Detection of individual mouse splenic T cells producing IFN-gamma and IL-5 using the enzyme-linked immunospot (ELISPOT) assay

A digital nanoplasmonic microarray immunosensor for multiplexed cytokine monitoring during CAR T-cell therapy from a leukemia tumor microenvironment model

The release of cytokines by chimeric antigen receptor (CAR) T-cells and tumor resident immune cells defines a significant part of CAR T-cell functional activity and patient immune responses during CAR T-cell therapy. However, few studies have so far precisely characterized the cytokine secretion dynamics in the tumor niche during CAR T-cell therapy, which requires multiplexed, and timely biosensing platforms and integration with biomimetic tumor microenvironment. Herein, we implemented a digital nanoplasmonic microarray immunosensor with a microfluidic biomimetic Leukemia-on-a-Chip model to monitor cytokine secretion dynamics during CD19 CAR T-cell therapy against precursor B-cell acute lymphocytic leukemia (B-ALL). The integrated nanoplasmonic biosensors achieved precise multiplexed cytokine measurements with low operating sample volume, short assay time, heightened sensitivity, and negligible sensor crosstalk. Using the digital nanoplasmonic biosensing approach, we measured the concentrations of six cytokines (TNF-α, IFN-γ, MCP-1, GM-CSF, IL-1β, and IL-6) during first 5 days of CAR T-cell treatment in the microfluidic Leukemia-on-a-Chip model. Our results revealed a heterogeneous secretion profile of various cytokines during CAR T-cell therapy and confirmed a correlation between the cytokine secretion profile and the CAR T-cell cytotoxic activity. The capability to monitor immune cell cytokine secretion dynamics in a biomimetic tumor microenvironment could further help in study of cytokine release syndrome during CAR T-cell therapy and in development of more efficient and safer immunotherapies.

A novel, accurate, and non-invasive liquid biopsy test to measure cellular immune responses as a tool to diagnose early-stage lung cancer: a clinical trials study

INTRODUCTION

Lung cancer remains the leading cause of death from cancer, worldwide. Developing early detection diagnostic methods, especially non-invasive methods, is a critical component to raising the overall survival rate and prognosis for lung cancer. The purpose of this study is to evaluate two protocols of a novel in vitro cellular immune response test to detect lung cancer. The test specifically quantifies the glycolysis metabolism pathway, which is a biomarker for the activation level of immune cells. It summarizes the results of two clinical trials, where each deploys a different protocol's version of this test for the detection of lung cancer. In the later clinical trial, an improved test protocol is applied.

METHOD

The test platform is based on changes in the metabolic pathways of the immune cells following their activation by antigenic stimuli associated with Lung cancer. Peripheral Blood Mononuclear Cells are loaded on a multiwell plate together with various lung tumor associated antigens and a fluorescent probe that exhibits a pH-dependent absorption shift. The acidification process in the extracellular fluid is monitored by a commercial fluorescence plate reader device in continuous reading for 3 h at 37 °C to document the fluorescent signal received from each well.

RESULTS

In the later clinical trial, an improved test protocol was applied and resulted in increased test accuracy. Specificity of the test increased to 94.0% and test sensitivity increased to 97.3% in lung cancer stage I, by using the improved protocol.

CONCLUSION

The improved protocol of the novel cellular immune metabolic response based test detects stage I and stage II of lung cancer with high specificity and sensitivity, with low material costs and fast results.

An adjuvanted zoster vaccine elicits potent cellular immune responses in mice without QS21

Herpes zoster (HZ) is caused by reactivation of latent varicella-zoster virus (VZV) when VZV-specific cellular immunity is insufficient to control reactivation. Currently, Shingrix, which contains the VZV gE protein and GSK’s AS01_B adjuvant composed of liposomes formulated with cholesterol, monophosphoryl lipid A (MPL) and QS21, is used for prevention of HZ. However, reactogenicity to Shingrix is common leading to poor patient compliance in receiving one or both shots. Here, we evaluated the immunogenicity of a newly formulated gE protein-based HZ vaccine containing Second-generation Lipid Adjuvant (SLA), a synthetic TLR4 ligand, formulated in an oil-in-water emulsion (SLA-SE) without QS21 (gE/SLA-SE). In VZV-primed mouse models, gE/SLA-SE-induced gE-specific humoral and cellular immune responses at comparable levels to those elicited by Shingrix in young mice, as both gE/SLA-SE and Shingrix induce polyfunctional CD4⁺ T-cell responses. In aged mice, gE/SLA-SE elicited more robust gE-specific T-cell responses than Shingrix. Furthermore, gE/SLA-SE-induced T-cell responses were sustained until 5 months after immunization. Thus, QS21-free, gE/SLA-SE is a promising candidate for development of gE-based HZ vaccines with high immunogenicity—particularly when targeting an older population.

Position-Scanning Peptide Libraries as Particle Immunogens for Improving CD8+ T-Cell Responses

Short peptides reflecting major histocompatibility complex (MHC) class I (MHC-I) epitopes frequently lack sufficient immunogenicity to induce robust antigen (Ag)-specific CD8+ T cell responses. In the current work, it is demonstrated that position-scanning peptide libraries themselves can serve as improved immunogens, inducing Ag-specific CD8+ T cells with greater frequency and function than the wild-type epitope. The approach involves displaying the entire position-scanning library onto immunogenic nanoliposomes. Each library contains the MHC-I epitope with a single randomized position. When a recently identified MHC-I epitope in the glycoprotein gp70 envelope protein of murine leukemia virus (MuLV) is assessed, only one of the eight positional libraries tested, randomized at amino acid position 5 (Pos5), shows enhanced induction of Ag-specific CD8+ T cells. A second MHC-I epitope from gp70 is assessed in the same manner and shows, in contrast, multiple positional libraries (Pos1, Pos3, Pos5, and Pos8) as well as the library mixture give rise to enhanced CD8+ T cell responses. The library mixture Pos1-3-5-8 induces a more diverse epitope-specific T-cell repertoire with superior antitumor efficacy compared to an established single mutation mimotope (AH1-A5). These data show that positional peptide libraries can serve as immunogens for improving CD8+ T-cell responses against endogenously expressed MHC-I epitopes.

Rapid Neutralization Testing System for Zika Virus Based on an Enzyme-Linked Immunospot Assay

Zika virus (ZIKV) is a mosquito-borne flavivirus that has been associated with neuropathology in fetuses and adults, imposing a serious health concern. Therefore, the development of a vaccine is a global health priority. Notably, neutralization tests have a significant value for vaccine development and virus diagnosis. The cytopathic effect (CPE)-based neutralization test (Nt-CPE) is a common neutralization method for ZIKV. However, this method has some drawbacks, such as being time-consuming and labor-intensive and having low-throughput, which precludes its application in the detection of large numbers of specimens. To improve this problem, we developed a neutralization test based on an enzyme-linked immunospot assay (Nt-ELISPOT) for ZIKV and performed the assay in a 96-well format. A monoclonal antibody (mAb), 11C11, with high affinity and reactivity to ZIKV was used to detect ZIKV-infected cells. To optimize this method, the infectious dose of ZIKV was set at a multiplicity of infection (MOI) of 0.0625, and a detection experiment was performed after incubating for 24 h. As a result, under these conditions, the Nt-ELISPOT had good consistency with the traditional Nt-CPE to measure neutralizing titers of sera and neutralizing antibodies. Additionally, three neutralizing antibodies against ZIKV were screened by this method. Overall, we successfully developed an efficient neutralization test for ZIKV that is high-throughput and rapid. This Nt-ELISPOT can potentially be applied to detecting neutralizing titers of large numbers of specimens in vaccine evaluation and neutralizing antibody screening for ZIKV.

Rapid selection and identification of functional CD8+ T cell epitopes from large peptide-coding libraries

Cytotoxic CD8⁺ T cells recognize and eliminate infected or malignant cells that present peptide epitopes derived from intracellularly processed antigens on their surface. However, comprehensive profiling of specific major histocompatibility complex (MHC)-bound peptide epitopes that are naturally processed and capable of eliciting a functional T cell response has been challenging. Here, we report a method for deep and unbiased T cell epitope profiling, using in vitro co-culture of CD8⁺ T cells together with target cells transduced with high-complexity, epitope-encoding minigene libraries. Target cells that are subject to cytotoxic attack from T cells in co-culture are isolated prior to apoptosis by fluorescence-activated cell sorting, and characterized by sequencing the encoded minigenes. We then validate this highly parallelized method using known murine T cell receptor/peptide-MHC pairs and diverse minigene-encoded epitope libraries. Our data thus suggest that this epitope profiling method allows unambiguous and sensitive identification of naturally processed and MHC-presented peptide epitopes.

A Multiagent Alphavirus DNA Vaccine Delivered by Intramuscular Electroporation Elicits Robust and Durable Virus-Specific Immune Responses in Mice and Rabbits and Completely Protects Mice against Lethal Venezuelan, Western, and Eastern Equine Encephalitis Virus Aerosol Challenges

There remains a need for vaccines that can safely and effectively protect against the biological threat agents Venezuelan (VEEV), western (WEEV), and eastern (EEEV) equine encephalitis virus. Previously, we demonstrated that a VEEV DNA vaccine that was optimized for increased antigen expression and delivered by intramuscular (IM) electroporation (EP) elicited robust and durable virus-specific antibody responses in multiple animal species and provided complete protection against VEEV aerosol challenge in mice and nonhuman primates. Here, we performed a comparative evaluation of the immunogenicity and protective efficacy of individual optimized VEEV, WEEV, and EEEV DNA vaccines with that of a 1 : 1 : 1 mixture of these vaccines, which we have termed the 3-EEV DNA vaccine, when delivered by IM EP. The individual DNA vaccines and the 3-EEV DNA vaccine elicited robust and durable virus-specific antibody responses in mice and rabbits and completely protected mice from homologous VEEV, WEEV, and EEEV aerosol challenges. Taken together, the results from these studies demonstrate that the individual VEEV, WEEV, and EEEV DNA vaccines and the 3-EEV DNA vaccine delivered by IM EP provide an effective means of eliciting protection against lethal encephalitic alphavirus infections in a murine model and represent viable next-generation vaccine candidates that warrant further development.

The miR-25-93-106b cluster regulates tumor metastasis and immune evasion via modulation of CXCL12 and PD-L1

The stromal microenvironment controls response to injury and inflammation, and is also an important determinant of cancer cell behavior. However, our understanding of its modulation by miRNA (miR) and their respective targets is still sparse. Here, we identified the miR-25-93-106b cluster and two new target genes as critical drivers for metastasis and immune evasion of cancer cells. Using miR-25-93-106b knockout mice or antagomiRs, we demonstrated regulation of the production of the chemoattractant CXCL12 controlling bone marrow metastasis. Moreover, we identified the immune checkpoint PD-L1 (CD274) as a novel miR-93/106b target playing a central role in diminishing tumor immunity. Eventually, upregulation of miR-93 and miR-106b via miR-mimics or treatment with an epigenetic reader domain (BET) inhibitor resulted in diminished expression of CXCL12 and PD-L1. These data suggest a potential new therapeutic rationale for use of BET inhibitors for dual targeting of cancers with strong immunosuppressive and metastatic phenotypes.

Membrane Microplates for One- and Two-Color ELISPOT and FLUOROSPOT Assays

Membranes are widely used as protein blotting matrices for a large variety of research applications including western blotting and enzyme-linked immunospot assay (ELISPOT). The largest advantage of using membranes versus solid plastic support is the porosity of membranes allowing for immobilization of high concentrations of proteins and antibodies which, in turn, increases the sensitivity of detection. Similar to plastic surfaces, polyvinylidene difluoride (PVDF) and nitrocellulose membranes create good microenvironment for live cells cultured in vitro and do not interfere with cellular physiology. It appears that PVDF-backed microplates are a golden standard for ELISPOT assays: such plates are inexpensive, easy to use and after assay development, membranes can be removed from the plates and archived. Given the convenience and reliability of membrane microplates, they are widely used in ELISPOT assays for basic research and clinical trials. The ELISPOT assay is an antibody "sandwich" technique aimed at trapping cell-secreted molecules between capture and detection antibodies, followed by either chromogenic enzymatic or fluorescence detection. This review covers the principles of the ELISPOT assay on membrane microplates including single-color and two-color detection techniques with the emphasis on assay design, choosing membrane microplates, and troubleshooting protocols.

Partial protective effect of intranasal immunization with recombinant Toxoplasma gondii rhoptry protein 17 against toxoplasmosis in mice

Toxoplasma gondii (T. gondii) is an obligate intracellular protozoan parasite that infects a variety of mammals, including humans. An effective vaccine for this parasite is therefore needed. In this study, RH strain T. gondii rhoptry protein 17 was expressed in bacteria as a fusion with glutathione S-transferase (GST) and the recombinant proteins (rTgROP17) were purified via GST-affinity chromatography. BALB/c mice were nasally immunised with rTgROP17, and induction of immune responses and protection against chronic and lethal T. gondii infections were investigated. The results revealed that mice immunised with rTgROP17 produced high levels of specific anti-rTgROP17 IgGs and a mixed IgG1/IgG2a response of IgG2a predominance. The systemic immune response was associated with increased production of Th1 (IFN-γand IL-2) and Th2 (IL-4) cytokines, and enhanced lymphoproliferation (stimulation index, SI) in the mice immunised with rTgROP17. Strong mucosal immune responses with increased secretion of TgROP17-specific secretory IgA (SIgA) in nasal, vaginal and intestinal washes were also observed in these mice. The vaccinated mice displayed apparent protection against chronic RH strain infection as evidenced by their lower liver and brain parasite burdens (59.17% and 49.08%, respectively) than those of the controls. The vaccinated mice also exhibited significant protection against lethal infection of the virulent RH strain (survival increased by 50%) compared to the controls. Our data demonstrate that rTgROP17 can trigger strong systemic and mucosal immune responses against T. gondii and that ROP17 is a promising candidate vaccine for toxoplasmosis.

Vaccination with cancer- and HIV infection-associated endogenous retrotransposable elements is safe and immunogenic

The expression of endogenous retrotransposable elements, including long interspersed nuclear element 1 (LINE-1 or L1) and human endogenous retrovirus, accompanies neoplastic transformation and infection with viruses such as HIV. The ability to engender immunity safely against such self-antigens would facilitate the development of novel vaccines and immunotherapies. In this article, we address the safety and immunogenicity of vaccination with these elements. We used immunohistochemical analysis and literature precedent to identify potential off-target tissues in humans and establish their translatability in preclinical species to guide safety assessments. Immunization of mice with murine L1 open reading frame 2 induced strong CD8 T cell responses without detectable tissue damage. Similarly, immunization of rhesus macaques with human LINE-1 open reading frame 2 (96% identity with macaque), as well as simian endogenous retrovirus-K Gag and Env, induced polyfunctional T cell responses to all Ags, and Ab responses to simian endogenous retrovirus-K Env. There were no adverse safety or pathological findings related to vaccination. These studies provide the first evidence, to our knowledge, that immune responses can be induced safely against this class of self-antigens and pave the way for investigation of them as HIV- or tumor-associated targets.

Linear fidelity in quantification of anti-viral CD8+ T cells

Enumeration of anti-viral CD8(+) T cells to make comparisons between mice, viruses and vaccines is a frequently used approach, but controversy persists as to the most appropriate methods. Use of peptide-MHC tetramers (or variants) and intracellular staining for cytokines, in particular IFNγ, after a short ex vivo stimulation are now common, as are a variety of cytotoxicity assays, but few direct comparisons have been made. It has been argued that use of tetramers leads to the counting of non-functional T cells and that measurement of single cytokines will fail to identify cells with alternative functions. Further, the linear range of these methods has not been tested and this is required to give confidence that relative quantifications can be compared across samples. Here we show for two acute virus infections and CD8(+) T cells activated in vitro that DimerX (a tetramer variant) and intracellular staining for IFNγ, alone or in combination with CD107 to detect degranulation, gave comparable results at the peak of the response. Importantly, these methods were highly linear over nearly two orders of magnitude. In contrast, in vitro and in vivo assays for cytotoxicity were not linear, suffering from high background killing, plateaus in maximal killing and substantial underestimation of differences in magnitude of responses.

Blockade of B7-H1 enhances dendritic cell-mediated T cell response and antiviral immunity in HBV transgenic mice

Dendritic cells (DCs) have been identified as the most effective antigen-presenting cell (APC), much attention has been directed toward the use of DCs in vaccine strategies for the treatment of cancer or chronic virus infection. B7-H1 (PD-L1) is a ligand for programmed cell death-1 (PD-1) and does not bind to other CD28 family members, it is expressed on resting and upregulated on activated B, T, myeloid, and dendritic cells (DCs). The overwhelming number of studies supports the role of B7-H1 as a negative regulator of T cell responses. RNA interference (RNAi) is a mechanism for sequence-specific posttranscriptional inhibition of gene expression via double stranded RNA molecules and it has recently been applied to mammalian cells with the use of small interfering RNAs (siRNAs). In the study, transfection of DCs with siRNA specific for B7-H1 gene resulted in the blockade of the expression of B7-H1 on DCs. The allostimulatory activity of DCs could be enhanced by silencing of B7-H1 on DCs. Blockade of B7-H1 on DCs inhibited the production of IFN-γ and IL-10 but not IL-2 and IL-4 in mixed lymphocyte reaction (MLR). HBV specific peptide-pulsed DCs could break tolerance and trigger specific CTL responses, the level of HBsAg and HBV DNA in sera of HBV transgenic mice decreased, whereas blockade of B7-H1 on DCs augmented the effects. These data strongly support the concept that blockade of B7-H1 can enhance DC-mediated antiviral immune responses.

ELISpot for measuring human immune responses to vaccines

The enzyme-linked immunosorbent spot (ELISpot) assay is one of the most commonly used methods to measure antigen-specific T cells in both mice and humans. Some of the primary reasons for the popularity of the method are that ELISpot is highly quantitative, can measure a broad range of magnitudes of response and is capable of assessing critical cellular immune-related activities such as IFN-γ secretion and granzyme B release. Furthermore, ELISpot is adaptable not only to the evaluation of a variety of T-cell functions, but also to B cells and innate immune cells. It is no wonder that ELISpot has evolved from a research tool to a clinical assay. Recent Phase I and II studies of cancer vaccines, tested in a variety of malignancies, have suggested that ELISpot may be a useful biomarker assay to predict clinical benefit after therapeutic immune modulation. This article will discuss the most common applications of ELISpot, overview the efforts that have been undertaken to standardize the assay and apply the method in the analysis of human clinical trials, and describe some important steps in the process of developing a clinical-grade ELISpot.

A DNA vaccine for venezuelan equine encephalitis virus delivered by intramuscular electroporation elicits high levels of neutralizing antibodies in multiple animal models and provides protective immunity to mice and nonhuman primates

We evaluated the immunogenicity and protective efficacy of a DNA vaccine expressing codon-optimized envelope glycoprotein genes of Venezuelan equine encephalitis virus (VEEV) when delivered by intramuscular electroporation. Mice vaccinated with the DNA vaccine developed robust VEEV-neutralizing antibody responses that were comparable to those observed after administration of the live-attenuated VEEV vaccine TC-83 and were completely protected from a lethal aerosol VEEV challenge. The DNA vaccine also elicited strong neutralizing antibody responses in rabbits that persisted at high levels for at least 6 months and could be boosted by a single additional electroporation administration of the DNA performed approximately 6 months after the initial vaccinations. Cynomolgus macaques that received the vaccine by intramuscular electroporation developed substantial neutralizing antibody responses and after an aerosol challenge had no detectable serum viremia and had reduced febrile reactions, lymphopenia, and clinical signs of disease compared to those of negative-control macaques. Taken together, our results demonstrate that this DNA vaccine provides a potent means of protecting against VEEV infections and represents an attractive candidate for further development.

Involvement of CD8+ T cell-mediated immune responses in LcrV DNA vaccine induced protection against lethal Yersinia pestis challenge

Yersinia pestis (Y. pestis) is the causative pathogen of plague, a highly fatal disease for which an effective vaccine, especially against mucosal transmission, is still not available. Like many bacterial infections, antigen-specific antibody responses have been traditionally considered critical, if not solely responsible, for vaccine-induced protection against Y. pestis. Studies in recent years have suggested the importance of T cell immune responses against Y. pestis infection but information is still limited about the details of Y. pestis antigen-specific T cell immune responses. In current report, studies are conducted to identify the presence of CD8+ T cell epitopes in LcrV protein, the leading antigen of plague vaccine development. Furthermore, depletion of CD8+ T cells in LcrV DNA vaccinated Balb/C mice led to reduced protection against lethal intranasal challenge of Y. pestis. These findings establish that an LcrV DNA vaccine is able to elicit CD8+ T cell immune responses against specific epitopes of this key plague antigen and that a CD8+ T cell immune response is involved in LcrV DNA vaccine-elicited protection. Future studies in plague vaccine development will need to examine if the presence of detectable T cell immune responses, in particular CD8+ T-cell immune responses, will enhance the protection against Y. pestis in higher animal species or humans.

In vivo antitumor activity of a recombinant IL-7/HGFbeta hybrid cytokine in mice

The immune cytokine interleukin (IL)-7 and the β-chain of hepatocyte growth factor (HGF) aggregate to form a naturally occurring heterodimer that stimulates the growth of common lymphoid progenitors and immature B and T lymphoid cells. We have cloned and expressed the heterodimer as a single-chain hybrid cytokine [recombinant (r) IL-7/HGFβ], which stimulates short-term hematopoietic stem cells as well as lymphoid precursors. Inasmuch as IL-7 and HGF are known to have antitumor and protumor activities, respectively, we determined here whether either of these activities is exhibited by rIL-7/HGFβ. We show that the in vivo administration of rIL-7/HGFβ markedly inhibits the growth of newly initiated and established tumors and the formation of pulmonary metastases in murine models of colon cancer and melanoma. The antitumor effect of rIL-7/HGFβ correlated with a marked increase in the number of tumor-infiltrating CD4(+) and CD8(+) T cells and activated dendritic cells. A major role for these immune cells in tumor suppression was indicated by the inability of rIL-7/HGFβ to inhibit the growth of tumor cells in vitro and in congenitally athymic mice. Analysis of interferon-γ-secreting T cells showed that the immune response was tumor specific. Our findings justify further evaluation of rIL-7/HGFβ as a novel experimental cancer therapy.

Immunization of newborn and adult mice with low numbers of BCG leads to Th1 responses, Th1 imprints and enhanced protection upon BCG challenge

Neonatal bacille Calmette–Guerin (BCG) vaccination is widely employed to protect against tuberculosis. Predominant Th1 but not mixed Th1/Th2 responses are thought to be protective. If so, effective vaccination must cause Th1 imprints. The immune system of infants differs from that of adults and such differences could critically affect neonatal vaccination. We demonstrate that BCG infection of infant and adult mice produces similar responses. Infection with low and high numbers of BCG, respectively, leads to sustained Th1 and mixed Th1/Th2 responses. Low-dose but not high-dose infection also results in Th1 imprints, guaranteeing a Th1 response upon high-dose challenge, and resulting in optimal bacterial clearance. Our observations on low-dose Th1 imprinting are intriguing in the context of the well-known madras trial. In this trial, the highest dose of BCG, which had insignificant side effects, was administered to over 250,000 human subjects. This high-dose vaccination resulted in insignificant protection against tuberculosis.

Engineering antigen-specific T cells from genetically modified human hematopoietic stem cells in immunodeficient mice

There is a desperate need for effective therapies to fight chronic viral infections. The immune response is normally fastidious at controlling the majority of viral infections and a therapeutic strategy aimed at reestablishing immune control represents a potentially powerful approach towards treating persistent viral infections. We examined the potential of genetically programming human hematopoietic stem cells to generate mature CD8+ cytotoxic T lymphocytes that express a molecularly cloned, “transgenic” human anti-HIV T cell receptor (TCR). Anti-HIV TCR transduction of human hematopoietic stem cells directed the maturation of a large population of polyfunctional, HIV-specific CD8+ cells capable of recognizing and killing viral antigen-presenting cells. Thus, through this proof-of-concept we propose that genetic engineering of human hematopoietic stem cells will allow the tailoring of effector T cell responses to fight HIV infection or other diseases that are characterized by the loss of immune control.

Studies of the anti-platelet factor 4/heparin immune response: adapting the enzyme-linked immunosorbent spot assay for detection of memory B cells against complex antigens

BACKGROUND

The anti-platelet factor 4 (PF4)/heparin immune response, which underlies heparin-induced thrombocytopenia (HIT), has several atypical features: relatively rapid onset even without previous heparin exposure, lack of immune anamnesis, and transience of antibody production.

STUDY DESIGN AND METHODS

We modified the enzyme-linked immunosorbent spot (ELISPOT) assay to investigate for PF4/heparin-specific memory B cells in cardiac surgery patients, in whom the high anti-PF4/heparin immunization rate made a prospective study feasible. The PF4-containing antigen complexes were attached to microtiter plates via a spacer, rather than using nitrocellulose, and the final reaction enzyme substrate was added in melted agarose which, after rapid hardening, localized color development of enzyme-tagged anti-immunoglobulin G (IgG) probes to single PF4/heparin-specific B cells. This modified ELISPOT assay was applied to 58 consecutive patients (testing blood from preoperative baseline and Postoperative Days 6 and 10), in which we compared detectability of PF4/heparin-specific B cells to tetanus toxin-specific B cells (comparator group with presumed vaccination).

RESULTS

No patient had detectable PF4/heparin-specific memory B cells at baseline. In 2 of 30 patients (6.7%) who formed anti-PF4/heparin IgG, PF4/heparin-specific memory B cells (three to four spots/well) were detected by Postoperative Day 10, whereas tetanus toxin-specific memory B cells were found in 12 of 24 (50.0%) patients tested (3-25 spots/well; p < 0.001).

CONCLUSIONS

HIT lacks a strong memory B-cell response, perhaps explaining transience and lack of anamnesis of the anti-PF4/heparin immune response. The technical modifications we describe for the ELISPOT assay, which permit detection of B-cell reactions to complex antigens, could be useful for studying other immunohematologic disorders, for example, drug-dependent thrombocytopenia and acquired hemophilia.

ELISPOT assay on membrane microplates

Membranes used for western blotting can be also used for ELISPOT, an enzyme-linked immunospot assay, which allows determining frequencies of cytokine-secreting immune system cells. In addition to their high antibody-retaining capacity PVDF and NC membranes provide good support to immune system cells cultured in vitro and do not affect their physiology. ELISPOT assays utilizing membrane-backed microplates are used in many areas of research including vaccine development, HIV research, cancer and infection disease research, autoimmune disease, and allergy research.ELISPOT utilizes the same antibody "sandwich" technique as enzyme-linked immunosorbent assay, but unlike the latter ELISPOT belongs to state-of-the-art techniques when outcome of the assay depends on skills and accuracy of the operator, a thorough selection of matched pairs of capture and detection antibodies, and using appropriate staining reagents. This review covers basics of ELISPOT assay including its immunochemical design, selection of reagents and membrane microplates, and some troubleshooting recommendations.

Estimation of low frequency antigen-presenting cells with a novel RELISPOT assay

Adequate presentation of self and foreign antigens is a key factor for efficient T-cell immunosurveillance against pathogens and tumors. Cells presenting foreign antigens usually comprise a rare population and are difficult to detect even at the peak of infection. Here we demonstrate a CD8(+) T-cell-based approach that allows detection of specific antigen-presenting cells (APC) at a frequency of less than 0.0005%. When T cells are in excess, they form rosettes with rare APCs, which appear as single spots in an IFN-gamma ELISPOT assay. Using this RELISPOT (Rosette ELISPOT) method we demonstrate the dynamic interplay between CD8 T cells and professional and non-professional APCs following virus challenge.

Kinase MEKK1 is required for CD40-dependent activation of the kinases Jnk and p38, germinal center formation, B cell proliferation and antibody production

Mice lacking activity of the kinase MEKK1 ('Map3k1(deltaKD)' mice) have defective activation of the kinase Jnk and increased production of T helper type 2 cytokines after T cell receptor ligation. Here we show that Map3k1(deltaKD) mice had defective germinal center formation and diminished production of antibodies recognizing thymus-dependent antigens. Those defects were B cell intrinsic, as MEKK1 was necessary for CD40-mediated activation of the kinases Jnk and p38 and transcription factor c-Jun, as well as for expression of cyclin D2 and activation-induced deaminase. MEKK1 was recruited to CD40 and adaptor molecule TRAF2 after CD40 ligation, and Map3k1(deltaKD) B cells were hypoproliferative after CD40 stimulation. Our data emphasize that MEKK1 is an essential component of signaling cascades needed for thymus-dependent antigen-induced B cell proliferation and antibody production.

Cell-Associated Double-Stranded RNA Enhances Antitumor Activity through the Production of Type I IFN

The efficacy of tumor cell vaccination largely depends on the maturation and activation status of the dendritic cell. Here we investigated the ability of soluble and tumor cell-associated dsRNA to serve as an adjuvant in the induction of protective adaptive antitumor responses. Our data showed that cell-associated dsRNA, but not soluble dsRNA, enhanced both tumor-specific CD8(+) and CD4(+) T cell responses. The cell-associated dsRNA increased the clonal burst of tumor-specific CD8(+) T cells and endowed them with an enhanced capacity for expansion upon a secondary encounter with tumor Ags, even when the CD8(+) T cells were primed in the absence of CD4(+) T cell help. The adjuvant effect of cell-associated dsRNA was fully dependent on the expression of TLR3 by the APCs and their subsequent production of type I IFNs, as the adjuvant effect of cell-associated dsRNA was completely abrogated in mice deficient in TLR3 or type I IFN signaling. Importantly, treatment with dsRNA-associated tumor cells increased the number of tumor-infiltrating lymphocytes and enhanced the survival of tumor-bearing mice. The data from our studies suggest that using cell-associated dsRNA as a tumor vaccine adjuvant may be a suitable strategy for enhancing vaccine efficacy for tumor cell therapy in cancer patients.

Individual mouse analysis of the cellular immune response to tumor antigens in peripheral blood by intracellular staining for cytokines

Among the experimental animal models, mice remain the most widely used for the evaluation of immunotherapeutic strategies. Vaccines against parasites and viral antigens are commonly administered to the appropriate mouse strain which also allows testing of the therapeutic effect. Similarly, in mice transgenic for human tumor associated antigens (TAA), cancer vaccines must lead to breakage of immune tolerance to elicit a significant effect on the tumor. However, one of the major drawbacks in the monitoring of cellular immune responses induced by vaccination is that functional immunological assays require suppression of the animals to collect the spleen or lymph nodes for analysis. Here, we report the application of a rapid intracellular staining (ICS) method to quantify antigen-specific T cells responses in small volumes of murine blood. Genetic vaccination with plasmid DNA followed by electroporation (DNA-EP) and the use of adenoviral vectors (Ad) encoding CEA as a model target antigen were applied to different strains of mice. Optimal blood volume, number of lymphocytes, sensitivity and reproducibility of intracellular staining for IFN-gamma were determined both in non-tolerant/wild type mice as well as in tolerant CEA transgenic mice upon restimulation of PBMCs with CEA peptides. Groups of vaccinated mice were then sacrificed and PBMCs and splenocytes from individual animals were compared for intracytoplasmic detection of IFN-gamma and TNF-alpha. A significant correlation was observed between splenic and blood immune responses. Finally, the cellular immune response was followed over time in groups of vaccinated mice. The kinetics of IFN-gamma producing effectors were measured after priming and successive boosting with adenoviral vectors. We show that intracellular staining for mouse PBMCs is a rapid and simple method to measure antigen-specific immune responses. It does not require animal euthanasia and mirrors the response observed in lymphoid organs such as the spleen.

Evaluation of immunological paradigms in a virus model: are dendritic cells critical for antiviral immunity and viral clearance?

We have examined the role of dendritic cells (DCs) in the antiviral immune response and viral clearance using a transgenic mouse model (CD11c-diphtheria toxin (DT) receptor GFP) that allows for their conditional ablation in vivo. DT administration systemically ablated conventional and IFN-producing plasmacytoid DCs (pDCs) in transgenic, but not nontransgenic littermates, without elimination of splenic macrophages. Unexpectedly, early (12 and 48 h postinfection) viral clearance of vesicular stomatitis virus was normal in DC-depleted mice despite markedly reduced serum titers of type I IFN. DC-depleted mice remained virus-free with the exception of a subset (approximately 30%) that developed overwhelming and fatal brain infections 6 days postinfection. However, DT treatment profoundly inhibited clonal expansion of naive CD8+ vesicular stomatitis virus-specific T cells without altering the primary Th1 and Th2 cytokine response. Optimal clonal expansion required pDCs because selective elimination of these cells in vivo with a depleting Ab also suppressed expansion of tetramer+ cells, although Th1/Th2 cytokine production remained unaltered. Collectively, these data indicate that conventional DCs and to a lesser extent pDCs are critical for proliferation of naive antiviral T cells. However, other components of the primary adaptive immune response (Th1/Th2 cytokines) are essentially normal in the absence of DCs, which may account for the efficient viral clearance seen in DC-depleted mice. Thus, sufficient redundancy exists in the immune system to sustain efficient viral clearance despite loss of an APC considered essential for induction of a primary antiviral immune response.

CD28-mediated costimulation impacts on the differentiation of DC vaccination-induced T cell responses

Costimulatory signals such as the ones elicited by CD28/B7 receptor ligation are essential for efficient T cell activation but their role in anti-tumour immune responses remains controversial. In the present study we compared the efficacy of DC vaccination-induced melanoma specific T cell responses to control the development of subcutaneous tumours and pulmonary metastases in CD28-deficient mice. Lack of CD28-mediated costimulatory signals accelerated tumour development in both model systems and also the load of pulmonary metastases was strongly increased by the end of the observation period. To scrutinize whether lack of CD28 signalling influences priming, homing or effector function of Trp-2(180-188)/K(b)-reactive T cells we investigated the characteristics of circulating and tumour infiltrating T cells. No difference in the frequency of Trp-2(180-188)/K(b)-reactive CD8+ T cells could be demonstrated among the cellular infiltrate of subcutaneous tumours after DC vaccination between both genotypes. However, the number of IFN-gamma-producing Trp-2-reactive cells was substantially lower in CD28-deficient mice and also their cytotoxicity was reduced. This suggests that CD28-mediated costimulatory signals are essential for differentiation of functional tumour-specific CD8+ T-effector cells despite having no impact on the homing of primed CD8+ T cells.

Enhancement of cancer radiation therapy by use of adenovirus-mediated secretable glucose-regulated protein 94/gp96 expression

Tumor-derived glucose-regulated protein 94 (GRP94/gp96) has shown great promise as a tumor vaccine. However, current protein-based approaches require the availability of large quantities of tumor tissue, which are often not possible. In addition, the efficacy of immunotherapy is often not ideal when used alone. In this study, we explored the therapeutic efficacy of a combined GRP94/gp96-based genetic immunotherapy and radiation therapy strategy in the weakly immunogenic and highly metastatic 4T1 murine mammary cancer model. An adenovirus encoding a modified, secretable form of GRP94 gene (AdsGRP94) was constructed and evaluated in various antitumor experiments. Lethally irradiated, virus-infected cells were used as vaccines. Adenoviral vectors were also injected directly into tumors in conjunction with tumor irradiation. Vaccination with lethally irradiated, AdsGRP94-infected 4T1 cells completely prevented subsequent tumor growth from challenge inoculations of as many as 10(7) cells per mouse. In established tumor models, vaccinations alone had minimal effect on local and metastatic tumor growth. However, when vaccination was combined with radiation therapy and i.t. AdsGRP94 injections, local tumor growth and pulmonary metastasis were markedly inhibited. In some cases, complete tumor regression was observed. In these cases, the mice were resistant to subsequent tumor challenge and remain tumor free up to 10 months after initial therapy. Our results indicate that combined AdsGRP94-based immunotherapy and radiation therapy may be a potentially effective strategy for cancer treatment.

Statistical evaluation for detection of peptide specific interferon-gamma secreting T-cells induced by HIV vaccine determined by ELISPOT assay

Interferon-gamma (IFN-gamma) secreting T-cells play an important role in immunodeficiency virus (HIV) disease pathogenesis. A common technique to determine the efficacy of the HIV vaccines in murine models is to compare the number of IFN-gamma secreting T-cells induced by HIV vaccine to a control group. The measurement of IFN-gamma secreting T-cells relies on an ELISPOT assay. This assay is carried out in triplicate wells from the same mouse on the same ELISPOT plate. The numbers of spot forming cells (SFC) from these wells are correlated counts. Traditionally, simple statistical methods, such as ANOVA or Kruskall-Wallis tests, are performed on means by mouse. These approaches ignore the fact that the data are correlated counts. Count data are usually assumed to follow the Poisson distribution. However, some count data exhibit overdispersion that can affect the test statistics. The negative binomial distribution is an alternative to the Poisson distribution in the presence of overdispersion. Hence, negative binomial regression is a more suitable approach for overdispersed count data. In this study, we used a negative binomial regression to determine that IL-12 was a good adjuvant. The results of the study using a negative binomial regression are discussed.

Impact of macrophage and dendritic cell subset elimination on antiviral immunity, viral clearance and production of type 1 interferon

We report herein that vesicular stomatitis virus (VSV) induced a concurrent primary Th1 (T helper 1) and Th2 cytokine response detectable ex vivo. Liposome-encapsulated clodronate-mediated elimination of CD8- marginal dendritic cells (DCs) and splenic macrophages (m Phi), but not CD8+ interdigitating DCs, prior to infection resulted in a markedly diminished chemokine and Th1 (IL-2, interferon-gamma) cytokine response, although the Th2 response (IL-4) remained relatively intact. Repopulation with marginal DCs and marginal metallophilic macrophages (MMM) restored Th1 cytokine profiles but did not restore chemokine responsiveness or reduce VSV-induced morbidity/mortality. Chemokine competency returned approximately 4 weeks post-depletion, which correlated temporally with repopulation of the spleen with marginal zone macrophages (MZM) and red pulp macrophages (RPM). Unexpectedly, virus-induced morbidity persisted for over 1 month post-depletion and was associated with virus dissemination and distinctive histological lesions in the liver. Depletion of interferon-producing plasmacytoid dendritic cells did not account for virus-induced morbidity because serum levels of type I interferon were not diminished in Cl2MBP-liposome-treated mice. Thus, distinct m Phi subsets are critical for chemokine production and viral clearance, and, in their absence, VSV disseminates even in the presence of high titers of interferon.

Adenoviruses as vaccine vectors

Adenoviruses have transitioned from tools for gene replacement therapy to bona fide vaccine delivery vehicles. They are attractive vaccine vectors as they induce both innate and adaptive immune responses in mammalian hosts. Currently, adenovirus vectors are being tested as subunit vaccine systems for numerous infectious agents ranging from malaria to HIV-1. Additionally, they are being explored as vaccines against a multitude of tumor-associated antigens. In this review we describe the molecular biology of adenoviruses as well as ways the adenovirus vectors can be manipulated to enhance their efficacy as vaccine carriers. We describe methods of evaluating immune responses to transgene products expressed by adenoviral vectors and discuss data on adenoviral vaccines to a selected number of pathogens. Last, we comment on the limitations of using human adenoviral vectors and provide alternatives to circumvent these problems. This field is growing at an exciting and rapid pace, thus we have limited our scope to the use of adenoviral vectors as vaccines against viral pathogens.

Human immunodeficiency virus type 1 gag-specific mucosal immunity after oral immunization with papillomavirus pseudoviruses encoding gag

Mucosal surfaces are the primary portals for human immunodeficiency virus (HIV) transmission. Because systemic immunization, in general, does not induce effective mucosal immune responses, a mucosal HIV vaccine is urgently needed. For this study, we developed papillomavirus pseudoviruses that express HIV-1 Gag. The pseudoviruses are synthetic, nonreplicating viruses, yet they can produce antigens for a long time in the immune system. Here we show that oral immunization of mice by the use of papillomavirus pseudoviruses encoding Gag generated mucosal and systemic Gag-specific cytotoxic T lymphocytes that effectively lysed Gag-expressing target cells. Furthermore, the pseudoviruses generated Gag-specific gamma interferon-producing T cells and serum immunoglobulin G (IgG) and mucosal IgA. In contrast, oral immunization with plasmid DNA encoding HIV-1 Gag did not induce specific immune responses. Importantly, oral immunization with the pseudoviruses induced Gag-specific memory cytotoxic T lymphocytes and protected mice against a rectal mucosal challenge with a recombinant vaccinia virus expressing HIV-1 Gag. Thus, papillomavirus pseudoviruses encoding Gag are a promising mucosal vaccine against AIDS.

CD4 on CD8(+) T cells directly enhances effector function and is a target for HIV infection

Costimulation of purified CD8(+) T lymphocytes induces de novo expression of CD4, suggesting a previously unrecognized function for this molecule in the immune response. Here, we report that the CD4 molecule plays a direct role in CD8(+) T cell function by modulating expression of IFN-gamma and Fas ligand, two important CD8(+) T cell effector molecules. CD4 expression also allows infection of CD8 cells by HIV, which results in down-regulation of the CD4 molecule and impairs the induction of IFN-gamma, Fas ligand, and the cytotoxic responses of activated CD8(+) T cells. Thus, the CD4 molecule plays a direct role in CD8 T cell function, and infection of these cells by HIV provides an additional reservoir for the virus and also may contribute to the immunodeficiency seen in HIV disease.

Shift from Systemic to Site-Specific Memory by Tumor-Targeted IL-2

IL-2 has been approved for treatment of patients with cancer. Moreover, it has been used as a component of vaccines against cancer. In this regard, we have recently demonstrated that dendritic cell-based peptide vaccination in mice required IL-2 to mount an effective immune response against established melanoma metastases. In this study, we confirm this observation by use of tumor-targeted IL-2. However, the development of a protective systemic memory was substantially impaired by this measure, i.e., mice, which successfully rejected s.c. tumors of B16 melanoma after vaccination with dendritic cells pulsed with tyrosinase-related protein 2-derived peptides plus a boost with targeted IL-2, failed to reject a rechallenge with experimental pulmonary metastases. Detailed analysis revealed a change in the distribution of the tumor-reactive T cell population: although targeted IL-2 expanded the local effector population, tyrosinase-related protein 2-reactive T cells were almost completely depleted from lymphatic tissues.

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.

The VITAL assay: a versatile fluorometric technique for assessing CTL- and NKT-mediated cytotoxicity against multiple targets in vitro and in vivo

Assessment of cell-mediated toxicity has traditionally been achieved by measuring the specific activity of enriched effector cell populations against antigen-loaded target cells labeled with radioactive isotopes in vitro. Fluorometric techniques are viewed as a promising alternative to the use of radioactive isotopes for these analyses. Direct assessment of cytotoxicity in vivo can be achieved by monitoring survival of injected fluorescent targets relative to a differentially labeled internal control population without specific antigen. We have developed this approach, incorporating the use of multiple target cell populations labeled with different dyes so that cytotoxicity can be assessed against titrated doses of a given antigen, or against a range of different antigens, simultaneously. We show that this assay, referred to as the VITAL assay, can be used to assess cytotoxic activity of CTL and iNKT cells in vivo and in vitro. CTL responses measured in vivo could be correlated with antigen doses used in immunization strategies, and also with the size of specific CTL populations enumerated in the blood with fluorescent MHC/peptide tetramers. The VITAL assay is, therefore, a sensitive technique allowing analysis of complex multi-epitope responses.

Nasal instillation of gpMBP can exacerbate murine EAE: effect of mucosal priming is an age-dependent phenomenon

Nasal installation or oral feeding of antigens can alter the subsequent immune response in animals and humans. Most mucosal treatments with antigens tend to down-regulate disease, inducing full tolerance or immune deviation; however, priming has also been reported. We evaluated the course of experimental autoimmune encephalomyelitis (EAE) in (SJL x B10.PL)F1 mice after nasal instillation of myelin basic protein. There was a tendency towards exacerbation of subsequent disease in animals if they were nasally exposed to gpMBP during the neonatal period (first week of life), compared to exposure during adulthood. Later, at 11 months of age, this tendency to exacerbate disappeared. Our results suggest that mucosal exposure during early life may regularly modulate the anti-self immune response upwards in individuals genetically predisposed to autoimmune diseases.

Immunologic monitoring

The development of reliable in vitro assays that could allow the quantitation and characterization of anti-donor alloimmune responses has always been a goal in clinical transplantation, both to predict presensitization to the transplanted tissue and to be able to identify rejection without resorting to more invasive tests. With recent development in our understanding of transplantation biology and therapeutics, there is a real expectation that these tests may be used to identify tolerance as much as to predict rejection. The traditional limiting dilution assays still have a contribution to make and are being complemented by an array of tools, such as ELISpot, flow cytometry-based techniques, and microarray analysis. The assays that have been informative, to date, are discussed in this review. This information will lead, at least, to a better understanding of how and when the rejection process occurs. More interestingly, the objective is to apply this information to evaluate tolerance-inducing strategies or to identify patients that have become tolerant to their graft and can be weaned of immunosuppression. Of course sensitive, accurate and specific immunologic monitoring has applications well beyond the field of transplantation.

Soluble HIV-specific T cell receptor: expression, purification and analysis of the specificity

We have produced soluble T cell receptor (TCR) derived from a human CD8(+) cytotoxic T lymphocyte (CTL) clone D3 that recognizes the immunodominant HIV Gag peptide SLYNTVATL (SL9) in association with major histocompatibility complex (MHC) class I protein HLA-A2. Drosophila Schneider cells (S2) were used to express genes coding the TCR alpha and beta chains under an inducible promoter. Both chains were labeled with two different tags: a (His)(6) was introduced at the C-terminal end of alpha chain, while beta chain was terminated by c-myc. Since an isolated alpha chain is unstable unless it is associated with a beta chain, this design permits rapid separation of alpha,beta-heterodimer from unpaired beta chain in a single step of Ni-NTA Agarose chromatography yielding 90% pure alpha,beta-TCR. Introduction of the c-myc epitope to the beta chain allows capture of soluble D3 from the culture supernatant by immobilized anti-c-myc antibody, without the need for receptor purification. The TCR specificity was then examined by analyzing the binding of peptide-HLA-A2/tetramer in an ELISA assay. Using this assay, we have also evaluated the binding of monomeric SL9-HLA-A2 complex to the immobilized D3 TCR and determined that the affinity measurement of the D3-SL9-HLA-A2 reaction is similar to that obtained by a biosensor instrument. We propose that the approach described here is generally useful for purification of other soluble TCRs and will allow rapid analysis of their specificity.

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Vaccinia assay for the rapid detection of functional HIV-specific CD8+ cytotoxic T lymphocytes

Human immunodeficiency virus (HIV)-specific T cells play a critical role in anti-virus immunity. Therefore, during the clinical development of immune-based therapies, it is important to perform a diagnostic test that rapidly quantifies and characterizes cellular immune responses. For detection of functional HIV-specific CD8(+) cytotoxic T cells (CTL), we used a rapid vaccinia assay that employs recombinant vaccinia virus-infected peripheral blood mononuclear cells (PBMC). This assay was compared with the traditional 51Cr-release CTL assay and with the peptide pool-based enzyme-linked immunospot assay (ELISPOT). We demonstrated a close correlation between these assays by using identical antigens in parallel assays. However, the vaccinia assay was the least expensive and time- and labor-consuming test. Regarding sensitivity, the vaccinia assay was similar to both the peptide pool-based ELISPOT and CTL assays. We showed that human histocompatibility leukocyte antigen (HLA)-Dr(+) cells are responsible for presenting recombinant vaccinia antigens to T cells. The recombinant vaccinia-based assay is a rapid, sensitive and quantitative test and is thus suitable for the detection of functional antigen-specific CD8(+) CTL in large-scale clinical studies.

CD8 T cell immunome analysis of Listeria monocytogenes

The identification of T cell epitopes is crucial for the understanding of the host response during infections with pathogenic microorganisms. Generally, the identification of relevant T cell responses is based on the analysis of T cell lines propagated in vitro. We used an ex vivo approach for the analysis of the CD8 T cell response against Listeria monocytogenes that is based upon the fractionation of naturally processed antigenic peptides and subsequent analysis with T cells in an enzyme-linked immunospot (ELISPOT) assay. Our data indicate that the direct ex vivo ELISPOT analysis of peptides extracted from infected tissues represents a versatile and potent test system for the analysis of the CD8 T cell immunome of microorganisms that furthermore requires neither the knowledge of the microbial genome nor of the specificity of responding T cells.

Total lymphoid irradiation nonmyeloablative preconditioning enriches for IL-4-producing CD4+-TNK cells and skews differentiation of immunocompetent donor CD4+ cells

Preconditioning with the nonmyeloablative regimen total lymphoid irradiation (TLI) before hematopoietic cell transplantation facilitates the establishment of mixed chimerism and protects against graft-versus-host disease. We reported that the development of mixed chimerism requires interleukin (IL)-4 and is associated with increased host anti-donor TH2 cells, but the effect of TLI on the differentiation of immunocompetent donor cells has not been investigated. To examine the extent to which TLI preconditioning influences donor T cells, we measured responses of transgenic CD4+cells specific for ovalbumin peptide (OVA-Tg) following in vivo and in vitro antigen stimulation in a TLI-preconditioned environment. OVA-Tg cells that were adoptively transferred into TLI-preconditioned mice that express cross-reactive antigens produced more IL-4 and less interferon-gamma and IL-2 than controls when stimulated with OVA peptide one week later. OVA-Tg primed in vitro with spleen from TLI-preconditioned mice generated more TH2 and fewer TH1 cells when stimulated in recall enzyme-linked immunosorbent spot (ELISPOT) assays with OVA peptide. Naive OVA-Tg up-regulated CD69 and CD25 normally following stimulation with OVA peptide in the presence of spleen from TLI-preconditioned mice, but proliferated less and secreted less IL-2 than controls. Surprisingly, naive OVA-Tg secreted IL-4 in primary cultures that were stimulated with OVA peptide in the presence of spleen from TLI-preconditioned mice. This response depends on CD4+cells from TLI-spleen, which constitutively produce IL-4 and are composed primarily of CD4+-natural killer T (TNK) cells. Thus, TLI preconditioning enriches for IL-4-secreting and TNK-like CD4+cells that may function in the protection from graft-versus-host disease by redirecting the differentiation of immunocompetent donor CD4+cells toward TH2 and away from pathogenic TH1 cells.

A high frequency of allergen-specific CD8+ Tc1 cells is associated with the murine immune response to the contact sensitizer trinitrophenyl

Chemical haptens induce a variety of allergic immune reactions by induction of hapten-specific T cells. Contact sensitizers such as the hapten trinitrochlorobenzene (TNCB) elicit an allergic response, which is confined to the area of antigen exposure. Despite this localized allergic response, we show here that the trinitrophenyl (TNP)-specific immune response is characterized by a rapid induction of CD8+ Tc1 type cytotoxic effector cells already after a single allergen contact which can be detected in all secondary lymphoid organs tested. We furthermore demonstrate that the rapid induction of CD8+ Tc1 effector cells correlates with an unusually high frequency of polyclonal TNP-specific CD8+ effector T cells with specificities for a variety of MHC class I binding TNP-peptides carrying the hapten in different positions. These data suggest that allergies to chemical haptens may in part be due to an unusually high frequency of polyclonal, allergen-specific effector cells which are detected in all secondary lymphoid organs.

Merozoite surface protein 1-specific immune response is protective against exoerythrocytic forms of Plasmodium yoelii

One of the difficulties in developing an effective malaria vaccine is the antigenic change of the parasite during the life cycle. It is desirable that vaccine-induced protective immunity be effective at different stages of parasite development. Merozoite surface protein 1 (MSP1) is a candidate vaccine antigen against blood-stage malaria, but it is also expressed in the exoerythrocytic forms. It was not known, however, whether the anti-MSP1 immune response is effective against the liver-stage malaria parasite. We generated a recombinant protein of MSP1 fused to heat-shock cognate protein 70 (hsc70) and studied its vaccination effect. When C57BL/6 mice were immunized with the fusion protein prior to challenge infection with Plasmodium yoelii sporozoites, the onset of parasitemia was delayed or no parasitemia was observed. To determine whether this was due to the protective immunity against liver-stage parasites, P. yoelii-specific rRNA in the infected liver was quantitated by real-time reverse transcription-PCR analysis. The level of parasite-specific rRNA was reduced in mice immunized with the fusion protein of MSP1 and hsc70 but not with hsc70 alone, indicating that MSP1-specific immunity can be protective against the exoerythrocytic form of the parasite. Furthermore, the adoptive transfer experiments of immune lymphocytes and serum into naive mice suggested that the protective immunity was dependent on cellular and not humoral immunity. Finally, the vaccine-induced protection was also observed in A/J, C3H, and BALB/c mice, suggesting that MSP1-specific protective immunity at the exoerythrocytic stage can be induced in animals over a wide range of genetic backgrounds.

Requirements for developing mixed-chimerism in nonmyeloablative total-lymphoid irradiated mice: role of IL-4 and immunoredirection

BACKGROUND

Adult mice treated with total-lymphoid irradiation (TLI) followed by hematopoietic cell transfer develop stable mixed-chimerism. The purpose of the study is to examine the requirements for the development of mixed-chimerism and characterize the immune responses associated with mixed-chimerism.

METHODS

T-cell number and function were examined in spleens of TLI-treated mice at various times after the completion of TLI by fluorescence-activated cell sorter (FACS) analysis and enzyme-linked immunosorbent assay (ELISA). TLI-treated BALB/c mice were injected with CAF(1) spleen cells between 2 and 28 days after completing TLI, with or without concurrent anti-IL-4. The extent of mixed-chimerism was determined using multiparameter FACS analysis. Enzyme-linked immunosorbent spot (ELISPOT) assays were used to measure anti-donor CD4+ and CD8+ immune responses.

RESULTS

TLI treatment results in transient lymphopenia, sparing CD4 cells relative to CD8 cells, followed by gradual, partial recovery over 28 days. Day 2 post-TLI T cells produce more interleukin (IL)-4, but less IL-2, interferon (IFN)-gamma and IL-10, while day 28 post-TLI T cells produce more IFN-gamma relative to IL-4. More than 70% of mice develop mixed-chimerism when injected with CAF(1) cells at 2 days post-TLI, while none become chimeric if injected at 28 days post-TLI. Mixed-chimeric mice contain more anti-donor Th2 CD4 cells and less anti-donor TC1 CD8 cells compared with nonchimeric mice and nonirradiated controls. Treatment with anti-IL-4 inhibits the development of mixed-chimerism ( <0.05), and these nonchimeric mice contain donor-reactive TC1 CD8 cells.

CONCLUSIONS

IL-4 plays a role in the development of mixed-chimerism, perhaps by inhibition of anti-donor TC1 CD8 cells or enhancement of anti-donor Th2 CD4 cells.

Improvement of the enzymatic stability of a cytotoxic T-lymphocyte-epitope model peptide for its oral administration

Oral administration of peptide antigens, to provide proper mucosal and/or systemic immunity, is largely ineffective. This is mainly due to the very small quantity of antigen that survives degradation in the intestine and that crosses the intestinal absorption membrane. The present study focuses on the improvement of the enzymatic stability of a 13 amino acid long peptide containing a cytotoxic T-lymphocytes (CTL)-epitope. Within this study, it is shown, that simple chemical modification at the N- and C-terminus of the peptide can provide significant stability towards enzymatic attack by intestinal exopeptidases. Around 50% of the modified peptide resisted enzymatic attack on native porcine intestinal mucosa within 3h of incubation at pH 6.8 and 37 degrees C, whereas unmodified control peptide was almost completely degraded within the same time period. Additionally, a mucoadhesive drug carrier matrix with specific inhibitory properties towards luminally secreted endopeptidases has been generated. The incorporation of the simply modified peptide in this delivery system should enhance the amount of biologically active antigen being available at the mucosal site for further presentation to immunomodulating systems. This might open the door for a successful oral immunotherapy.

Decreased IL-2, IFN-gamma, and IL-10 production by aged mice during the acute phase of E55+ retrovirus infection

We previously reported that aged mice demonstrated a 12-week delay in virus clearance compared to young mice after infection with E55+ murine leukemia retrovirus (E55+MuLV). The current study demonstrates that both the levels of IL-2, IFN-gamma, and IL-10 and the number of cells producing IL-2 and IFN-gamma were lower at 2 and 4 weeks postinfection (p.i.) in aged compared to young mice after virus-specific stimulation of spleen cells in vitro. In both age groups, IL-2 and IL-10 were produced by CD4(+) T and B cells, respectively. IFN-gamma was produced mainly by CD4(+) T cells at 2 weeks p.i. and by CD4(+) and CD8(+) T cells at 4 weeks p.i. in young, but primarily by CD8(+) T cells, in aged mice. Therefore, delayed virus clearance is associated with age-related decreases in type 1 and type 2 cytokines and a shift in the primary source of at least one cytokine.

Oxidised mannan-listeriolysin O conjugates induce Th1/Th2 cytokine responses after intranasal immunisation

Clearance of infectious organisms does not always require polarised Th1 or Th2 responses and it may be advantageous for both Th1 and Th2 responses to be elicited for effective protection against an invading pathogen. It was the aim of this study to investigate oxidised mannan as a possible Th1/Th2 adjuvant. Oxidised mannan was conjugated to two candidate antigens and delivered intranasally to mice. Immunisation with the oxidised conjugate resulted in significant antigen specific proliferative responses, IL-2, IFN-gamma and IL-4 production when compared to unconjugated controls.