Phenotypic Stability of Mature Dendritic Cells Tuned by TLR or CD40 to Control the Efficiency of Cytotoxic T Cell Priming

Rapamycin combined with donor immature dendritic cells promotes liver allograft survival in association with CD4(+) CD25(+) Foxp3(+) regulatory T cell expansion

AIM

  To determine whether donor immature dendritic cells (imDCs) combined with a short postoperative course of rapamycin (Rapa) has the ability to expand the CD4(+) CD25(+) Foxp3(+) regulatory T (Treg) cells and prolong liver allograft survival.

METHODS

  Orthotopic liver transplantation (OLT) was performed from Lewis rats to Brown Norway recipients. Three days before transplantation, animals were injected intravenously with 2 × 10(6) donor bone marrow-derived imDCs. Recipient rats (the combined treated group) also received Rapa for 7 d after liver transplantation. Additional groups received either imDCs alone, Rapa alone, or saline alone. Every six recipients from each group were killed at 14 days, 28 days after OLT. The changes of CD4(+) CD25(+) Foxp3(+) Treg cells in peripheral blood and spleen, histological changes of liver grafts, and serum cytokine levels were investigated. The other six recipients were left in each group to observe the animal survival.

RESULTS

  Donor imDCs followed by a short postoperative course of Rapa induced long-term allograft survival. The percentage of CD4(+) CD25(+) Foxp3(+) Treg cells in CD4(+) T cells in the combination treatment group were significantly higher compared with the acute rejection group. Moreover, within the CD4(+) CD25(+) T cell population the combination treatment recipients maintained a higher incidence of Foxp3(+) T cells compared with the other groups. Despite the lower serum levels of interleukin (IL)-2, IL-12, and interferon-γ in the combined treated group, the cytokine levels in the combined treated group at 7 days after OLT was nearly twice that at 3 days after OLT but decreased significantly compared with the other groups at 28 days after OLT. Serum IL-10 level in the combined treated group was higher than the other groups.

CONCLUSIONS

  A single imDC infusion followed by a short postoperative course of Rapa prolongs liver allograft survival and enhances the expansion of Treg cells. This optimal protocol may be a promising administration protocol for the peritransplant tolerance induction.

Rapamycin-treated mature dendritic cells have a unique cytokine secretion profile and impaired allostimulatory capacity

Rapamycin (RAPA, sirolimus) is a recently introduced immunosuppressive agent. Its effect on the differentiation and antigen uptake of immature dendritic cells (iDCs) has been studied. However, whether it can also modulate the function of mature DCs (mDCs) is unknown. We investigated the effects of RAPA on rat bone marrow-derived DCs at different stages of maturation. RAPA affected maturation, increased apoptosis and reduced lipopolysaccharide (LPS)-induced IL-12 and IL-10 production in iDCs. However, mDCs were resistant to RAPA-induced apoptosis. RAPA-mDCs produced significantly less IL-10 and TNF-alpha when compared with mature DCs but similar amounts of IL-12. RAPA did not affect constitutive NF-kappaB activity, but inhibited allostimulatory activity in mature DCs. In conclusion, mDCs treated with RAPA are reprogrammed to produce a unique cytokine secretion profile and exhibit low allostimulatory capacity, which may play an important role in rapamycin-based immunomodulation.

Attenuated expression of A20 markedly increases the efficacy of double-stranded RNA-activated dendritic cells as an anti-cancer vaccine

A20 is a zinc finger protein with ubiquitin-modifying activity. A20 has been described as negatively regulating signaling induced by the TNF receptor and TLR family in a number of cell types, including mouse bone marrow-derived dendritic cells (DCs). However, the expression and effect of A20 in activated human monocyte-derived DCs have not been previously evaluated. We report that DCs activated with the TLR3 ligand poly(I:C) up-regulate A20. Down-regulating A20 demonstrated its role in the functional activation of DCs. A20 down-regulated DCs showed higher activation of the transcription factors NF-kappaB and activator protein-1, which resulted in increased and sustained production of IL-6, IL-10, and IL-12p70. We additionally silenced the immunosuppressive cytokine IL-10 and demonstrated that IL-10 inhibits T cell proliferation. We further demonstrated that A20 down-regulated DCs skew naive CD4+ T cells toward IFN-gamma producing Th1 cells, a process which is dependent on IL-12p70 and which is unaffected by IL-10. Furthermore, A20 and/or IL-10 down-regulated DCs had an enhanced capacity to prime Melan-A/MART-1 specific CD8+ T cells. Finally, we demonstrated that potent T cell stimulatory DCs are generated by the simultaneous delivery of poly(I:C12U), A20, or A20/IL-10 small interfering RNA and Ag-encoding mRNA, introducing a one step approach to improve DC-based vaccines. Together these findings demonstrate that A20 negatively regulates NF-kappaB and activator protein-1 in DCs and that down-regulation of A20 results in DCs with enhanced T cell stimulatory capacity.

Immune modulatory oligonucleotides in the prevention and treatment of allergen-induced eustachian tube dysfunction in the animal model

This article reviews the current literature investigating the applications and success of immune modulatory oligonucleotides as immunotherapy to treat and prevent allergen-induced eustachian tube dysfunction in animal models. Synthetic DNA-based immunotherapy agents composed of unmethylated cytosine-guanine dinucleotides (CpG ODNs) that bind to Toll-like receptors have been found to have tremendous potential as therapeutic agents and adjuvants. CpG ODNs can induce a shift in the cytokine profile and immune response that favors the T-helper type 1 pathway and suppresses the T-helper type 2 pathway. This makes CpG ODNs promising candidates for treating allergic diseases. Current CpG ODN studies have demonstrated prevention and treatment of acute allergen inflammation of the eustachian tube in an animal model of otitis media. Immune modulatory oligonucleotides in immunotherapy, administered systemically or topically, have been shown to be safe and effective in the animal model.

Incorporation of CD40 ligand into the envelope of pseudotyped single-cycle Simian immunodeficiency viruses enhances immunogenicity

A vaccine for the prevention of human immunodeficiency virus (HIV) infection is desperately needed to control the AIDS pandemic. To address this problem, we developed vesicular stomatitis virus glycoprotein-pseudotyped replication-defective simian immunodeficiency viruses (dSIVs) as an AIDS vaccine strategy. The dSIVs retain characteristics of a live attenuated virus without the drawbacks of potential virulence caused by replicating virus. To improve vaccine immunogenicity, we incorporated CD40 ligand (CD40L) into the dSIV envelope. CD40L is one of the most potent stimuli for dendritic cell (DC) maturation and activation. Binding of CD40L to its receptor upregulates expression of major histocompatibility complex class I, class II, and costimulatory molecules on DCs and increases production of proinflammatory cytokines and chemokines, especially interleukin 12 (IL-12). This cytokine polarizes CD4(+) T cells to Th1-type immune responses. DC activation and mixed lymphocyte reaction (MLR) studies were performed to evaluate the immunogenicity of CD40L-dSIV in vitro. Expression levels of CD80, CD86, HLA-DR, and CD54 on DCs transduced with the dSIV incorporating CD40L (CD40L-dSIV) were significantly higher than on those transduced with dSIV. Moreover, CD40L-dSIV-transduced DCs expressed up to 10-fold more IL-12 than dSIV-transduced DCs. CD40L-dSIV-transduced DCs enhanced proliferation and gamma interferon secretion by naive T cells in an MLR. In addition, CD40L-dSIV-immunized mice exhibited stronger humoral and cell-mediated immune responses than dSIV-vaccinated animals. The results show that incorporating CD40L into the dSIV envelope significantly enhances immunogenicity. As a result, CD40L-dSIVs can be strong candidates for development of a safe and highly immunogenic AIDS vaccine.

Induction of cytotoxic T-lymphocyte and antibody responses against highly pathogenic avian influenza virus infection in mice by inoculation of apathogenic H5N1 influenza virus particles inactivated with formalin

We investigated whether a vaccine derived from an apathogenic reassortant type A H5N1 influenza strain could induce immune responses in vivo that mediated protection from highly pathogenic avian influenza virus infection in mice. After two subcutaneous immunizations with formalin-inactivated H5N1 whole virus particles (whole particle vaccine), significant killing specific for cells presenting a nucleoprotein peptide from the vaccine strain of the virus was observed. Similar vaccination with viruses treated with ether and formalin, which are commonly used for humans as ether-split vaccines, induced little or no cytotoxic T-cell response. Furthermore, whole particle vaccines of the apathogenic H5N1 strain were more effective than ether-split vaccines at inducing antibody production able to neutralize a highly pathogenic H5N1 strain. Finally, whole particle vaccines of H5N1 protected mice against infection by an H5N1 highly pathogenic avian influenza virus more effectively than did ether-split vaccines. These results suggest that formalin-inactivated virus particles of apathogenic strains are effective for induction of both cytotoxic T-lymphocyte and antibody responses against highly pathogenic avian influenza viruses in vivo, resulting in protection from infection by a highly pathogenic H5N1 virus.

CD40-CD40 ligand interaction between dendritic cells and CD8+ T cells is needed to stimulate maximal T cell responses in the absence of CD4+ T cell help

Stimulation of CD40 on APCs through CD40L expressed on helper CD4+ T cells activates and "licenses" the APCs to prime CD8+ T cell responses. Although other stimuli, such as TLR agonists, can also activate APCs, it is unclear to what extent they can replace the signals provided by CD40-CD40L interactions. In this study, we used an adoptive transfer system to re-examine the role of CD40 in the priming of naive CD8+ T cells. We find an approximately 50% reduction in expansion and cytokine production in TCR-transgenic T cells in the absence of CD40 on all APCs, and on dendritic cells in particular. Moreover, CD40-deficient and CD40L-deficient mice fail to develop endogenous CTL responses after immunization. Surprisingly, the role for CD40 and CD40L are observed even in the absence of CD4+ T cells; in this situation, the CD8+ T cell itself provides CD40L. Furthermore, we show that although TLR stimulation improves T cell responses, it cannot fully substitute for CD40. Altogether, these results reveal a direct and unique role for CD40L on CD8+ T cells interacting with CD40 on APCs that affects the magnitude and quality of CD8+ T cell responses.

Peptides coupled to the surface of a kind of liposome protect infection of influenza viruses

In our previous study, OVA conjugated on the surface of a liposome, we termed Oleoyl liposome, which consisted of dioleoyl phosphatidyl choline, dioleoyl phosphatidyl ethanolamine, dioleoyl phosphatidyl glycerol acid and cholesterol in a 4:3:7:2 molar ratio, induced OVA-specific IgG antibody production but not OVA-specific IgE antibody production that is detrimental to the host. Furthermore, OVA(257-264)-Oleoyl liposome elicited CTL responses in the presence of CpG and rejected E.G7 tumors in mice. In this study we tested whether a peptide-Oleoyl liposome conjugates are capable of inducing protection against viral growth. Subcutaneous inoculation of NP(366-374)-Oleoyl liposome with CpG inhibited growth of influenza viruses in lungs of mice. Thus, surface-linked liposomal peptide might serve as an effective vaccine without detrimental effects in the presence of immune potentiators.

Immunosuppressive components ofAscaris suumdown-regulate expression of costimulatory molecules and function of antigen-presenting cellsvia an IL-10-mediated mechanism

High-molecular-weight components (PI) of Ascaris suum suppress both cell-mediated and humoral responses against ovalbumin (OVA) via an IL-4/IL-10-dependent mechanism. The aim of this work was to investigate the effect of PI on the ability of APC to activate T cells and the role of IL-10 in this process. Flow cytometry analyses of MHC class II, CD80, CD86 and CD40 molecules on LN cells from mice immunized with OVA or OVA+PI showed that PI inhibits expression of these molecules on unfractionated cells and on purified CD11c(+) cells. A low proliferative response was obtained when OVA-specific TCR-Tg T cells were incubated with CD11c(+) cells from OVA+PI-immunized mice pulsed with OVA, when compared to those incubated with cells from OVA-immunized mice. Similar results were obtained using as APC CD11c(+) cells from OVA-immunized mice pulsed with OVA+PI, which also expressed less of the four markers. The inhibitory effect of PI on both the expression of costimulatory molecules and the induction of T cell proliferation was abolished in IL-10-deficient mice. Our data indicate that the potent immunosuppressive effect of A. suum extract components on the host immune system is primarily related to their property of down-regulating the Ag-presenting ability of DC via an IL-10-mediated mechanism.

Involvement of IL-10 in exhaustion of myeloid dendritic cells and rescue by CD40 stimulation

It has recently been shown that immature dendritic cells (DCs) stimulated by a danger signal undergo transient maturation followed by exhaustion. However, the exact mechanism for this has not been elucidated. In this study, we show that interleukin-10 (IL-10) secreted from transiently matured DCs stimulated by danger signals is responsible for this rapid DC exhaustion. Blocking of the autocrine IL-10 enabled transient mature DCs to maintain the mature phenotype for several days. However, these DCs remained phenotypically unstable because the addition of IL-10 altered the transient mature DCs to exhausted DCs. More importantly, stimulation of DCs by CD40 protected transient mature DCs from IL-10-dependent exhaustion, with the result that mature DCs remained stable in the presence of IL-10. Furthermore, in vivo administration of stable mature DCs pulsed with ovalbumin protein induced antigen-specific cytotoxic T lymphocytes (CTLs) effectively, whereas neither exhausted DCs nor transient mature DCs were able to prime a strong antigen-specific CTL response. These results indicate that DC-T cell engagement via CD40-CD154 is required for stable DC maturation leading to effective CTL induction. Otherwise, DCs stimulated solely by a danger signal are temporarily activated, but then rapidly lose their immune-activating capacity under the influence of autocrine IL-10.

CpG oligodeoxynucleotides as DNA adjuvants in vertebrates and their applications in immunotherapy

The genomes of bacterial and viral DNA contain a much higher frequency of unmethylated CpG dinucleotides than those of vertebrates. This difference in genome structure allows the innate immune system of vertebrates to distinguish bacterial or viral DNA from self-DNA, and consequently to perceive a 'danger signal' when bacterial or viral DNA is encountered. Multiple sources of evidence suggest that CpG motifs, including bacterial DNA and CpG ODNs (synthetic oligodeoxynucleotides containing unmethylated CpG), are capable of evoking a range of immunostimulatory effects in vertebrates and have a tremendous potential to be used as therapeutic agents and adjuvants. CpG motifs with different sequences have been shown to induce various types or levels of immunostimulatory responses whereas the immunostimulatory effects of CpG motifs are species-specific. A better understanding of CpG recognition at the molecular level is fundamental to the identification of those motifs that have desired immunostimulatory responses. It is hoped that this would allow the optimization and application of CpG motifs as therapeutic agents and adjuvants, for numerous diseases in various species.

Generation of a multimeric form of CD40L with potent immunostimulatory activity using streptavidin as a chaperon

Effective aggregation of cell surface immune receptors with their ligands is critical in promoting humoral and cellular immune responses. Simulation of these interactions using soluble multimeric ligands having potent adjuvant effects may prove an effective alternative to agonistic antibodies as immunotherapeutics. Multimeric ligands may effectively engage their receptors, leading to aggregation and effective signal transduction. We exploited the structural characteristics of streptavidin (SA) for the generation of multimeric chimeric proteins. Streptavidin forms stable tetramers and oligomers under physiological conditions, and, as such, chimeric molecules with SA are expected to possess similar features. Two chimeric molecules consisting of the extracellular domains of human and mouse CD40L and a modified form of core streptavidin were generated. These proteins form stable oligomers that could only be dissociated into monomers by heating at 100 degrees C, but not 60 degrees C, under denaturing conditions. The chimeric proteins vigorously stimulated B cells, monocytes, and dendritic cells for the production of cytokines and chemokines and upregulation of immunostimulatory molecules. The use of SA as a chaperon presents a novel approach to generate multimeric immunological molecules with potent activities and their use as potential therapeutics for the treatment of cancer and other immune-based disorders.