Vaginal submucosal dendritic cells,but not Langerhans cells,induce protective Th1 responses to herpes simplex virus-2

Herpes simplex virus (HSV) type 2 infection occurs primarily at the genital mucosal surfaces and is a leading cause of ulcerative lesions. Despite the availability of animal models for HSV-2 infection, little is known regarding the mechanism of immune induction within the vaginal mucosa. Here, we examined the cell types responsible for the initiation of protective Th1 immunity to HSV-2. Intravaginal inoculation of HSV-2 led to a rapid recruitment of submucosal dendritic cells (DCs) to the infected epithelium. Subsequently, CD11c(+) DCs harboring viral peptides in the context of MHC class II molecules emerged in the draining lymph nodes and were found to be responsible for the stimulation of IFNgamma secretion from HSV-specific CD4(+) T cells. Other antigen-presenting cells including B cells and macrophages did not present viral peptides to T cells in the draining lymph nodes. Next, we assessed the relative contribution to immune generation by the Langerhans cells in the vaginal epithelium, the submucosal CD11b(+) DCs, and the CD8alpha(+) lymph node DCs. Analysis of these DC populations from the draining lymph nodes revealed that only the CD11b(+) submucosal DCs, but not Langerhans cell-derived or CD8alpha(+) DCs, presented viral antigens to CD4(+) T cells and induced IFNgamma secretion. These results demonstrate a previously unanticipated role for submucosal DCs in the generation of protective Th1 immune responses to HSV-2 in the vaginal mucosa, and suggest their importance in immunity to other sexually transmitted diseases.     

Rapid cytotoxic T lymphocyte activation occurs in the draining lymph nodes after cutaneous herpes simplex virus infection as a result of early antigen presentation and not the presence of virus

Localized cutaneous herpes simplex virus type 1 (HSV-1) infection leads to arming and initial expansion of cytotoxic T lymphocytes (CTLs) in the draining popliteal lymph nodes (PLNs) followed by migration and further proliferation in the spleen. To accurately characterize the sequence of events involved in the activation and generation of anti-HSV CTLs, we used T cell receptor (TCR) transgenic mice specific for the immunodominant epitope from HSV glycoprotein B (gB(498-505)). We describe the detection of the initiation of antigen presentation in the draining lymph nodes by 4-6 h after infection with HSV-1. Analysis of CD69 up-regulation revealed activation of gB-specific CD8(+) T cells by 6-8 h after infection. Furthermore, we show that T cell proliferation begins no sooner than 24 h after activation and is marked by the concurrent appearance of CTL activity in the PLNs. These events are not dependent on the presence of virus in the draining lymph nodes, and suggest a requirement for recruitment of professional antigen-presenting cells to the site of T cell activation. Consequently, we have defined the initiation of the CD8(+) T cell-mediated response to cutaneous HSV-1 infection, demonstrating that the immune response to localized viral infection depends only on the appearance of cells presenting virus-derived antigen and commences with remarkable swiftness.     

Vaccination with a DNA vaccine encoding herpes simplex virus type 1 VP22 linked to antigen generates long-term antigen-specific CD8-positive memory T cells and protective immunity

Intradermal vaccination with DNA encoding herpes simplex virus type 1 (HSV-1) VP22 linked to antigen leads to spread of antigen within the epithelium and results in enhanced antigen-specific CD8+ T cell immune responses in vaccinated mice. In this study, we characterized the number of antigen-expressing dendritic cells (DCs) in the draining lymph nodes of vaccinated mice and determined whether the linkage of VP22 to antigen would influence the ability of antigen-expressing DCs to activate antigen-specific CD8+ T cells in vivo. Vaccination with DNA encoding HSV-1 VP22 linked to human papillomavirus type 16 E7 antigen generated more antigen-expressing DCs in the draining lymph nodes of vaccinated mice than E7 alone. In addition, the linkage of VP22 to E7 improved the MHC class I presentation of E7 in transfected DCs and led to enhanced activation of E7-specific CD8+ T cells. We also observed that vaccination with DNA encoding VP22 linked to E7 generated more E7-specific CD8+ memory T cells, and enhanced long-term protective antitumor immunity against an E7-expressing tumor in vaccinated mice compared with vaccination with DNA encoding E7 alone. Thus, administration of DNA encoding VP22 linked to antigen represents a plausible approach for the development of protective DNA vaccines.     

Respiratory Dendritic Cell Subsets Differ in Their Capacity to Support the Induction of Virus-Specific Cytotoxic CD8+ T Cell Responses

Dendritic cells located at the body surfaces, e.g. skin, respiratory and gastrointestinal tract, play an essential role in the induction of adaptive immune responses to pathogens and inert antigens present at these surfaces. In the respiratory tract, multiple subsets of dendritic cells (RDC) have been identified in both the normal and inflamed lungs. While the importance of RDC in antigen transport from the inflamed or infected respiratory tract to the lymph nodes draining this site is well recognized, the contribution of individual RDC subsets to this process and the precise role of migrant RDC within the lymph nodes in antigen presentation to T cells is not clear. In this report, we demonstrate that two distinct subsets of migrant RDC - exhibiting the CD103⁺ and CD11b^hi phenotype, respectively - are the primary DC presenting antigen to naïve CD4⁺ and CD8⁺ T lymphocytes in the draining nodes in response to respiratory influenza virus infection. Furthermore, the migrant CD103⁺ RDC subset preferentially drives efficient proliferation and differentiation of naive CD8⁺ T cells responding to infection into effector cells, and only the CD103⁺ RDC subset can present to naïve CD8⁺ T cells non-infectious viral vaccine introduced into the respiratory tract. These results identify CD103⁺ and CD11b^hi RDC as critical regulators of the adaptive immune response to respiratory tract infection and potential targets in the design of mucosal vaccines.     

Cross-presenting CD103+ dendritic cells are protected from influenza virus infection

CD8⁺ cytotoxic T cells are critical for viral clearance from the lungs upon influenza virus infection. The contribution of antigen cross-presentation by DCs to the induction of anti-viral cytotoxic T cells remains controversial. Here, we used a recombinant influenza virus expressing a nonstructural 1–GFP (NS1-GFP) reporter gene to visualize the route of antigen presentation by lung DCs upon viral infection in mice. We found that lung CD103⁺ DCs were the only subset of cells that carried intact GFP protein to the draining LNs. Strikingly, lung migratory CD103⁺ DCs were not productively infected by influenza virus and thus were able to induce virus-specific CD8⁺ T cells through the cross-presentation of antigens from virally infected cells. We also observed that CD103⁺ DC resistance to infection correlates with an increased anti-viral state in these cells that is dependent on the expression of type I IFN receptor. These results show that efficient cross-priming by migratory lung DCs is coupled to the acquisition of an anti-viral status, which is dependent on the type I IFN signaling pathway.     

Clearance of influenza virus from the lung depends on migratory langerin+CD11b- but not plasmacytoid dendritic cells

Although dendritic cells (DCs) play an important role in mediating protection against influenza virus, the precise role of lung DC subsets, such as CD11b- and CD11b+ conventional DCs or plasmacytoid DCs (pDCs), in different lung compartments is currently unknown. Early after intranasal infection, tracheal CD11b-CD11chi DCs migrated to the mediastinal lymph nodes (MLNs), acquiring co-stimulatory molecules in the process. This emigration from the lung was followed by an accumulation of CD11b+CD11chi DCs in the trachea and lung interstitium. In the MLNs, the CD11b+ DCs contained abundant viral nucleoprotein (NP), but these cells failed to present antigen to CD4 or CD8 T cells, whereas resident CD11b-CD8+ DCs presented to CD8 cells, and migratory CD11b-CD8- DCs presented to CD4 and CD8 T cells. When lung CD11chi DCs and macrophages or langerin+CD11b-CD11chi DCs were depleted using either CD11c-diphtheria toxin receptor (DTR) or langerin-DTR mice, the development of virus-specific CD8+ T cells was severely delayed, which correlated with increased clinical severity and a delayed viral clearance. 120G8+ CD11cint pDCs also accumulated in the lung and LNs carrying viral NP, but in their absence, there was no effect on viral clearance or clinical severity. Rather, in pDC-depleted mice, there was a reduction in antiviral antibody production after lung clearance of the virus. This suggests that multiple DCs are endowed with different tasks in mediating protection against influenza virus.     

CD8(+) but not CD8(-) dendritic cells cross-prime cytotoxic T cells in vivo

Bone marrow-derived antigen-presenting cells (APCs) take up cell-associated antigens and present them in the context of major histocompatibility complex (MHC) class I molecules to CD8(+) T cells in a process referred to as cross-priming. Cross-priming is essential for the induction of CD8(+) T cell responses directed towards antigens not expressed in professional APCs. Although in vitro experiments have shown that dendritic cells (DCs) and macrophages are capable of presenting exogenous antigens in association with MHC class I, the cross-presenting cell in vivo has not been identified. We have isolated splenic DCs after in vivo priming with ovalbumin-loaded beta2-microglobulin-deficient splenocytes and show that they indeed present cell-associated antigens in the context of MHC class I molecules. This process is transporter associated with antigen presentation (TAP) dependent, suggesting an endosome to cytosol transport. To determine whether a specific subset of splenic DCs is involved in this cross-presentation, we negatively and positively selected for CD8(-) and CD8(+) DCs. Only the CD8(+), and not the CD8(-), DC subset demonstrates cross-priming ability. FACS((R)) studies after injection of splenocytes loaded with fluorescent beads showed that 1 and 0.6% of the CD8(+) and the CD8(-) DC subsets, respectively, had one or more associated beads. These results indicate that CD8(+) DCs play an important role in the generation of cytotoxic T lymphocyte responses specific for cell-associated antigens.     

Major histocompatibility complex class II presentation of cell-associated antigen is mediated by CD8alpha+ dendritic cells in vivo

Antigen-specific B cells express major histocompatibility complex class II and can present antigen directly to T cells. Adoptive transfer experiments using transgenic B and T cells demonstrated that antigen-specific B cells can also efficiently transfer antigen to another cell for presentation to T cells in vivo. To identify the antigen-presenting cell that receives antigens from B cells, a strategy was developed to follow the traffic of B cell-derived proteins in vivo. B cells were labeled with the fluorescent dye CFSE and loaded with antigen, before adoptive transfer into recipient mice. Populations of splenocytes from the recipient mice were later assayed for the presence of fluorescent proteins and for the ability to activate T cells. A small number of CD8alpha+CD4-CD11b(lo) dendritic cells (DCs) contain proteins transferred from B cells and these DCs effectively present antigens derived from the B cells to T cells. The results suggest that CD8alpha+ DCs sample the cells and membranes in their environment for presentation to T cells circulating through the T cell zone. This function of CD8alpha+ DCs may be relevant to the priming of an immune response or the induction of T cell tolerance.     

High Levels of a Major Histocompatibility Complex II–Self Peptide Complex on Dendritic Cells from the T Cell Areas of Lymph Nodes

T lymphocytes recirculate continually through the T cell areas of peripheral lymph nodes. During each passage, the T cells survey the surface of large dendritic cells (DCs), also known as interdigitating cells. However, these DCs have been difficult to release from the lymph node. By emphasizing the use of calcium-free media, as shown by Vremec et al. (Vremec, D., M. Zorbas, R. Scollay, D.J. Saunders, C.F. Ardavin, L. Wu, and K. Shortman. 1992. J. Exp. Med. 176:47–58.), we have been able to release and enrich DCs from the T cell areas. The DCs express the CD11c leukocyte integrin, the DEC-205 multilectin receptor for antigen presentation, the intracellular granule antigens which are recognized by monoclonal antibodies M342, 2A1, and MIDC-8, very high levels of MHC I and MHC II, and abundant accessory molecules such as CD40, CD54, and CD86. When examined with the Y-Ae monoclonal which recognizes complexes formed between I-A^b and a peptide derived from I-Eα, the T cell area DCs expressed the highest levels. The enriched DCs also stimulated a T-T hybridoma specific for this MHC II–peptide complex, and the hybridoma underwent apoptosis. Therefore DCs within the T cell areas can be isolated. Because they present very high levels of self peptides, these DCs should be considered in the regulation of self reactivity in the periphery.     

Acquisition and presentation of follicular dendritic cell-bound antigen by lymph node-resident dendritic cells

Follicular dendritic cells (DCs [FDCs]) are prominent stromal cell constituents of B cell follicles with the remarkable ability to retain complement-fixed antigens on their cell surface for extended periods of time. These retained immune complexes have long been known to provide the antigenic stimulus that drives antibody affinity maturation, but their role in cellular immunity has remained unclear. In this study, we show that FDC-retained antigens are continually sampled by lymph node-resident DCs for presentation to CD8 T cells. This novel pathway of antigen acquisition was detectable when FDCs were loaded with purified antigens bound into classical antigen-antibody immune complexes, as well as after pregnancy, when they are loaded physiologically with antigens associated with the complement-fixed microparticles released from the placenta into maternal blood. In both cases, ensuing antigen presentation was profoundly tolerogenic, as it induced T cell deletion even under inflammatory conditions. These results significantly broaden the scope of FDC function and suggest new ways that the complement system and persistent antigen presentation might influence T cell activation and the maintenance of peripheral immune tolerance.     

Presentation of tumor antigens by dendritic cells genetically modified with viral and nonviral vectors

Genetic modification of dendritic cells (DCs) with recombinant vectors encoding tumor antigens may aid in developing new immunotherapeutic treatments for patients with cancer. Here, we characterized antigen presentation by human DCs genetically modified with plasmid cDNAs, RNAs, adenoviruses, or retroviruses, encoding the melanoma antigen gp100 or the tumor-testis antigen NY-ESO-1. Monocyte-derived DCs were electroporated with cDNAs or RNAs, or transduced with adenoviruses. CD34+ hematopoietic stem cell-derived DCs were used for retroviral transduction. Genetically modified DCs were coincubated with CD8+ and CD4+ T cells that recognized major histocompatibility complex class I- and class II-restricted epitopes from gp100 and NY-ESO-1, and specific recognition was evaluated by interferongamma secretion. Cytokine release by both CD8+ and CD4+ T cells was consistently higher in response to DCs modified with adenoviruses than cDNAs or RNAs, and maturation of DCs after genetic modification did not consistently alter patterns of recognition. Also, retrovirally transduced DCs encoding gp100 were well recognized by both CD8+ and CD4+ T cells. These data suggest that DCs transduced with viral vectors may be more efficient than DCs transfected with cDNAs or RNAs for the induction of tumor reactive CD8+ and CD4+ T cells in vitro and in human vaccination trials.     

Major Histocompatibility Complex Class I–restricted Cross-presentation Is Biased towards High Dose Antigens and Those Released during Cellular Destruction

Naive T cells recirculate mainly within the secondary lymphoid compartment, but once activated they can enter peripheral tissues and perform effector functions. To activate naive T cells, foreign antigens must traffic from the site of infection to the draining lymph nodes, where they can be presented by professional antigen presenting cells. For major histocompatibility complex class I–restricted presentation to CD8⁺ T cells, this can occur via the cross-presentation pathway. Here, we investigated the conditions allowing antigen access to this pathway. We show that the level of antigen expressed by peripheral tissues must be relatively high to facilitate cross-presentation to naive CD8⁺ T cells. Below this level, peripheral antigens did not stimulate by cross-presentation and were ignored by naive CD8⁺ T cells, although they could sensitize tissue cells for destruction by activated cytotoxic T lymphocytes (CTLs). Interestingly, CTL-mediated tissue destruction facilitated cross-presentation of low dose antigens for activation of naive CD8⁺ T cells. This represents the first in vivo evidence that cellular destruction can enhance access of exogenous antigens to the cross-presentation pathway. These data indicate that the cross-presentation pathway focuses on high dose antigens and those released during tissue destruction.     

PD1-based DNA vaccine amplifies HIV-1 GAG-specific CD8+ T cells in mice

Viral vector–based vaccines that induce protective CD8⁺ T cell immunity can prevent or control pathogenic SIV infections, but issues of preexisting immunity and safety have impeded their implementation in HIV-1. Here, we report the development of what we believe to be a novel antigen-targeting DNA vaccine strategy that exploits the binding of programmed death-1 (PD1) to its ligands expressed on dendritic cells (DCs) by fusing soluble PD1 with HIV-1 GAG p24 antigen. As compared with non–DC-targeting vaccines, intramuscular immunization via electroporation (EP) of the fusion DNA in mice elicited consistently high frequencies of GAG-specific, broadly reactive, polyfunctional, long-lived, and cytotoxic CD8⁺ T cells and robust anti-GAG antibody titers. Vaccination conferred remarkable protection against mucosal challenge with vaccinia GAG viruses. Soluble PD1–based vaccination potentiated CD8⁺ T cell responses by enhancing antigen binding and uptake in DCs and activation in the draining lymph node. It also increased IL-12–producing DCs and engaged antigen cross-presentation when compared with anti-DEC205 antibody-mediated DC targeting. The high frequency of durable and protective GAG-specific CD8⁺ T cell immunity induced by soluble PD1–based vaccination suggests that PD1-based DNA vaccines could potentially be used against HIV-1 and other pathogens.     

CD8(+) T cells mediate CD40-independent maturation of dendritic cells in vivo.

Induction of cytotoxic T lymphocyte (CTL) responses against minor histocompatibility antigens is dependent upon the presence of T cell help and requires the interaction of CD40 on dendritic cells (DCs) with CD40 ligand on activated T helper cells (Th). This study demonstrates that CD40 is neither involved in Th-dependent nor Th-independent antiviral CTL responses. Moreover, the data show that DC maturation occurs in vivo after viral infection in the absence of CD40 and Th. This maturation did not require viral infection of DCs but was mediated by peptide-specific CD8(+) T cells. Surprisingly, naive CD8(+) T cells were able to trigger DC maturation within 24 h after activation in vivo and in vitro. Moreover, peptide-activated CD8(+) T cells were able to induce maturation in trans, as DCs that failed to present the relevant antigen in vivo also underwent maturation. Upon isolation, the in vivo-stimulated DCs were able to convert a classically Th-dependent CTL response (anti-HY) into a Th-independent response in vitro. Thus, antiviral CD8(+) T cells are sufficient for the maturation of DCs in the absence of CD40.     

CD4+ T cells that enter the draining lymph nodes after antigen injection participate in the primary response and become central-memory cells

We explored the relationship between the time of naive CD4+ T cell exposure to antigen in the primary immune response and the quality of the memory cells produced. Naive CD4+ T cells that migrated into the skin-draining lymph nodes after subcutaneous antigen injection accounted for about half of the antigen-specific population present at the peak of clonal expansion. These late-arriving T cells divided less and more retained the central-memory marker CD62L than the T cells that resided in the draining lymph nodes at the time of antigen injection. The fewer cell divisions were related to competition with resident T cells that expanded earlier in the response and a reduction in the number of dendritic cells displaying peptide-major histocompatibility complex (MHC) II complexes at later times after antigen injection. The progeny of late-arriving T cells possessed the phenotype of central-memory cells, and proliferated more extensively during the secondary response than the progeny of the resident T cells. The results suggest that late arrival into lymph nodes and exposure to antigen-presenting cells displaying lower numbers of peptide-MHC II complexes in the presence of competing T cells ensures that some antigen-specific CD4+ T cells divide less in the primary response and become central-memory cells.     

Efficient targeting of protein antigen to the dendritic cell receptor DEC-205 in the steady state leads to antigen presentation on major histocompatibility complex class I products and peripheral CD8+ T cell tolerance

To identify endocytic receptors that allow dendritic cells (DCs) to capture and present antigens on major histocompatibility complex (MHC) class I products in vivo, we evaluated DEC-205, which is abundant on DCs in lymphoid tissues. Ovalbumin (OVA) protein, when chemically coupled to monoclonal alphaDEC-205 antibody, was presented by CD11c+ lymph node DCs, but not by CD11c- cells, to OVA-specific, CD4+ and CD8+ T cells. Receptor-mediated presentation was at least 400 times more efficient than unconjugated OVA and, for MHC class I, the DCs had to express transporter of antigenic peptides (TAP) transporters. When alphaDEC-205:OVA was injected subcutaneously, OVA protein was identified over a 4-48 h period in DCs, primarily in the lymph nodes draining the injection site. In vivo, the OVA protein was selectively presented by DCs to TCR transgenic CD8+ cells, again at least 400 times more effectively than soluble OVA and in a TAP-dependent fashion. Targeting of alphaDEC-205:OVA to DCs in the steady state initially induced 4-7 cycles of T cell division, but the T cells were then deleted and the mice became specifically unresponsive to rechallenge with OVA in complete Freund's adjuvant. In contrast, simultaneous delivery of a DC maturation stimulus via CD40, together with alphaDEC-205:OVA, induced strong immunity. The CD8+ T cells responding in the presence of agonistic alphaCD40 antibody produced large amounts of interleukin 2 and interferon gamma, acquired cytolytic function in vivo, emigrated in large numbers to the lung, and responded vigorously to OVA rechallenge. Therefore, DEC-205 provides an efficient receptor-based mechanism for DCs to process proteins for MHC class I presentation in vivo, leading to tolerance in the steady state and immunity after DC maturation.     

Protective T cell immunity in mice following protein-TLR7/8 agonist-conjugate immunization requires aggregation, type I IFN, and multiple DC subsets

The success of a non-live vaccine requires improved formulation and adjuvant selection to generate robust T cell immunity following immunization. Here, using protein linked to a TLR7/8 agonist (conjugate vaccine), we investigated the functional properties of vaccine formulation, the cytokines, and the DC subsets required to induce protective multifunctional T cell immunity in vivo. The conjugate vaccine required aggregation of the protein to elicit potent Th1 CD4+ and CD8+ T cell responses. Remarkably, the conjugate vaccine, through aggregation of the protein and activation of TLR7 in vivo, led to an influx of migratory DCs to the LN and increased antigen uptake by several resident and migratory DC subsets, with the latter effect strongly influenced by vaccine-induced type I IFN. Ex vivo migratory CD8-DEC205+CD103-CD326- langerin-negative dermal DCs were as potent in cross-presenting antigen to naive CD8+ T cells as CD11c+CD8+ DCs. Moreover, these cells also influenced Th1 CD4+ T cell priming. In summary, we propose a model in which broad-based T cell-mediated responses upon vaccination can be maximized by codelivery of aggregated protein and TLR7/8 agonist, which together promote optimal antigen acquisition and presentation by multiple DC subsets in the context of critical proinflammatory cytokines.     

Antigen acquisition by dendritic cells: intestinal dendritic cells acquire antigen administered orally and can prime naive T cells in vivo

In the rat, mesenteric lymphadenectomy allows collection of dendritic cells (DC) derived from the small intestine after cannulation of the thoracic duct. We prepared rats this way and administered antigens by oral feeding or intraintestinal injection. DC enriched from the thoracic duct lymph collected over the first 24 h from these animals are able to stimulate sensitized T cells in vitro and to prime popliteal lymph node CD4+ T cells after footpad injection, while B and T cells from the same thoracic duct lymph are inert in priming. 500 or less DC pulsed in vitro with antigen can prime T cells in vivo, whereas 100 times more B cells or macrophages pulsed in vitro are quite inert. 1 mg of ovalbumin administered orally is sufficient to load DC for in vivo priming of T cells. Antigen could not be detected directly in DC but was present in macrophages in the lamina propria. Direct presentation of antigen by DC to T cells was demonstrated by injecting F1 recipients with parental DC and showing restriction of T cell sensitization to the major histocompatibility complex of the injected DC. Antigen-bearing DC do not induce a detectable primary antibody response but a small secondary antibody response can be detected after a boosting injection. These results show that acquisition of antigens by DC in the intestine is very similar to what occurs in vitro or in other tissues, suggesting that there may be no special difference in antigen handling at mucosal surfaces. One implication of these results is that hypotheses designed to explain oral tolerance must take into account the presence of immunostimulatory, antigen-bearing DC in animals that have received oral antigens.     

Influenza virus-induced dendritic cell maturation is associated with the induction of strong T cell immunity to a coadministered,normally nonimmunogenic protein

We evaluated the proposal that during microbial infection, dendritic cells (DCs) undergo maturation and present a mixture of peptides derived from the microbe as well as harmless environmental antigens. Mice were exposed to an aerosol of endotoxin free ovalbumin (OVA) in the absence or presence of influenza virus. In its absence, OVA failed to induce B and T cell responses and even tolerized, but with influenza, OVA-specific antibodies and CD8+ cytolytic T lymphocytes developed. With or without infection, OVA was presented selectively in the draining mediastinal lymph nodes, as assessed by the comparable proliferation of infused, CD8+ and CD4+, TCR transgenic T cells. In the absence of influenza, these OVA-specific T cells produced little IL-2, IL-4, IL-10, and IFN-gamma, but with infection, both CD4+ and CD8+ T cells made high levels of IL-2 and IFN-gamma. The OVA plus influenza-treated mice also showed accelerated recovery to a challenge with recombinant vaccinia OVA virus. CD11c+ DCs from the mediastinal lymph nodes of infected mice selectively stimulated both OVA- and influenza-specific T cells and underwent maturation, with higher levels of MHC class II, CD80, and CD86 molecules. The relatively slow (2-3 d) kinetics of maturation correlated closely to the time at which OVA inhalation elicited specific antibodies. Therefore respiratory infection can induce DC maturation and simultaneously B and T cell immunity to an innocuous antigen inhaled concurrently.     

Transcutaneous immunization induces mucosal CTLs and protective immunity by migration of primed skin dendritic cells

Transcutaneous immunization (TCI), the application of vaccines on the skin, induces robust systemic and mucosal antibodies in animal models and in humans. The means by which mucosal immune responses to vaccine antigens are elicited by TCI has not been well characterized. We examined the effect of TCI with an HIV peptide vaccine on the induction of mucosal and systemic CTL responses and protective immunity against mucosal challenge with live virus in mice. Robust HIV-specific CTL responses in the spleen and in the gut mucosa were detected after TCI. The responses were dependent upon the addition of an adjuvant and resulted in protection against mucosal challenge with recombinant vaccinia virus encoding HIV gp160. Although it is clear that adjuvant-activated DCs migrated mainly to draining lymph nodes, coculture with specific T cells and flow cytometry studies with DCs isolated from Peyer's patches after TCI suggested that activated DCs carrying skin-derived antigen also migrated from the skin to immune-inductive sites in gut mucosa and presented antigen directly to resident lymphocytes. These results and previous clinical trial results support the observation that TCI is a safe and effective strategy for inducing strong mucosal antibody and CTL responses.