Incorporation of cells into an ELISA system enhances antigen-driven lymphokine detection

Interferon-γ Response of Mycobacterium avium subsp. paratuberculosis Infected Goats to Recombinant and Synthetic Mycobacterial Antigens

Despite its potential for early diagnosis of Mycobacterium avium subsp. paratuberculosis (MAP) infection, the IFN-γ release assay is not used routinely, because of low specificity of the established crude antigen preparation Johnin (PPDj). Limited data are available assessing the potential of MAP-derived protein and lipopeptide antigens to replace PPDj in assays for goats, while cattle and sheep have been studied more extensively. Furthermore, MAP infection is claimed to interfere with the diagnosis of bovine tuberculosis when other crude antigen preparations (PPDb, PPDa) are applied. In this study, the diagnostic potential of MAP-derived recombinant protein antigens, synthetic MAP lipopentapeptides and of Mycobacterium bovis-specific peptide cocktails was assessed compared to crude mycobacterial antigen preparations in experimentally infected goats. Goats were inoculated with MAP, or Mycobacterium avium subsp. hominissuis (MAH) as surrogate for environmental mycobacteria, non-exposed animals served as controls. Mycobacterium avium Complex-specific antibody and PPDj-induced IFN-γ responses were monitored in vivo. Infection status was assessed by pathomorphological findings and bacteriological tissue culture at necropsy 1 year after inoculation. The IFN-γ response to 13 recombinant protein antigens of MAP, two synthetic MAP lipopentapeptides and three recombinant peptide cocktails of Mycobacterium bovis was investigated at three defined time points after infection. At necropsy, MAP or MAH infection was confirmed in all inoculated goats, no signs of infection were found in the controls. Antibody formation was first detected 3-6 weeks post infection (wpi) in MAH-inoculated and 11-14 wpi in the MAP-inoculated goats. Maximum PPDj-induced IFN-γ levels in MAH and MAP exposed animals were recorded 3-6 and 23-26 wpi, respectively. Positive responses continued with large individual variation. Antigens Map 0210c, Map 1693c, Map 2020, Map 3651cT(it), and Map 3651c stimulated increased whole blood IFN-γ levels in several MAP-inoculated goats compared to MAH inoculated and control animals. These IFN-γ levels correlated with the intensity of the PPDj-induced responses. The two synthetic lipopentapeptides and the other MAP-derived protein antigens had no discriminatory potential. Stimulation with Mycobacterium bovis peptide cocktails ESAT6-CFP10, Rv3020c, and Rv3615c did not elicit IFN-γ production. Further work is required to investigate if test sensitivity will increase when mixtures of the MAP-derived protein antigens are applied.

Induction of IL-10 cytokine and the suppression of T cell proliferation by specific peptides from red cell band 3 and in vivo effects of these peptides on autoimmune hemolytic anemia in NZB mice

PURPOSE

The anion channel protein band 3 is the main target of the pathogenic red blood cells (RBC) autoantibodies in New Zealand black (NZB) mice. CD4 T cells from NZB mice with autoimmune hemolytic anemia respond to band 3. Previously, we have shown that IL-10 and peptides containing a dominant T cell epitope from red cell band 3 modulate autoimmune hemolytic anemia in NZB mice. Because of the immunoregulatory role of IL-10 in autoimmune diseases, we aim to identify individual band 3 peptides that induce high IL-10 production and simultaneously suppress CD4 T cell proliferation and to investigate the effect intranasal administration of IL-10 producing band 3 peptides on autoantibody responses of NZB mice.

METHODS

Splenic CD4 T cells of NZB mice were isolated and stimulated by co-culture of T cells with individual band 3 peptides. IL-10 production was measured by enzyme-linked immunosorbent assay and proliferative response of CD4 T cells was estimated by incorporation of [³H] thymidine assay. NZB mice were given either PBS, or peptides 25 (241-251) and 29 (282-296) or both peptides intranasally on three occasions at 2-day intervals. The mice were bled at 6, 10 and 18 weeks after peptide inhalation, and the number of RBC auto-antibodies was measured by DELAT and hematocrit values were assessed.

RESULTS

Peptides 25 (241-251) and 29 (282-296) induced the highest IL-10 production by CD4 T cells. These peptides also inhibited the peak T cell proliferative response. 6 and 10 weeks after peptide inhalation, the total IgG, IgG1 and IgG2a in mice treated with both peptides 241-251 and 282-296 were significantly higher than control (P < 0.05). However, no significant difference in the mean hematocrit between of the peptide-treated mice and the control group was found.

CONCLUSIONS

Although band 3 peptides 241-251 and 282-296 induced to the highest IL-10 production by CD4 T cells in vitro but fail to reverse the RBC autoantibody response in vivo. Modifications to improve solubility these peptides might help to modulate the immune response toward a T helper-2 profile and decrease the severity of anemia.

Systemic gene transfer of binding immunoglobulin protein (BiP) prevents disease progression in murine collagen-induced arthritis

Summary Recombinant human binding immunoglobulin protein (BiP) has previously demonstrated anti-inflammatory properties in multiple models of inflammatory arthritis. We investigated whether these immunoregulatory properties could be exploited using gene therapy techniques. A single intraperitoneal injection of lentiviral vector containing the murine BiP (Lenti-mBiP) or green fluorescent protein (Lenti-GFP) transgene was administered in low- or high-dose studies during early arthritis. Disease activity was assessed by visual scoring, histology, serum cytokine and antibody production measured by cell enzyme-linked immunosorbent assay (ELISA) and ELISA, respectively. Lentiviral vector treatment caused significant induction of interferon (IFN)-γ responses regardless of the transgene; however, further specific effects were directly attributable to the BiP transgene. In both studies Lenti-mBiP suppressed clinical arthritis significantly. Histological examination showed that low-dose Lenti-mBiP suppressed inflammatory cell infiltration, cartilage destruction and significantly reduced pathogenic anti-type II collagen (CII) antibodies. Lenti-mBiP treatment caused significant up-regulation of soluble cytotoxic T lymphocyte antigen-4 (sCTLA-4) serum levels and down-regulation of interleukin (IL)-17A production in response to CII cell restimulation. In-vitro studies confirmed that Lenti-mBiP spleen cells could significantly suppress the release of IL-17A from CII primed responder cells following CII restimulation in vitro, and this suppression was associated with increased IL-10 production. Neutralization of CTLA-4 in further co-culture experiments demonstrated inverse regulation of IL-17A production. In conclusion, these data demonstrate proof of principle for the therapeutic potential of systemic lentiviral vector delivery of the BiP transgene leading to immunoregulation of arthritis by induction of soluble CTLA-4 and suppression of IL-17A production.

Murine mast cells secrete and respond to interleukin-33

Interleukin-33 (IL-33) appears to play a crucial role in the expression of allergic diseases, but its cellular source and regulatory mechanisms remain to be fully elucidated. Mast cells, one of the major effecter cell populations in mediating allergy, express high levels of IL-33 receptor, ST2, and have been shown to express IL-33 transcripts. In this study, we aimed to examine the secretion of IL-33 in mast cells and their response to IL-33. We have successfully detected secreted IL-33 from cell supernatants through a modified enzyme-linked immunosorbent assay (ELISA) technique-cell-based ELISA. Activation of bone marrow-derived cultured mast cells (BMMCs) by crosslinkage of an antigen [ovalbumin (OVA)] and OVA-specific IgE mAbs significantly induced the expression of IL-33 transcripts, cytosolic and secreted proteins. In addition, the Toll-like receptor (TLR) 2 and TLR-9 ligands could trigger IL-33 mRNA expression. Exposure of BMMCs to IL-33 significantly increased the levels of IL-13 and IL-6 expression, concomitant with enhanced activation of mitogen-activated protein kinase (MAPKs) (ERK, p38, and JNK) and nuclear factor-kappa B. These results suggest that mouse BMMCs are capable of producing and serving as endogenous sources of IL-33, and that IL-33 plays an important role in regulating mast cell functions.

Complex effects of vitamin E and vitamin C supplementation on in vitro neonatal mononuclear cell responses to allergens

Low maternal dietary vitamin E (but not vitamin C) intake during pregnancy has been associated with increased in vitro cord blood mononuclear cell (CBMC) proliferative responses, childhood wheezing and asthma. We investigated whether these associations reflect direct effects of vitamin E by investigating the effects of supplementing CBMC cultures with physiological concentrations of vitamin E. CBMC from seventy neonates were cultured supplemented with either nothing, α-tocopherol or ascorbic acid. Proliferative, IFN-γ, IL-4, IL-10 and TGF-β responses were measured. In general, vitamin E supplementation was associated with a trend for reduced proliferative responses after stimulation with antigens and house dust mite, and with increased proliferation after stimulation with timothy grass allergen. There was a trend for CBMC cultures to exhibit decreased secretion of IFN-γ, IL-10 and IL-4. Supplementation with vitamin C had no effect on CBMC proliferation, but increased IFN-γ and IL-4 production, and decreased IL-10 production. In conclusion, in vitro vitamin E and C supplementation of CBMC modifies neonatal immune function, but not in a manner predicted by observational epidemiological studies. The observed associations between vitamin E and childhood respiratory disease are complex, and the nature and form of nutritional intervention need to be carefully considered before inclusion in trials.

Indoleamine 2,3 dioxygenase contributes to transferable tolerance in rat red blood cell inducible model of experimental autoimmune haemolytic anaemia

Autoimmune haemolytic anaemia (AIHA) is caused by autoantibodies against red blood cell (RBC) surface antigens that render RBC susceptible to Fc-mediated phagocytosis and complement-mediated lysis. Experimental AIHA can be induced by injection of rat RBC to naive mice, but a lymphocyte-mediated regulatory mechanism eventually suppresses the production of autoantibodies specific for mouse RBC. Critically, this tolerogenic response can be transferred to naive mice by splenocytes from the rat RBC-immunized mouse. Here we investigate whether indoleamine 2,3 dioxygenase (IDO) or the initiators of IDO cascade, including the cytotoxic T lymphocyte antigen (CTLA)-4 receptor and its soluble isoform, contribute to this tolerogenic mechanism. Splenocytes from experimental AIHA mice were transferred adoptively to naive mice under the cover of anti-CTLA-4, anti-soluble CTLA-4 antibodies or IDO inhibitor 1-methyl tryptophan (1-MT). Recipient mice were immunized with rat RBC and levels of antibody against self-RBC and rat-RBC were monitored. Our results indicate that transfer of tolerance to naive recipients is dependent upon IDO-mediated immunosuppression, as mice receiving previously tolerized splenocytes under the cover of 1-MT were refractory to tolerance and developed haemolytic disease upon further challenge with rat RBC. Initiators of IDO activity, CTLA-4 or soluble CTLA-4 did not mediate this tolerogenic process but, on their blockade, boosted antigen-specific effector immune responses.

Opa+ and Opa- isolates of Neisseria meningitidis and Neisseria gonorrhoeae induce sustained proliferative responses in human CD4+ T cells

T cells may interact with a number of bacterial surface antigens, an encounter which has the potential to downmodulate host immune responses. Neisseria meningitidis, a human colonizer and an agent of septicemia and meningitis, expresses Opa proteins which interact with the CEACAM1 receptor expressed on activated T cells. Since CEACAM1 can act as an inhibitory receptor and T cells in subepithelial tissues may encounter whole bacteria, which often express Opa proteins in vivo, this study assessed primarily if Opa proteins expressed on meningococci affect T-cell functions. In addition, Opa-containing outer membrane vesicles (OMV) have been used as vaccine antigens, and therefore Opa+ and Opa- OMV were also studied. While Opa+ bacteria adhered to CEACAM-expressing T cells, both the Opa+ and Opa- phenotypes induced no to a small transient depression, followed by a prolonged increase in proliferation as well as cytokine production. Such responses were also observed with heat-killed bacteria or OMV. In addition, while anti-CEACAM antibodies alone inhibited proliferation, on coincubation of T cells with bacteria and the antibodies, bacterial effects predominated and were Opa independent. Thus, while Opa proteins of N. meningitidis can bind to T-cell-expressed CEACAM1, this is not sufficient to overcome the T-cell recognition of bacterial factors, which results in a proliferative and cytokine response, an observation consistent with the ability of the host to establish lasting immunity to Opa-expressing meningococci that it frequently encounters. The data also imply that Opa-proficient vaccine preparations may not necessarily inhibit T-cell functions via CEACAM1 binding.

Systemic administration of tolerogenic dendritic cells ameliorates murine inflammatory arthritis

The expression of various cell surface molecules and the production of certain cytokines are important mechanisms by which dendritic cells (DC) are able to bias immune responses. This paper describes the effects of the inflammatory cytokine tumor necrosis factor (TNF)-α on DC phenotype and function. TNF-α treatment resulted in upregulation of MHC class II and CD86 in the absence of increased cell surface CD40 and CD80 or the production of IL-12. Additionally TNF-α treated cells were able to bias T cell responses towards an anti-inflammatory profile. On a note of caution this tolerogenic phenotype of the DC was not stable upon subsequent TLR-4 ligation as a 4 hour pulse of the TNF-α treated DC with lipopolysaccharide (LPS) resulted in the restoration of IL-12 production and an enhancement of their T cell stimulatory capacity which resulted in an increased IFN-γ production. However, TNF-α treated DC, when administered in vivo, were shown to ameliorate disease in collagen induced arthritis, an experimental model of inflammatory joint disease. Mice receiving TNF-α treated DC but not LPS matured DC had a delayed onset, and significantly reduced severity, of arthritis. Disease suppression was associated with reduced levels of collagen specific IgG2a and decreased inflammatory cell infiltration into affected joints. In summary the treatment of DC with TNF-α generates an antigen presenting cell with a phenotype that can reduce the pro-inflammatory response and direct the immune system towards a disease modifying, anti-inflammatory state.

Human eosinophils constitutively express multiple Th1, Th2, and immunoregulatory cytokines that are secreted rapidly and differentially

Eosinophils are innate immune leukocytes implicated in the initiation and maintenance of type 2 immune responses, including asthma and allergy. The ability to store and rapidly secrete preformed cytokines distinguishes eosinophils from most lymphocytes, which must synthesize cytokine proteins prior to secretion and may be a factor in the apparent Th2 bias of eosinophils. Multiple studies confirm that human eosinophils from atopic or hypereosinophilic donors can secrete over 30 cytokines with a varying and often opposing immune-polarizing potential. However, it remains unclear whether all of these cytokines are constitutively preformed and available for rapid secretion from eosinophils in the circulation of healthy individuals or are restricted to eosinophils from atopic donors. Likewise, the relative concentrations of cytokines stored within eosinophils have not been studied. Here, we demonstrate that human blood eosinophils are not singularly outfitted with Th2-associated cytokines but rather, constitutively store a cache of cytokines with nominal Th1, Th2, and regulatory capacities, including IL-4, IL-13, IL-6, IL-10, IL-12, IFN-gamma, and TNF-alpha. We demonstrate further rapid and differential release of each cytokine in response to specific stimuli. As agonists, strong Th1 and inflammatory cytokines elicited release of Th2-promoting IL-4 but not Th1-inducing IL-12. Moreover, a large quantity of IFN-gamma was secreted in response to Th1, Th2, and inflammatory stimuli. Delineations of the multifarious nature of preformed eosinophil cytokines and the varied stimulus-dependent profiles of rapid cytokine secretion provide insights into the functions of human eosinophils in mediating inflammation and initiation of specific immunity.

Mechanisms of T-lymphocyte accumulation during experimental pleural infection induced by Mycobacterium bovis BCG

Tuberculous pleurisy is a frequent extrapulmonary manifestation characterized by accumulation of fluid and inflammatory cells in the pleural space. Here, we investigated the mechanisms of T-lymphocyte accumulation in the pleural space by using a murine model of pleurisy induced by Mycobacterium bovis BCG. Intrathoracic (i.t.) injection of BCG (4.5 x 10(5) bacteria/cavity) induced accumulation of T lymphocytes in the pleural cavities of C57BL/6 mice. We observed the presence of CFU in pleural washes conducted 1, 2, 3, 7, and 15 days after pleurisy induction. Pretreatment with fucoidan inhibited T-lymphocyte accumulation at 1 day, but not at 15 days, after BCG-induced pleurisy. Accordingly, adoptive transfer of fluorescein isothiocyanate-labeled blood mononuclear cells to infected mice showed that T lymphocytes migrated into the pleural cavity 1 day (but not 15 days) after BCG injection. Cell-free pleural wash fluids recovered from mice 1 day after BCG i.t. stimulation (day 1 BCG-PW), but not day 7 or day 15 BCG-PW, induced in vitro T-cell transmigration, which was dependent on L-, P-, and E-selectins. In contrast, day 7 BCG-PW (but not day 1 BCG-PW) induced in vitro T-lymphocyte proliferation via interleukin-2 (IL-2) and gamma interferon (IFN-gamma). Accordingly, in vivo IL-2 or IFN-gamma neutralization abolished T-lymphocyte accumulation 7 days after pleurisy induction. Our results demonstrate that pleural infection induced by BCG leads to T-lymphocyte accumulation in two waves. The acute phase depends on selectin-mediated migration, while the second wave of T-lymphocyte accumulation seems to depend on a local proliferation induced by cytokines produced in situ.

Distinct T cell recognition of naturally processed and cryptic epitopes within the immunodominant 35-55 region of myelin oligodendrocyte glycoprotein

We have assessed the complexity in T cell recognition of the immunodominant 35-55 region of myelin oligodendrocyte glycoprotein (MOG) in C57BL/6 mice. Immunization with the p35-55 peptide generated two types of T cell, recognizing either a cryptic, or a naturally-processed epitope. Clear differences in the recognition of residues within a core sequence of 40-48 were observed. The majority of the p35-55-reactive repertoire in vivo appeared responsive to the intact autoantigen, supporting the notion of a failure of central tolerance to this region of MOG. Our data also provide a basis for exploring the requirements for antigen processing of MOG.

Analysing the effect of novel therapies on cytokine expression in experimental arthritis

Type II collagen-induced arthritis (CIA) is an animal model of rheumatoid arthritis that has been used extensively to address questions of disease pathogenesis and to validate novel therapeutic targets. Susceptibility to CIA is strongly associated with major histocompatibility complex class II genes, and the development of arthritis is accompanied by a robust T- and B-cell response to type II collagen. The main pathological features of CIA include proliferative synovitis with infiltration of inflammatory cells, pannus formation, cartilage degradation, erosion of bone and fibrosis. Pro-inflammatory cytokines, such as tumour necrosis factor alpha and interleukin-1beta, are expressed in the arthritic joints in both murine CIA and human rheumatoid arthritis, and blockade of these molecules results in amelioration of disease. Hence, there is a great deal of interest in the development of small-molecular-weight inhibitors of pro-inflammatory cytokines. There is also interest in the development and testing of drugs with the capacity to modulate the immune pathways involved in driving the inflammatory response in arthritis. For these reasons, there is a need to monitor the effect of novel treatments on cytokine expression in vivo. In this review, we outline the various techniques used to detect cytokines in experimental arthritis and describe how these techniques have been used to quantify changes in cytokine expression following therapeutic intervention.

Treatment of murine collagen-induced arthritis by the stress protein BiP via interleukin-4-producing regulatory T cells: a novel function for an ancient protein

OBJECTIVE

Following the demonstration that the stress protein, BiP, prevented induction of collagen-induced arthritis (CIA) in HLA-DRB*0101+/+ (HLA-DR1+/+) mice, we investigated the immunotherapeutic ability of BiP to suppress disease during the active phase of CIA in HLA-DR1+/+ and DBA/1 mice.

METHODS

BiP was administered either subcutaneously or intravenously to DBA/1, HLA-DR1+/+, or interleukin-4 (IL-4)-knockout mice at the onset of arthritis. Immune cells were used in adoptive transfer studies or were restimulated in culture with BiP or type II collagen (CII). Proliferation and cytokine release were measured. In addition, serum anti-CII antibodies were measured by enzyme-linked immunosorbent assay. Disease progression was scored using a visual analog scale.

RESULTS

BiP was successful in suppressing established CIA in HLA-DR1+/+ and DBA/1 mice. Serum levels of anticollagen IgG antibodies were reduced in BiP-treated mice. T cells from BiP-immunized mice produced Th2 cytokines, in particular, IL-4. Treatment with BiP was also shown to increase the production of CII-specific IL-5, IL-10, and interferon-gamma at the termination of the study. Development of severe CIA was prevented by the intravenous transfer of BiP-specific cells at the time of CIA induction in HLA-DR1+/+ mice or by transferring BiP-specific cells to DBA/1 mice at the onset of disease. BiP failed to ameliorate the development of CIA in IL-4-/-, HLA-DR1+/+ mice.

CONCLUSION

These novel results show that BiP can suppress active CIA by the induction of regulatory cells that act predominantly via IL-4. Thus, BiP is a potential immunotherapeutic agent for the treatment of patients with rheumatoid arthritis.

Protection of non-obese diabetic mice from autoimmune diabetes by Escherichia coli heat-labile enterotoxin B subunit

Autoimmune diabetes in the non-obese diabetic (NOD) mouse is associated with development of inflammation around the islets at around 4-5 weeks of age, which may be prolonged until frank diabetes begins to occur around 12 weeks of age. Although many interventions can halt disease progression if administration coincides with the beginning of the anti-beta cell response, very few are able to prevent diabetes development once insulitis is established. Here we describe a strategy which blocks cellular infiltration of islets and prevents diabetes. Intranasal treatment with the B-subunit of Escherichia coli heat labile enterotoxin (EtxB), a protein that binds GM1 ganglioside (as well as GD1b, asialo-GM1 and lactosylceramide with lower affinities), protected NOD mice from developing diabetes in a receptor-binding dependent manner. Protection was associated with a significant reduction in the number of macrophages, CD4(+) T cells, B cells, major histocompatibility complex class II(+) cells infiltrating the islets. Despite this, treated mice showed increased number of interleukin-10(+) cells in the pancreas, and a decrease in both T helper 1 (Th1) and Th2 cytokine production in the pancreatic lymph node. Disease protection was also transferred with CD4(+) splenocytes from treated mice. Taken together, these results demonstrated that EtxB is a potent immune modulator capable of blocking diabetes.

Circumventing tolerance at the T cell or the antigen-presenting cell surface: Antibodies that ligate CD40 and OX40 have different effects

An adjuvant can be defined as an agent that non-specifically promotes the immune response to an accompanying antigen. Ligation of CD40 on the surface of the antigen-presenting cell leads to upregulation of OX40 ligand which, in turn, ligates OX40 on the activated T cell resulting in prolonged T cell proliferation/survival, boosting the immune response. Thus agonistic anti-CD40 and anti-OX40 might be viewed as "adjuvant antibodies" and have been shown in diverse experimental systems to either boost immune responses or prevent the establishment of immunological tolerance. Here we describe that both these antibodies are able to prevent the induction of tolerance induced using soluble peptide antigen. However, unlike lipopolysaccharide, they are not sufficient to convert tolerance to immunity (i.e. they are not true adjuvants in this system). Using mice that are prone to either Th1 or Th2 immunity under identical immunization conditions, we show that the effects of anti-OX40 are quantitative -- boosting whichever response is dominant. In contrast, anti-CD40 boosts Th1 immunity and converts a Th2 response to Th1. We conclude that, although these two antibodies seem to impact on the same molecular pathway of costimulation to prevent tolerance, their effects are qualitatively distinct and their use cannot be viewed as interchangeable.

The immunogenicity of a conformationally restricted peptide mimetic of meningococcal lipooligosaccharide

Life-threatening meningitis and septicaemia caused by Neisseria meningitidis are a public health priority, and their prevention by vaccination is a major objective. Meningococcal capsular polysaccharide-based vaccines are effective against the major invasive serogroups, except for serogroup B, the capsule of which mimics human polysaccharides and is poorly immunogenic. An alternative vaccine candidate that has the potential to offer cross-protection against antigenically diverse meningococci is the lipooligosaccharide (LOS). The structurally constrained peptide mimetic, C22, of a bactericidal antibody epitope within LOS was previously shown to elicit cross-reactive antibodies to meningococcal LOS when complexed to NeutrAvidintrade mark as a carrier protein. The immunogenicity of this antigen in H-2(d) (BALB/c) and H-2(k) (C3H/HeN) haplotype mice was further investigated. Anti-LOS immunoglobulin G (IgG) antibody titres increased with the vaccine dose and correlated with the anti-C22 peptide antibody titres in both haplotypes. Antigen-stimulated Th1/Th2 cytokine secretion by splenocytes and antibody isotypes indicated a Th2-type immune response with IgG1 antibodies and a low titre of IgG2b. There was no serum bactericidal activity observed against the meningococcus.

Immune modulation of collagen-induced arthritis by intranasal cytokine gene delivery: A model for the therapy of rheumatoid arthritis

OBJECTIVE

To develop a passively targeted, patient-compliant, intranasal interleukin-10 (IL-10) gene therapy delivery system and to investigate its therapeutic benefit in experimental collagen-induced arthritis, a model of rheumatoid arthritis.

METHODS

Arthritis was induced in DBA/1 mice and monitored following intranasal administration of an IL-10 plasmid (pG-IL-10) or the empty vector 2 days (days -2 and 19) prior to collagen injection (prophylactic group, as a single dose after collagen boost on day 21 (early therapy group, or as a single dose upon acquisition of a disease score of 3 (late therapy group. IL-10-induced alterations in cytokine secretion and proliferation by spleen and lymph node cells were assessed on days 31 and 65 and correlated with histologic changes and bone erosions assessed on day 65.

RESULTS

Intranasal delivery of pG-IL-10 significantly delayed arthritis onset and reduced disease severity in the prophylactic group and early therapy group, reduced cellular infiltration and bone loss in the early therapy group, and reduced T cell proliferation in response to collagen on days 31 and 65 in these two groups, with a significant reduction in tumor necrosis factor alpha production on day 65. Within the late therapy group, disease progression was arrested for the rest of the study. The intranasally administered pG-IL-10 targeted monocytes and macrophages and showed dissemination to inflamed joints and draining lymph nodes in vivo. Importantly, systemic levels of IL-10 (in serum) were transient (peaking on day 2) and undetectable by day 4.

CONCLUSION

Intranasal IL-10 gene delivery significantly reduces bone destruction, shows evidence of reducing joint inflammation, and may be mediated by high local levels of IL-10 produced by transfected monocytes trafficking to inflamed joints and draining lymph nodes.

A time-resolved fluorescence immunoassay (DELFIA) increases the sensitivity of antigen-driven cytokine detection

In an effort to improve the quantification of the low levels of cytokines released in response to antigenic stimulation of T cells, a sandwich dissociation-enhanced lanthanide fluoroimmunoassay (DELFIA) was developed and compared to a standard sandwich ELISA. The DELFIA enhanced the sensitivity of a mouse IL-2 assay 8- to 27-fold, and a human GM-CSF assay 10-fold, as compared to colorimetric ELISA. The increase in sensitivity allows for the use of lower sample volumes per well, and the ability to run more assays per supernatant sample. This sensitive, nonisotopic alternative to other cytokine detection methods will be useful for those researchers wanting to quantitate low levels of antigen-driven cytokine production.

Nasal delivery of antigen with the B subunit of Escherichia coli heat-labile enterotoxin augments antigen-specific T-cell clonal expansion and differentiation

Escherichia coli heat-labile enterotoxin has unique immunogenic and adjuvant properties when administered mucosally to mice. These properties have revealed the potential for its use in the development of mucosal vaccines, an area of increasing interest. However, the inherent toxicity mediated by the A subunit precludes its widespread use. This problem has led to attempts to dissociate toxicity from adjuvant function by use of the B subunit. The ability of the B subunit of E. coli heat-labile enterotoxin (EtxB) to enhance responses against antigens coadministered intranasally is demonstrated here with the use of the DO11.10 adoptive-transfer model, in which ovalbumin (OVA)-specific adoptively transferred T cells can be monitored directly by flow cytometry. Intranasal delivery of OVA with EtxB resulted in increased T-cell proliferative and systemic antibody responses against antigens. The increased Th2 cytokine production detected following in vitro restimulation of splenocyte and cervical lymph node (CLN) cells from the immunized mice correlated with increased OVA-specific immunoglobulin G1 antibody production. Flow cytometric analysis of T cells from mice early after immunization directly revealed the ability of EtxB to support antigen-specific clonal expansion and differentiation. Furthermore, while responses were first detected in the CLNs, they rapidly progressed to the spleen, where they were further sustained. Examination of CD69 expression on dividing cells supported the notion that activation induced by the presence of antigens is not sufficient to drive T-cell differentiation. Furthermore, a lack of CD25 expression on dividing cells suggested that EtxB-mediated T-cell clonal expansion may occur without a sustained requirement for interleukin 2.

A sensitive in situ ELISA for quantitative measurements of cytokines and antibodies secreted by culture lymphocytes

Cytokines are usually measured using ELISA and ELISPOT. We have developed an in situ ELISA by combining the advantages of the highly sensitive ELISPOT and the quantitative conventional ELISA techniques to measure cytokines and antibodies secreted by culture lymphocytes. In this assay, lymphocytes were cultured on ELISA plates pre-coated with either a special antigen or mAbs against IL-4, IFN-gamma. The caprtured lymphokines or immunoglobulins were subsequently measured by conventional ELISA procedures. As a comparison, a conventional ELISA was carried out in parallel. The in situ ELISA measured a 5-fold increase in antigen-stimulated IL-4 and IFN-gamma, compared to the conventional ELISA. It also rquired 10,000 times fewer lymphocytes to produce a detectable level of antigen-specific antibodies than the conventional ELISA. We conclude that the in situ ELISA is much more sensitive than a conventional ELISA and less costly and easier to perform than ELISPOT, providing a useful tool to quantitatively measure cell-secreted molecules.

Peptides containing a dominant T-cell epitope from red cell band 3 have in vivo immunomodulatory properties in NZB mice with autoimmune hemolytic anemia

The major target of the pathogenic red blood cell (RBC) autoantibodies in New Zealand black (NZB) mice is the anion channel protein band 3, and CD4+ T cells from NZB mice respond to band 3. Here, we demonstrate that a band 3 peptide 861-875, which is the predominant sequence recognized by NZB T cells in vitro, bears a dominant helper epitope able to modulate the autoimmune hemolyic anemia in vivo. The development of RBC-bound autoantibodies and anemia was accelerated in NZB mice injected with peptide 861-874, which is relatively insoluble, and inhalation of the peptide primed T cells for both peptide 861-874 and band 3 responses. By contrast, inhalation of a soluble analog (Glu861, Lys875) of peptide 861-874 deviated the autoimmune response toward a T helper-2 (Th2) profile, with marked increases in the ratio of interleukin-4 to interferon-gamma produced by splenic T cells responding in vitro to either peptide 861-874 or band 3. Moreover, in mice that had received such treatment, the proportion of RBC-bound immunoglobulin G (IgG) molecules that were of the Th2-associated IgG1 isotype was also increased, and anemia was less severe. It is concluded that NZB autoimmune hemolytic anemia is helper dependent and that nasal administration of different peptides containing the dominant T-cell epitope can have potentially detrimental or beneficial effects on the disease.

Absence of CD4+CD25+ regulatory T cells is associated with a loss of regulation leading to increased pathology in Helicobacter pylori-infected mice

Helicobacter pylori induces symptomatic chronic gastritis in a subpopulation of infected individuals. The mechanism(s) determining the development and severity of pathology leading to symptoms are not fully understood. In a mouse model of H. pylori infection we analysed the influence of immunoregulatory CD4+CD25+ T cells on H. pylori colonization and gastritis. Athymic C57BL/6 nu/nu mice were reconstituted with (a) lymph node (LN) cells (b) LN cells depleted of CD25+ T cells (CD25(-) LN) or (c) not reconstituted at all. Mice were then infected orally with 3 x 10(8)H. pylori SS1 bacteria. At 2 and 6 weeks after the inoculation there was a significant (P < 0.001) reduction in H. pylori colonization in athymic mice transferred with CD25(-) LN cells compared to mice transferred with LN cells. Colonization was still reduced at 12 weeks after inoculation. Mice transferred with CD25(-) LN cells showed an earlier onset and increased severity of gastritis as compared to mice receiving LN cells. Splenic cells isolated from mice receiving CD25(-) LN cells produced the highest level of IFN-gamma on stimulation with H. pylori antigens in vitro, had a higher H. pylori-specific DTH response and increased infiltration of CD4+ T cells and macrophages in the gastric mucosa. Athymic mice not transferred with T cells had persistent high H. pylori colonization and displayed a normal gastric epithelium without inflammatory cells. In conclusion, CD4+CD25+ cells reduce immunopathology in H. pylori infection, possibly by reducing the activation of IFN-gamma producing CD4+ T cells, even at the expense of a higher H. pylori load in the gastric mucosa.

Workshop report on some new ideas about the treatment of systemic lupus erythematosus

Our increased understanding of the pathogenesis of systemic lupus erythematosus is leading to new ideas about its therapy. In this session of the workshop the use of LJP 394 a B cell toleragen and the use of an anti-CD20 monoclonal antibody were discussed in some detail. Their rationale and early clinical results were reviewed; both have shown encouraging clinical and serological benefit. Definitive double-blind clinical trials are still, however, awaited. In addition, the intriguing notion of using a nasal instillation of a histone peptide was described and early work in an experimental model presented.

Enhanced tumour growth after DNA vaccination against human papilloma virus E7 oncoprotein: evidence for tumour-induced immune deviation

We have examined the induction of anti-tumour immunity in a murine model using a gene vaccine approach to deliver a well defined tumour antigen. The vaccines expressed the human papilloma virus type 16 (HPV 16) E7 oncoprotein, and protection was measured against HPV 16-expressing C3R tumour cell line in vivo. In control mice injected with saline, C3R cells initially formed tumours but then regressed completely. As expected, animals injected with a peptide that represents the D(b)-presented CTL epitope from E7 (RAHYNIVTF) were completely protected from tumour growth. Contrary to expectation, however, we consistently saw enhanced tumour growth, delayed regression, or tumour outgrowth in mice vaccinated with two different E7-expressing DNA vaccines. We found no evidence for loss of D(b) or K(b) class I MHC molecules from C3R cells recovered from outgrown tumours, and fluorescent MHC/peptide tetramer staining revealed E7 gene vaccination did not delete RAHYNIVTF-specific CD8(+) T cells. However, we did observe an effect on cytokine production. Splenocytes from E7 gene vaccinated animals responded to re-stimulation in vitro with C3R cells by producing IL-4 but background levels of IFN-gamma. We also observed that cytokine production and E7 peptide-specific CTL were only detectable in vaccinated animals after C3R challenge, but not after DNA priming alone. We conclude that 'prime-boosting' is necessary to observe tumour-specific T cell responses with the gene vaccine approach, but that boosting with tumour cells causes skewing of the primed cells in a T2 direction that is incompatible with protective anti-tumour immunity.

Protection against recurrent ocular herpes simplex virus type 1 disease after therapeutic vaccination of latently infected mice

The potential of therapeutic vaccination of animals latently infected with herpes simplex virus type 1 (HSV-1) to enhance protective immunity to the virus and thereby reduce the incidence and severity of recurrent ocular disease was assessed in a mouse model. Mice latently infected with HSV-1 were vaccinated intranasally with a mixture of HSV-1 glycoproteins and recombinant Escherichia coli heat-labile enterotoxin B subunit (rEtxB) as an adjuvant. The systemic immune response induced was characterized by high levels of virus-specific immunoglobulin G1 (IgG1) in serum and very low levels of IgG2a. Mucosal immunity was demonstrated by high levels of IgA in eye and vaginal secretions. Proliferating T cells from lymph nodes of vaccinated animals produced higher levels of interleukin-10 (IL-10) than were produced by such cells from mock-vaccinated animals. This profile suggests that vaccination of latently infected mice modulates the Th1-dominated proinflammatory response usually induced upon infection. After reactivation of latent virus by UV irradiation, vaccinated mice showed reduced viral shedding in tears as well as a reduction in the incidence of recurrent herpetic corneal epithelial disease and stromal disease compared with mock-vaccinated mice. Moreover, vaccinated mice developing recurrent ocular disease showed less severe signs and a quicker recovery rate. Spread of virus to other areas close to the eye, such as the eyelid, was also significantly reduced. Encephalitis occurred in a small percentage (11%) of mock-vaccinated mice, but vaccinated animals were completely protected from such disease. The possible immune mechanisms involved in protection against recurrent ocular herpetic disease in therapeutically vaccinated animals are discussed.

Absence of CD4+CD25+ regulatory T cells is associated with a loss of regulation leading to increased pathology in Helicobacter pylori-infected mice

Helicobacter pylori induces symptomatic chronic gastritis in a subpopulation of infected individuals. The mechanism(s) determining the development and severity of pathology leading to symptoms are not fully understood. In a mouse model of H. pylori infection we analysed the influence of immunoregulatory CD4+CD25+ T cells on H. pylori colonization and gastritis. Athymic C57BL/6 nu/nu mice were reconstituted with (a) lymph node (LN) cells (b) LN cells depleted of CD25+ T cells (CD25(-) LN) or (c) not reconstituted at all. Mice were then infected orally with 3 x 10(8)H. pylori SS1 bacteria. At 2 and 6 weeks after the inoculation there was a significant (P < 0.001) reduction in H. pylori colonization in athymic mice transferred with CD25(-) LN cells compared to mice transferred with LN cells. Colonization was still reduced at 12 weeks after inoculation. Mice transferred with CD25(-) LN cells showed an earlier onset and increased severity of gastritis as compared to mice receiving LN cells. Splenic cells isolated from mice receiving CD25(-) LN cells produced the highest level of IFN-gamma on stimulation with H. pylori antigens in vitro, had a higher H. pylori-specific DTH response and increased infiltration of CD4+ T cells and macrophages in the gastric mucosa. Athymic mice not transferred with T cells had persistent high H. pylori colonization and displayed a normal gastric epithelium without inflammatory cells. In conclusion, CD4+CD25+ cells reduce immunopathology in H. pylori infection, possibly by reducing the activation of IFN-gamma producing CD4+ T cells, even at the expense of a higher H. pylori load in the gastric mucosa.

Immune responses against SIV envelope glycoprotein, using recombinant SV40 as a vaccine delivery vector

Vaccination protocols using viral gene delivery vectors have often generated relatively weak responses, largely owing to difficulties in boosting immune responses effectively following the primary injection. Because recombinant gene delivery vectors derived from SV40 permit multiple inoculations, to yield incremental immune responses, we tested the use of rSV40s to deliver lentiviral envelope antigens for immunization. An rSV40 carrying SIVmac239 envelope glycoprotein gp130 cDNA (SV(gp130)) was given multiple times to BALB/c mice, with or without a prior priming inoculation using vaccinia virus carrying the same SIV envelope cDNA (VVenvSIV). Sera from these mice were tested for antibodies binding gp130, applying a novel cell-based ELISA protocol that used as targets cloned P815 cells stably transfected with plasmid-derived gp130 cDNA. The same gp130-expressing clone of P815 cells, labeled with 51Cr was used as targets for direct lymphocyte-mediated cytolytic assays using spleen and popliteal lymph node cells as effectors. After six inoculations with SV(gp130), mice made detectable anti-gp130 antibody responses, but high levels of splenic and popliteal lymph node cytotoxic activity were apparent after as few as three injections of SV(gp130) (>40% specific lysis). A single primary inoculation with VVenvSIV preceding SV(gp130) boosts significantly enhanced antibody responses against SIV gp130, but had little effect on cytotoxic lymphocyte responses. Thus, rSV40 vectors may be useful vehicles for delivering lentiviral envelope antigens to elicit protective humoral and cell-mediated immune responses.

Cholera toxin and its B subunit promote dendritic cell vaccination with different influences on Th1 and Th2 development

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-1beta 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.

B cells regulate autoimmunity by provision of IL-10

To assess the importance of B cell control of T cell differentiation, we analyzed the course of the T helper type 1 (T(H)1)-driven disease experimental autoimmune encephalomyelitis in mice with an altered B cell compartment. We found that recovery was dependent on the presence of autoantigen-reactive B cells. B cells from recovered mice produced interleukin 10 (IL-10) in response to autoantigen. With a bone marrow chimeric system, we generated mice in which IL-10 deficiency was restricted to B cells but not T cells. In the absence of IL-10 production by B cells, the pro-inflammatory type 1 immune response persisted and mice did not recover. These data show that B cell-derived IL-10 plays a key role in controlling autoimmunity.

Histone peptide-induced nasal tolerance: suppression of murine lupus

Induced mucosal tolerance has been shown to be beneficial in preventing or treating a number of murine and human autoimmune disorders. However, this particular form of therapy has not been thoroughly tested in systemic lupus erythematosus. In this study, we investigated the conditions for induction of nasal tolerance using a histone peptide named H471 expressing a dominant T cell epitope in the histone protein H4 of mononucleosome in lupus-prone SNF(1) female mice. We also tested the effect of chronic peptide nasal treatment on the development of autoimmune reactivities in these mice. Results demonstrated that a dose-dependent nasal tolerance to peptide H471 can be achieved before or after peptide sensitization in SNF(1) mice. In addition, tolerance to mononucleosomes was induced by nasal instillation of SNF(1) mice with H471. This was accompanied by an increase in IL-10 and suppression of IFN-gamma production by lymph node cells. Suppression of Th1-type cytokines was also observed in SNF(1) mice that were nasally administered with H471 before intradermal injection with the peptide. Finally, chronic nasal instillation of mice with the H471 peptide not only suppressed the development of autoantibodies, but also altered the severity of glomerulonephritis in lupus-prone SNF(1) mice.

Modulation of human monocytes by Escherichia coli heat-labile enterotoxin B-subunit; altered cytokine production and its functional consequences

In murine systems, the B subunit of Escherichia coli heat-labile enterotoxin (EtxB) is a potent immunomodulator capable of suppressing Th1-mediated autoimmune diseases. This results from its ability to bind cell surface receptors, principally GM1-ganglioside, and as a consequence down-regulate the pathological T helper type 1 (Th1) response. The capacity of EtxB to alter human T-cell responses has not been investigated. Here we show that EtxB, but not the receptor non-binding mutant EtxB (G33D), triggers the release of interleukin (IL)-10, IL-6 and tumour necrosis factor-alpha (TNF-alpha) by human monocytes. The production of IL-8, transforming growth factor-beta (TGF-beta) or IL-12 was not enhanced by EtxB. Indeed, EtxB was shown to inhibit IL-12 secretion in monocytes stimulated with interferon-gamma (IFN-gamma) and lipopolysaccharide (LPS) by an IL-10-independent mechanism. When EtxB-treated monocytes were used as antigen presenting cells in an allogeneic mixed lymphocyte reaction (MLR), IL-10 and IFN-gamma production were increased in comparison to levels seen in cultures stimulated with untreated monocytes; proliferation was unaltered. This modulation of the T-cell response was not only evident in the primary MLR triggered by EtxB-treated monocytes, but also upon restimulation of the responding T cells with fresh untreated monocytes; indicating that presentation by EtxB-treated monocytes leads to altered T-cell differentiation. Sorting experiments showed that IL-10 secreting T cells from the MLR cultures were strong suppressors of T-cell proliferation following their addition into a fresh primary MLR.

Escherichia coli heat-labile enterotoxin B subunit prevents autoimmune arthritis through induction of regulatory CD4+ T cells

OBJECTIVE

The receptor-binding B subunit of Escherichia coli heat-labile enterotoxin (EtxB) is a highly stable, nontoxic protein that is capable of modulating immune responses. This study was conducted to determine whether mucosal administration of EtxB can block collagen-induced arthritis (CIA) and to investigate the mechanisms involved.

METHODS

Clinical arthritis in DBA/1 mice was monitored following mucosal administration of EtxB on 4 occasions. The dependence of disease prevention on receptor binding by EtxB and the associated alterations to the immune response to type II collagen (CII) were assessed. Adoptive transfer experiments and lymph node cell cocultures were used to investigate the underlying mechanisms.

RESULTS

Both intranasal and intragastric delivery of EtxB were effective in preventing CIA; a 1-microg dose of EtxB was protective after intranasal administration. A non-receptor-binding mutant of EtxB failed to prevent disease. Intranasal EtxB lowered both the incidence and severity of arthritis when given either at the time of disease induction or 25 days later. EtxB markedly reduced levels of anti-CII IgG2a antibodies and interferon-gamma (IFNgamma) production while not affecting levels of IgG1, interleukin-4 (IL-4), or IL-10. Disease protection could be transferred by CD4+ T cells from treated mice, an effect that was abrogated upon depletion of the CD25+ population. In addition, CD4+CD25+ T cells from treated mice were able to suppress anti-CII IFNgamma production by CII-primed lymph node cells.

CONCLUSION

Mucosal administration of EtxB can be used to prevent or treat CIA. Modulation of the anti-CII immune response by EtxB is associated with a reduction in Th1 cell reactivity without a concomitant shift toward Th2. Instead, EtxB mediates its effects through enhancing the activity of a population of CD4+ regulatory T cells.

In vivo kinetics of the immunoglobulin E response to allergen: bystander effect of coimmunization and relationship with anaphylaxis

BACKGROUND

Murine models of hypersensitivity to allergens are useful tools for the evaluation of preclinical strategies to down-regulate the IgE response.

OBJECTIVE

To monitor the long-term kinetics of T and B cell responses to allergen as a function of allergen dosage and to investigate the effect of parallel immunization with a second antigen; to correlate B cell response with anaphylaxis.

METHODS

CBA/J mice were sensitized every other week by subcutaneous injections of phospholipase A2 (PLA2) and/or ovalbumin (OVA) adsorbed to alum. Specific antibody isotype responses, T cell proliferation, T cell cytokine production and anaphylaxis were assessed throughout the sensitization phase.

RESULTS

Low-dose immunization with PLA2 (0.1 microg) favoured a long-term, specific T helper (Th)2 response with high IgE and IL-4 production in contrast to high-dose PLA2 (10 microg) immunization, which biased the immune response towards a Th1 response with high IgG2a and low IL-4 production. Parallel immunization with an unrelated antigen (ovalbumin) had a significant bystander effect on the immunization with PLA2, which was also dose-dependent. Finally, although anaphylaxis as measured by rectal temperature drop was allergen-specific, it could be induced in the high- and low-dose immunization groups, and was not solely dependent on IgE levels.

CONCLUSION

Though low-dose allergen immunization appears to induce an efficient IgE response, the intensity and quality of this response may be modulated by bystander effects of parallel immunization and does not correlate strictly with anaphylaxis. This observation has relevance to the design of clinical immunotherapy protocols using murine model-based data.

Modeling the T-helper cell response in acute and chronic hepatitis B virus infection using T-cell receptor transgenic mice

Chronicity following hepatitis B virus (HBV) infection may be maintained by high levels of viral proteins circulating in the serum. To examine the characteristics of T cells capable of co-existing with the secreted hepatitis B e-antigen (HBeAg), T-cell receptor (TCR) transgenic (Tg) mice were produced. To insure that HBeAg-specific T cells would not be deleted in the presence of serum HBeAg, the TCR alpha and beta-chain genes used to produce the TCR-Tg mice were derived from T-cell hybridomas from HBeAg-Tg mice. A TCR-Tg lineage (11/4-12) was produced that possessed a high frequency (approximately 67%) of CD4(+) T cells that expressed a TCR-Tg specific for the HBeAg. As predicted, when 11/4-12 TCR-Tg mice were bred with HBeAg-Tg mice no deletion of the HBeAg-specific CD4(+) T cells occurred in the thymus or the spleen. Functional analysis of the TCR-Tg T cells revealed that the HBeAg-specific CD4(+) T cells escaped deletion in the thymus and periphery by virtue of low avidity. Regardless of their low avidity, HBeAg-specific TCR-Tg T cells could be activated by exogenous HBeAg as measured by cytokine production in vitro and T-helper cell function for anti-HBe antibody production in vitro and in vivo. Furthermore, activated TCR-Tg HBeAg-specific T cells polarized to the Th(1) subset were able to elicit liver injury when transferred into HBeAg or HBcAg-Tg recipients. Therefore, HBeAg-specific CD4(+) T cells that can survive deletion or anergy in the presence of circulating HBeAg nonetheless are capable of being activated and of mediating liver injury in vivo.

Nasal administration of Schistosoma mansoni egg antigen-cholera B subunit conjugate suppresses hepatic granuloma formation and reduces mortality in S. mansoni-infected mice

Granulomatous inflammation in schistosomiasis is a delayed-type hypersensitivity reaction mediated by CD4+ T cells specific for parasite egg antigens (Ags). In an attempt to control T-cell responses leading to excessive harmful inflammation and granuloma formation, especially in the liver, BALB/c mice were intranasally (i.n.) treated with soluble Schistosoma mansoni egg Ags (SEA) conjugated to cholera toxin B subunit (CTB), a mucosa-binding protein with demonstrated capacity to suppress inflammatory T-cell functions after mucosal administration. Treatment with CTB-SEA significantly conjugate a reduced liver granuloma formation in infected mice associated with decreased SEA specific Th1- and Th2-type immune responses by liver leukocytes. Importantly, treatment with CTB-SEA conjugate also significantly reduced the mortality in chronically infected mice. In S. mansoni-infected large-granuloma forming CBA mice, i.n. treatment with purified Sm-p40, the major egg antigen, conjugated to CTB likewise significantly inhibited hepatic egg granuloma formation. A reduction of SEA-driven lymphoproliferation and of interferon (IFN)-gamma, interleukin (IL)-4 and IL-5 production, together with an increase in transforming growth factor (TGF)-beta1 production, were observed in splenic cells from CTB-Sm-p40-treated SEA-sensitized mice, as well as in liver leukocytes from CTB-Sm-p40-treated schistosome-infected mice. These results indicate that mucosal administration of SEA or purified Sm-p40 antigen in conjunction with CTB is highly effective in curtailing immunopathologic manifestations of schistosomiasis in vivo in infected hosts.

Cholera toxin B subunit as a carrier molecule promotes antigen presentation and increases CD40 and CD86 expression on antigen-presenting cells

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.

Importance of dose of type II collagen in suppression of collagen-induced arthritis by nasal tolerance

OBJECTIVE

To determine the influence of the dose of collagen given nasally on the induction of specific mucosal tolerance in collagen-induced arthritis.

METHODS

The severity of clinical arthritis induced in DBA/1 mice was studied after the nasal administration (before disease induction) of 1 of 4 doses (across a 2-log range) of bovine type II collagen (CII). Parameters of immunity included lymphocyte proliferation and cytokine production in vitro in response to antigen stimulation, and the production of anticollagen IgG antibody subclasses.

RESULTS

The 3 highest doses (20, 80, and 320 microg) ameliorated disease severity, whereas the lowest dose (5 microg) aggravated disease. These findings correlated well with antigen-specific T cell proliferation and cytokine and antibody production. T cell proliferation was suppressed by the higher doses of CII, whereas the low dose enhanced T cell proliferation, indicating it primed the T cells. Suppression of T cell proliferation could be overcome by the addition of exogenous interleukin-2 (IL-2) to these cultures. Decreased T cell proliferation was associated with suppression of both Th1 (interferon-gamma [IFNgamma]) and Th2 (IL-4) cytokines and all the subclasses of anticollagen IgG in mice receiving 20, 80, or 320 microg of collagen. Overall, the highest dose of collagen (320 microg) was less effective at suppressing the immune response and disease than the 20-microg or 80-microg doses. There was an increased production of antibodies of all IgG isotypes, and of the Th1-associated cytokines IFNgamma and IL-2, in animals that had received the lowest dose of 5 microg collagen nasally.

CONCLUSION

Nasal administration of antigens is effective in inducing tolerance and reducing disease severity, but the effects are dose dependent. Low doses can prime the immune system and aggravate disease; high doses may not suppress disease. Suppression of the immune response, which correlates with suppression of disease, is not obviously associated with a type I to type II T cell switch, but rather with an overall suppression of both forms of T cell response, with a potential role for anergy of T cells in this process.

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.

Evidence for a role of ganglioside GM1 in antigen presentation: binding enhances presentation of Escherichia coli enterotoxin B subunit (EtxB) to CD4(+) T cells

Successful antigen presentation by antigen-presenting cells is governed by a number of factors including the efficiency of antigen capture by cell-surface receptors, targeting to compartments of antigen processing, surface expression of MHC II-peptide complexes and presence of co-stimulatory signals. Ganglioside GM1 is an important component of membrane glycosphingolipids, and has been implicated in cell differentiation, apoptosis and signal transduction pathways. Using the B subunit of Escherichia coli enterotoxin (EtxB), a potent immunogen that binds GM1 with high affinity, and a non-binding mutant of EtxB, EtxB(G33D), we demonstrate that GM1 is intimately involved in several aspects of antigen presentation. Thus, GM1-mediated presentation of EtxB by B cells and CD11c(+) dendritic cells (DC) significantly enhanced the proliferation and cytokine expression of EtxB-specific CD4(+) T cells. Investigation regarding potential mechanisms revealed that EtxB binding directly augments the expression of MHC class II on B cells, and fractionation of B cells demonstrated that EtxB binding to GM1 results in rapid internalization and targeting to class II-rich compartments. GM1-mediated uptake of antigens and access to class II compartments in B cells can be exploited to significantly enhance the presentation of ovalbumin-conjugated to EtxB. These results demonstrate that GM1 can play an important role in antigen presentation via the MHC II pathway.

Differential roles of B cells and IFN-gamma-secreting CD4(+) T cells in innate and adaptive immune control of genital herpes simplex virus type 2 infection in mice

The role of B, CD4(+) T and CD8(+) T cells in both primary genital infection with attenuated herpes simplex virus type 2 (HSV-2) and development of protective immunity to a later challenge with virulent HSV-2 using lymphocyte-deficient mice has been elucidated. Following primary inoculation with attenuated thymidine kinase-deficient (TK(-)) HSV-2, B cell-deficient (microMT) mice developed a local viraemia and transient genital inflammation, suggesting a role for B cells in the innate control of local infection and inflammation. Natural antibodies are implicated in this process, as passive transfer of normal serum into microMT mice significantly reduced HSV-2 TK(-) shedding in the vaginal lumen, although it did not affect subsequent inflammation. Protection against lethal HSV-2 challenge was noted in HSV-2-vaccinated wild-type, CD8(+) T cell-deficient and microMT mice and was characterized by strong virus-specific IFN-gamma responses in vitro and delayed type hypersensitivity (DTH) responses in vivo. In contrast, CD4(+) T cell-deficient (CD4(-/-)) mice had impaired HSV-2-specific IFN-gamma production and DTH responses and succumbed rapidly to genital HSV-2 challenge. However, protective responses to HSV-2 could be induced in HSV-2-vaccinated CD4(-/-) mice by treatment with recombinant IFN-gamma. Taken together, these results suggest that CD4(+) T cells secreting IFN-gamma are critical for immune protection against lethal genital HSV-2 re-infection, whereas B cells/natural antibodies have anti-viral and -inflammatory effects in the innate control of a primary infection.

Interaction of Bordetella pertussis with mast cells, modulation of cytokine secretion by pertussis toxin

Together with macrophages and dendritic cells, mast cells have recently been shown to interact with certain pathogenic bacteria and present microbial antigens to the immune system. We show here that Bordetella pertussis can adhere to and be phagocytosed by mast cells. In addition, mast cells are able to process and present B. pertussis antigens to T lymphocytes. Furthermore, exposure of mast cells to B. pertussis induced the release of the proinflammatory cytokines tumour necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6). The release of IL-6 was strongly reduced by pertussis toxin expressed by B. pertussis. The production of IL-10, but not that of IL-4, by mast cells was also inhibited by pertussis toxin. Depletion of mast cells in vivo resulted in significant reduction of early TNF-alpha production in bronchoalveolar lavage (BAL) fluids of B. pertussis-infected mice. These data suggest that mast cells may play a role in the induction of immune responses against B. pertussis through the release of cytokines, especially TNF-alpha.

Activity-dependent release of endogenous brain-derived neurotrophic factor from primary sensory neurons detected by ELISA in situ

To define activity-dependent release of endogenous brain-derived neurotrophic factor (BDNF), we developed an in vitro model using primary sensory neurons and a modified ELISA, termed ELISA in situ. Dissociate cultures of nodose-petrosal ganglion cells from newborn rats were grown in wells precoated with anti-BDNF antibody to capture released BDNF, which was subsequently detected using conventional ELISA. Conventional ELISA alone was unable to detect any increase in BDNF concentration above control values following chronic depolarization with 40 mM KCl for 72 hr. However, ELISA in situ demonstrated a highly significant increase in BDNF release, from 65 pg/ml in control to 228 pg/ml in KCl-treated cultures. The efficacy of the in situ assay appears to be related primarily to rapid capture of released BDNF that prevents BDNF binding to the cultured cells. We therefore used this approach to compare BDNF release from cultures exposed for 30 min to either continuous depolarization with elevated KCl or patterned electrical field stimulation (50 biphasic rectangular pulses of 25 msec, at 20 Hz, every 5 sec). Short-term KCl depolarization was completely ineffective at evoking any detectable release of BDNF, whereas patterned electrical stimulation increased extracellular BDNF levels by 20-fold. In addition, the magnitude of BDNF release was dependent on stimulus pattern, with high-frequency bursts being most effective. These data indicate that the optimal stimulus profile for BDNF release resembles that of other neuroactive peptides. Moreover, our findings demonstrate that BDNF release can encode temporal features of presynaptic neuronal activity.

Protective mucosal immunity to ocular herpes simplex virus type 1 infection in mice by using Escherichia coli heat-labile enterotoxin B subunit as an adjuvant

The potential of nontoxic recombinant B subunits of cholera toxin (rCtxB) and its close relative Escherichia coli heat-labile enterotoxin (rEtxB) to act as mucosal adjuvants for intranasal immunization with herpes simplex virus type 1 (HSV-1) glycoproteins was assessed. Doses of 10 microg of rEtxB or above with 10 microg of HSV-1 glycoproteins elicited high serum and mucosal anti-HSV-1 titers comparable with that obtained using CtxB (10 microg) with a trace (0.5 microg) of whole toxin (Ctx-CtxB). By contrast, doses of rCtxB up to 100 microg elicited only meager anti-HSV-1 responses. As for Ctx-CtxB, rEtxB resulted in a Th2-biased immune response with high immunoglobulin G1 (IgG1)/IgG2a antibody ratios and production of interleukin 4 (IL-4) and IL-10 as well as gamma interferon by proliferating T cells. The protective efficacy of the immune response induced using rEtxB as an adjuvant was assessed following ocular challenge of immunized and mock-immunized mice. Epithelial disease was observed in both groups, but the immunized mice recovered by day 6 whereas mock-immunized mice developed more severe corneal disease leading to stromal keratitis. In addition, a significant reduction in the incidence of lid disease and zosteriform spread was observed in immunized animals and there was no encephalitis compared with 95% encephalitis in mock-immunized mice. The potential of such mucosal adjuvants for use in human vaccines against pathogens such as HSV-1 is discussed.

Functional characterization of a swine CD4(+)/CD8(+) double positive lymphoblastoid T-cell line with a CD25(+)/CD45RA(-) phenotype generated in vitro with interleukin-2

A dual expressing (CD4(+)/CD8(+)) porcine lymphoblastoid T-cell line (pIL-2d) generated from peripheral blood mononuclear (MN) cells shown to be highly responsive to exogenous interleukin-2 (IL-2) was characterized. The swine MN cells were initially stimulated with concanavalin A (Con A), and sub-passaged using decreasing amounts of conditioned medium (CM), which was prepared from culture fluids of Con A activated porcine MN cells, until a steady growth was observed. The resulting pIL-2d cells require exogenous IL-2 from CM and are highly responsive to recombinant human IL-2 (rhIL-2). The pIL-2d cells exhibited a specific, dose-dependent proliferative response to stimulation with IL-2. The specificity of this proliferative response was confirmed to be IL-2 induced by its inhibition with an anti-swine IL-2 receptor (alpha-swIL-2R) monoclonal antibody (mAb). Furthermore, the pIL-2d cells are highly responsive to exogenous IL-2 contained in culture fluids derived from antigen-driven blastogenic tests performed with lymphocytes of vaccinated swine. This property makes the pIL-2d cells an ideal functional adjunct to immunochemical or molecular tests that are commonly used to measure total porcine IL-2. Interestingly, the phenotype of the pIL-2d cells after five or more passages was shown by flow cytometric analysis to be CD4(+)/CD8(+)/CD45RA(-)/CD25(+) and to remain unchanged thereafter. Although, the mechanism of selection and maintenance of the CD4(+)/CD8(+) DP cells developed here remains unclear, our data suggest that an oligoclonal or polyclonal expansion and maintenance of cells of this phenotype was mediated by exogenous IL-2.

Evaluation of interleukin-4 concentration by ELISA is influenced by the consumption of IL-4 by cultured cells

The ability to accurately measure cytokine secretion by immune cells is critical to the evaluation of immune mechanisms in the context of Th1 and Th2 responses. In this study, we demonstrated that in vitro consumption of interleukin-4 (IL-4) by stimulated cells influences the concentration of IL-4 in the culture supernatant. In contrast, evaluation of IL-4-secreting cells by ELISPOT is not influenced by the consumption of IL-4 by cultured cells. These discrepancies influence the cytokine profile when responses are evaluated in relation to the secretion of other cytokines, for example, interferon-gamma (IFN-gamma). This information ultimately should enable investigators to evaluate immune responses accurately without concerns of bias resulting from in vitro consumption of IL-4, thus providing much more reliable interpretations of the type of immune response being evaluated.

Comparison of chemiluminescent assays and colorimetric ELISAs for quantification of murine IL-12, human IL-4 and murine IL-4: chemiluminescent substrates provide markedly enhanced sensitivity

Many available ELISAs lack the sensitivity required to reliably quantify levels of cytokines released in response to antigenic stimulation. In an effort to increase sensitivity of these assays, we compare the sensitivity of standard colorimetric ELISAs and corresponding chemiluminescent assays for three cytokines which are usually produced in very low quantities: mouse IL-12 p70, human IL-4 and mouse IL-4. Use of a chemiluminescent substrate enhanced the sensitivity of these assays 12-29-fold as compared to current colorimetric ELISAs. Accompanying this increase in sensitivity was an increase in dynamic range, a decrease in the time required to obtain maximum sensitivity and a decrease in the concentration of reagents required. These findings are of particular interest to those wanting to quantitate levels of any cytokine which is typically produced in low levels.

EliCell: a gel-phase dual antibody capture and detection assay to measure cytokine release from eosinophils

Eosinophils contain many preformed cytokines and chemokines, which are stored in specific granules along with cationic granule proteins. Mobilization and release of these granule contents can be selective and mediated by vesicular transport. We have developed a sensitive method to detect and quantitate eosinophil vesicular transport-mediated release of specific eosinophil proteins. Our EliCell assay is based on microscopic observations of individual viable eosinophils embedded in an agarose matrix that contains immobilized antibody to the protein of interest. Following stimulation of eosinophils, released protein is bound by the capture antibody at its site of release and is detected by a fluorochrome-conjugated detection antibody. We have validated this assay by evaluating interferon-gamma-induced release of RANTES from eosinophils. Extracellularly released RANTES was visualized as focal immunoflourescent staining and was quantitated by scoring the numbers of eosinophils releasing RANTES and by measuring the fluorescent intensity over individual eosinophils. In comparison with ELISA assays of RANTES released into supernatant fluids by interferon-gamma-stimulated eosinophils, EliCell assays were more sensitive enabling detection of RANTES release at earlier times and at lower levels of interferon-gamma stimulation. The EliCell assay provides a sensitive method to study the regulated release of eosinophil-derived cytokines, chemokines and other granule proteins.

Inducing tolerance by intranasal administration of long peptides in naive and primed CBA/J mice

To assess the capacity of a peptide-based immunotherapy to induce systemic tolerance via the nasal route, we designed three long overlapping peptides of 44-60 aa covering the entire sequence of phospholipase A2 (PLA2), a major bee venom allergen. Both prophylactic and therapeutic intranasal administrations of long peptides to PLA2-hypersensitive CBA/J mice induced specific T cell tolerance to the native allergen. In prophylactic conditions, this tolerance was marked by a suppression of subsequent specific IgE response, whereas the therapeutic approach in presensitized mice induced a more than 60% decrease in PLA2-specific IgE. This decline was associated with a shift in the cytokine response toward a Th1 profile, as demonstrated by decreased PLA2-specific IgG1 and enhanced IgG2a levels, and by a decline in the specific IL-4/IFN-gamma ratios. T cell transfer from long peptide-tolerized mice to naive animals abrogated the expected anti-PLA2 IgE and IgG1 Ab response, as well as specific T cell proliferation, but enhanced specific IgG2a response upon sensitization with PLA2. These events were strongly suggestive of a clonal anergy affecting more profoundly Th2 than the Th1 subsets. In conclusion, these results demonstrate that allergen-derived long peptides delivered via the nasal mucosa may offer an alternative to immunotherapy with native allergens without the inherent risk of systemic anaphylactic reactions. Moreover, long peptides, in contrast to immunotherapy strategies based on short peptides, have the advantage of covering all potential T cell epitopes, and may represent novel and safe tools for the therapy of allergic diseases.

Nondeletional T-cell receptor transgenic mice: model for the CD4(+) T-cell repertoire in chronic hepatitis B virus infection

Chronicity after infection with the hepatitis B virus (HBV) can occur for a variety of reasons. However, once established, chronicity may be maintained by high levels of viral proteins circulating in the serum. To examine the characteristics of T cells capable of coexisting with the secreted hepatitis B e antigen (HBeAg), T-cell receptor (TCR) transgenic (Tg) mice were produced. To ensure that HBeAg-specific T cells would not be deleted in the presence of serum HBeAg, the TCR alpha- and beta-chain genes used to produce the TCR-Tg mice were derived from T-cell hybridomas produced from immunizing HBeAg-Tg mice. A TCR-Tg lineage (11/4-12) was produced that possessed a high frequency ( approximately 67%) of CD4(+) T cells that expressed a Tg TCR specific for the HBeAg. As predicted, when 11/4-12 TCR-Tg mice were bred with HBeAg-Tg mice no deletion of the HBeAg-specific CD4(+) T cells occurred in the thymus or the spleen. Functional analysis of the TCR-Tg T cells revealed that the HBeAg-specific CD4(+) T cells escaped deletion in the thymus and periphery by virtue of low avidity. Regardless of their low avidity, HBeAg-specific TCR-Tg T cells could be activated by exogenous HBeAg, as measured by cytokine production in vitro and T-helper-cell function for anti-HBe antibody production in vitro and in vivo. Furthermore, activated TCR-Tg HBeAg-specific T cells polarized to the Th1 subset were able to elicit liver injury when transferred into HBeAg or HBcAg-Tg recipients. Therefore, HBeAg-specific CD4(+) T cells that can survive deletion or anergy in the presence of circulating HBeAg nonetheless are capable of being activated and of mediating liver injury in vivo. The 11/4-12 TCR-Tg lineage may serve as a monoclonal model for the HBe/HBcAg-specific CD4(+) T-cell repertoire present in chronically infected HBV patients.