable even when using anti-human Ig antisera as primary antibody reagents. This development should be useful for other ELISPOT assays where species specific anti-Ig reagents are not always available and, most importantly, for enumerating cells producing immunoreactive substances in such minute amounts that they may escape detection by conventional ELISPOT assays. Furthermore, a functional simian HIV-specific ELISPOT assay could prove valuable for assessing the humoral immunogenicity of future candidate vaccines against the acquired immunodeficiency syndrome (AIDS).

Dendritic cell vaccination protects mice against lethality caused by genital herpes simplex virus type 2 infection.

We have evaluated the ability of antigen pulsed bone-marrow derived dendritic cells (bmDC), to induce protective immunity against a genital tract infection with herpes simplex virus type 2 (HSV-2) in mice. Intravenous but not vaginal administrations of bmDC pulsed in vitro with UV-inactivated HSV-2, or with purified HSV-2 envelope glycoproteins gave rise to complete protection against disease, as well as death caused by genital herpes infection. Protection was dependent on the antigens being presented by the bmDC as neither the antigens alone, nor the mock-pulsed bmDC prevented disease. Immunity was associated with HSV-2 specific IFN-gamma and antibody production, and was shown to be dependent on CD4(+) cells secreting IFN-gamma. Thus, ex vivo antigen-pulsed bmDC represents a powerful tool for the study of protective immunity to genital herpes infection, and for the identification of protective antigens. These findings might also have an impact on the design of vaccines against other sexually transmitted viral diseases.