Single-cytokine-producing CD4 memory cells predominate in type 1 and type 2 immunity

Development and Evaluation of an Immunoinformatics-Based Multi-Peptide Vaccine against Acinetobacter baumannii Infection

Multi-drug-resistant (MDR) Acinetobacter baumannii is an opportunistic pathogen associated with hospital-acquired infections. Due to its environmental persistence, virulence, and limited treatment options, this organism causes both increased patient mortality and incurred healthcare costs. Thus, prophylactic vaccination could be ideal for intervention against MDR Acinetobacter infection in susceptible populations. In this study, we employed immunoinformatics to identify peptides containing both putative B- and T-cell epitopes from proteins associated with A. baumannii pathogenesis. A novel Acinetobacter Multi-Epitope Vaccine (AMEV2) was constructed using an A. baumannii thioredoxin A (TrxA) leading protein sequence followed by five identified peptide antigens. Antisera from A. baumannii infected mice demonstrated reactivity to rAMEV2, and subcutaneous immunization of mice with rAMEV2 produced high antibody titer against the construct as well as peptide components. Immunization results in increased frequency of IL-4-secreting splenocytes indicative of a Th2 response. AMEV2-immunized mice were protected against intranasal challenge with a hypervirulent strain of A. baumannii and demonstrated reduced bacterial burden at 48 h. In contrast, all mock vaccinated mice succumbed to infection within 3 days. Results presented here provide insight into the effectiveness of immunoinformatic-based vaccine design and its potential as an effective strategy to combat the rise of MDR pathogens.

Reagent Tracker™ Platform Verifies and Provides Audit Trails for the Error-Free Implementation of T-Cell ImmunoSpot® Assays

ELISPOT and FluoroSpot assays, collectively called ImmunoSpot assays, permit to reliable detection of rare antigen-specific T cells in freshly isolated cell material, such as peripheral blood mononuclear cells (PBMC). Establishing their frequency within all PBMC permits to assess the magnitude of antigen-specific T-cell immunity; the simultaneous measurement of their cytokine signatures reveals these T-cells' lineage and effector functions, that is, the quality of T-cell-mediated immunity. Because of their unparalleled sensitivity, ease of implementation, robustness, and frugality in PBMC utilization, T-cell ImmunoSpot assays are increasingly becoming part of the standard immune monitoring repertoire. For regulated workflows, stringent audit trails of the data generated are a requirement. While this has been fully accomplished for the analysis of T-cell ImmunoSpot assay results, such are missing for the wet laboratory implementation of the actual test performed. Here we introduce a solution for enhancing and verifying the error-free implementation of T-cell ImmunoSpot assays.

Unbiased, High-Throughput Identification of T Cell Epitopes by ELISPOT

Recent systematic immune monitoring efforts suggest that, in humans, epitope recognition by T cells is far more complex than has been assumed based on minimalistic murine models. The increased complexity is due to the higher number of HLA loci in humans, the typical heterozygosity for these loci in the outbred population, and the high number of peptides that each HLA restriction element can bind with an affinity that suffices for antigen presentation. The sizable array of potential epitopes on any given antigen is due to each individual's unique HLA allele makeup. Of this individualized potential epitope space, chance events occurring in the course of the T cell response determine which epitopes induce dominant T cell expansions. Establishing the actually-engaged T cell repertoire in each human subject, including the individualized peptides targeted, therefore requires the systematic testing of all peptides that constitute the potential epitope space in that person. The goal of comprehensive, high-throughput epitope mapping can be readily established by the methods described in this chapter.

Natural T cell autoreactivity to melanoma antigens: clonally expanded melanoma-antigen specific CD8 + memory T cells can be detected in healthy humans

We used four-color ImmunoSpot® assays, in conjunction with peptide pools that cover the sequence of tyrosinase (Tyr), melanoma-associated antigen A3 (MAGE-A3), melanocyte antigen/melanoma antigen recognized by T cells 1 (Melan-A/MART-1), glycoprotein 100 (gp100), and New York esophageal squamous cell carcinoma-1 (NY-ESO-1) to characterize the melanoma antigen (MA)-specific CD8 + cell repertoire in PBMC of 40 healthy human donors (HD). Tyr triggered interferon gamma (IFN-γ)-secreting CD8 + T cells in 25% of HD within 24 h of antigen stimulation ex vivo. MAGE-A3, Melan-A/MART-1, and gp100 also induced recall responses in 10%, 7.5%, and 2.5% of HD, respectively. At this time point, these CD8 + T cells did not yet produce GzB (granzyme B). However, they engaged in GzB production after 72 h of antigen stimulation. By this 72-h time point, 57.5% of the HD responded to at least one, and typically several, of the MA. A closer characterization of the Tyr-specific CD8 + T cell repertoire indicated that it was low-affinity, and to primarily entail a stem cell-like subpopulation. Collectively, our data reveal pre-existing endogenous T cell immunity against melanoma antigens in healthy donors, and analogous to natural autoantibodies, we have termed this "natural T cell autoreactivity".

Multiplex ImmunoSpot® Assays for the Study of Functional B Cell Subpopulations

B cells mediate humoral immunity by producing antibody molecules, but they also participate in innate and acquired immune functions via the secretion of effector molecules such as cytokines, chemokines, and granzyme. B cell subpopulations releasing such effector molecules have been implicated in immunobiology and a number of diseases.Unlike antigen-specific T cells that can be identified by multimer staining, and then counter-stained to define T cell subpopulations, antigen-specific B cells cannot be detected by flow cytometry. Staining antigen-specific B cells with labeled antigen, in large, has been unsuccessful. Instead, antigen-specific B cells can be and are commonly studied by ELISPOT. In the ELISPOT approach, the B cell is identified via the antibody that it secretes being captured on a membrane by the antigen itself. Should it be feasible to measure simultaneously antibody production and the secretion of other secretory B cell products, it would then be possible to identify B cell subpopulations that co-express effector molecules. Here we introduce multiplex ELISPOT assays in which measurements of antibody secretion are combined with the detection of Granzyme B, IL-6, IL-10, IFN-γ, and TNF-α. Such multiplex assays will help define effector B cell subpopulations, as well as the understanding of their role in health and disease.

A novel dendritic cell-based direct ex vivo assay for detection and enumeration of circulating antigen-specific human T cells

Although a variety of assays have been used to examine T cell responses in vitro, standardized ex vivo detection of antigen-specific CD4⁺ T cells from human circulatory PBMCs remains constrained by low-dimensional characterization outputs and the need for polyclonal, mitogen-induced expansion methods to generate detectable response signals. To overcome these limitations, we developed a novel methodology utilizing antigen-pulsed autologous human dendritic target cells in a rapid and sensitive assay to accurately enumerate antigen-specific CD4⁺ T cell precursor frequency by multiparametric flow cytometry. With this approach, we demonstrate the ability to reproducibly quantitate poly-functional T cell responses following both primary and recall antigenic stimulation. Furthermore, this approach enables more comprehensive phenotypic profiling of circulating antigen-specific CD4⁺ T cells, providing valuable insights into the pre-existing polarization of antigen-specific T cells in humans. Combined, this approach permits sensitive and detailed ex vivo detection of antigen-specific CD4⁺ T cells delivering an important tool for advancing vaccine, immune-oncology and other therapeutic studies.

Four Color ImmunoSpot® Assays for Identification of Effector T-Cell Lineages

Single color IFN-γ ELISPOT assays have evolved as a highly sensitive T cell immune monitoring platform. By detecting individual T cells that secrete IFN-γ in response to antigen exposure, these assays permit the measurement of the frequency of antigen-specific T cells among white blood cells. These assays therefore are well suited to assess clonal expansions, that is, whether a (Th1) T cell response has been induced to an antigen in a test subject. Single color IFN-γ ELISPOT assays are not suited, however, to provide information on the Th2/Th17 quality of the T cell response, nor do they provide insights into the differentiation state of CD8 cells. Recently it has been established that co-expression profiles of IL-2, TNF-α, and granzyme B along with IFN-γ permit to identify CD8 cell subpopulations. Naïve CD8 cells, central CD8 memory cells, CD8 terminal effector cells, polyfunctional CD8 cells, stem-cell like CD8 memory cells, dysfunctional- and senescent CD8 cells all differ in the extent they produce these molecules upon antigen re-encounter. We therefore have developed, and introduce here, a four color T cell ELISPOT assay in which the co-expression levels of IFN-γ, IL-2, TNF-α, and granzyme B can be established for individual antigen-specific CD8 cells, thereby identifying the activation/differentiation state of these cells.

Delayed Activation Kinetics of Th2- and Th17 Cells Compared to Th1 Cells

During immune responses, different classes of T cells arise: Th1, Th2, and Th17. Mobilizing the right class plays a critical role in successful host defense and therefore defining the ratios of Th1/Th2/Th17 cells within the antigen-specific T cell repertoire is critical for immune monitoring purposes. Antigen-specific Th1, Th2, and Th17 cells can be detected by challenging peripheral blood mononuclear cells (PBMC) with antigen, and establishing the numbers of T cells producing the respective lead cytokine, IFN-γ and IL-2 for Th1 cells, IL-4 and IL-5 for Th2, and IL-17 for Th-17 cells, respectively. Traditionally, these cytokines are measured within 6 h in flow cytometry. We show here that 6 h of stimulation is sufficient to detect peptide-induced production of IFN-γ, but 24 h are required to reveal the full frequency of protein antigen-specific Th1 cells. Also the detection of IL-2 producing Th1 cells requires 24 h stimulation cultures. Measurements of IL-4 producing Th2 cells requires 48-h cultures and 96 h are required for frequency measurements of IL-5 and IL-17 secreting T cells. Therefore, accounting for the differential secretion kinetics of these cytokines is critical for the accurate determination of the frequencies and ratios of antigen-specific Th1, Th2, and Th17 cells.

Brief Report: CD14brightCD16- monocytes and sCD14 level negatively associate with CD4-memory T-cell frequency and predict HCV-decline on therapy

During HIV+ hepatitis C virus (HCV)+ coinfection CD14CD16 monocytes produce soluble immune-activation markers that predict disease progression and poor response to interferon (IFN)-α treatment. We evaluated relationships among immune activation, monocyte phenotype, CD4-memory T cells, and HCV-, cytomegalovirus-, and cytomegalovirus/Epstein-Barr virus/influenza-specific IFN-γ-response before and during IFN-α treatment. Effector-memory and central-memory CD4 T-cell frequencies were lower in HCV+ HIV+ donors than in uninfected donors and correlated negatively with HCV level, CD14CD16 monocytes, and plasma sCD14. sCD14 and CD14CD16 monocytes negatively correlated with IFN-α-dependent HCV decline. CD4 effector-memory T cells positively associated with cytomegalovirus/Epstein-Barr virus/influenza(CEF)-specific IFN-γ response, while sCD14 negatively associated with both CD4 effector-memory T cells and CEF-specific IFN-γ response. These data support a role for memory-CD4 T cells in HCV containment and link immune activation and CD14CD16-monocyte frequency to the failure of IFN-dependent HCV clearance.

Characterization of the HCMV-Specific CD4 T Cell Responses that Are Associated with Protective Immunity

Most humans become infected with human cytomegalovirus (HCMV). Typically, the immune system controls the infection, but the virus persists and can reactivate in states of immunodeficiency. While substantial information is available on the contribution of CD8 T cells and antibodies to anti-HCMV immunity, studies of the T_H1, T_H2, and T_H17 subsets have been limited by the low frequency of HCMV-specific CD4 T cells in peripheral blood mononuclear cell (PBMC). Using the enzyme-linked Immunospot^® assay (ELISPOT) that excels in low frequency measurements, we have established these in a sizable cohort of healthy HCMV controllers. Cytokine recall responses were seen in all seropositive donors. Specifically, interferon (IFN)-γ and/or interleukin (IL)-17 were seen in isolation or with IL-4 in all test subjects. IL-4 recall did not occur in isolation. While the ratios of T_H1, T_H2, and T_H17 cells exhibited substantial variations between different individuals these ratios and the frequencies were relatively stable when tested in samples drawn up to five years apart. IFN-γ and IL-2 co-expressing polyfunctional cells were seen in most subjects. Around half of the HCMV-specific CD4 cells were in a reversible state of exhaustion. The data provided here established the T_H1, T_H2, and T_H17 characteristic of the CD4 cells that convey immune protection for successful immune surveillance against which reactivity can be compared when the immune surveillance of HCMV fails.

Approaches for monitoring of non virus-specific and virus-specific T-cell response in solid organ transplantation and their clinical applications

Opportunistic viral infections are still a major complication following solid organ transplantation. Immune monitoring may allow the identification of patients at risk of infection and, eventually, the modulation of immunosuppressive strategies. Immune monitoring can be performed using virus-specific and non virus-specific assays. This article describes and summarizes the pros and cons of the different technical approaches. Among the assays based on non virus-specific antigens, the enumeration of T-cell subsets, the quantification of cytokines and chemokines and the quantification of intracellular adenosine triphosphate following mitogen stimulation are described and their clinical applications to determine the risk for viral infection are discussed. In addition, current specific methods available for monitoring viral-specific T-cell responses are summarized, such as peptide-MHC multimer staining, intracellular cytokine staining, enzyme-linked immunospot and virus-specific IFN-γ ELISA assays, and their clinical applications to determine the individual risk for opportunistic viral infections with human cytomegalovirus, Epstein-Barr virus and polyoma BK virus are discussed. The standardization of the procedure, the choice of the antigen(s) and the criteria to define cut-off values for positive responses are needed for some of these approaches before their implementation in the clinic. Nevertheless, immune monitoring combined with virological monitoring in transplant recipients is increasingly regarded as a helpful tool to identify patients at risk of infection as well as to assess treatment efficacy.

Potential recombinant vaccine against influenza A virus based on M2e displayed on nodaviral capsid nanoparticles

Influenza A virus poses a major threat to human health, causing outbreaks from time to time. Currently available vaccines employ inactivated viruses of different strains to provide protection against influenza virus infection. However, high mutation rates of influenza virus hemagglutinin (H) and neuraminidase (N) glycoproteins give rise to vaccine escape mutants. Thus, an effective vaccine providing protection against all strains of influenza virus would be a valuable asset. The ectodomain of matrix 2 protein (M2e) was found to be highly conserved despite mutations of the H and N glycoproteins. Hence, one to five copies of M2e were fused to the carboxyl-terminal end of the recombinant nodavirus capsid protein derived from Macrobrachium rosenbergii. The chimeric proteins harboring up to five copies of M2e formed nanosized virus-like particles approximately 30 nm in diameter, which could be purified easily by immobilized metal affinity chromatography. BALB/c mice immunized subcutaneously with these chimeric proteins developed antibodies specifically against M2e, and the titer was proportional to the copy numbers of M2e displayed on the nodavirus capsid nanoparticles. The fusion proteins also induced a type 1 T helper immune response. Collectively, M2e displayed on the nodavirus capsid nanoparticles could provide an alternative solution to a possible influenza pandemic in the future.

ELISPOT Assays in 384-Well Format: Up to 30 Data Points with One Million Cells

Comprehensive immune monitoring requires that frequencies of T cells, producing different cytokines, are measured to establish the magnitude of Th1, Th2, and Th17 components of cell-mediated immunity. Antigen titration provides additional information about the affinity of T cell response. In tumor immunity, it is also advisable to account for determinant spreading by testing multiple epitopes. Efforts for comprehensive immune monitoring would require substantial numbers of PBMC to run the above tests systematically, which in most test cases is limiting. Immune monitoring with ELISPOT assays have been performed, thus far, in a 96-well format. In this study we show that one can increase cell utilization by performing the assay in 384-well plates whose membrane surface area is one third that of 96-well plates. Systematic testing of PBMC for antigen-specific T cell response in the two formats demonstrated that the 384-well assay corresponds to a one-in-three miniaturization of the 96-well assay. The lowest number of cells that can be used in the 384-well format, while allowing for sufficient contact with APC, is 33,000 PBMC/well. Therefore, with one million PBMC typically obtained from 1 mL of blood, a 30 well T cell ELISPOT assay can be performed in a 384-well format.

ELISPOTs Produced by CD8 and CD4 Cells Follow Log Normal Size Distribution Permitting Objective Counting

Each positive well in ELISPOT assays contains spots of variable sizes that can range from tens of micrometers up to a millimeter in diameter. Therefore, when it comes to counting these spots the decision on setting the lower and the upper spot size thresholds to discriminate between non-specific background noise, spots produced by individual T cells, and spots formed by T cell clusters is critical. If the spot sizes follow a known statistical distribution, precise predictions on minimal and maximal spot sizes, belonging to a given T cell population, can be made. We studied the size distributional properties of IFN-γ, IL-2, IL-4, IL-5 and IL-17 spots elicited in ELISPOT assays with PBMC from 172 healthy donors, upon stimulation with 32 individual viral peptides representing defined HLA Class I-restricted epitopes for CD8 cells, and with protein antigens of CMV and EBV activating CD4 cells. A total of 334 CD8 and 80 CD4 positive T cell responses were analyzed. In 99.7% of the test cases, spot size distributions followed Log Normal function. These data formally demonstrate that it is possible to establish objective, statistically validated parameters for counting T cell ELISPOTs.

Interferon-gamma ELISPOT detecting reactivity of T cells to TSH receptor peptides in Graves' disease

OBJECTIVE

While thyrotrophin receptor (TSHR) is recognized as the main autoantigen in Graves' disease (GD), the actual antigen specificity of T cells that infiltrate the thyroid and the orbit is unknown. Identifying T cell responses to TSHR peptides has been difficult in the past due to the low frequency of autoreactive T cells and to the diversity of the putative epitopes identified by proliferation assays.

METHODS

We used the interferon-gamma ELISPOT assay to identify T cell reactivity to TSHR peptides in patients with GD. Peripheral blood T cells were exposed in vitro to four pools of 10 overlapping TSHR peptides.

RESULTS

T cells from 11 of 31 (35%) patients with GD and 1 of 22 (4%) healthy controls reacted to at least one peptide pool (P = 0·009). Mean time since diagnosis was 3·2 years in responder patients and 5·6 years in nonresponders (P = 0·07). In two patients, T cell reactivity was observed shortly after radioiodine treatment and not thereafter.

CONCLUSIONS

Our findings demonstrate that the ELISPOT assay is effective to test T cell reactivity in patients with GD and that patients with GD have significantly more interferon-gamma responses towards TSHR peptides than controls. The data suggest that screening for T cell responses in patients with GD might be more efficient in recent-onset disease or after radioiodine treatment.

The kinetics of myelin antigen uptake by myeloid cells in the central nervous system during experimental autoimmune encephalomyelitis

Induction of experimental autoimmune encephalomyelitis (EAE) in susceptible animals requires reactivation of encephalitogenic CD4(+) T cells by APCs in the CNS. However, it has remained unresolved from where APCs in the CNS acquire myelin Ag for T cell activation and under which conditions, that is, whether only during EAE or also in the naive CNS. In this study, we investigated the kinetics of myelin Ag uptake by CNS APCs during EAE and in the naive CNS. Our results show that during EAE CX3CR1(+)CD11b(+) microglia were the first APCs in the CNS to contain myelin Ag upon induction of disease, albeit in very small numbers. Dendritic cells (DCs) arrived in the CNS in sizable numbers significantly later (day 5 postimmunization), without detectable myelin Ag, but acquired it by day 7 postimmunization. Furthermore, a sharp increase in neuroantigen-containing DCs coincided with the onset of EAE symptoms. Importantly, in naive mice a low but consistent number of microglia contained myelin Ag, suggesting release by oligodendrocytes under steady state conditions. Although microglia isolated from naive brain and spinal cord did not elicit a strong CD4(+) T cell response in vitro, myelin Ag-containing microglia may still play a local role in modulating encephalitogenic CD4(+) T cell responses in early EAE prior to the arrival of other professional APCs, such as DCs. Finally, newly arriving DCs in the CNS not yet loaded with myelin Ag before the onset of EAE may be a potential therapeutic target.

Clinical validation of IFNγ/IL-10 and IFNγ/IL-2 FluoroSpot assays for the detection of Tr1 T cells and influenza vaccine monitoring in humans

The type of T cell polarization and simultaneous production of multiple cytokines have been correlated with vaccine efficacy. ELISpot is a T cell detection technique optimized for the measurement of a secreted cytokine at the single cell level. The FluoroSpot assay differs from ELISpot by the use of multiple fluorescent-labeled anticytokine detection antibodies, allowing optimal measurement of multiple cytokines. In the present study, we show that an IFNγ/IL-10 FluoroSpot assay is more sensitive than flow cytometry to detect Tr1 regulatory T cells, an immunosuppressive T cell population characterized by the production of IL-10 and IFNγ. As many tolerogenic vaccines are designed to induce these Tr1 cells, this FluoroSpot test could represent a standard method for the detection of these cells in the future. The use of an IFNγ/IL-2 FluoroSpot assay during influenza vaccine monitoring showed that the influenza-specific IL-2-producing T-cell response was the dominant response both before and after vaccine administration. This study therefore questions the rationale of using the single-color IFNγ ELISpot as the standard technique to monitor vaccine-specific T-cell response. Using this same test, a trend was also observed between baseline levels of IFNγ T cell response and T cell vaccine response. In addition, a lower IFNγ+IL-2+ T-cell response after vaccine was observed in the group of patients treated with TNFα inhibitors (P=0.08). This study therefore supports the use of the FluoroSpot assay due to its robustness, versatility and the complementary information that it provides compared with ELISpot or flow cytometry to monitor vaccine-specific T-cell responses.

Granzyme B ELISPOT assay to measure influenza-specific cellular immunity

The immunogenicity and efficacy of influenza vaccination are markedly lower in the elderly. Granzyme B (GrzB), quantified in fresh cell lysates, has been suggested to be a marker of cytotoxic T lymphocyte (CTL) response and a predictor of influenza illness among vaccinated older individuals. We have developed an influenza-specific GrzB ELISPOT assay using cryopreserved PBMCs. This method was tested on 106 healthy older subjects (ages 50-74) at baseline (Day 0) and three additional time points post-vaccination (Day 3, Day 28, Day 75) with influenza A/H1N1-containing vaccine. No significant difference was seen in GrzB response between any of the time points, although influenza-specific GrzB response appears to be elevated at all post-vaccination time points. There was no correlation between GrzB response and hemagglutination inhibition (HAI) titers, indicating no relationship between the cytolytic activity and humoral antibody levels in this cohort. Additionally, a significant negative correlation between GrzB response and age was observed. These results reveal a reduction in influenza-specific GrzB response as one ages. In conclusion, we have developed and optimized an influenza-specific ELISPOT assay for use with frozen cells to quantify the CTL-specific serine protease GrzB, as a measure of cellular immunity after influenza vaccination.

Imaging of Protein Secretion from a Single Cell Using Plasmonic Substrates

Detecting, imaging, and monitoring cell function on a single cell basis is very important in the field of immunology research where many molecules are secreted from cells in response to external stimuli including immunization. Here we introduce substrates with plasmonic nanoparticles and fluorescence microscopy as promising imaging methods for studies on molecular processes controlling cell behavior, particularly secretion of cytokines. We developed unique composition of silver and silica layers of plasmonic nanostructures which resulted in fluorescence enhancement of more than 200-fold for ensemble of molecules in the immunoassay. For the proof of concept demonstration, we used primary mouse macrophages and imaged tumor necrosis alpha (TNF-α) secretion after stimulation of the cells with lipopolysaccharide (LPS). We demonstrate that metal-enhanced fluorescence assay provides imaging capability detection of cytokine secretion from a single cell without extensive biochemical procedures as required with standard methods. In addition it is demonstrated that cell viability can be controlled during secretion.

Neuroantigen-Specific CD4 Cells Expressing Interferon-γ (IFN-γ), Interleukin (IL)-2 and IL-3 in a Mutually Exclusive Manner Prevail in Experimental Allergic Encephalomyelitis (EAE)

Experimental allergic encephalomyelitis (EAE) is mediated by neuroantigen-specific pro-inflammatory T cells of the Th1 and Th17 effector class. Th-17 cells can be clearly defined by expression of IL-17, but not IFN-γ, IL-2 or IL-3. Th1 cells do not express IL-17, but it is unclear presently to what extent they co-express the cytokines canonically assigned to Th1 immunity (i.e., IFN-γ, IL-2 and IL-3) and whether CD4 cells producing these cytokines indeed belong to a single Th1 lineage. It is also unclear to what extent the Th1 response in EAE entails polyfunctional T cells that co-express IFN-γ and IL-2. Therefore, we dissected the Th1 cytokine signature of neuroantigen-specific CD4 cells studying at single cell resolution co-expression of IFN-γ, IL-2 and IL-3 using dual color cytokine ELISPOT analysis. Shortly after immunization, in the draining lymph nodes (dLN), the overall cytokine signature of the neuroantigen-specific CD4 cells was highly type 1-polarized, but IFN-γ, IL-2, and IL-3 were each secreted by different CD4 cells in a mutually exclusive manner. This single cell - single cytokine profile was stable through the course of chronic EAE-polyfunctional CD4 cells co-expressing IL-2 and IFN-γ presented less than 5% of the neuroantigen-specific T cells, even in the inflamed CNS itself. The neuroantigen-specific CD4 cells that expressed IFN-γ, IL-2 and IL-3 in a mutually exclusive manner exhibited similar functional avidities and kinetics of cytokine production, but showed different tissue distributions. These data suggest that Th1 cells do not belong to a single lineage, but different Th1 subpopulations jointly mediate Th1 immunity.

Resting of Cryopreserved PBMC Does Not Generally Benefit the Performance of Antigen-Specific T Cell ELISPOT Assays

T cell monitoring is increasingly performed using cryopreserved PBMC. It has been suggested that resting of PBMC after thawing, that is, culturing them overnight in test medium, produces higher antigen-induced spot counts in ELISPOT assays. To evaluate the importance of overnight resting, we systematically tested cryopreserved PBMC from 25 healthy donors. CEF peptides (comprising CMV, EBV and flu antigens) were used to stimulate CD8 cells and mumps antigen to stimulate CD4 cells. The data show that resting significantly increased antigen-elicited T cell responses only for CEF high responder PBMC. The maximal gain observed was doubling of spot counts. For CEF low responders, and for mumps responders of either low- or high reactivity levels, resting had no statistically significant effect on the observed spot counts. Therefore, resting is not a generally applicable approach to improve ELISPOT assay performance, but can be recommended only for clinical subject cohorts and antigens for which it has a proven benefit. Because resting invariably leads to losing about half of the PBMC available for testing, and because doubling the PBMC numbers plated into the assay reliably doubles the antigen-induced spot counts, we suggest the latter approach as a simple and reliable alternative to resting for enhancing the performance of ELISPOT assays. Our data imply that resting is not required if PBMC were cryopreserved and thawed under conditions that minimize apoptosis of the cells. Therefore, this study should draw attention to the need to optimize freezing and thawing conditions for successful T cell work.

Dissecting the T Cell Response: Proliferation Assays vs. Cytokine Signatures by ELISPOT

Chronic allograft rejection is in part mediated by host T cells that recognize allogeneic antigens on transplanted tissue. One factor that determines the outcome of a T cell response is clonal size, while another is the effector quality. Studies of alloimmune predictors of transplant graft survival have most commonly focused on only one measure of the alloimmune response. Because differing qualities and frequencies of the allospecific T cell response may provide distinctly different information we analyzed the relationship between frequency of soluble antigen and allo-antigen specific memory IFN-g secreting CD4 and CD8 T cells, their ability to secrete IL-2, and their proliferative capacity, while accounting for cognate and bystander proliferation. The results show proliferative responses primarily reflect on IL-2 production by antigen-specific T cells, and that proliferating cells in such assays entail a considerable fraction of bystander cells. On the other hand, proliferation (and IL-2 production) did not reflect on the frequency of IFN-γ producing memory cells, a finding particularly accentuated in the CD8 T cell compartment. These data provide rationale for considering both frequency and effector function of pre-transplant T cell reactivity when analyzing immune predictors of graft rejection.

Distinguishing Latent from Active Mycobacterium tuberculosis Infection Using Elispot Assays: Looking Beyond Interferon-gamma

Mycobacterium tuberculosis (MTB) is a global heath epidemic, its threat amplified by HIV infection and the emergence of multidrug-resistant tuberculosis (MDR-TB). Interferon (IFN)-gamma release assays (IGRAs) have improved the accuracy of detection of MTB exposure in some subject groups as compared to the Tuberculin Skin Test (TST). However, as IFN-gamma is produced by both fully rested and more recently activated populations of memory T cells, it is not surprising that the measurement of this cytokine alone cannot accurately distinguish Latent TB Infected (LTBI) subjects from those with active (infectious) disease. Accurate and rapid diagnosis of infectious individuals would allow medication to be properly allocated and other actions taken to more effectively curtail MTB spread. Analysis of multi-cytokine profiles ex vivo after stimulation of PBMCs from LTBI and active MTB subjects indicate the real possibility of successfully discerning these two disease states within 24 hours of a subject’s blood draw. Due to the unparalleled sensitivity, low cost, and ease of use of Elispot assays, we propose that via a multiplex Elispot platform the accurate distinction of LTBI from active MTB-infected individuals is within reach.

Cytomegalovirus (CMV)-Specific Perforin and Granzyme B ELISPOT Assays Detect Reactivation of CMV Infection in Inflammatory Bowel Disease

The role of cytomegalovirus (CMV) infection in the pathogenesis and exacerbation of Inflammatory Bowel Disease (IBD) has been unresolved. Typically, the CMV genome remains dormant in infected cells, but a breakdown of immune surveillance can lead to re-activation of viral replication in the gut mucosa, which is not necessarily associated with viremia or changes in antibody titers. We hypothesized that the detection of CMV-specific CD8 effector T cells should permit the distinction between dormant and active CMV infection. As CD8 effector T cells, unlike memory CD8 T cells, have perforin (PFN) and granzyme B (GzB) preformed in their cytoplasmic granules, we employed single cell resolution ELISPOT assays to measure the CMV antigen-triggered release of these molecules by CD8 T cells isolated from subjects with IBD, and age-matched healthy controls. The frequencies of CMV-specific (GzB) and PFN-producing CD8 T cells were increased in IBD patients compared to healthy controls. Furthermore, the increased CMV reactivity was associated with active IBD disease and with longer disease duration. Notably, PCR on serum frequently failed to detect CMV DNA during flares. The data show that during active IBD there is a flare of CD8 T cell activity against CMV in a substantial proportion of IBD patients, suggesting CMV reactivation that serum PCR does not detect. While it remains open whether CMV reactivation is a cause or consequence of IBD, our data suggest that monitoring CMV antigen-specific effector CD8 T cells with GzB and PFN ELISPOT analysis can provide novel insights into the role of CMV infection in IBD. Additionally, our data have implications for the fields of transplantation, HIV, cancer, and autoimmune diseases, in all of which patient care critically depends on sensitive and reliable detection of a reactivation of CMV infection.

Simultaneous Detection of Antigen-Specific IgG- and IgM-Secreting Cells with a B Cell Fluorospot Assay

The traditional enzyme-linked immunospot (ELISpot) assay is the gold standard for the enumeration of antigen-specific B cells. Since B cell availability from biological samples is often limited, either because of sample size/volume or the need of performing multiple analyses on the same sample, the implementation of ELISpot assay formats that allow the simultaneous detection of multiple antibody types is desirable. While dual-color ELISpot assays have been described, technical complexities have so far prevented their wide utilization as well as further expansion of their multicolor capability. An attractive solution is to replace the chromogenic reaction of the traditional ELISpot assay with a fluorescent detection system (fluorospot assay). Fluorospot assays using fluorophore-conjugated secondary antibodies in conjunction with fluorescence enhancers, FITC/anti-FITC and biotin/avidin amplification systems and dedicated equipment for spot detection have been developed to enumerate T-cells secreting two or three specific cytokines and, more recently, IgG and IgA antibody-secreting cells (ASCs). We hereby report a method for a multiplex B cell fluorospot assay that utilizes quantum-dot nanocrystals as reporters without further amplification systems or need of dedicated equipment. With this method we simultaneously enumerated HIV-1 gp41 envelope glycoprotein-specific IgG and IgM antibody-secreting cells with sensitivity comparable to that of the traditional ELISpot assay.

Evaluation of antigen specific recognition and cell mediated cytotoxicity by a modified lysispot assay in a rat colon carcinoma model

Background

Antigen-specific CD8+ cytotoxic T lymphocytes represent potent effector cells of the adaptive immune response against viruses as well as tumours. Therefore assays capable at exploring the generation and function of cytotoxic T lymphocytes represent an important objective for both clinical and experimental settings.

Methods

Here we show a simple and reproducible assay for the evaluation of antigen-specific CD8+ cytotoxic T lymphocytes based on a LysiSpot technique for the simultaneous determination of antigen-specific IFN-γ production and assessment of tumor cytolysis. The assay was developed within an experimental model of colorectal carcinoma, induced by the colorectal tumor cell line DHD-K12 that induces tumors in BDIX rats and, in turn, elicits a tumor- specific immune response.

Results

Using DHD-K12 cells transfected to express Escherichia coli β-galactosidase as target cells, and by the fine setting of spot colours detection, we have developed an in vitro assay that allows the recognition of cytotoxic T lymphocytes induced in BDIX rats as well as the assessment of anti-tumour cytotoxicity. The method highlighted that in the present experimental model the tumour antigen-specific immune response was bound to killing target cells in the proportion of 55%, while 45% of activated cells were not cytotoxic but released IFN-γ. Moreover in this model by an ELISPOT assay we demonstrated the specific recognition of a nonapeptide epitope called CSH-275 constitutionally express in DHD-K12 cells.

Conclusions

The assay proved to be highly sensitive and specific, detecting even low frequencies of cytotoxic/activated cells and providing the evaluation of cytokine-expressing T cells as well as the extent of cytotoxicity against the target cells as independent functions. This assay may represent an important tool to be adopted in experimental settings including the development of vaccines or immune therapeutic strategies

Dual- and triple-color fluorospot

Cytokine ELISPOT has become a powerful routine tool for the analysis of disease- as well as vaccine-induced T-cell responses. The method is limited, however, in that only one cytokine at a time is assessed. Fluorospot is based on the principle of ELISPOT, but facilitates the analysis of single cells secreting several cytokines, e.g., polyfunctional T cells, suggested to be of protective importance in various infectious diseases. By detecting each cytokine with a specific fluorophore and analyzing differentially colored spots by fluorophore--specific filter systems, cells producing single or multiple cytokines are identified. Fluorospot maintains the simplicity and sensitivity of the ELISPOT while taking the analysis a step forward toward multiplex analysis.

Unique strengths of ELISPOT for T cell diagnostics

The T cell system plays an essential role in infections, allergic reactions, tumor and transplant rejection, as well as autoimmune diseases. It does so by the selective engagement of different antigen-specific effector cell lineages that differentially secrete cytokines and other effector molecules. These T cell subsets may or may not have cytolytic activity, can preferentially migrate to different tissues, and display variable capabilities to expand clonally. The quest of T cell immune diagnostics is to understand which specific effector function and T cell lineage is associated with a given clinical outcome, be it positive or adverse. No single assay can measure all of the relevant parameters. In this chapter, we review the unique contributions that ELISPOT assays can make toward understanding T cell-mediated immunity. ELISPOT assays have an unsurpassed sensitivity in detecting low frequency antigen-specific T cells that secrete effector molecules, including granzyme and perforin. They provide robust, highly reproducible data - even by first time users. Because ELISPOT assays require roughly tenfold less cell material than flow cytometry, ELISPOT is ideally suited for all measurements requiring parallel testing under multiple conditions. These include defining (a) T cell reactivity to individual peptides of extensive libraries, thereby establishing the fine-specificity of the response, and determinant mapping; (b) reactivity to different concentrations of the antigen in serial dilutions to measure the avidity of the T cell response; or (c) different secretory products released by T cells which define their respective effector lineage/functions. Further, because T cells survive ELISPOT assays unaffected, they can be retested for the acquisition of additional information in follow-up assays. These strengths of ELISPOT assays the weaknesses of flow cytometry-based measurements. Thus, the two assays systems compliment each other in the quest to understand T cell-mediated immunity in vivo.

How ELISPOT morphology reflects on the productivity and kinetics of cells' secretory activity

Over the past decade, ELISPOT has become well-established as a mainstream technology for the study of immune responses in vivo mainly due to its unique ability to detect rare antigen-specific lymphocytes ex vivo. The primary readout for ELISPOT assays has traditionally been the measurement of the frequency of analyte-secreting cells within a test population. While it has been generally appreciated that ELISPOT is a high-information-content assay system in which spot morphologies provide additional valuable information on the amount of analyte secreted by individual cells as well as the kinetics of the secretory process, the precise relationships involved have not been fully characterized and the specific relevant information -conveyed by spot morphologies has remained largely unexplored. In an attempt to bridge this gap, we formulated an in silico kinetic model for spot formation and derived a solution for the model in both a general and a numerical form. Both solutions suggested a logarithmic relationship between spot size and cell productivity. This chapter involves an in-depth analysis of the relationship between observed spot morphologies and cells' secretory functions (as well as an examination of additional assay parameters), and predictions based on the mathematical model are verified under experimental assay conditions where possible.

Systemic immune activation in HIV infection is associated with decreased MDC responsiveness to TLR ligand and inability to activate naive CD4 T-cells

Background

HIV infection is characterized by ineffective anti-viral T-cell responses and impaired dendritic cell (DC) functions, including response to Toll-Like Receptor (TLR) ligands. Because TLR responsiveness may affect a host's response to virus, we examined TLR ligand induced Myeloid and Plasmacytoid DC (MDC and PDC) activation of naïve T-cells in HIV+ subjects.

Methods

Freshly purified MDC and PDC obtained from HIV+ subjects and healthy controls were cultured in the presence and absence of TLR ligands (poly I∶C or R-848). We evaluated indices of maturation/activation (CD83, CD86, and HLA-DR expression), cytokine secretion (IFN-alpha and IL-6), and ability to activate allogeneic naïve CD4 T-cells to secrete IFN-gamma and IL-2.

Results

MDC from HIV+ subjects had increased spontaneous IL-6 production and increased CD83 and CD86 expression when compared to MDC of controls. MDC IL-6 expression was associated with plasma HIV level. At the same time, poly I∶C induced HLA-DR up-regulation on MDC was reduced in HIV+ persons when compared to controls. The latter finding was associated with impaired ability of MDC from HIV+ subjects to activate allogeneic naïve CD4 T-cells. PDC from HIV+ persons had increased spontaneous and TLR ligand induced IL-6 expression, and increased HLA-DR expression at baseline. The latter was associated with an intact ability of HIV PDC to activate allogeneic naïve CD4 T-cells.

Conclusion

These results have implications for the ability of the HIV+ host to form innate and adaptive responses to HIV and other pathogens.

Search for chronic beryllium disease among sarcoidosis patients in Ontario, Canada

Chronic beryllium disease (CBD) is clinically similar to other granulomatous diseases such as sarcoidosis. It is often misdiagnosed if a thorough occupational history is not taken. When appropriate, a beryllium lymphocyte proliferation tests (BeLPT) need to be performed. We aimed to search for CBD among currently diagnosed pulmonary sarcoidosis patients and to identify the occupations and exposures in Ontario leading to CBD. Questionnaire items included work history and details of possible exposure to beryllium. Participants who provided a history of previous work with metals underwent BeLPTs and an ELISPOT on the basis of having a higher pretest probability of CBD. Among 121 sarcoid patients enrolled, 87 (72%) reported no known previous metal dust or fume exposure, while 34 (28%) had metal exposure, including 17 (14%) with beryllium exposure at work or home. However, none of these 34 who underwent testing had positive test results. Self-reported exposure to beryllium or metals was relatively common in these patients with clinical sarcoidosis, but CBD was not confirmed using blood assays in this population.

Enumeration of functional T-cell subsets by fluorescence-immunospot defines signatures of pathogen burden in tuberculosis

Background

IFN-γ and IL-2 cytokine-profiles define three functional T-cell subsets which may correlate with pathogen load in chronic intracellular infections. We therefore investigated the feasibility of the immunospot platform to rapidly enumerate T-cell subsets by single-cell IFN-γ/IL-2 cytokine-profiling and establish whether immunospot-based T-cell signatures distinguish different clinical stages of human tuberculosis infection.

Methods

We used fluorophore-labelled anti-IFN-γ and anti-IL-2 antibodies with digital overlay of spatially-mapped colour-filtered images to enumerate dual and single cytokine-secreting M. tuberculosis antigen-specific T-cells in tuberculosis patients and in latent tuberculosis infection (LTBI). We validated results against established measures of cytokine-secreting T-cells.

Results

Fluorescence-immunospot correlated closely with single-cytokine enzyme-linked-immunospot for IFN-γ-secreting T-cells and IL-2-secreting T-cells and flow-cytometry-based detection of dual IFN-γ/IL-2-secreting T-cells. The untreated tuberculosis signature was dominated by IFN-γ-only-secreting T-cells which shifted consistently in longitudinally-followed patients during treatment to a signature dominated by dual IFN-γ/IL-2-secreting T-cells in treated patients. The LTBI signature differed from active tuberculosis, with higher proportions of IL-2-only and IFN-γ/IL-2-secreting T-cells and lower proportions of IFN-γ-only-secreting T-cells.

Conclusions

Fluorescence-immunospot is a quantitative, accurate measure of functional T-cell subsets; identification of cytokine-signatures of pathogen burden, distinct clinical stages of M. tuberculosis infection and long-term immune containment suggests application for treatment monitoring and vaccine evaluation.

Dual effects of the alloresponse by Th1 and Th2 cells on acute and chronic rejection of allotransplants

The contribution of direct and indirect alloresponses by CD4(+) Th1 and Th2 cells in acute and chronic rejection of allogeneic transplants remains unclear. In the present study, we addressed this question using a transplant model in a single MHC class I-disparate donor-recipient mouse combination. BALB/c-dm2 (dm2) mutant mice do not express MHC class I L(d) molecules and reject acutely L(d+) skin grafts from BALB/c mice. In contrast, BALB/c hearts placed in dm2 mice are permanently accepted in the absence of chronic allograft vasculopathy. In this model, CD4(+) T cells are activated following recognition of a donor MHC class I determinant, L(d) 61-80, presented by MHC Class II A(d) molecules on donor and recipient APC. Pre-transplantation of recipients with L(d) 61-80 peptide emulsified in complete Freund's adjuvant induced a Th1 response, which accelerated the rejection of skin allografts, but it had no effect on cardiac transplants. In contrast, induction of a Th2 response to the same peptide abrogated the CD8(+) cytotoxic T cells response and markedly delayed the rejection of skin allografts while it induced de novo chronic rejection of heart transplants. This shows that Th2 cells activated via indirect allorecognition can exert dual effects on acute and chronic rejection of allogeneic transplants.

IFN regulatory factor 4 regulates the expression of a subset of Th2 cytokines

Th2 cells can be subdivided into subpopulations depending on the level of a cytokine and the subsets of cytokines they produce. We have recently identified the ETS family transcription factor PU.1 as regulating heterogeneity in Th2 populations. To define additional factors that might contribute to Th2 heterogeneity, we examined the PU.1 interacting protein IFN-regulatory factor (IRF)4. When Th2 cells are separated based on levels of IL-10 secretion, IRF4 expression segregates into the subset of Th2 cells expressing high levels of IL-10. Infection of total Th2 cells, and IL-10 nonsecreting cells, with retrovirus-expressing IRF4, resulted in increased IL-4 and IL-10 expression, no change in IL-5 or IL-13 production and decreased Il9 transcription. Transfection of an IRF4-specific small interfering RNA into Th2 cells decreases IL-10 production. IRF4 directly binds the Il10 gene as evidenced by chromatin immunoprecipitation assay, and regulates Il10 control elements in a reporter assay. IRF4 interacts with PU.1, and in PU.1-deficient T cells there was an increase in IRF4 binding to the Il10 gene, and in the ability of IRF4 to induce IL-10 production compared with wild-type cells and Il10 promoter activity in a reporter assay. Further heterogeneity of IRF4 expression was observed in Th2 cells analyzed for expression of multiple Th2 cytokines. Thus, IRF4 promotes the expression of a subset of Th2 cytokines and contributes to Th2 heterogeneity.

Vaccination with tumor cells pulsed with foreign peptide induces immunity to the tumor itself

EMT-6 mammary carcinoma and B16 melanoma (B16M) cells are lethal and barely immunogenic in syngeneic BALB/c and C57BL/6 mice, respectively. We show that mice vaccinated with tumor cells pulsed with a MHC class I-restricted peptide develop a T cell response, not only to the peptide, but also to the unpulsed tumor. These mice display protective immunity against the unpulsed tumor, and their T cells adoptively transfer tumor-specific protection to immunodeficient SCID mice. Our data have implications for cancer vaccine strategies. Grafting a single well-defined foreign peptide on tumor cells might suffice to trigger anti-tumor immunity.

T helper cytokine patterns: defined subsets, random expression, and external modulation

Although T cell effector subsets, defined by cytokine patterns, have been recognized for more than 20 years, the functional cytokine expression patterns in vivo are still in considerable doubt, particularly for human T cells. At least three new subsets have been recently identified, but the committed cytokine pattern of a T cell (e.g., Th1 cells produce IL-2, interferon-gamma, and lymphotoxin) may differ from the expression pattern of one cell on one occasion, which may be a subset of its full potential. Recent advances in flow cytometry allowed detailed cytokine patterns of antigen-stimulated cells to be identified directly ex vivo. These patterns are clearly more diverse than the major subsets identified as committed phenotypes. Additional contributions to diversity may include new committed subsets, random expression of only part of the committed pattern, and modification of the expression patterns by cytokines and other mediators.

Th1 responses to beta-amyloid in young humans convert to regulatory IL-10 responses in Down syndrome and Alzheimer's disease

A beta(1-42)-specific antibodies and T-cell proliferation point to the existence of a memory response to A beta(1-42) in humans. Using ELISPOT, we studied A beta(1-42)-specific T cells in individuals of various ages, and in subjects with Trisomy 21 or Alzheimer's disease. We show for the first time that A beta(1-42)-specific Th1-type T-cell memory is present in young humans, producing high levels of IFN-gamma and IL-2. With increasing age, the production of IFN-gamma and IL-2 decreases but is not discontinued in healthy subjects and is accompanied by a sharp rise in CD4(+) T-cell-derived regulatory IL-10 production. In contrast, individuals with Trisomy 21 and with Alzheimer's disease produce IL-10 only in the absence of any effector cytokine. This signifies a switch from a Th1 effector to an IL-10 mediated regulatory response.

Lack of disease specificity limits the usefulness of in vitro costimulation in HIV- and HCV-infected patients

Measurements of antigen-specific T cell responses in chronic diseases are limited by low frequencies of antigen-specific cells in the peripheral blood. Therefore, attempts have been made to add costimulatory molecules such as anti-CD28 or IL-7/IL-15 to ELISPOT assays to increase sensitivity. While this approach has been successful under certain circumstances, results are often inconsistent. To date, there are no comprehensive studies directly comparing the in vitro effects of multiple costimulatory molecules in different disease settings. Therefore, in the present study we tested the effects of IL-7/IL-15, IFN-α, anti-ICOS, and anti-CD28 on antigen-specific T cell responses in patients infected with HCV or HIV versus healthy individuals. Our data show that none of the aforementioned molecules could significantly increase ELISPOT sensitivity, neither in HCV nor in HIV. Moreover, all of them caused false-positive responses to HCV and HIV antigens in healthy individuals. Our results question the broad use of in vitro costimulation.

Automated analysis of two- and three-color fluorescent Elispot (Fluorospot) assays for cytokine secretion

The Elispot effectively measures the frequencies of cells secreting particular molecules, especially low-frequency cells such as antigen-specific T cells. The Fluorospot assay adapted this analysis to two products per cell, and this has now been extended to three-color measurement of both mouse and human cytokine-secreting cells. Due to the increased data complexity, and particularly the need to define single-, double- and triple-producing cells, it is critical to objectively quantify spot number, size, intensity, and coincidence with other spots. An automated counting program, Exploraspot, was therefore developed to detect and quantify Fluorospots in automated fluorescence microscope images. Morphological parameters, including size, intensity, location, circularity and others are calculated for each spot, exported in FCS format, and further analyzed by gating and graphical display in popular flow cytometry analysis programs. The utility of Exploraspot is demonstrated by identification of single-, double- and triple-secreting T cells; tolerance of variable background fluorescence; and estimation of the numbers of genuine versus random multiple events.

Myelin-reactive type B T cells and T cells specific for low-affinity MHC-binding myelin peptides escape tolerance in HLA-DR transgenic mice

Genes of the MHC show the strongest genetic association with multiple sclerosis (MS), but the underlying mechanisms have remained unresolved. In this study, we asked whether the MS-associated MHC class II molecules, HLA-DRB1*1501, HLA-DRB5*0101, and HLA-DRB1*0401, contribute to autoimmune CNS demyelination by promoting pathogenic T cell responses to human myelin basic protein (hMBP), using three transgenic (Tg) mouse lines expressing these MHC molecules. Unexpectedly, profound T cell tolerance to the high-affinity MHC-binding hMBP82-100 epitope was observed in all Tg mouse lines. T cell tolerance to hMBP82-100 was abolished upon back-crossing the HLA-DR Tg mice to MBP-deficient mice. In contrast, T cell tolerance was incomplete for low-affinity MHC-binding hMBP epitopes. Furthermore, hMBP82-100-specific type B T cells escaped tolerance in HLA-DRB5*0101 Tg mice. Importantly, T cells specific for low-affinity MHC-binding hMBP epitopes and hMBP82-100-specific type B T cells were highly encephalitogenic. Collectively, the results show that MS-associated MHC class II molecules are highly efficient at inducing T cell tolerance to high-affinity MHC-binding epitope, whereas autoreactive T cells specific for the low-affinity MHC-binding epitopes and type B T cells can escape the induction of T cell tolerance and may promote MS.

Hepatitis C virus-specific T-cell gamma interferon and proliferative responses are more common in perihepatic lymph nodes than in peripheral blood or liver

The activation state, differentiation state, and functions of liver lymphocytes and perihepatic lymph nodes during chronic hepatitis C virus (HCV) infection are not well understood. Here, we performed phenotypic and functional analyses of freshly prepared lymphocytes isolated from the livers, perihepatic lymph nodes, and peripheral blood compartments of chronic HCV-infected and disease control subjects with end-stage liver disease undergoing liver transplantation. We measured lymphocyte subset frequency and memory T-cell gamma interferon (IFN-gamma) and proliferative responses to HCV peptide and control viral antigens in direct ex vivo assays. We found higher frequencies of CD4 cells in the lymph node compartment than in the other compartments for both HCV-infected and disease control subjects. Lymph node CD4 and CD8 cells less commonly expressed the terminal differentiation marker CD57, a finding consistent with an earlier differentiation state. In HCV-infected subjects, HCV-specific IFN-gamma-producing and proliferative responses were commonly observed in the lymph node fraction, while they were uncommonly observed in the peripheral blood or liver fractions. In contrast, control viral CD4 protein antigen and CD8 peptide antigen-specific IFN-gamma responses were commonly observed in the periphery and uncommonly observed in the lymph nodes of these same subjects. These findings are consistent with a selective defect in HCV-specific T-cell effector function or distribution in patients with advanced chronic HCV infection. The high frequency of HCV-reactive T cells in perihepatic lymph nodes indicates that a failure to generate or sustain T-lymphocyte HCV reactivity is not responsible for the paucity of functional cells even in end-stage liver disease.

T cell cytokine polarity as a determinant of immunoglobulin A (IgA) glycosylation and the severity of experimental IgA nephropathy

Immunoglobulin A (IgA) glycosylation, recognized as an important pathogenic factor in IgA nephropathy (IgAN), is apparently controlled by the polarity of T helper (Th) cytokine responses. To examine the role of cytokine polarity in IgAN, inbred mice were immunized by intraperitoneal priming with inactivated Sendai virus (SeV) emulsified in either complete Freund's adjuvant (CFA) or incomplete Freund's adjuvant (IFA), which promote Th1- or Th2-immune response, respectively, and then boosted identically twice orally with aqueous suspensions of inactivated virus. Next, some mice were challenged intranasally with infectious SeV. Mice primed with CFA or IFA had equal reductions in nasal viral titre relative to non-immune controls, and equally increased serum levels of SeV-specific IgA antibody. Mice primed with CFA showed higher SeV-specific IgG than those with IFA. Splenocytes from mice primed with IFA produced copious amounts of interleukin (IL)-4 and IL-5, but little interferon-gamma and IL-2; those primed with CFA had reciprocal cytokine recall responses. Total serum IgA and especially SeV-specific IgA from mice primed with IFA showed a selective defect in sialylation and galactosylation. Although the frequency and intensity of glomerular deposits and haematuria did not differ, glomerulonephritis in mice primed with IFA and challenged with infectious virus was more severe than in those given CFA, as judged by serum creatinine level. We conclude that the polarity of T cell cytokines controls the pattern of IgA glycosylation and exerts direct or indirect effects on functional glomerular responses to immune complex deposition.

Expression of cytokine mRNA in lymphocytes of malnourished children

INTRODUCTION

Protein-calorie malnutrition represents a significant worldwide health problem and is associated with an increased risk for infections. The purpose of this study was to evaluate possible changes in type 1/type 2 responses balance in malnourished children.

RESULTS

The data obtained in the present study showed that the expression levels of tumor necrosis factor-alpha, interleukin (IL)-4, and IL-10 were more highly, in contrast IL-2, gamma interferon, and IL-6 genes were expressed less in all groups of malnourished children compared with the well-nourished infected children. It is important to indicate that the data collected in the present work agree with the results obtained by different authors, who showed differences in the production of cytokines in malnourished children.

CONCLUSION

In conclusion, the results suggest that alterations in the balance of type 1/type 2 immune responses exist in malnourished children, and this could be the reason that the immunological system of the malnourished children is incapable of eradicating infections.

The lipophilic hapten parthenolide induces interferon-gamma and interleukin-13 production by peripheral blood-derived CD8+ T cells from contact allergic subjects in vitro

BACKGROUND

Peripheral blood mononuclear cells (PBMC) from persons with contact allergy to nickel react in vitro predominantly with nickel-induced CD4+ T cell-mediated production of both T-cell type 1 and 2 cytokines.

OBJECTIVES

The aim of the present study was to investigate if the contact allergen parthenolide, a sesquiterpene lactone of lipophilic character, elicits an immune response which differs from that induced by water-soluble nickel ions.

PATIENTS AND METHODS

Ten allergic subjects with strong (n = 6), moderate (n = 2), or weak (n = 2) patch-test reactivity to parthenolide and five patch test-negative control subjects participated in the study. PBMC from the subjects were analysed for in vitro reactivity with parthenolide by an enzyme-linked immunospot (ELISpot) assay, measuring cytokine production at the single-cell level.

RESULTS

The allergic group, but not the control group, responded to parthenolide with increased numbers of cells producing interferon (IFN)-gamma, interleukin (IL)-2, IL-4, IL-5 (P < 0.05 for all) and IL-13 (P < 0.01). The responses manifested by T-cell type 1 (IFN-gamma and IL-2) and type 2 (IL-4, IL-5 and IL-13) cytokines were positively correlated between cytokines. Subjects with a strong or moderate, but not weak or negative, patch-test reaction displayed detectable in vitro responses. In contrast to the CD4+ T cell-mediated peripheral reactivity induced by nickel, cell depletion experiments identified the parthenolide-reactive IFN-gamma- and IL-13-producing cells as CD8+ T cells.

CONCLUSIONS

The finding that the PBMC reactivity to parthenolide in humans involves a CD8+ T cell-mediated type 1 and 2 cytokine response warrants further studies on the relationship between the chemical nature of a hapten and the resulting immune response.

Maternal transmission of resistance to development of allergic airway disease

Parental phenotype is known to influence the inheritance of atopic diseases, such as allergic asthma, with a maternal history being a more significant risk factor for progeny than paternal history. We hypothesized that recall Th1- or Th2-type immune responses during pregnancy would result in transfer of maternal factors that would differentially impact development of immune responsiveness in offspring. Following weaning, susceptibility and severity of allergic airway disease (a murine model of human asthma) was evaluated in progeny, disease being elicited by immunization with OVA-Al(OH)(3) and challenge with aerosolized OVA. We found that progeny of mothers with Th1-biased immunity to OVA subjected to recall aerosol challenge during pregnancy had reduced levels of Ag-specific IgE and airway eosinophilia compared with progeny of mothers with Th2-biased immunity to OVA or naive mothers. Interestingly, progeny of mothers with Th1-type immunity to a heterologous albumin, BSA, were not protected from developing OVA-induced allergic airway disease. These findings demonstrated that maternal transfer of protection from development of allergic airway disease to offspring in this model of maternal Th1-type immunity was Ag specific.

The secretory IFN-gamma response of single CD4 memory cells after activation on different antigen presenting cell types

It is unknown to what extent the heterogeneity of antigen presenting cells (APC) influences the IFN-gamma response of CD4 memory cells. We re-stimulated DO11.10 T cell receptor (TCR)-transgenic cells and wild-type CD4 memory cells with OVA-peptide 323-339 presented on purified dendritic cells (DC), macrophages, and B cells. Using IFN-gamma ELISPOT assays, we measured the number of cytokine producing T cells and the amount of cytokine produced by individual T cells at different time points after antigen encounter. The data showed that, when CD4 cells recognized antigen on DC, the induction of cytokine production was accelerated compared to macrophages and B cells. In contrast, the per-cell cytokine productivity was independent of the type of APC by which the T cells were re-stimulated. Moreover, the peptide concentration required for CD4 cell activation was comparable for the different APC. The data suggest that DC induce cytokine production in memory cells with accelerated activation kinetics, whereas 24 h of antigen stimulation on DC, macrophages, and B cells results in comparable levels of T cell activation. These data have implications for the understanding of T cell memory responses when T cells re-encounter antigen on different APC as well as for the monitoring of memory T cell responses ex vivo.

Immune reconstitution prevents metastatic recurrence of murine osteosarcoma

Primary tumors developing in immunocompetent hosts escape immunosurveillance by acquiring immune evasive properties. This raises the prospect that metastases derived from such tumors will also evade immunity. To investigate whether immune surveillance plays a role in preventing metastases, we studied a murine model which mimics the clinical progression of osteosarcoma: primary tumor growth in the lower extremity, amputation, minimal residual disease followed by the development of overt metastases. K7M2 implants readily escaped immune surveillance since normal BALB/c mice, T cell deficient SCID and T/NK cell deficient SCID-bg mice showed no difference in the rate of growth of primary osteosarcomas. However, both SCID and SCID-bg mice had higher rates of metastases than immunocompetent mice. Similarly, immune reconstitution following transfer of naive T cells to SCID or SCID-bg mice did not impact primary tumor growth, but significantly diminished metastatic recurrence. T cells in osteosarcoma bearing mice produced IFNgamma in response to tumor and IFNgamma production by immune reconstituting T cells was required to prevent metastases. These results demonstrate an important role for T cell based immune surveillance in preventing metastases, even when metastases develop from tumors that adeptly evade immunosurveillance. The results further suggest that T cell depleting cancer therapies may eliminate beneficial immune responses and that immune reconstitution of lymphopenic cancer patients could prevent metastatic recurrence of solid tumors.

Neonatal induction of myelin-specific Th1/Th17 immunity does not result in experimental autoimmune encephalomyelitis and can protect against the disease in adulthood

The neonatal immune system is believed to be biased towards T helper type 2 (Th2) immunity, but under certain conditions neonates can also develop Th1 immune responses. Neonatal Th2 immunity to myelin antigens is not pathogenic and can prevent induction of experimental autoimmune encephalomyelitis (EAE) in adulthood, but the consequences of neonatally induced Th1 immunity to self-antigens have remained unresolved. Here, we show that neonatal injection of mice with myelin antigens emulsified in complete Freund's adjuvant (CFA) induced vigorous production of IFN-gamma and IL-17, but not IL-5, consistent with myelin-specific Th1/Th17 immunity. Importantly, the myelin-specific Th1/Th17 cells persisted in the mice until adulthood without causing symptoms of EAE. Intraperitoneal, but not subcutaneous injection of neonates with myelin antigens protected against induction of EAE as adults. Intraperitoneally injected neonates showed a substantial decrease of the number and avidity of myelin-reactive Th17 cells, suggesting a decrease in IL-17 producing precursor cells as the mechanism of protection from EAE upon re-injection with myelin antigens as adults. The results could provide a rationale for the presence of autoreactive T cells found in healthy human individuals without autoimmune disease.