Cross-dressing and antigen transfer after DC targeting induce robust T cell response

Cutaneous dendritic cells (DC) are critical in protecting host from environmental insults as well as maintaining skin homeostasis. Using mouse models that are lack certain subset of cutaneous DC, studies have showed the distinct function of different subsets of skin DC, However, the interaction between skin DC subsets is less known. By targeting antigen to Langerhans cells (LC), we showed that endogenous CD4+ T cell response is independent of MHC II expression on LC. We also showed that LC handed over antigen to CD11b+ dDC and DN dDC. At the same time, MHC II deficient LC acquired MHC-II in the lymph node through cross-dressing. We demonstrated unexpected collaboration between cutaneous DC subsets, and provided insight on DC targeted vaccine design.

Therapeutic HPV Cancer Vaccine Targeted to CD40 Elicits Effective CD8+ T-cell Immunity

Human papillomavirus (HPV), particularly HPV16 and HPV18, can cause cancers in diverse anatomical sites, including the anogenital and oropharyngeal (throat) regions. Therefore, development of safe and clinically effective therapeutic vaccines is an important goal. Herein, we show that a recombinant fusion protein of a humanized antibody to CD40 fused to HPV16.E6/7 (αCD40-HPV16.E6/7) can evoke HPV16.E6/7-specific CD8⁺ and CD4⁺ T-cell responses in head-and-neck cancer patients in vitro and in human CD40 transgenic (hCD40Tg) mice in vivo The combination of αCD40-HPV16.E6/7 and poly(I:C) efficiently primed HPV16.E6/7-specific T cells, particularly CD8⁺ T cells, in hCD40Tg mice. Inclusion of montanide enhanced HPV16.E6/7-specific CD4⁺, but not CD8⁺, T-cell responses. Poly(I:C) plus αCD40-HPV16.E6/7 was sufficient to mount both preventative and therapeutic immunity against TC-1 tumors in hCD40Tg mice, significantly increasing the frequency of HPV16-specific CD8⁺ CTLs in the tumors, but not in peripheral blood. In line with this, tumor volume inversely correlated with the frequency of HPV16.E6/7-specific CD8⁺ T cells in tumors, but not in blood. These data suggest that CD40-targeting vaccines for HPV-associated malignancies can provide a highly immunogenic platform with a strong likelihood of clinical benefit. Data from this study offer strong support for the development of CD40-targeting vaccines for other cancers in the future. Cancer Immunol Res; 4(10); 823-34. ©2016 AACR.

A novel therapeutic vaccination delays cART-resistant HIV-1 reservoir rebound in HIV-1 infected humanized mice

Highly active anti-retroviral therapy (HAART) prevents disease progression but does not eradiate HIV, and this therapy often does not fully restore HIV patients’ immune status. Thus, there remains an unmet need to develop new stratagies to “cure” (eradication or control of HIV-1 with no ART) individuals of HIV infection. Modulating host’s cellular immune response is a promising way to cure HIV infection. We have developed a prototype vaccine with a string of 5 highly conserved T cell epitope rich regions of HIV-1 Gag, Nef and Pol fused to a monoclonal antibody that bind the antigen presenting cell activating receptor CD40(aCD40.HIV5pep). Here we use the humanized mouse model to evaluate the therapeutic effect of the aCD40.HIV5pep vaccine to chronic HIV infection. We first screened a batch of novel TLR adjuvants which have the potential to enhance the immunogenicity of aCD40.HIV5pep in vivo and showed that when vaccinated with Poly I:C as adjuvants, aCD40.HIV5pep can induce human CD8+ CTL response in humanized mice. Interestingly, we found that Poly I:C treatment can activate cART-resistant HIV-1 reservoir in in the presence of cART in chronically infected humanized mice. Finally, we showed that Poly I:C plus aCD40.HIV5pep therapeutic vaccination significantly delayed HIV virus rebound in HIV-1 infected humanized mice after withdraw of cART treatment. Our proof-of-concept study in humanized mice has significant implication for the development of therapeutic vaccine to cue HIV infection.

Targeting HIV-1 Env gp140 to LOX-1 Elicits Immune Responses in Rhesus Macaques

Improved antigenicity against HIV-1 envelope (Env) protein is needed to elicit vaccine-induced protective immunity in humans. Here we describe the first tests in non-human primates (NHPs) of Env gp140 protein fused to a humanized anti-LOX-1 recombinant antibody for delivering Env directly to LOX-1-bearing antigen presenting cells, especially dendritic cells (DC). LOX-1, or 1ectin-like oxidized low-density lipoprotein (LDL) receptor-1, is expressed on various antigen presenting cells and endothelial cells, and is involved in promoting humoral immune responses. The anti-LOX-1 Env gp140 fusion protein was tested for priming immune responses and boosting responses in animals primed with replication competent NYVAC-KC Env gp140 vaccinia virus. Anti-LOX-1 Env gp140 vaccination elicited robust cellular and humoral responses when used for either priming or boosting immunity. Co-administration with Poly ICLC, a TLR3 agonist, was superior to GLA, a TLR4 agonist. Both CD4+ and CD8+ Env-specific T cell responses were elicited by anti-LOX-1 Env gp140, but in particular the CD4+ T cells were multifunctional and directed to multiple epitopes. Serum IgG and IgA antibody responses induced by anti-LOX-1 Env gp140 against various gp140 domains were cross-reactive across HIV-1 clades; however, the sera neutralized only HIV-1 bearing sequences most similar to the clade C 96ZM651 Env gp140 carried by the anti-LOX-1 vehicle. These data, as well as the safety of this protein vaccine, justify further exploration of this DC-targeting vaccine approach for protective immunity against HIV-1.

Opposing Roles of Dectin-1 Expressed on Human Plasmacytoid Dendritic Cells and Myeloid Dendritic Cells in Th2 Polarization

Dendritic cells (DCs) can induce and control host immune responses. DC subset-dependent functional specialties and their ability to display functional plasticity, which is mainly driven by signals via pattern recognition receptors, identify DCs as immune orchestrators. A pattern recognition receptor, Dectin-1, is expressed on myeloid DCs and known to play important roles in Th17 induction and activation during fungal and certain bacterial infections. In this study, we first demonstrate that human plasmacytoid DCs express Dectin-1 in both mRNA and protein levels. More interestingly, Dectin-1-activated plasmacytoid DCs promote Th2-type T cell responses, whereas Dectin-1-activated myeloid DCs decrease Th2-type T cell responses. Such contrasting outcomes of Th2-type T cell responses by the two DC subsets are mainly due to their distinct abilities to control surface OX40L expression in response to β-glucan. This study provides new insights for the regulation of host immune responses by Dectin-1 expressed on DCs.

Targeting antigen to CD40 reinforces dendritic cells to cross-prime antigen-specific CD8+ T cells (APP3P.110)

Dendritic cells are major antigen-presenting cells that can efficiently cross-prime antigen-specific CD8+ T cells. Thus, targeting antigen to dendritic cells via surface receptors is an appealing strategy to mount CD8+ T cell-mediated immunity against intracellular pathogens and cancers. Nonetheless, which targeted receptor is the most efficient at priming CD8+ T cells remains elusive. Herein, we report the superior function of CD40 over nine different lectins and scavenger receptors at priming antigen-specific CD8+ T cells. A quantitative analysis of intracellular trafficking of antibody-bound receptors revealed that αCD40 monoclonal antibody localized mainly at the plasma membrane and subsequently accumulated at early endocytic compartments whereas αLOX-1 and αDectin-1 monoclonal antibodies localized at both early and late endocytic compartments in dendritic cells. Regardless of the differences in their subcellular localizations, targeting antigen to CD40 and lectins resulted in the same pattern of peptide epitope-specific IFNg+CD8+ T cell responses. We also report that poly(I:C) can significantly enhance both CD8+ and CD4+ T cell responses elicited by targeting antigen to CD40 in both human in vitro and in human CD40 transgenic mouse in vivo settings. This study provides key information for the rational design of DC-targeting vaccines against cancers and intracellular pathogens.

Toll-like receptor ligands differentially activate human innate immune system and distinctively enhance antigen-specific T cell response to vaccination in humanized mice (VAC4P.1105)

TLR-Ls represent a new class of novel vaccine adjuvant. However, their immunologic effects in humans remain poorly defined in vivo. Here we investigated how TLR-Ls stimulated human immune system in vivo and their application as immune adjuvant using the humanized mouse model. To our surprise, we found that various TLR-Ls (CpG-A/CpG-B/CpG-C, R848, R837, MPLA and Poly I:C) stimulated human cytokines very differently in humanized mice in vivo compared to that in human PBMCs in vitro. The different in vivo response to TLR-Ls was not due to the improper development of human immune cells in vivo because splenocytes from humanized mice showed identical responses as human PBMC in vitro to various TLR-Ls. Importantly, the human innate immune response to specific TLR-Ls in humanized mice in vivo was different from that reported in C57/BL6 mice, but similar to that reported in nonhuman primates. Furthermore, we showed that distinct TLR-Ls differentially activated and mobilized human pDCs, mDCs and monocytes in different organs in vivo. Finally, we showed that Poly I:C and R848 were superior to CpG-B, for enhancing antigen specific CD4+ and CD8+ T cell responses to a CD40-targeting HIV candidate vaccine in humanized mice, which correlated with their ability to activate human CD141+ mDCs and IL-12 induction. Thus, we conclude that humanized mice serve as a highly relevant model to evaluate and rank the human immunologic effects of novel adjuvants in vivo prior to testing in humans.

Candida albicans morphology and DC subsets determines T helper differentiation (MUC2P.920)

Candida albicans is a dimorphic fungus responsible for chronic mucocutaneous and often fatal systemic infections. Mucocutaneous immunity to C. albicans requires Th17 differentiation that is thought to depend on recognition of filamentous C. albicans while systemic resistance is considered T cell independent. Using a murine skin infection model, we compared in vivo T helper responses to yeast and filamentous C. albicans. Unexpectedly, we found that only yeast induced Th17 responses through a mechanism that required Dectin-1 mediated expression of IL-6 by Langerhans cells. Filamentous forms induced Th1 without Th17 due to the absence of Dectin-1 ligation. Notably, Th17 responses provided selective protection against secondary cutaneous infection while Th1 provided protection against systemic infection. Thus, C. albicans morphology drives distinct Th responses that provide tissue specific protection. These findings provide novel insight into compartmentalization of Th responses, C. albicans pathogenesis and have critical implications for vaccine strategies.

Skin dendritic cells induce follicular helper T cells and protective humoral immune responses (VAC4P.1101)

Skin-resident dendritic cells (DC) play a crucial role in initiation of adaptive immune responses against cutaneous pathogens as well as in the maintenance of peripheral tolerance. Recent studies have suggested that steady-state Langerhans cells (LC) induce regulatory T cells against self-antigens. However, the immune response induced by skin DC against foreign antigen in the absence of adjuvants has not been addressed. Here we report that, using anti-huLangerin/ muLangerin antibodies, we could specifically target antigens to LC or CD103+ dermal DC. Presentation of the foreign peptide 2W1S by either LC or CD103+ dDC was sufficient for expansion of naïve CD4+ T cells and induction of T follicular helper cell (Tfh) differentiation. Notably, topical application of peptide or protein also efficiently induced Tfh. The expansion of Tfh specific to foreign peptide was accompanied by activation and expansion of antigen-specific B cells and the development of a robust antibody response that provided systemic protection against influenza infection. This study not only reveals a major unappreciated function of skin DC in humoral response, but also provides insight into DC-targeted vaccine design.

Dectin-1 expressed on pDCs and mDCs displays opposing roles in TH2 polarization (INC6P.321)

Dendritic cells (DCs) can induce and control host immune responses. DC subset-dependent functional specialties and their ability to display functional plasticity, which is mainly driven by signals via pattern-recognition receptors (PRRs), identify DCs as immune orchestrators. A PRR, Dectin-1 is expressed on myeloid DCs (mDCs) and is known to play an important role in TH17 responses. Here, we demonstrate that human plasmacytoid DCs (pDCs) express Dectin-1. Interestingly, Dectin-1-activated pDCs promote TH2 induction and activation, whereas Dectin-1-activated mDCs decrease both. This counter-regulation of TH2 by the two DC subsets is mainly due to their distinct abilities to control OX40L expression through different mechanisms. This study provides new insights for the regulation of host immune responses by DCs during microbial infections.

A novel vaccine for mantle cell lymphoma based on targeting cyclin D1 to dendritic cells via CD40

Background

Mantle cell lymphoma (MCL) is a distinct clinical pathologic subtype of B cell non-Hodgkin’s lymphoma often associated with poor prognosis. New therapeutic approaches based on boosting anti-tumor immunity are needed. MCL is associated with overexpression of cyclin D1 thus rendering this molecule an interesting target for immunotherapy.

Methods

We show here a novel strategy for the development of recombinant vaccines carrying cyclin D1 cancer antigens that can be targeted to dendritic cells (DCs) via CD40.

Results

Healthy individuals and MCL patients have a broad repertoire of cyclin D1-specific CD4⁺ and CD8⁺ T cells. Cyclin D1-specific T cells secrete IFN-γ. DCs loaded with whole tumor cells or with selected peptides can elicit cyclin D1-specific CD8⁺ T cells that kill MCL tumor cells. We developed a recombinant vaccine based on targeting cyclin D1 antigen to human DCs via an anti-CD40 mAb. Targeting monocyte-derived human DCs in vitro with anti-CD40-cyclin D1 fusion protein expanded a broad repertoire of cyclin D1-specific CD4⁺ and CD8⁺ T cells.

Conclusions

This study demonstrated that cyclin D1 represents a good target for immunotherapy and targeting cyclin D1 to DCs provides a new strategy for mantle cell lymphoma vaccine.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-015-0131-7) contains supplementary material, which is available to authorized users.

Candida albicans morphology and dendritic cell subsets determine T helper cell differentiation

Candida albicans is a dimorphic fungus responsible for chronic mucocutaneous and systemic infections. Mucocutaneous immunity to C. albicans requires T helper 17 (Th17) cell differentiation that is thought to depend on recognition of filamentous C. albicans. Systemic immunity is considered T cell independent. Using a murine skin infection model, we compared T helper cell responses to yeast and filamentous C. albicans. We found that only yeast induced Th17 cell responses through a mechanism that required Dectin-1-mediated expression of interleukin-6 (IL-6) by Langerhans cells. Filamentous forms induced Th1 without Th17 cell responses due to the absence of Dectin-1 ligation. Notably, Th17 cell responses provided protection against cutaneous infection while Th1 cell responses provided protection against systemic infection. Thus, C. albicans morphology drives distinct T helper cell responses that provide tissue-specific protection. These findings provide insight into compartmentalization of Th cell responses and C. albicans pathogenesis and have critical implications for vaccine strategies.

Facile syntheses of functionalized toll-like receptor 7 agonists

Protein conjugates of toll-like receptor 7 agonists have been shown to elicit powerful immune responses. In order to facilitate our studies in this area our group has developed efficient syntheses for a number of functionalized derivatives that retain immune stimulatory activity.

Transcriptional fingerprints of antigen-presenting cell subsets in the human vaginal mucosa and skin reflect tissue-specific immune microenvironments

Background

Dendritic cells localize throughout the body, where they can sense and capture invading pathogens to induce protective immunity. Hence, harnessing the biology of tissue-resident dendritic cells is fundamental for the rational design of vaccines against pathogens.

Methods

Herein, we characterized the transcriptomes of four antigen-presenting cell subsets from the human vagina (Langerhans cells, CD14^- and CD14⁺ dendritic cells, macrophages) by microarray, at both the transcript and network level, and compared them to those of three skin dendritic cell subsets and blood myeloid dendritic cells.

Results

We found that genomic fingerprints of antigen-presenting cells are significantly influenced by the tissue of origin as well as by individual subsets. Nonetheless, CD14⁺ populations from both vagina and skin are geared towards innate immunity and pro-inflammatory responses, whereas CD14^- populations, particularly skin and vaginal Langerhans cells, and vaginal CD14^- dendritic cells, display both Th2-inducing and regulatory phenotypes. We also identified new phenotypic and functional biomarkers of vaginal antigen-presenting cell subsets.

Conclusions

We provide a transcriptional database of 87 microarray samples spanning eight antigen-presenting cell populations in the human vagina, skin and blood. Altogether, these data provide molecular information that will further help characterize human tissue antigen-presenting cell lineages and their functions. Data from this study can guide the design of mucosal vaccines against sexually transmitted pathogens.

Electronic supplementary material

The online version of this article (doi:10.1186/s13073-014-0098-y) contains supplementary material, which is available to authorized users.

C-type lectin-like receptor LOX-1 promotes dendritic cell-mediated class-switched B cell responses

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a pattern-recognition receptor for a variety of endogenous and exogenous ligands. However, LOX-1 function in the host immune response is not fully understood. Here, we report that LOX-1 expressed on dendritic cells (DCs) and B cells promotes humoral responses. On B cells LOX-1 signaling upregulated CCR7, promoting cellular migration toward lymphoid tissues. LOX-1 signaling on DCs licensed the cells to promote B cell differentiation into class-switched plasmablasts and led to downregulation of chemokine receptor CXCR5 and upregulation of chemokine receptor CCR10 on plasmablasts, enabling their exit from germinal centers and migration toward local mucosa and skin. Finally, we found that targeting influenza hemagglutinin 1 (HA1) subunit to LOX-1 elicited HA1-specific protective antibody responses in rhesus macaques. Thus, LOX-1 expressed on B cells and DC cells has complementary functions to promote humoral immune responses.

Macrophage- and neutrophil-derived TNF-α instructs skin langerhans cells to prime antiviral immune responses

Dendritic cells are major APCs that can efficiently prime immune responses. However, the roles of skin-resident Langerhans cells (LCs) in eliciting immune responses have not been fully understood. In this study, we demonstrate for the first time, to our knowledge, that LCs in cynomolgus macaque skin are capable of inducing antiviral-specific immune responses in vivo. Targeting HIV-Gag or influenza hemagglutinin Ags to skin LCs using recombinant fusion proteins of anti-Langerin Ab and Ags resulted in the induction of the viral Ag-specific responses. We further demonstrated that such Ag-specific immune responses elicited by skin LCs were greatly enhanced by TLR ligands, polyriboinosinic polyribocytidylic acid, and R848. These enhancements were not due to the direct actions of TLR ligands on LCs, but mainly dependent on TNF-α secreted from macrophages and neutrophils recruited to local tissues. Skin LC activation and migration out of the epidermis are associated with macrophage and neutrophil infiltration into the tissues. More importantly, blocking TNF-α abrogated the activation and migration of skin LCs. This study highlights that the cross-talk between innate immune cells in local tissues is an important component for the establishment of adaptive immunity. Understanding the importance of local immune networks will help us to design new and effective vaccines against microbial pathogens.

Induction and activation of human Th17 by targeting antigens to dendritic cells via dectin-1

Recent compelling evidence indicates that Th17 confer host immunity against a variety of microbes, including extracellular and intracellular pathogens. Therefore, understanding mechanisms for the induction and activation of Ag-specific Th17 is important for the rational design of vaccines against pathogens. To study this, we employed an in vitro system in which influenza hemagglutinin (HA) 1 was delivered to dendritic cells (DCs) via Dectin-1 using anti-human Dectin-1 (hDectin-1)-HA1 recombinant fusion proteins. We found that healthy individuals maintained broad ranges of HA1-specific memory Th17 that were efficiently activated by DCs targeted with anti-hDectin-1-HA1. Nonetheless, these DCs were not able to induce a significant level of HA1-specific Th17 responses even in the presence of the Th17-promoting cytokines IL-1β and IL-6. We further found that the induction of surface IL-1R1 expression by signals via TCRs and common γ-chain receptors was essential for naive CD4(+) T cell differentiation into HA1-specific Th17. This process was dependent on MyD88, but not IL-1R-associated kinase 1/4. Thus, interruptions in STAT3 or MyD88 signaling led to substantially diminished HA1-specific Th17 induction. Taken together, the de novo generation of pathogen-specific human Th17 requires complex, but complementary, actions of multiple signals. Data from this study will help us design a new and effective vaccine strategy that can promote Th17-mediated immunity against microbial pathogens.

Targeting concatenated HIV antigens to human CD40 expands a broad repertoire of multifunctional CD4+ and CD8+ T cells

OBJECTIVE

Targeting HIV antigens directly to dendritic cells using monoclonal antibodies against cell-surface receptors has been shown to evoke potent cellular immunity in animal models. The objective of this study was to configure an anti-human CD40 antibody fused to a string of five highly conserved CD4 and CD8 T-cell epitope-rich regions of HIV-1 Gag, Nef and Pol (αCD40.HIV5pep), and then to demonstrate the capacity of this candidate therapeutic vaccine to target these HIV peptide antigens to human dendritic cells to expand functional HIV-specific T cells.

METHODS

Antigen-specific cytokine production using intracellular flow cytometry and multiplex bead-based assay, and suppression of viral inhibition, were used to characterize the T cells expanded by αCD40.HIV5pep from HIV-infected patient peripheral blood mononuclear cell (PBMC) and dendritic cell/T-cell co-cultures.

RESULTS

This candidate vaccine expands memory CD4 and CD8 T cells specific to multiple epitopes within all five peptide regions across a wide range of major histocompatibility complex (MHC) haplotypes from HIV-infected patient PBMC and dendritic cell/T-cell co-cultures. These in vitro expanded HIV antigen-specific CD4 and CD8 T cells produce multiple cytokines and chemokines. αCD40.HIV5pep-expanded CD8 T cells have characteristics of cytotoxic effector cells and are able to kill autologous target cells and suppress HIV-1 replication in vitro.

CONCLUSION

Our data demonstrate the therapeutic potential of this CD40-targeting HIV candidate vaccine in inducing a broad repertoire of multifunctional T cells in patients.

Serum from patients with SLE instructs monocytes to promote auto-antigen specific IgG and IgA responses (P4028)

The persistent development of autoantibodies is a hallmark of systemic lupus erythematosus (SLE). Previous work using SLE serum demonstrated that monocyte differentiation into dendritic cells (DCs) is a type I IFN-dependent manner and such SLE-DCs activate T cells. However, whether SLE-DCs promote B cell responses has not been elucidated. Here, we demonstrate that SLE-DCs can efficiently stimulate naïve and memory B cells to differentiate into polyclonal IgG- and IgA-plasmablasts (PBs) resembling those found in the blood of SLE patients. More importantly, when SLE-DCs were stimulated with SLE neutrophils, these SLE-DCs were able to induce ss-DNA specific IgG and IgA from naïve B cells. SLE-DC-mediated IgG-PB differentiation is dependent on BAFF and IL-10, whereas IgA-PB differentiation is mainly dependent on APRIL. Moreover, SLE-DCs as well as monocytes from SLE patients express CD138 and thus can trans-present CD138-bound APRIL to B cells, which is crucial for inducing IgA switching and PB differentiation. The expression of CD138-bound APRIL is not dependent of IFNα, explaining why DCs generated with IFNα (IFN-DCs) are less efficient at inducing IgA responses. Nonetheless, both SLE-DCs and IFN-DCs induce the expression of Bcl-XL in PBs and support their survival, thereby leading to increased Ig production. Taken together, our study suggests that a direct interplay between SLE-DCs and peripheral B cells contribute to SLE pathogenic autoantibody responses.

Langerhans cell and CD103+ dermal dendritic cell promote Tfh in the steady-state (P1094)

Directing antigen to dendritic cells via antibody/antigen conjugates that target antigen-uptake receptors is a highly efficient vaccination technique and also allows for in vivo examination of the effect of antigen presentation by particular DC subsets. Classic experiments determined that antigen presentation in the absence of DC activation led to deletional tolerance. To study the effects of antigen presentation isolated to LC or CD103+ dDC in the steady-state, we performed a series of experiments in which either 1) transgenic mice that express human Langerin only in LC were immunized with anti-human Langerin/antigen complexes or 2) mice lacking LC were immunized with anti-mouse Langerin/antigen complexes. In both cases the DC remained unactivated and antigen was exclusively found on either LC or CD103+ dDC, respectively. Both DC subsets, were able to promote proliferation of MHC-II tetramer binding endogenous CD4 T cells that peaked at day 7 and slowly declined over time without evidence of deletion. Both subsets induced strong expansion of a population of antigen-specific CXCR5+, PD-1+ CD4 T cells that expressed IFNγ, IL-21 and IL-4 which is most consistent with follicular helper T cells (Tfh). In addition, immunization led to the formation of germinal centers in regional LN and was accompanied with a robust humoral response. Thus, presentation in the steady-state by LC and CD103+ dDC promotes Tfh and humoral responses but not deletional tolerance.

Dendritic cells and vaccine design for sexually-transmitted diseases

Dendritic cells (DCs) are major antigen presenting cells (APCs) that can initiate and control host immune responses toward either immunity or tolerance. These features of DCs, as immune orchestrators, are well characterized by their tissue localizations as well as by their subset-dependent functional specialties and plasticity. Thus, the level of protective immunity to invading microbial pathogens can be dependent on the subsets of DCs taking up microbial antigens and their functional plasticity in response to microbial products, host cellular components and the cytokine milieu in the microenvironment. Vaccines are the most efficient and cost-effective preventive medicine against infectious diseases. However, major challenges still remain for the diseases caused by sexually-transmitted pathogens, including HIV, HPV, HSV and Chlamydia. We surmise that the establishment of protective immunity in the female genital mucosa, the major entry and transfer site of these pathogens, will bring significant benefit for the protection against sexually-transmitted diseases. Recent progresses made in DC biology suggest that vaccines designed to target proper DC subsets may permit us to establish protective immunity in the female genital mucosa against sexually-transmitted pathogens.

Noncovalent assembly of anti-dendritic cell antibodies and antigens for evoking immune responses in vitro and in vivo

Targeting of Ags directly to dendritic cells (DCs) through anti-DC receptor Ab fused to Ag proteins is a promising approach to vaccine development. However, not all Ags can be expressed as a rAb directly fused to a protein Ag. In this study, we show that noncovalent assembly of Ab-Ag complexes, mediated by interaction between dockerin and cohesin domains from cellulose-degrading bacteria, can greatly expand the range of Ags for this DC-targeting vaccine technology. rAbs with a dockerin domain fused to the rAb H chain C terminus are efficiently secreted by mammalian cells, and many Ags not secreted as rAb fusion proteins are readily expressed as cohesin directly fused to Ag either via secretion from mammalian cells or as soluble cytoplasmic Escherichia coli products. These form very stable and homogeneous complexes with rAb fused to dockerin. In vitro, these complexes can efficiently bind to human DC receptors followed by presentation to Ag-specific CD4⁺ and CD8⁺ T cells. Low doses of the HA1 subunit of influenza hemagglutinin conjugated through this means to anti-Langerin rAbs elicited Flu HA1-specific Ab and T cell responses in mice. Thus, the noncovalent assembly of rAb and Ag through dockerin and cohesin interaction provides a useful modular strategy for development and testing of prototype vaccines for elicitation of Ag-specific T and B cell responses, particularly when direct rAb fusions to Ag cannot be expressed.

CD34-derived dendritic cells transfected ex vivo with HIV-Gag mRNA induce polyfunctional T-cell responses in nonhuman primates

The pivotal role of DCs in initiating immune responses led to their use as vaccine vectors. However, the relationship between DC subsets involved in antigen presentation and the type of elicited immune responses underlined the need for the characterization of the DCs generated in vitro. The phenotypes of tissue-derived APCs from a cynomolgus macaque model for human vaccine development were compared with ex vivo-derived DCs. Monocyte/macrophages predominated in bone marrow (BM) and blood. Myeloid DCs (mDCs) were present in all tested tissues and were more highly represented than plasmacytoid DCs (pDCs). As in human skin, Langerhans cells (LCs) resided exclusively in the macaque epidermis, expressing CD11c, high levels of CD1a and langerin (CD207). Most DC subsets were endowed with tissue-specific combinations of PRRs. DCs generated from CD34(+) BM cells (CD34-DCs) were heterogeneous in phenotype. CD34-DCs shared properties (differentiation and PRR) of dermal and epidermal DCs. After injection into macaques, CD34-DCs expressing HIV-Gag induced Gag-specific CD4(+) and CD8(+) T cells producing IFN-γ, TNF-α, MIP-1β, or IL-2. In high responding animals, the numbers of polyfunctional CD8(+) T cells increased with the number of booster injections. This DC-based vaccine strategy elicited immune responses relevant to the DC subsets generated in vitro.