T helper cells, IL-2 and the generation of cytotoxic T-cell responses

Therapeutic effect of multiple functional minicircle vector encoding anti-CD25/IL-10/CXCR3 in allograft rejection model

BACKGROUND/AIMS

We previously proposed minicircle vector technology as the potential platform for the development and production of new biologics. In this study, we have designed a novel target molecule for the treatment of allograft rejection and evaluated its feasibility as the therapeutic agent in this disease using the minicircle vector system.

METHODS

We engineered vectors to carry cassette sequences for anti-CD25, interleukin-10 (IL-10), and C-X-C motif chemokine receptor 3 (CXCR3) fusion protein, and then isolated minicircle vectors from the parent vectors. We verified the substantial production of anti-CD25/IL-10/CXCR3 fusion protein from minicircles and their duration in HEK293T cells and mice models. We also evaluated whether minicircle-derived anti-CD25/IL-10/CXCR3 has therapeutic effects in a skin allograft in mice model.

RESULTS

We confirmed the production of anti-CD25/IL-10/CXCR3 from minicircle by its significant availability in cells transfected with the minicircle and in its conditioned media. After a single injection of minicircle by hydrodynamic injection via mouse tail vein, luminescence or red fluorescence was maintained until 40 days in the liver tissue, suggesting the production of anti-CD25/IL-10/CXCR3 protein from minicircles via protein synthesis machinery in the liver. Mice treated with the minicircle encoding anti-CD25/IL-10/CXCR3 showed prolonged skin allograft survival times accompanied by improved immunologic regulation e.g., reduction of the lymphocyte population of Th1, Th2, and Th17 and an induction of regulatory T cells.

CONCLUSION

These findings implied that self-generated anti-CD25/IL-10/CXCR3 protein drug by minicircle technology is functionally active and relevant for reducing allograft rejection. The minicircle vector system may be useful for developing new biological drugs, avoiding manufacturing or practical problems.

Immunoregulatory activities of the selenylated polysaccharides of Lilium davidii var. unicolor Salisb in vitro and in vivo

Studies have demonstrated that the modification of selenylation can improve the activity of polysaccharides. Lilium davidii var. unicolor Salisb (known as "lily bulb") is the dried succulent bulb of the genus Lilium in the family Liliaceae. We wished to investigate the immunoregulatory activities of the selenized polysaccharides of lily bulb (sLP). We undertook experiments in vitro and in vivo taking the unmodified polysaccharides of lily bulb (LP) as controls. The results of in vitro studies showed that sLP could promote the phagocytosis of RAW 264.7 cells significantly, increase the content of interleukin (IL)-1β and IL-2, enhance the activity of acid phosphatase, and increase the surface molecular expression of CD86 and CD80. The results of in vivo studies showed that sLP could improve the index of immune organs, increase the contents of interferon-γ, IL-6, immunoglobulin (Ig)G and IgM in serum, and promote lymphocyte proliferation. The immunoregulatory activities of sLP were significantly more robust than those of LP in vitro and in vivo. These results indicated that selenylation could enhance the immune-enhancement activity of LP significantly.

Some Common SNPs of the T-Cell Homeostasis-Related Genes Are Associated with Multiple Sclerosis, but Not with the Clinical Manifestations of the Disease, in the Polish Population

Purpose

Multiple sclerosis (MS) is an autoimmune disease, and genetic factors play an important role in its pathogenesis and progression. The aim of our study was to evaluate the frequencies of alleles and genetic variants of the T-cell homeostasis-related genes, in subjects with MS, as well as to investigate the association with MS clinical manifestations and disability.

Methods

94 subjects with MS and 160 healthy individuals have been genotyped for seven common single-nucleotide variants in IL-2RA, CTLA4, CD40, and PADI4 genes. The ages of onset, duration of the disease, and clinical condition of the MS subjects were analysed. We used the Chi² test confirmed with Fisher's exact test for statistical analysis.

Results

The frequency of allele T and CT/TT genotypes (rs7093069) in the IL2RA gene, as well as the T allele and CT/TT genotypes in rs12722598, were significantly higher in the control group. The significant differences between studied groups we also found for the G allele and GG/GA genotypes of rs3087243 in CTLA4 gene, which were more common among the control group. The heterozygous genotype TC (rs1883832) of CD40 gene was more common in the control subjects, and the frequency of the alleles and genotypes in the rs1748033 of the PADI4 gene did not differ between the studied groups. Between the studied genotypes, we did not observe any significant differences in the age of onset and duration of disease, including sex stratification.

Conclusion

Our results highlight the protective role of some of the T-cell homeostasis-related genetic variants in MS development, but not in its clinical manifestation.

Leukocyte populations in peripheral blood of dromedary camels with clinical endometritis

Endometritis represents the main cause of reproductive failure in dromedary camels. In dromedary camels, associations between endometritis-causing pathogen-species, disease severity, and systemic changes in the immune system have not been evaluated. In the current study, there was use of flow cytometry and immunofluorescence of membrane proteins for the evaluation of leukocyte subsets and the cellular phenotype in blood of camels with clinical endometritis and evaluations of associations with disease severity and endometritis-causing pathogens. Animals with endometritis had markedly larger numbers of total leukocytes and neutrophils. Although total lymphocyte and monocyte counts did not differ between camels with and without clinical endometritis, there were lesser numbers of total and effector CD4-positive T cells in camels with endometritis. Among monocytes, number of camel inflammatory monocytes (Mo-II) was markedly greater, whereas Mo-III numbers were less in the blood of camels with clinical endometritis. Number of inflammatory monocytes was also indicative of endometritis severity grade. Among camels with clinical endometritis, E. coli- and S. aureus-infected animals had similar endometritis grades and comparable phenotype and composition patterns of leukocytes. Neutrophils and monocytes of camels with clinical endometritis had fewer cell adhesion molecules (i.e., CD11a and CD18). Collectively, the results from the current study allowed for identification of associations between endometritis severity grade and larger numbers of inflammatory monocytes. The results also indicate there is no association between endometritis pathogen-species and changes in phenotype or composition of blood leukocytes.

Host cell in vivo production of the synthetic drug anti-CD25/IL-10 using minicircle vector

Synthetic biologic drugs are highly successful for induction therapy in transplantation, but the development of novel biologics is limited because of the high cost of synthesis and purification. In this study, we developed a novel strategy for the production of synthetic protein drugs in vivo by the host itself. We utilized minicircle (MC) technology, which can robustly express a target molecule and secrete it from cells, as an indirect method to produce a protein of interest in vivo. We designed an MC vector containing the sequences of basiliximab (anti-CD25 mAb) and IL-10. We verified the substantial production of the anti-CD25/IL-10 protein from the MC in vitro and in vivo. The therapeutic effect of MC-derived anti-CD25/IL-10 was evaluated in a skin allograft mouse model by single intravenous infusion. Mice treated with the MC encoding anti-CD25/IL-10 exhibited prolonged skin allograft survival times accompanied by improved histologic changes and immunologic regulation. These findings indicate that the anti-CD25/IL-10 protein drug obtained by MC technology is functionally active and relevant for reducing allograft rejection. This self-reproducible strategy for synthetic protein drugs using MCs is a promising tool for transplantation.-Lim, S. W., Shin, Y. J., Luo, K., Quan, Y., Ko, E. J., Chung, B. H., Yang, C. W. Host cell in vivo production of the synthetic drug anti-CD25/IL-10 using minicircle vector.

Learning to control tissue damage while fighting Aspergillus

Aspergillus moulds are increasingly being recognised as significant human pathogens that can cause life-threatening infections in the context of host immune dysregulation, particularly in the lung. It is now clear that there is a close relationship between infection susceptibility and the fine regulation of pulmonary immunity and inflammation. While the contribution of IL-17/Th17 responses to both physiological and pathological lung inflammation is now well established, the cellular interactions, soluble factors, and signalling pathways that determine Th17 cell responses to fungal infection remain unclear. Here, we identify potential key mediators of fungus-DC-T cell interactions in the respiratory tract, with a focus on the DC-derived cytokines thought to exert a major influence on generation of pathological Th17 cells. We review recent data indicating a crucial role for Aspergillus-induced autophagy in lung DCs on subsequent T-cell polarization and modulation of 'stemness', which appears critical for avoiding pathological lung inflammation and promoting disease resolution.

An immunogenic phenotype in paternal antigen-specific CD8+ T cells at embryo implantation elicits later fetal loss in mice

Central to pregnancy success is a state of T cell tolerance to paternal antigens, which is initiated at conception. The role and regulation of specific phenotypes of CD8⁺ T cells in mediating pregnancy tolerance is not clear. This study aimed to investigate the impact on pregnancy outcome of altering the cytokine environment during maternal CD8⁺ T cell priming in early pregnancy. Transgenic Act-mOVA male mice were mated to C57BL/6 (B6) females to generate fetuses expressing ovalbumin (OVA) as a model paternal antigen. OVA-reactive CD8⁺ OT-I T cells were activated in vitro with OVA in the presence of either transforming growth factor-β1 (TGFB1) plus interleukin-10 (IL10), or IL2, to mimic normal or dysregulated uterine conditions, respectively, and transferred into pregnant mice on gestational day 3.5. OT-I T cells activated with TGFB1 and IL10, like naive OT-I T cells, did not alter embryo implantation or fetal viability. In contrast, OT-I T cells activated with IL2 caused extensive fetal loss manifesting in mid-gestation. IL2-activated OT-I T cells expressed less FOXP3 and higher interferon-γ (IFNG) than cells activated with TGFB1 and IL10. Fetal loss did not occur in females mated with B6 males, demonstrating the antigen specificity of fetal loss, and was not abrogated by maternal genetic C1q deficiency indicating a mechanism independent of antibody-mediated cytotoxicity. These data indicate that alternative phenotypes generated in maternal CD8⁺ T cells at the time of priming with paternal antigens can impact pregnancy outcome, such that inappropriate activation of CD8⁺ T cells before implantation is capable of causing antigen-specific fetal loss later in pregnancy.

Cytokine production associated with smallpox vaccine responses

Smallpox was eradicated 34 years ago due to the success of the smallpox vaccine; yet, the vaccine continues to be studied because of its importance in responding to potential biological warfare and the adverse events associated with current smallpox vaccines. Interindividual variations in vaccine response are observed and are, in part, due to genetic variation. In some cases, these varying responses lead to adverse events, which occur at a relatively high rate for the smallpox vaccine compared with other vaccines. Here, we aim to summarize the cytokine responses associated with smallpox vaccine response to date. Along with a description of each of these cytokines, we describe the genetic and adverse event data associated with cytokine responses to smallpox vaccination.

Protein malnutrition alters spleen cell proliferation and IL-2 and IL-10 production by affecting the STAT-1 and STAT-3 balance

Protein malnutrition (PM) is an important public health problem that affects resistance to infection by impairing a number of physiological processes. PM induces structural changes in the lymphoid organs that affect the roles of the immune and inflammatory responses in a crucial way. The activation of different transcription factors, including signal transducer and activator of transcription (STAT) family members, leads to the production of different cytokines, which are mediators essential to mounting adequate immune and inflammatory responses. In this study, malnourished animals presented anemia, leukopenia, and a severe reduction in spleen cellularity, with reduced numbers of most cell populations, as well as increased percentages of CD3(+) and CD4(+) cells. The proliferation rates were reduced, and cells were increasingly observed in the G0/G1 cell cycle phase; further, IL-2 production was reduced, while IL-10 production was increased. In spleen cells from malnourished animals, STAT-3 protein expression was increased, with a concomitant reduction in STAT-1 expression. Knowing that STAT-1 and STAT-3 are key transcription factors in both immunity and inflammatory pathways, these results infer, at least in part, a mechanistic pathway that affects the manner or intensity of the immune response in malnourished individuals, increasing susceptibility to infection.

Comparative analysis of cellular immune responses and cytokine levels in sheep experimentally infected with bluetongue virus serotype 1 and 8

Protective immunity in sheep with bluetongue virus (BTV) infection as well as the role of BTV-induced cytokines during immune response remains unclear. Understanding the basis immunological mechanisms in sheep experimentally infected with serotypes 1 and 8 (BTV-1 and -8) was the aim of this study. A time-course study was carried out in order to evaluate cell-mediated immune response and serum concentrations of cytokines (IL-1β, TNFα, IL-12, IFNγ, IL-4 and IL-10) with inflammatory and immunological functions. Depletion of T cell subsets (mainly CD4(+), γδ and CD25(+)) together with the absence of cytokines (IFNγ and IL-12) involved in the regulation of cell-mediated antiviral immunity at the first stage of the disease suggested that both BTV-1 and BTV-8 might impair host's capability against primary infections which would favor viral replication and spreading. However, cellular immune response and cytokines elicited an immune response in sheep that efficiently reduced viremia in the final stage of the experiment. Recovery of T cell subsets (CD4(+) and CD25(+)) together with a significant increase of CD8(+) T lymphocytes in both infected groups were observed in parallel with the decrease of viremia. Additionally, the recovery of CD4(+) T lymphocytes together with the significant increase of IL-4 serum levels at the final stage of the experiment might contribute to humoral immune response activation and neutralizing antibodies production against BTV previously described in the course of this experiment. These results suggested that both cellular and humoral immune response may contribute to protective immunity against BTV-1 and BTV-8 in sheep. The possible role played by IL-10 and CD25(+) cells in controlling inflammatory and immune response in the final stage of the experiment has also been suggested.

Effect of selenylation modification on immune-enhancing activity of Atractylodes macrocephala polysaccharide

The Atractylodes macrocephala polysaccharide (AMP) was extracted purified and modified in selenylation by Nitric acid-sodium selenite method to get nine selenizing AMPs (sAMPs), sAMP(1)-sAMP(9). In vitro test their effects on chicken peripheral lymphocyte proliferation were determined by MTT assay. The results showed that nine sAMPs and AMP at five concentrations could significantly promote lymphocyte proliferation, the actions in six sAMPs were significantly stronger than that in AMP, and in sAMP(9) was the strongest. In vivo test, 14-day-old chickens vaccinated with ND vaccine were injected respectively with sAMP(9) and AMP, the peripheral lymphocytes proliferation, serum antibody titer, IFN-γ, IL-2 and IL-6 contents were determined. The results displayed that the sAMP could significantly promote lymphocyte proliferation and elevate the antibody titers and content of IFN-γ, IL-2 and IL-6 in comparison with unmodified AMP. These results indicate that selenylation modification can significantly enhance the immune-enhancing activity of AMP.

Helper cell-independent antitumor activity of potent CD8+ T cell epitope peptide vaccines is dependent upon CD40L

Peptide vaccines derived from CD8⁺ T-cell epitopes have shown variable efficacy in cancer patients. Thus, some peptide vaccines are capable of activating CD8⁺ T-cell responses, even in the absence of CD4⁺ T-cell epitopes or dendritic cell (DC)-activating adjuvants. However, the mechanisms underlying the clinical activity of these potent peptides are poorly understood. Using CT26 and ovalbumin-expressing B16 murine allograft tumor models, we found that the antitumor effect of helper cell-independent CD8 T-cell peptide vaccines is inhibited by the blockade of CD40 ligand (CD40L) in vivo. Furthermore, in vitro stimulation with antigenic peptides of cells derived from immunized mice induced the expression of CD40L on the surface of CD8⁺ T cells and fostered DC maturation, an effect that was partially inhibited by CD40L-blocking antibodies. Interestingly, CD40L blockade also inhibited CD8⁺ T-cell responses, even in the presence of fully mature DCs, suggesting a role for CD40L not only in promoting DC maturation but also in mediating CD8⁺ T-cell co-stimulation. Importantly, these potent peptides share features with bona fide CD4 epitopes, since they foster responses against less immunogenic CD8⁺ T-cell epitopes in a CD40L-dependent manner. The analysis of peptides used for the vaccination of cancer patients in clinical trials showed that these peptides also induce the expression of CD40L on the surface of CD8⁺ T cells. Taken together, these results suggest that CD40L expression induced by potent CD8⁺ T-cell epitopes can activate antitumor CD8⁺ T-cell responses, potentially amplifying the immunological responses to less immunogenic CD8⁺ T-cell epitopes and bypassing the requirement for CD4⁺ helper T cells in vaccination protocols.

Reversal of global CD4+ subset dysfunction is associated with spontaneous clinical resolution of pulmonary sarcoidosis

Sarcoidosis pathogenesis is characterized by peripheral anergy and an exaggerated, pulmonary CD4(+) Th1 response. In this study, we demonstrate that CD4(+) anergic responses to polyclonal TCR stimulation are present peripherally and within the lungs of sarcoid patients. Consistent with prior observations, spontaneous release of IL-2 was noted in sarcoidosis bronchoalveolar lavage CD4(+) T cells. However, in contrast to spontaneous hyperactive responses reported previously, the cells displayed anergic responses to polyclonal TCR stimulation. The anergic responses correlated with diminished expression of the Src kinase Lck, protein kinase C-θ, and NF-κB, key mediators of IL-2 transcription. Although T regulatory (Treg) cells were increased in sarcoid patients, Treg depletion from the CD4(+) T cell population of sarcoidosis patients did not rescue IL-2 and IFN-γ production, whereas restoration of the IL-2 signaling cascade, via protein kinase C-θ overexpression, did. Furthermore, sarcoidosis Treg cells displayed poor suppressive capacity indicating that T cell dysfunction was a global CD4(+) manifestation. Analyses of patients with spontaneous clinical resolution revealed that restoration of CD4(+) Th1 and Treg cell function was associated with resolution. Conversely, disease progression exhibited decreased Th1 cytokine secretion and proliferative capacity, and reduced Lck expression. These findings implicate normalized CD4(+) T cell function as a potential therapeutic target for sarcoidosis resolution.

The role of IL-2 in the activation and expansion of regulatory T-cells and the development of experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is an autoimmune disease that affects ≈ 400,000 people in the US. It is a chronic, disabling disease with no cure, and the current treatment includes use of immunosuppressive drugs that often exhibit toxic side effects. Thus, there is a pressing need for alternate and more effective treatment strategies that target the components of inflammatory cells. In recent years, regulatory T-cells (Tregs) have been found to play an important role in preventing the development of autoimmunity. Thus, expansion of Tregs in vivo has the therapeutic potential against autoimmune diseases. Because Tregs constitutively express IL-2 receptors (IL-2Rs), we tested the effect of administration of IL-2 on the development of experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis (MS). We used IL-2 both before (pre-treatment) or after (post-treatment) immunization with myelin oligodendrocyte glycoprotein (MOG35-55) peptide to induce EAE. The data demonstrated that pre-treatment with a moderate dose of IL-2 caused significant amelioration of EAE. Tissue histopathology of the central nervous system also confirmed the effectiveness of IL-2 pre-treatment by decreasing cellular infiltration in the spinal cord and preserving tissue integrity. IL-2 pretreatment expanded Treg cells while preventing the induction of Th17 during EAE development. In contrast, post-treatment with IL-2 failed to suppress EAE despite induction of Tregs. Together, these studies demonstrate that while expansion of Tregs using IL-2, prior to immunization or the onset of disease, can suppress the immune response, their role is limited after the antigen-specific response is triggered. Because IL-2 is used to treat certain types of cancers, and Tregs have applications in preventing the rejection of transplants, our studies also provide useful information on the use and limitations of Tregs in such clinical manifestations.

Impact of cytokine and cytokine receptor gene polymorphisms on cellular immunity after smallpox vaccination

We explored associations between SNPs in cytokine/cytokine receptor genes and cellular immunity in subjects following primary smallpox vaccination. We also analyzed the genotype-phenotype associations discovered in the Caucasian subjects among a cohort of African-Americans. In Caucasians we found 277 associations (p<0.05) between gene SNPs and inter-individual variations in IFN-α, IL-12p40, IL-1β, IL-2, and TNF-α secretion levels. A collection of SNPs in the IL1RN, IL2RB, IL4R, IL6, IL10RB, IL12A, and IL12RB2 genes had consistent associations among both Caucasians and African-Americans. A regulatory SNP (rs452204) in the IL1RN gene was significantly associated with higher levels of IL-2 secretion in an allele dose-dependent manner in both race groups (p=0.05 for Caucasians and p=0.002 for African-Americans). IL12RB2 polymorphism rs3790567 was associated with a dose-related decrease in IL-1β secretion (p=0.009 for Caucasians and p=0.01 for African-Americans). Our results demonstrate that variations in smallpox vaccine-induced cytokine responses are modulated by genetic polymorphisms in cytokine and cytokine receptor genes.

Maternal perinatal undernutrition attenuates T-cell function in adult male rat offspring

OBJECTIVE

We investigated the impact of maternal food restriction during gestation and lactation on the number and function of peripheral T cells in adult male offspring.

STUDY DESIGN

Pregnant rats either received ad libitum (control) feed or were 50% food restricted (FR) from day zero of gestation to delivery and during the lactation period. After weaning, pups from control and FR mother rats were fed normally until they reached 8 weeks of age. At 8 weeks of age, blood parameters, plasma cytokine levels, and T cell number and function were determined in 10 male offspring from each group.

RESULTS

FR offspring exhibited decreased numbers of total and CD4+ and CD8+ T lymphocytes and a significant reduction in plasma IL-2 and IL-7 compared with control offspring. In addition, T lymphocytes from FR offspring exhibited a 2-fold decrease in IL-2- and IL-7-mediated AKT and STAT5 phosphorylation, altered actin polymerization, and diminished superantigen-mediated proliferation and cytokine production as compared with control offspring.

CONCLUSIONS

aken together, these findings suggest that early undernutrition, particularly during the prenatal and lactation periods, attenuates T cell survival and the immune response.

T cell receptor-dependent regulation of lipid rafts controls naive CD8+ T cell homeostasis

T cell receptor (TCR) contact with self ligands keeps T cells alive and is shown here to cause naive CD8(+), but not CD4(+), T cells to be hypersensitive to certain gamma(c) cytokines, notably interleukin (IL)-2, IL-15, and IL-7. Hypersensitivity of CD8(+) T cells to IL-2 was dependent on a low-level TCR signal, associated with high expression of CD5 and GM1, a marker for lipid rafts, and was abolished by disruption of lipid rafts. By contrast, CD4(+) T cells expressed low amounts of GM1 and were unresponsive to IL-2. Physiologically, sensitivity to IL-7 and IL-15 maintains survival of resting CD8(+) T cells, whereas sensitivity to IL-2 may be irrelevant for normal homeostasis but crucial for the immune response. Thus, TCR contact with antigen upregulates GM1 and amplifies responsiveness of naive CD8(+) T cells to IL-2, thereby making the cells highly sensitive to exogenous IL-2 from CD4(+) T helper cells.

Cognate CD4 help is essential for the reactivation and expansion of CD8 memory T cells directed against the hematopoietic cell–specific dominant minor histocompatibility antigen, H60

In contrast to previous notions of the help-independency of memory CD8 T cells during secondary expansion, here we show that CD4 help is indispensable for the re-expansion of once-helped memory CD8 T cells, using a hematopoietic cell–specific dominant minor histocompatibility (H) antigen, H60, as a model antigen. H60-specific memory CD8 T cells generated during a helped primary response vigorously expanded only when rechallenged under helped conditions. The help requirement for an optimal secondary response was confirmed by a reduction in peak size by CD4 depletion, and was reproduced after skin transplantation. Helpless conditions or noncognate separate help during the secondary response resulted in a significant reduction in the peak size and different response kinetics. Providing CD4 help again during a tertiary challenge restored robust memory expansion; however, the repeated deprivation of help further reduced clonal expansion. Adoptively transferred memory CD8 T cells did not proliferate in CD40L−/− hosts. In the CD40−/− hosts, marginal memory expansion was detected after priming with male H60 cells but was completely abolished by priming with peptide-loaded CD40−/− cells, suggesting the essential role of CD40 and CD40L in memory responses. These results provide insight into the control of minor H antigen-specific CD8 T-cell responses, to maximize the graft-versus-leukemia response.

Combined triggering of dendritic cell receptors results in synergistic activation and potent cytotoxic immunity

Elimination of malignant cells and intracellular infections involves collaboration between CTLs and Th1 inflammation. Dendritic cells drive this response via costimulation and cytokines. We have defined key signals required for the exponential expansion of specific CD8(+) T cells in vivo in mice. Immunization with two or more TLR agonists, anti-CD40, IFN-gamma, and surfactant were sufficient to drive unprecedented levels of CD8 response to peptide or protein Ag and highly polarized Th1 CD4 responses. CD40 signaling was required for CD8 expansion but could be provided by a concomitant CD4 Th response in place of anti-CD40. Triggering of these pathways activated migration and activation of myeloid and plasmacytoid dendritic cells and secretion of IL-12. Cross-presentation can thus be exploited to induce potent cytotoxic responses and long-term memory to peptide/protein Ags. When combined with a tumor-associated peptide from tyrosinase-related protein 2, our combined adjuvant approach effectively halted tumor growth in an in vivo melanoma model and was more effective than anti-CD40 and a single TLR agonist. Antitumor immunity was associated with long-lived effector memory CD8 cells specific for the naturally processed and presented tumor Ag, and tumor protection was partially but not entirely dependent on CD8 T cells. This flexible strategy is more effective than existing adjuvants and provides a technological platform for rapid vaccine development.

Reduced protection from simian immunodeficiency virus SIVmac251 infection afforded by memory CD8+ T cells induced by vaccination during CD4+ T-cell deficiency

Adaptive CD4(+) and CD8(+) T-cell responses have been associated with control of human immunodeficiency virus/simian immunodeficiency virus (HIV/SIV) replication. Here, we have designed a study with Indian rhesus macaques to more directly assess the role of CD8 SIV-specific responses in control of viral replication. Macaques were immunized with a DNA prime-modified vaccinia virus Ankara (MVA)-SIV boost regimen under normal conditions or under conditions of antibody-induced CD4(+) T-cell deficiency. Depletion of CD4(+) cells was performed in the immunized macaques at the peak of SIV-specific CD4(+) T-cell responses following the DNA prime dose. A group of naïve macaques was also treated with the anti-CD4 depleting antibody as a control, and an additional group of macaques immunized under normal conditions was depleted of CD8(+) T cells prior to challenge exposure to SIV(mac251). Analysis of the quality and quantity of vaccine-induced CD8(+) T cells demonstrated that SIV-specific CD8(+) T cells generated under conditions of CD4(+) T-cell deficiency expressed low levels of Bcl-2 and interleukin-2 (IL-2), and plasma virus levels increased over time. Depletion of CD8(+) T cells prior to challenge exposure abrogated vaccine-induced protection as previously shown. These data support the notion that adaptive CD4(+) T cells are critical for the generation of effective CD8(+) T-cell responses to SIV that, in turn, contribute to protection from AIDS. Importantly, they also suggest that long-term protection from disease will be afforded only by T-cell vaccines for HIV that provide a balanced induction of CD4(+) and CD8(+) T-cell responses and protect against early depletion of CD4(+) T cells postinfection.

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.

Generation of mammaglobin-A-specific CD4 T cells and identification of candidate CD4 epitopes for breast cancer vaccine strategies

BACKGROUND

Mammaglobin-A (MGB) is a breast cancer-associated antigen that is an attractive target for immune intervention. MGB has been shown to induce a specific CD8 T cell response in breast cancer patients, but little is known about a possible MGB-specific CD4 T cell response.

METHODS

Peripheral blood-derived CD4(+)CD25(-) T cells were stimulated in vitro with MGB-pulsed antigen-presenting cells (APC). The MGB and human leukocyte antigen (HLA) class II specificity of the CD4 T cell lines was confirmed by cytokine release following restimulation with autologous and allogenic APC pulsed with MGB from different sources. Candidate HLA class II-restricted epitopes were identified by computer algorithm and validated in cytokine release assays.

RESULTS

MGB-specific CD4 T cells were successfully generated in cultures from six of seven donors. Restimulation of MGB-specific CD4 T cells with MGB-pulsed APC induced significantly higher levels of interferon (IFN)-gamma release than APC pulsed with an irrelevant protein (P = 0.0004). Cultures from five of seven donors showed a pure Th1 type response as evidenced by the absence of interleukin (IL)-4. MGB-specific CD4 T cells recognized both recombinant and naturally processed MGB presented by APC. This recognition was HLA class II-restricted, as HLA-DR mismatched APC were not recognized. MGB-specific CD4 T cells from three of four donors recognized MGB-derived, HLA class II-restricted peptides pulsed onto APC.

CONCLUSIONS

We have successfully generated MGB-specific CD4 T cell cultures and identified candidate MGB HLA class II epitopes. These studies should facilitate study of the CD4 T cell response to MGB, and the development and monitoring of vaccine strategies targeting this unique antigen.

AFP-specific CD4+ helper T-cell responses in healthy donors and HCC patients

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide, and is often diagnosed at an advanced stage. We have investigated alpha-fetoprotein (AFP) as a tumor-associated antigen for HCC. We identified major histocompatibility complex class I-restricted peptide epitopes derived from AFP and studied CD8 T-cell responses in vivo and in vitro in ongoing immunotherapy studies. Helper T cells are of critical importance in shaping the immune response; therefore, we investigated the frequency and function of AFP-specific CD4 T cells in the general population and among HCC patients. CD4 T-cell responses were assessed by direct ex vivo multicytokine enzyme-linked immunospot assay and by measurement of cytokine levels using a multicytokine assay. Our analysis indicates that healthy donors have very low frequencies of AFP-specific CD4 T-cell responses, which are of TH1 type, detectable ex vivo. In contrast, these T cells were either reduced or eliminated in HCC patients at advanced stages of disease. To better activate these cells, we compared the stimulatory capacity of both AFP protein-fed and AdVhAFP-engineered dendritic cells (DC). Healthy donors have CD4 T-cell responses, which were activated in response to AFP protein-fed DC whereas HCC patients do not demonstrate significant responses to AFP protein. AdVhAFP-transduced DC were capable of activating higher frequency TH1 CD4 responses to AFP in both healthy donors and AFP-positive HCC patients. Importantly, CD4 T-cell cytokine expression profiles were skewed towards interleukin-2 and interferon-gamma production when activated by adenovirally engineered DC, which has therapeutic implications for vaccination efforts.

Lentiviral Vectors Encoding HIV-1 Polyepitopes Induce Broad CTL Responses In Vivo

Lentiviral vectors have been tested as vaccination vectors in anti-tumoral and anti-viral models. They efficiently transduce dendritic cells and stimulate strong T-cell responses against the encoded antigen. However, their capacity to stimulate a cytotoxic T-lymphocyte (CTL) response against several antigens has not been evaluated. Broad anti-human immunodeficiency virus 1 (HIV-1) T-cell immune responses are important for the control of HIV replication. We evaluated the potential of polyepitope-encoding lentiviral vectors to induce broad anti-HIV CTL responses. We constructed two lentiviral vectors coding for an HLA-A2- or HLA-B7-restricted polyepitope and evaluated their immunogenicity by direct injection of vector particles in HLA-A2 or HLA-B7 transgenic mice. In vitro cytotoxicity assays showed that a single immunization induces a strong, diversified, and long-lasting CTL response in both mouse models. CTL responses were directed against all 13 epitopes in the HLA-A2 system and 8 out of 12 in the HLA-B7 system. A second immunization augmented the number of responding mice in the HLA-A2 system but not in the HLA-B7 system. HLA-B7-immunized mice mounted strong interferon-gamma (IFN-gamma)-secreting T-cell responses against a majority of the epitopes and lysed peptide-loaded target cells in vivo. CTL responses in HLA-B7 mice were only partially dependent on CD4 T-cell help. This work underlines the potential of lentiviral vectors as candidates for therapeutic vaccination against acquired immunodeficiency syndrome.

IL-2 responsiveness of CD4 and CD8 lymphocytes: further investigations with human IL-2Rbeta transgenic mice

Responsiveness to IL-2 varies from one lympho-mononuclear subset to another. NK lymphocytes and monocytes spontaneously respond to IL-2 whereas it is generally accepted that T and B lymphocytes need to be activated to fully acquire this competence. To further investigate this phenomenon, we studied human IL-2Rbeta (hIL-2Rbeta) transgenic mice constitutively expressing heterospecific, intermediate-affinity IL-2R (hIL-2Rbeta/mouse IL-2Rgamma(c)). We noted that the B lymphocytes and monocytes from spleens of these hIL-2Rbeta transgenic animals failed to grow when cultured in IL-2-containing medium. Under the same experimental conditions, CD4 lymphocytes survived, again without growth, whereas CD8 lymphocytes and NK cells were able to proliferate and develop potent LAK cytotoxicity. The properties of these CD4 and CD8 lymphocytes were then compared after purification. Both subsets expressed functional IL-2R able to induce global protein phosphorylation and, more precisely, signal transducer and activation of transcription 5 and Erk phosphorylation. Therefore, the differential growth potential of these CD4 and CD8 lymphocytes cannot be explained by the lack of IL-2R-dependent early signaling events. When the entrance of purified CD4 and CD8 lymphocytes into the cell cycle was analyzed, we found that the CD4 lymphocytes were unable to enter the G1 phase in the absence of anti-CD3 stimulation. This correlates with the effect of IL-2 on cyclin-dependent kinase inhibitor p27(kip1). In CD4 lymphocytes, IL-2 does not affect p27(kip1) expression. But in CD8 lymphocytes, IL-2 down-modulates p27(kip1). These results indicate that, aside from IL-2R expression and function, IL-2 responsiveness is also controlled by lineage-specific mechanisms.

CD8+T cells produce IL-2, which is required for CD4+CD25+T cell regulation of effector CD8+T cell development for contact hypersensitivity responses

Interleukin (IL)-2 functions to promote, as well as down-regulate, expansion of antigen-reactive CD4+ and CD8+ T cells, but the role of IL-2 in hapten-specific CD8+ T cell priming for contact hypersensitivity (CHS) responses remains untested. Using enzyme-linked immunospot to enumerate numbers of hapten-specific CD4+ and CD8+ T cells producing IL-2 in hapten-sensitized mice, the number of IL-2-producing CD8+ T cells was tenfold that of CD4+ T cells. Hapten-primed CD4+ T cells produced low amounts of IL-2 during culture with hapten-presenting Langerhans cells, whereas production by hapten-primed CD8+ T cells was fivefold greater. CD8+ T cells did not express CD25 during hapten priming, but treatment with anti-IL-2 or anti-CD25 monoclonal antibodies during hapten sensitization increased hapten-specific effector CD8+ T cells as well as the magnitude and duration of the CHS response. These results indicate that CD8+ T cells are the primary source of IL-2 and that this IL-2 is required for the function of a population of CD(4+)CD25+ T cells to restrict the development of the hapten-reactive effector CD8+ T cells that mediate CHS responses.

Assessment by flow cytometry of cytokine production in malnourished children

Malnutrition in children is associated with an increased risk of infection and death. Multiple abnormalities in the immune response, including cytokine production, in protein energy-malnourished children have been described and could account for the increased severity and frequency of infections. In this study, we used flow cytometry to investigate the effects of malnutrition on the production of cytokines (interleukin-2 [IL-2], gamma interferon [IFN-gamma], IL-4, and IL-10) in CD4+ and CD8+ cells and the activation capability (as indicated by CD69+ and CD25+ cells). CD4+ and CD8+ cells from malnourished children showed increased production of IL-4 and IL-10 cytokines and decreased production of IL-2 and IFN-gamma cytokines compared to that in cells from well-nourished, uninfected and well-nourished, infected children. In addition, malnourished children showed impaired activation capability, since the fluorescence intensity of CD69+ and CD25+ cells was lower than that in cells from well-nourished, uninfected and well-nourished, infected children. These results indicate that malnutrition alters the capacity of CD4+ and CD8+ cells to produce IL-2, IFN-gamma, IL-4, and IL-10 in response to stimulus. We concluded that both cytokine production and activation capacity were impaired in malnourished children. This functional impairment may be involved in the failure to develop a specific immune response and the predisposition to infection in these children.

The HIV-1 HLA-A2-SLYNTVATL is a help-independent CTL epitope

The CTL response to the HLA-A*0201-restricted, HIV-1 p17 Gag(77-85) epitope (SLYNTVATL; SL9) has been extensively studied in patients. Although this reactivity is exceptionally prominent in chronically infected patients and inversely correlated to viral load, SL9-specific CTLs (SL9-CTLs) are rarely detected in acute infection. To explore the cellular basis for this unusual manifestation, SL9-CTLs primed ex vivo from naive circulating CD8(+) T cells of healthy, seronegative donors were generated and characterized. SL9 appeared to differ from other well-studied A*0201-restricted epitopes in several significant respects. In contrast to published reports for influenza and melanoma peptides and the HIV gag IV9 epitope studied here in parallel, SL9-CTLs were primed by immature but not mature autologous dendritic cells. Highly activated SL9-CTLs produce sufficient autocrine mediators to sustain clonal expansion and CTL differentiation for months without CD4(+) T cells or exogenous IL-2. Moreover, SL9-CTLs were sensitive to paracrine IL-2-induced apoptosis. IL-2 independence and sensitivity to paracrine IL-2 were also characteristic of SL9-CTLs immunized by dendritic cells transduced by a nonreplicating lentiviral vector encoding full-length Gag. In vitro-primed SL9-CTLs resembled those derived from patients in degeneracy of recognition and functional avidities for both SL9 and its natural mutations. Together, these data show that SL9 is a highly immunogenic, help-independent HIV epitope. The scarcity of SL9-CTLs in acute infection may result from cytokine-induced apoptosis with the intense activation of the innate immunity. In contrast, SL9-CTLs that constitutively produce autocrine help would predominate during CD4-diminished chronic infection.

CD4+ CD25+ T cells responding to serologically defined autoantigens suppress antitumor immune responses

A variety of tumor-derived antigens have been defined by IgG antibodies in tumor bearers' sera with serological identification of antigens by recombinant expression cloning (SEREX), a serological expression cloning method. The majority of these antigens show no structural abnormality and seem to be wild-type autoantigens. Coimmunization with DNA encoding these autoantigens and tumor-specific cytotoxic T lymphocytes epitopes heightened CD8+ T cell responses and increased resistance to tumor challenge in a CD4+ T cell-dependent manner. In contrast, immunization with these SEREX-defined autoantigens alone leads to heightened susceptibility to tumor challenge. This suppressive effect of immunization is mediated by CD4+ CD25+ T cells. In mice immunized with one of the SEREX-defined autoantigens, Dna J-like 2, the number of alpha-GalCer/CD1d tetramer+ CD3+ T cells [representing natural killer T (NKT) cells] was reduced in the pulmonary compartment, whereas no evident change in the number of other T cell subsets was observed. Experiments with Jalpha281-/- mice lacking most NKT cells indicate that NKT cells are primarily responsible for metastasis suppression and that their activity is inhibited by immunization with Dna J-like 2. We propose that SEREX identifies a pool of autoantigens that maintains and regulates immunological homeostasis via CD4+ CD25+ regulatory T cells.

In vivo administration of a lentiviral vaccine targets DCs and induces efficient CD8(+) T cell responses

The present study evaluates the potential of third-generation lentivirus vectors with respect to their use as in vivo-administered T cell vaccines. We demonstrate that lentivector injection into the footpad of mice transduces DCs that appear in the draining lymph node and in the spleen. In addition, a lentivector vaccine bearing a T cell antigen induced very strong systemic antigen-specific cytotoxic T lymphocyte (CTL) responses in mice. Comparative vaccination performed in two different antigen models demonstrated that in vivo administration of lentivector was superior to transfer of transduced DCs or peptide/adjuvant vaccination in terms of both amplitude and longevity of the CTL response. Our data suggest that a decisive factor for efficient T cell priming by lentivector might be the targeting of DCs in situ and their subsequent migration to secondary lymphoid organs. The combination of performance, ease of application, and absence of pre-existing immunity in humans make lentivector-based vaccines an attractive candidate for cancer immunotherapy.