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Mucosal immune responses to meningococcal C polysaccharide-protein conjugate in mice.

Mucosal delivery of vaccines represents an attractive approach because this is a region of first contact point for inhaled antigens. We have obtained a meningococcal group C polysaccharide-tetanus toxoid conjugate (MGCP-TT) and evaluated it for intranasal route in mice. The conjugate was obtained by a developed method in our laboratory. The specific IgA in saliva and specific IgA and IgG in serum were measured by ELISA methods and bactericidal antibodies in sera against a meningococcal group C strain were measured. The conjugated elicited a significant increase in anti-MGCP salivary IgA and serum IgG and bactericidal antibodies concentrations, while specific serum IgA was not observed. These results indicated that after conjugation, there was a change in the responses for MGCP from thymus-independent to thymus-dependent and that it was effective by intranasal route.

Administration, Intranasal↗

Neuroendocrine regulation of mucosal immunity.

In view of the extensive innervation of the gastrointestinal tract, including the mucosa, and the high number of immune effector cells present in this tissue, we have studied the effects of certain neurotransmitters on immune responses. We have concentrated on the effects of the neuropeptides substance P (SP), somatostatin (SOM) and vasoactive intestinal peptide (VIP). We have found that SP causes an increase in the proliferation of Peyer's patch lymphocytes as well as immunoglobulin (especially IgA) synthesis, when compared to splenic cells; and that there is a greater expression of SP receptors on lymphocytes derived from Peyer's patches compared to the spleen, without a significant difference in the expression between subsets of T and B cells. Furthermore, we have shown that intraepithelial leukocytes (IEL) show significantly increased cytotoxic activity following incubation with SP; whereas splenic lymphocytes were not stimulated in the same system. The effects of SOM where bi-directional depending upon the concentration employed but in general, SOM was inhibitory, in terms of proliferation, as was VIP. Although many more experiments are required to prove a physiological significance for the results that we have obtained, and to examine the whole gamut of neurotransmitters, we suggest that neuroendocrine regulation may play an important part in mucosal immunity.

Animals↗

Interleukin 4 in inflammatory bowel disease and mucosal immune reactivity.

BACKGROUND & AIMS: Interleukin (IL) 4 has immunoregulatory and anti-inflammatory activities, but little is known about IL-4 in the human gut. We investigated production of IL-4 by isolated lamina propria mononuclear cells (LPMCs) from normal and inflamed intestine and its capacity to modulate local immune responses. METHODS: IL-4 levels were measured by enzyme-linked immunosorbent assay in cultures of control and inflammatory bowel disease LPMCs, and the effect of IL-4 on LPMC proliferation and interaction with IL-2, IL-1 beta, lipopolysaccharide, bacterial antigens, superantigen, and antibodies to various T-cell receptors was investigated. RESULTS: Various stimuli induced LPMCs to produce IL-4, but inflammatory bowel disease cells expressed IL-4 messenger RNA and secreted protein in significantly lower amounts than control cells. IL-4 failed to stimulate proliferation by fresh LPMCs, but a vigorous dose-dependent response was observed after preactivation by phytohemagglutinin, IL-2, or IL-4. When added to fresh LPMCs, IL-4 inhibited IL-2-induced proliferation. IL-4 amplified proliferation to IL-1 beta, lipopolysaccharide, peptidoglycan-polysaccharide complexes, staphylococcus enterotoxin A, and antibodies to the CD3 and CD28 receptors but not to tetanus toxoid. CONCLUSIONS: Decreased production of IL-4 in inflammatory bowel disease may cause defective immunosuppressive and anti-inflammatory mechanisms and may contribute to disease pathogenesis. The ability of IL-4 to differentially modulate LPMC reactivity probably influences mucosal immune homeostasis.

Adolescent↗

The role of humoral mucosal immunity in the induction and maintenance of chronic airway infections.

The respiratory mucosa is protected primarily by a secretory immune system that is under complex and only partly understood immunoregulatory control. Secretory immunoglobulins (SIgA and SIgM) protect the mucosal surface by immune exclusion of antigens. However, the fact that most IgA produced in the respiratory tract belongs to the IgA1 subclass renders SIgA in this region susceptible to IgA-specific proteases produced by Haemophilus influenzae, Streptococcus pneumonia, and Neisseria meningitidis. Immunoglobulin G can also perform immune exclusion at respiratory surfaces but, like IgE, it reaches the secretions merely by passive diffusion. The phlogistic properties of antibodies belonging to these classes explain their potential involvement in maintaining mucosal inflammation. In patients with selective IgA deficiency, SIgA is lacking and is not regularly compensated for satisfactorily by SIgM. In such patients unexplained immunoregulatory mechanisms, perhaps involving the local microbiota, give rise to a large number of IgD-producing cells in the upper respiratory tract. Immunoglobulin D cannot act as a secretory antibody and might block the protective properties of IgG; this could explain why these patients are particularly prone to recurrent infections. Our observations show that there are large individual variations in the mucosal immune system with regard to humoral immunity in the upper respiratory tract.

Antibody Formation↗

Mucosal immunity and protection after intranasal immunization with recombinant adenovirus expressing herpes simplex virus glycoprotein B.

A recombinant adenovirus (Ad) expressing glycoprotein B (gB) of herpes simplex virus (HSV) type 1 (AdgB8) was evaluated as a mucosal vaccine candidate. When administered intranasally (inl) to C57B1/6 mice, AdgB8 induced levels of serum anti-HSV gB IgG antibodies similar to those of mice immunized intraperitoneally (ip), which neutralized both HSV-1 and -2. Mice immunized inl with AdgB8 produced secretory IgA specific for HSV gB, but mice immunized ip did not. Splenic anti-HSV cytotoxic T lymphocytes (CTL) were observed after inl and ip immunization; however, there was a time-dependent decrease in the anti-HSV CTL activity from spleens of inl immunized mice. Anti-HSV CTL were also present in the mediastinal lymph nodes after inl but not ip AdgB8 immunization. Furthermore, mice immunized inl with AdgB8 were protected against heterologous inl challenge with HSV-2, and this protection lasted longer than in ip-immunized mice. These results indicate that mucosal immunization with a recombinant adenovirus can induce mucosal and systemic immune responses and provide long-term protection from mucosally or sexually transmitted viruses.

Administration, Intranasal↗

Cytokine regulation of the mucosal immune system: in vivo stimulation by interferon-gamma of secretory component and immunoglobulin A in uterine secretions and proliferation of lymphocytes from spleen.

The secretory immune system in the female reproductive tract is known to be regulated by sex hormones and antigen. The purpose of the present study was to examine the control by interferon-gamma (IFN gamma) of the secretory component (SC), the polymeric immunoglobulin A (IgA) receptor, and IgA in uterine secretions and to determine whether IFN gamma influences the proliferation of spleen cells in response to mitogens. When measured by RIA, SC levels in uterine secretions were elevated when increasing doses of IFN gamma (1000-5000 U/uterus) were placed in the uterine lumen of ovariectomized rats. In contrast, IFN alpha-beta (5000 U/uterus) placed in the uterine lumen had no effect on uterine SC levels. To determine whether IgA movement increases in response to IFN gamma, animals were treated with estradiol to increase uterine tissue IgA levels without stimulating the accumulation of IgA or SC in uterine secretions. Under these conditions, intrauterine IFN gamma increased SC and IgA levels in uterine secretions, suggesting that in vivo IFN gamma stimulation of uterine SC increases the transport of IgA from tissue to lumen. Analysis of uterine tissues indicated that intrauterine IFN gamma had no apparent effect on epithelial cell morphology. In contrast, intraepithelial lymphocytes and polymorphonuclear leucocytes, which were sparse in control tissues, increased markedly with IFN gamma treatment. This increase was antagonized when estradiol was administered along with IFN gamma. In other studies, IFN gamma placed in the uterine lumen significantly increased spleen cell proliferation in response to Concanavalin-A, phytohaemagglutinin, and lipopolysaccharide mitogens relative to those in spleen cells from control animals. These studies demonstrate that in vivo treatment with IFN gamma stimulates the mucosal immune system in the female reproductive tract by increasing SC and IgA levels in the uterine lumen and promoting the infiltration of intraepithelial lymphocytes and polymorphonuclear leucocytes into uterine tissue. Further, it suggests that antigen, in stimulating a local uterine response, may act through cytokines, particularly IFN gamma, to regulate the transport of IgA into uterine secretions as well as modulate lymphocyte proliferation at sites distal to the uterus.

Animals↗

Innate and adaptive mucosal immunity in protection against HIV infection.

Control of the HIV pandemic requires an effective vaccine. The difficulties in developing a preventive vaccine are generally believed to be due to the rapid rate of mutation of HIV that escapes cytotoxic lymphocytes (CTL) and the problems in induction of neutralising antibodies to wild strains of HIV. These difficulties should re-orientate vaccine strategy into four somewhat neglected areas of immunisation. Innate immunity, with its rapid protective response to infection that is independent of memory and relies on an optimal mucosal adjuvant. Targeting the genital and rectal mucosa, with the associated lymph nodes, as an immune response has to be elicited directly on encountering HIV during sexual intercourse. Stimulating a broadly based adaptive immune response that enhances the memory CD4(+) and CD8(+) T cells and B cells, induces maturation of dendritic cells and results in Th1 polarised immunity. Taking advantage of "experiments of nature", by utilising host antigens, as manifested by protection against HIV infection in homozygous Delta32 CCR5 individuals and in allo-immunity.

AIDS Vaccines↗

Impaired mucosal immune responses in interleukin 4-targeted mice.

Interleukin 4-targeted (IL-4-/-) mice are defective in T helper (Th)2 cytokine production as determined after nematode infection. As Th2 cells appear to be selectively induced by oral immunization we investigated the ability of IL-4-/- mice to respond to perorally administered antigen. We found that IL-4-/- mice failed to respond to soluble protein antigens given perorally together with cholera toxin (CT) as a mucosal adjuvant. In contrast to wild-type mice no or poor anti-keyhole limpet hemocyanin (KLH) or anti-ovalbumin (OVA) B cell responses were observed in gut lamina propria, spleen, or serum of IL-4-/- mice after oral immunization. In addition, mucosal immunization failed to stimulate antigen-specific T cell responses in these mice. The lack of responsiveness was specific for mucosal administration of antigen and was not seen after intravenous injections with antigen and CT-adjuvant. The systemic adjuvant effect of CT was not impaired in IL-4-/- mice as evidenced by the strong enhancement of anti-KLH responses after intravenous immunization with KLH plus CT as opposed to KLH alone. However, CT as an immunogen, in contrast to KLH or OVA, stimulated significant mucosal and systemic immune responses in IL-4-/- mice after oral immunization. Both serum and intestinal IgA anti-CT antibodies were demonstrable in IL-4-/- mice as well as in wild-type mice. Total IgA levels in gut lavage and in serum of immunized IL-4-/- mice were of similar magnitude as in wild-type mice, suggesting that the ability of naive B cells to undergo isotype switch-differentiation from IgM to IgA in IL-4-/- mice did not appear to be impaired. Immunohistochemical analysis of Peyer's patches demonstrated a complete inability to form germinal centers in IL-4-/- mice in contrast to wild-type mice. Our data suggest that IL-4-/- mice are unable to respond to oral/mucosal immunization due to a failure to stimulate antigen-specific cells required to induce germinal center reactions in the Peyer's patches. Our findings demonstrate that IL-4 and probably functional Th2 cells are required for induction of gut mucosal antibody responses.

Adjuvants, Immunologic↗

Mice immunized by primary vaginal Candida albicans infection develop acquired vaginal mucosal immunity.

It has been postulated that systemic cell-mediated immunity (CMI) is an important host defense mechanism against Candida infections of the vagina. However, in an estrogen-dependent murine model of experimental vaginal candidiasis, we recently showed that systemic Candida-specific Th1-type CMI induced by immunization with Candida culture filtrate antigen had no effect on vaginal Candida population levels during the course of a vaginal infection. In the present study, mice given a second vaginal inoculation in the presence of peripheral Candida-specific Th1-type CMI induced by prior vaginal infection had anamnestic-type increased delayed-type hypersensitivity (DTH) responses, concomitant with significantly fewer Candida organisms in the vagina than in primary-infected mice. In addition, organisms in secondary-infected mice were fragmented and superficial penetration into the epithelium was reduced. The systemic presence of Candida-specific T suppressor (Ts) cells that significantly suppressed the infection-derived anamnestic DTH reactivity did not abrogate the protective effect in the vagina. Additional experiments showed that vaginally immunized mice were not protected from gastrointestinal or systemic candidiasis and, in contrast to mice with a second vaginal infection, did not demonstrate anamnestic DTH reactivity. These results suggest that a moderate level of local protection against a Candida vaginal infection can be achieved by vaginal immunization but that the protective role of acquired peripheral Candida-specific Th1-type reactivity at the vaginal mucosa appears to be limited.

Animals↗

Regional accumulation of Pgp-1+ memory cells in senescent mucosal immune system.

The proportion of memory cells expressing the Pgp-1 surface marker, and subsets of T cells expressing L3T4 (CD4+ helper cells), Lyt-2 (CD8+ suppressor/cytotoxic cells), LFA-1 (lymphocyte function-associated antigen-1), and interleukin-2 receptors (IL-2R) on the cell surface in the spleen, regional lymph nodes (PLN), mesenteric LN (MLN), bronchial or mediastinal LN (BLN), Peyer's patches (PP), thymus, and bone marrow (BM) was studied in C57BL/6J mice of varying ages. Monoclonal antibodies (Mabs) IM7.8.1, FD4, GK1.5, 3.155, and FD441.8 were used to measure Pgp-1, IL-2R, L3T4 Lyt-2, and LFA-1 expressions, respectively. Optimal dose and kinetic studies were determined. The percentages of positive cells were determined by monoclonal antibody staining and flow cytometry or immunofluorescence microscopy. Using flow cytometric analysis, we found significant age-associated increases in the percentages of Pgp-1+ cells in the MLN as compared with a slight, but not significant, increase in the spleen. There were significant age-related increases in the percentages of Lyt-2+ cells in the spleen with no change in the MLN. The percentages of cells with the other phenotypic markers, L3T4, LFA-1, and IL-2R did not change with age in the spleen or MLN. Using immunofluorescence microscopy, the percentages of Thy-1.2+, Lyt-1+, and Lyt-2+ cells in different anatomical immune tissues did not change with age, except in the BLN and PP where there were significant age-related declines of the percentages of Thy-1.2+ and Lyt-2+ cells in the BLN, and of Lyt-1+ cells in the PP. These results indicate elevated levels of Pgp-1+ memory senescent cells in the MLN and these age-related shifts or changes in T lymphocyte subsets with age could contribute to the conserved immune responsiveness of senescent mucosal T lymphocytes.

Aging↗

Mucosal immune response to an HIV C4/V3 peptide following nasal or intestinal immunization of rabbits.

The HIV env-encoded synthetic peptide T1-SP10MN(A) contains immunodominant epitopes of the C4/V3 regions of gp120. The mucosal immunogenicity of this peptide in various vaccine preparations was first tested in rabbits using chronically isolated Thiry-Vella (T-V) ileal loops. Intestinal and serum samples collected from rabbits immunized via T-V loops demonstrated secretory IgA (S-IgA) and IgG anti-T1-SP10MN(A), respectively, when assayed by ELISA. Intranasal delivery of the peptide supplemented with cholera toxin (CT) resulted in serum IgG and S-IgA anti-T1-SP10MN(A) in vaginal and nasal secretions. This study further demonstrates the utility of rabbits as a convenient animal model for HIV vaccine research and the relationship between nasal immunization and vaginal immunity.

AIDS Vaccines↗

Intranasal inoculation of a recombinant influenza virus containing exogenous nucleotides in the NS segment induces mucosal immune response against the exogenous gene product in mice.

To establish a mucosal vaccine system, we evaluated the immunogenicity of a recombinant influenza virus, designated NS2Acat, in which the chloramphenicol acetyltransferase (CAT) reporter gene is fused in frame to the NS1 gene in the NS gene segment. The NS2Acat replicated slightly within the lungs in BALB/c mice after intranasal administration, accompanying expression of the CAT and the viral HA mRNA. NS2Acat induced delayed-type hypersensitivity (DTH) and sensitized the CAT-specific T lymphocytes in the regional lymph nodes, which proliferated and synthesized several cytokines in vitro upon antigenic challenge. These results suggest that NS2Acat is capable of eliciting a respiratory immune response against the fused gene product.

Administration, Intranasal↗

Eosinophilic gastroenteritis: a problem of the mucosal immune system?

The gastrointestinal immune system is a major component of the mucosal barrier, which provides an appropriate immunologic homeostasis between host and numerous foreign antigens, including microbial and dietary antigens. However, under certain pathological circumstances created by disturbance of the immunologic balance, allergic responses associated with the gastrointestinal tract can be triggered by abnormal immune responses against selected food protein antigens. Among the several types of immune competent cells, eosinophils are generally considered to play a central role for the development of allergic diseases in gastrointestinal tissue. Although most research has been focused on the molecular and cellular understanding of eosinophils in the peripheral tissues and lung, recent studies elucidate the unique trafficking and regulation mechanisms of eosinophils in the gastrointestinal tissues. In this review, we summarize current findings in the regulatory mechanism of gastrointestinal eosinophils. Furthermore, several unique murine models for eosinophilic gastroenteritis, which can be applied for the elucidation of underlying mechanisms of eosinophil-mediated gastrointestinal allergy, and the development of new mucosal immune therapy for the control of food allergy are reviewed.

Animals↗

Mucosal immunization with a genetically engineered pertussis toxin S1 fragment-cholera toxin subunit B chimeric protein.

A chimeric protein consisting of a divalent pertussis toxin (PT) S1 fragment linked to the cholera toxin (Ctx) A(2)B fragment was constructed. The chimera induced a mucosal immunoglobulin A (IgA) and a serum IgG immune response to PT and CtxB in BALB/c mice following intranasal immunization. The immune sera neutralized PT in vitro. In the mouse model of Bordetella pertussis respiratory infection, the chimera-immunized animals showed a significant reduction in bacterial lung counts (P = 0.01) from that of the sham control group. Thus, a divalent S1 fragment CtxA2B chimera is an immunogenic antigen and can elicit a protective immunity.

Administration, Intranasal↗

Human circulating specific antibody-forming cells after systemic and mucosal immunizations: differential homing commitments and cell surface differentiation markers.

Circulating spontaneous antibody-secreting cells (ASC) induced by mucosal and systemic immunizations in human volunteers have been characterized with respect to differentiation stage and homing commitments. Irrespective of the immunization route, the large majority of ASC co-expressed CD19 and HLA-DR, which are normally lost during the transition of plasmablasts to plasmocytes, as well as CD38, a marker of activated B cell blasts, expressed also by plasmocytes. However, these cells expressed neither CD28, a molecule acquired by plasmocytes, nor CD22 and CD37, which are lost during the transition of plasmablasts to plasmocytes. Therefore, the large majority of ASC found in peripheral blood after oral and parenteral immunizations are terminally differentiated B cells, but not fully differentiated plasmocytes. As a whole, the mucosally derived ASC population seemed to be more homogenously differentiated. CD25 was detected on few ASC, whereas ASC expressing CD71 were more numerous, especially among systemically derived ASC. Almost all ASC expressed the adhesion molecules CD44 and alpha 4-integrins, irrespective of immunization route. However, virtually all systemically derived ASC expressed L-selectin, recognizing the peripheral lymph node addressin, whereas only a minority of mucosally induced blood ASC expressed L-selectin. These studies are the first to demonstrate in humans that circulating precursors of mucosal B cell immunoblasts utilize organ-specific recognition mechanisms distinct from those of corresponding systemic B cells and appear to be more advanced in the B lineage maturation pathway. Specialization of receptor expression could explain both the unification of immune responses in diverse mucosal sites and the physiologic segregation of mucosal from non-mucosal immune mechanisms in humans.

Adult↗

Manipulating systemic and mucosal immune responses with skin-deliverable adjuvants.

Most medically important bacterial and viral pathogens gain entry into the body either via the skin or a mucosal surface. Vaccination provides a viable and cost-effective strategy for the prevention of such diseases and it has always been a principal aim with vaccinologists, to be able to promote simultaneously, protective immune responses both systemically and at mucosal surfaces. The paradigm that mucosal immunity is best stimulated by exposure to antigen via a mucosal route simply because inductive sites such as Peyer's patches and bronchial associated lymphoid tissues are located in the mucosal epithelium, has promoted a plethora of immunizing strategies aimed at delivering both antigen and adjuvant to mucosal surfaces. We have developed a novel adjuvant system capable of intradermal delivery of antigens complexed in an ISCOSOME delivery vehicle. This adjuvant, referred to as a skin and mucosal adjuvant or SAMA4, was efficacious in eliciting both systemic and mucosal IgG and IgA antibodies in sheep, pigs and mice. SAMA4 does not induce granulomatous lesions at the site of vaccine delivery and can be used to deliver adjuvanted antigens by other routes including intranasal, oral and intravaginal. Using ovalbumin as a test antigen, intradermally delivered ovalbumin-SAMA4 complexes was found to be very effective in promoting a cytotoxic T cell response. Attempts to dissect the mode of action of SAMA4 by flow cytometric analysis of lymphocyte populations from the spleen, lung, liver and thymus revealed an effect of route of vaccine delivery upon the composition of specific lymphocyte subsets in these various organ compartments. From this, it can be inferred that SAMA4 induced a route-dependent re-mobilization and alteration in lymphocyte trafficking patterns. Other mucosal adjuvants such as cholera toxin B and microspheres, when injected intradermally, tended to promote primarily, an IgG and not an IgA response against hte carrier antigen.

Animals↗

Systemic and mucosal immune responses of pigs to parenteral immunization with a pepsin-digested Serpulina hyodysenteriae bacterin.

Serpulina hyodysenteriae infection of pigs, swine dysentery, causes a mucohemorrhagic diarrhoea resulting in significant economic losses to swine producers. The pathogenesis of this disease is poorly understood. Regardless, commercial vaccines have been developed and are in use. Thus, the present study was designed to examine cellular immune responses induced by parenteral S. hyodysenteriae vaccination. Significant antigen-specific interferon-gamma (IFN-gamma) and blastogenic responses were detected from peripheral blood lymphocytes isolated from vaccinated pigs. However, poor IFN-gamma responses were detected from colonic lymph node lymphocytes from these same pigs despite significant antigen-specific blastogenic responses. In addition, peripheral blood IFN-gamma responses were diminished by either in vitro depletion of CD4 expressing cells or by in vitro treatment with porcine IL-10. Colonic lymph node IFN-gamma responses were not inhibited by treatment with porcine IL-10. Vaccination also resulted in increased percentages of both mucosal and peripheral blood CD8 single positive cells with concurrent decreases in percentages of CD4 single positive cells as compared to percentages of these same populations from non-vaccinated pigs. In conclusion, these studies show that parenteral S. hyodysenteriae vaccination results in cellular immune responses detectable both peripherally (systemic immunity) as well as at the site of infection (mucosal immunity). However, it appears that regulatory mechanisms affecting IFN-gamma production in response to S. hyodysenteriae antigen differ between peripheral and colonic compartments.

Animals↗

Gene expression and mucosal immune responses after vaginal DNA immunization in mice using a controlled delivery matrix.

IgA antibodies in the vaginal tract are essential as a first defense line against microorganisms that enter the body via mucosal surfaces. Several studies have shown that direct application of DNA to the vaginal mucosal surface can induce secretion of IgA molecules specific to the expressed protein. The major challenge of formulating effective vaccines is to overcome the barriers to DNA administration caused by the estrus cycle and physical environment of the vaginal tract. In this study, we investigated whether controlled delivery of DNA to the vaginal surface would induce long-term IgA antibody production by applying controlled delivery matrices to the vaginal tract. The controlled DNA delivery matrices were composed of poly(ethylene-co-vinyl acetate) (EVAc) and loaded with a model plasmid encoding sperm-specific lactate dehydrogenase C(4) (LDH-C(4)). These EVAc matrices provided a controlled and sustained DNA release to the vaginal mucosal surface. The DNA released from the EVAc disks was functionally active and capable of transfecting vaginal tissues. When inserted into the vaginal tract of mice, the DNA-loaded EVAc matrices triggered the immune system and induced specific IgA to LDH-C(4) in the vaginal secretions. These results demonstrate that the EVAc disks are efficient and convenient vehicles for delivering DNA to the vaginal tract and providing long-term local immunity.

Administration, Intravaginal↗