Ligation of CD11c during vaccination promotes germinal centre induction and robust humoral responses without adjuvant

Controlling Antigen Fate in Therapeutic Cancer Vaccines by Targeting Dendritic Cell Receptors

Antigen-presenting cells (APCs) orchestrate immune responses and are therefore of interest for the targeted delivery of therapeutic vaccines. Dendritic cells (DCs) are professional APCs that excel in presentation of exogenous antigens toward CD4+ T helper cells, as well as cytotoxic CD8+ T cells. DCs are highly heterogeneous and can be divided into subpopulations that differ in abundance, function, and phenotype, such as differential expression of endocytic receptor molecules. It is firmly established that targeting antigens to DC receptors enhances the efficacy of therapeutic vaccines. While most studies emphasize the importance of targeting a specific DC subset, we argue that the differential intracellular routing downstream of the targeted receptors within the DC subset should also be considered. Here, we review the mouse and human receptors studied as target for therapeutic vaccines, focusing on antibody and ligand conjugates and how their targeting affects antigen presentation. We aim to delineate how targeting distinct receptors affects antigen presentation and vaccine efficacy, which will guide target selection for future therapeutic vaccine development.

Cell-targeted vaccines: implications for adaptive immunity

Recent advancements in immunology and chemistry have facilitated advancements in targeted vaccine technology. Targeting specific cell types, tissue locations, or receptors can allow for modulation of the adaptive immune response to vaccines. This review provides an overview of cellular targets of vaccines, suggests methods of targeting and downstream effects on immune responses, and summarizes general trends in the literature. Understanding the relationships between vaccine targets and subsequent adaptive immune responses is critical for effective vaccine design. This knowledge could facilitate design of more effective, disease-specialized vaccines.

Haemagglutinin antigen selectively targeted to chicken CD83 overcomes interference from maternally derived antibodies in chickens

Maternally derived antibodies (MDAs) are important for protecting chickens against pathogens in the neonatal stage however, they often interfere with vaccine performance. Here, we investigated the effects of MDAs on a targeted antigen delivery vaccine (TADV), which is developed by conjugating H9 subtype avian influenza virus haemagglutinin (HA) antigen to single chain fragment variable (scFv) antibodies specific for the chicken antigen presenting cell receptor CD83. Groups of 1-day-old chickens carrying high levels of MDAs (MDA++) and 14-day old chickens carrying medium levels of MDAs (MDA+) were immunised with TADV (rH9HA-CD83 scFv), untargeted rH9HA or inactivated H9N2 vaccines. Immunogenicity in these vaccinated chickens was compared using haemagglutination inhibition (HI) and enzyme-linked immunosorbent assays (ELISA). The results showed that the TADV (rH9HA-CD83 scFv) induced significantly higher levels of H9HA-specific antibody titres compared to the untargeted rH9HA and inactivated H9N2 vaccines in MDA++ and MDA+ chickens. Overall, the data demonstrates immune responses induced by TADV are not affected by the MDA in chickens.

Selectively targeting haemagglutinin antigen to chicken CD83 receptor induces faster and stronger immunity against avian influenza

The immunogenicity and protective efficacy of vaccines can be enhanced by the selective delivery of antigens to the antigen-presenting cells (APCs). In this study, H9N2 avian influenza virus haemagglutinin (HA) antigen, was targeted by fusing it to single-chain fragment variable (scFv) antibodies specific to CD83 receptor expressed on chicken APCs. We observed an increased level of IFNγ, IL6, IL1β, IL4, and CxCLi2 mRNA upon stimulation of chicken splenocytes ex vivo by CD83 scFv targeted H9HA. In addition, CD83 scFv targeted H9HA induced higher serum haemagglutinin inhibition activity and virus neutralising antibodies compared to untargeted H9HA, with induction of antibodies as early as day 6 post primary vaccination. Furthermore, chickens vaccinated with CD83 scFv targeted H9HA showed reduced H9N2 challenge virus shedding compared to untargeted H9HA. These results suggest that targeting antigens to CD83 receptors could improve the efficacy of poultry vaccines.

Targeting Haemagglutinin Antigen of Avian Influenza Virus to Chicken Immune Cell Receptors Dec205 and CD11c Induces Differential Immune-Potentiating Responses

Improving the immunogenicity and protective efficacy of vaccines is critical to reducing disease impacts. One strategy used to enhance the immunogenicity of vaccines is the selective delivery of protective antigens to the antigen presenting cells (APCs). In this study, we have developed a targeted antigen delivery vaccine (TADV) system by recombinantly fusing the ectodomain of hemagglutinin (HA) antigen of H9N2 influenza A virus to single chain fragment variable (scFv) antibodies specific for the receptors expressed on chicken APCs; Dec205 and CD11c. Vaccination of chickens with TADV containing recombinant H9HA Foldon-Dec205 scFv or H9HA Foldon-CD11c scFv proteins elicited faster (as early as day 6 post primary vaccination) and higher anti-H9HA IgM and IgY, haemagglutination inhibition, and virus neutralisation antibodies compared to the untargeted H9HA protein. Comparatively, CD11c scFv conjugated H9HA protein showed higher immunogenic potency compared to Dec205 scFv conjugated H9HA protein. The higher immune potentiating ability of CD11c scFv was also reflected in ex-vivo chicken splenocyte stimulation assay, whereby H9HA Foldon-CD11c scFv induced higher levels of cytokines (IFNγ, IL6, IL1β, and IL4) compared to H9HA Foldon-Dec205 scFv. Overall, the results conclude that TADV could be a better alternative to the currently available inactivated virus vaccines.

Targeting Dendritic Cells with Antigen-Delivering Antibodies for Amelioration of Autoimmunity in Animal Models of Multiple Sclerosis and Other Autoimmune Diseases

The specific targeting of dendritic cells (DCs) using antigen-delivering antibodies has been established to be a highly efficient protocol for the induction of tolerance and protection from autoimmune processes in experimental autoimmune encephalomyelitis (EAE), a model of multiple sclerosis (MS), as well as in some other animal disease models. As the specific mechanisms of such induced tolerance are being investigated, the newly gained insights may also possibly help to design effective treatments for patients. Here we review approaches applied for the amelioration of autoimmunity in animal models based on antibody-mediated targeting of self-antigens to DCs. Further, we discuss relevant mechanisms of immunological tolerance that underlie such approaches, and we also offer some future perspectives for the application of similar methods in certain related disease settings such as transplantation.

Conjugation of an scFab domain to the oligomeric HIV envelope protein for use in immune targeting

A promising strategy for the enhancement of vaccine-mediated immune responses is by directly targeting protein antigens to immune cells. Targeting of antigens to the dendritic cell (DC) molecule Clec9A has been shown to enhance antibody affinity and titers for model antigens, and influenza and enterovirus antigens, and may be advantageous for immunogens that otherwise fail to elicit antibodies with sufficient titers and breadth for broad protection, such as the envelope protein (Env) of HIV. Previously employed targeting strategies often utilize receptor-specific antibodies, however it is impractical to conjugate a bivalent IgG antibody to oligomeric antigens, including HIV Env trimers. Here we designed single chain variable fragment (scFv) and single chain Fab (scFab) constructs of a Clec9A-targeting antibody, expressed as genetically fused conjugates with the soluble ectodomain of Env, gp140. This conjugation did not affect the presentation of Env neutralising antibody epitopes. The scFab moiety was shown to be more stable than scFv, and in the context of gp140 fusions, was able to mediate better binding to recombinant and cell surface-expressed Clec9A, although the level of binding to cell-surface Clec9A was lower than that of the anti-Clec9A IgG. However, binding to Clec9A on the surface of DCs was not detected. Mouse immunization experiments suggested that the Clec9A-binding activity of the scFab-gp140 conjugate was insufficient to enhance Env-specific antibody responses. This is an important first proof of principle study demonstrating the conjugation of a scFab to an oligomeric protein antigen, and that an scFab displays better antigen binding than the corresponding scFv. Future developments of this technique that increase the scFab affinity will provide a valuable means to target oligomeric proteins to cell surface antigens of interest, improving vaccine-generated immune responses.

Targeting Conventional Dendritic Cells to Fine-Tune Antibody Responses

Dendritic cells (DCs) facilitate cross talk between the innate and adaptive immune system. They sense and phagocytose invading pathogens, and are not only capable of activating naïve T cells, but can also determine the polarization of T cell responses into different effector subtypes. Polarized T cells in turn have a crucial role in antibody class switching and affinity maturation, and consequently the quality of the resulting humoral immunity. Targeting vaccines to DCs thus provides a great deal of opportunities for influencing the humoral immune responses, by fine-tuning the T cell response as well as regulating antigen availability for B cells. In this review we aim to outline how different DC targeted vaccination strategies can be utilized to induce a desired humoral immune response. A range of factors, including route of vaccine administration, use of adjuvants, choice of DC subset and surface receptor to target have been reported to influence the resulting immune response and will be reviewed herein. Finally, we will discuss opportunities for designing improved vaccines and challenges with translating this knowledge into clinical or veterinary medicine.

Advancing immunomodulation by in vivo antigen delivery to DEC-205 and other cell surface molecules using recombinant chimeric antibodies

A targeted delivery of defined antigens in vivo allows for the probing of relevant functions of the immune system. Recombinant chimeric antibodies, produced by genetically modifying original monoclonal antibodies specific for molecules expressed on dendritic cells and other immune cells, have paved the way for the development of such strategies and have become reliable tools for achieving a specific immunomodulation. These antibodies have proven important in both basic research and clinical applications, extending data obtained in disease models of autoimmunity and cancer. Here we will describe the advances gained from the experimental and therapeutic strategies based on the targeting of the specific antigens by recombinant chimeric antibodies to the multilectin receptor DEC-205 and other cell surface molecules.

Endocytosis Deficient Murine Xcl1-Fusion Vaccine Enhances Protective Antibody Responses in Mice

Targeting antigen to surface receptors on dendritic cells (DCs) can improve antibody response against subunit vaccines. We have previously observed that human XCL1-fusion vaccines target murine Xcr1⁺ DCs without actively inducing endocytosis of the antigen, resulting in enhanced antibody responses in mice. However, the use of foreign chemokines for targeting is undesirable when translating this observation to human or veterinary medicine due to potential cross-reactive responses against the endogenous chemokine. Here we have identified a mutant version of murine Xcl1, labeled Xcl1(Δ1) owing to removal of a conserved valine in position 1 of the mature chemokine, that retains specific binding to Xcr1⁺ DCs without inducing endocytosis of the receptor. DNA immunization with Xcl1(Δ1) conjugated to influenza hemagglutinin (HA) induced improved antibody responses, with higher end point titers of IgG compared to WT Xcl1-HA. The Xcl1(Δ1) fusion vaccine also resulted in an increased number of HA reactive germinal center B cells with higher avidity toward the antigen, and serum transfer experiments show that Xcl1(Δ1)-HA induced antibody responses provided better protection against influenza infection as compared to WT Xcl1-HA. In summary, our observations indicate that targeting antigen to Xcr1⁺ DCs in an endocytosis deficient manner enhances antibody responses. This effect was obtained by introducing a single mutation to Xcl1, suggesting our strategy may easily be translated to human or veterinary vaccine settings.

Enhanced germinal center reaction by targeting vaccine antigen to major histocompatibility complex class II molecules

Enhancing the germinal center (GC) reaction is a prime objective in vaccine development. Targeting of antigen to MHCII on APCs has previously been shown to increase antibody responses, but the underlying mechanism has been unclear. We have here investigated the GC reaction after targeting antigen to MHCII in (i) a defined model with T and B cells of known specificity using adjuvant-free vaccine proteins, and (ii) an infectious disease model using a DNA vaccine. MHCII-targeting enhanced presentation of peptide: MHCII on APCs, and increased the numbers of GC B cells, TFH, and plasma cells. Antibodies appeared earlier and levels were increased. BCR of GC B cells and serum antibodies had increased avidity for antigen. The improved responses required cross-linking of BCR and MHCII in either cis or trans. The enhanced GC reaction induced by MHCII-targeting of antigen has clear implications for design of more efficient subunit vaccines.

Structural Immunology of Complement Receptors 3 and 4

Complement receptors (CR) 3 and 4 belong to the family of beta-2 (CD18) integrins. CR3 and CR4 are often co-expressed in the myeloid subsets of leukocytes, but they are also found in NK cells and activated T and B lymphocytes. The heterodimeric ectodomain undergoes considerable conformational change in order to switch the receptor from a structurally bent, ligand-binding in-active state into an extended, ligand-binding active state. CR3 binds the C3d fragment of C3 in a way permitting CR2 also to bind concomitantly. This enables a hand-over of complement-opsonized antigens from the cell surface of CR3-expressing macrophages to the CR2-expressing B lymphocytes, in consequence acting as an antigen presentation mechanism. As a more enigmatic part of their functions, both CR3 and CR4 bind several structurally unrelated proteins, engineered peptides, and glycosaminoglycans. No consensus motif in the proteinaceous ligands has been established. Yet, the experimental evidence clearly suggest that the ligands are primarily, if not entirely, recognized by a single site within the receptors, namely the metal-ion dependent adhesion site (MIDAS). Comparison of some recent identified ligands points to CR3 as inclined to bind positively charged species, while CR4, by contrast, binds strongly negative-charged species, in both cases with the critical involvement of deprotonated, acidic groups as ligands for the Mg²⁺ ion in the MIDAS. These properties place CR3 and CR4 firmly within the realm of modern molecular medicine in several ways. The expression of CR3 and CR4 in NK cells was recently demonstrated to enable complement-dependent cell cytotoxicity toward antibody-coated cancer cells as part of biological therapy, constituting a significant part of the efficacy of such treatment. With the flexible principles of ligand recognition, it is also possible to propose a response of CR3 and CR4 to existing medicines thereby opening a possibility of drug repurposing to influence the function of these receptors. Here, from advances in the structural and cellular immunology of CR3 and CR4, we review insights on their biochemistry and functions in the immune system.

CD11c-specific bio-nanocapsule enhances vaccine immunogenicity by targeting immune cells

BACKGROUND

Various nanocarriers have been used to deliver subunit vaccines specifically to dendritic cells (DCs) for the improvement of immunogenicity. However, due to their insufficient DC priming ability, these vaccines could not elicit effective innate immunity. We have recently developed a DC-targeting bio-nanocapsule (BNC) by displaying anti-CD11c IgGs via protein A-derived IgG Fc-binding Z domain on the hepatitis B virus envelope L protein particles (α-DC-ZZ-BNC).

RESULTS

After the chemical modification with antigens (Ags), the α-DC-ZZ-BNC-Ag complex could deliver Ags to DCs efficiently, leading to effective DC maturation and efficient endosomal escape of Ags, followed by Ag-specific T cell responses and IgG productions. Moreover, the α-DC-ZZ-BNC modified with Japanese encephalitis virus (JEV) envelope-derived D3 Ags could confer protection against 50-fold lethal dose of JEV injection on mice.

CONCLUSION

The α-DC-ZZ-BNC-Ag platform was shown to induce humoral and cellular immunities effectively without any adjuvant.

A Rift Valley fever virus Gn ectodomain-based DNA vaccine induces a partial protection not improved by APC targeting

Rift Valley fever virus, a phlebovirus endemic in Africa, causes serious diseases in ruminants and humans. Due to the high probability of new outbreaks and spread to other continents where competent vectors are present, vaccine development is an urgent priority as no licensed vaccines are available outside areas of endemicity. In this study, we evaluated in sheep the protective immunity induced by DNA vaccines encoding the extracellular portion of the Gn antigen which was either or not targeted to antigen-presenting cells. The DNA encoding untargeted antigen was the most potent at inducing IgG responses, although not neutralizing, and conferred a significant clinical and virological protection upon infectious challenge, superior to DNA vaccines encoding the targeted antigen. A statistical analysis of the challenge parameters supported that the anti-eGn IgG, rather than the T-cell response, was instrumental in protection. Altogether, this work shows that a DNA vaccine encoding the extracellular portion of the Gn antigen confers substantial—although incomplete—protective immunity in sheep, a natural host with high preclinical relevance, and provides some insights into key immune correlates useful for further vaccine improvements against the Rift Valley fever virus.

A vaccine made from the genome of Rift Valley fever virus (RVFV) offers partial protection, but pieces of the puzzle are missing, say scientists. French and Spanish researchers, led by the French National Institute for Agricultural Research’s Isabelle Schwartz-Cornil, tested in sheep three slightly-differing vaccine candidates using RVFV genes. Such DNA vaccines are designed to generate proteins which a host’s immune system can use to arm itself against a genuine viral infection. Two of the candidates, designed to target cells that would present the viral proteins to the host’s immune system, provided some benefit to the vaccinated sheep. However, the third untargeted candidate, was the most efficient at protecting sheep, although not completely, and at boosting antibody levels despite not neutralizing the virus. These results provide hope for DNA vaccines against RVFV, and offer direction for future research effort.

Generation of Immunity against Pathogens via Single-Domain Antibody-Antigen Constructs

mAbs specific for surface proteins on APCs can serve as Ag-delivery vehicles that enhance immunogenicity. The practical use of such constructs is limited by the challenge of expressing and modifying full-sized mAbs. We generated single-domain Ab fragments (VHHs) specific for class II MHC (MHCII), CD11b, and CD36. VHH sequences were modified by inclusion of a C-terminal sortase motif to allow site-specific conjugation with various Ag payloads. We tested T cell activation using VHHs that target distinct APC populations; anti-MHCII adducts elicited strong activation of CD4⁺ T cells, whereas anti-CD11b showed CD8⁺ T cell activation superior to targeting via MHCII and CD36. Differences in Ag presentation among constructs were unrelated to dendritic cell subtype or routing to acidic compartments. When coupled to antigenic payloads, anti-MHCII VHH primed Ab responses against GFP, ubiquitin, an OVA peptide, and the α-helix of influenza hemagglutinin's stem; the last afforded protection against influenza infection. The versatility of the VHH scaffold and sortase-mediated covalent attachment of Ags suggests their broader application to generate desirable immune responses.

Direct Delivery of Antigens to Dendritic Cells via Antibodies Specific for Endocytic Receptors as a Promising Strategy for Future Therapies

Dendritic cells (DCs) are the most potent professional antigen presenting cells and are therefore indispensable for the control of immunity. The technique of antibody mediated antigen targeting to DC subsets has been the basis of intense research for more than a decade. Many murine studies have utilized this approach of antigen delivery to various kinds of endocytic receptors of DCs both in vitro and in vivo. Today, it is widely accepted that different DC subsets are important for the induction of select immune responses. Nevertheless, many questions still remain to be answered, such as the actual influence of the targeted receptor on the initiation of the immune response to the delivered antigen. Further efforts to better understand the induction of antigen-specific immune responses will support the transfer of this knowledge into novel treatment strategies for human diseases. In this review, we will discuss the state-of-the-art aspects of the basic principles of antibody mediated antigen targeting approaches. A table will also provide a broad overview of the latest studies using antigen targeting including addressed DC subset, targeted receptors, outcome, and applied coupling techniques.

Polarizing T and B Cell Responses by APC-Targeted Subunit Vaccines

Current influenza vaccines mostly aim at the induction of specific neutralizing antibodies. While antibodies are important for protection against a particular virus strain, T cells can recognize epitopes that will offer broader protection against influenza. We have previously developed a DNA vaccine format by which protein antigens can be targeted specifically to receptors on antigen presenting cells (APCs). The DNA-encoded vaccine proteins are homodimers, each chain consisting of a targeting unit, a dimerization unit, and an antigen. The strategy of targeting antigen to APCs greatly enhances immune responses as compared to non-targeted controls. Furthermore, targeting of antigen to different receptors on APCs can polarize the immune response to different arms of immunity. Here, we discuss how targeting of hemagglutinin to MHC class II molecules increases Th2 and IgG1 antibody responses, whereas targeting to chemokine receptors XCR1 or CCR1/3/5 increases Th1 and IgG2a responses, in addition to CD8(+) T cell responses. We also discuss these results in relation to work published by others on APC-targeting. Differential targeting of APC surface molecules may allow the induction of tailor-made phenotypes of adaptive immune responses that are optimal for protection against various infectious agents, including influenza virus.

Conformation of the human immunoglobulin G2 hinge imparts superagonistic properties to immunostimulatory anticancer antibodies

Monoclonal antibody (mAb) drugs that stimulate antitumor immunity are transforming cancer treatment but require optimization for maximum clinical impact. Here, we show that, unlike other immunoglobulin isotypes, human IgG2 (h2) imparts FcγR-independent agonistic activity to immune-stimulatory mAbs such as anti-CD40, -4-1BB, and -CD28. Activity is provided by a subfraction of h2, h2B, that is structurally constrained due its unique arrangement of hinge region disulfide bonds. Agonistic activity can be transferred from h2 to h1 by swapping their hinge and CH1 domains, and substitution of key hinge and CH1 cysteines generates homogenous h2 variants with distinct agonistic properties. This provides the exciting opportunity to engineer clinical reagents with defined therapeutic activity regardless of FcγR expression levels in the local microenvironment.

Dendritic cell-targeted vaccines--hope or hype?

The development of an effective vaccine that elicits a strong and durable T cell response against intracellular pathogens and cancer is a challenge. One strategy to enhance the effectiveness of vaccination is by targeting dendritic cells (DCs). In this Opinion article, we discuss existing DC-targeting approaches that induce adaptive immunity. We highlight the crucial issues that need to be addressed to move the field forward and discuss whether targeting DCs could be better than current vaccine approaches.

The antigen presenting cells instruct plasma cell differentiation

The professional antigen presenting cells (APCs), including many subsets of dendritic cells and macrophages, not only mediate prompt but non-specific response against microbes, but also bridge the antigen-specific adaptive immune response through antigen presentation. In the latter, typically activated B cells acquire cognate signals from T helper cells in the germinal center of lymphoid follicles to differentiate into plasma cells (PCs), which generate protective antibodies. Recent advances have revealed that many APC subsets provide not only “signal 1” (the antigen), but also “signal 2” to directly instruct the differentiation process of PCs in a T-cell-independent manner. Herein, the different signals provided by these APC subsets to direct B cell proliferation, survival, class switching, and terminal differentiation are discussed. We furthermore propose that the next generation of vaccines for boosting antibody response could be designed by targeting APCs.

Controlling immune responses by targeting antigens to dendritic cell subsets and B cells

Delivering antigens in vivo by coupling them to mAbs specific for unique receptors on antigen-presenting cells (APCs) is a promising approach for modulating immune responses. Antigen delivery to receptors found on myeloid dendritic cell (DC) subsets, plasmacytoid DCs and B cells has shown them all to be viable targets to stimulate either the cellular or humoral arms of the immune system. It is now evident that antigen-targeting approaches can also be used to invoke antigen-specific inhibition of immune responses. The outcome of activation versus inhibition is determined by a combination of factors that include the choice of APC, the receptor that is targeted, whether to include an adjuvant and, if so, which adjuvant to employ. In addition to their use as a means to modulate immune responses, antigen-targeting systems are also a useful method to investigate the function of DC subsets and the early mechanistic events that underlie the initiation of both cellular and humoral immune responses. In this review, we focus on the literature surrounding the control of B-cell responses when antigen is delivered to various APC subsets.

Extrafollicular B cell activation by marginal zone dendritic cells drives T cell-dependent antibody responses

DCIR2⁺ DCs can initiate extrafollicular B cell responses to T cell–dependent antigen.

Dendritic cells (DCs) are best known for their ability to activate naive T cells, and emerging evidence suggests that distinct DC subsets induce specialized T cell responses. However, little is known concerning the role of DC subsets in the initiation of B cell responses. We report that antigen (Ag) delivery to DC-inhibitory receptor 2 (DCIR2) found on marginal zone (MZ)–associated CD8α⁻ DCs in mice leads to robust class-switched antibody (Ab) responses to a T cell–dependent (TD) Ag. DCIR2⁺ DCs induced rapid up-regulation of multiple B cell activation markers and changes in chemokine receptor expression, resulting in accumulation of Ag-specific B cells within extrafollicular splenic bridging channels as early as 24 h after immunization. Ag-specific B cells primed by DCIR2⁺ DCs were remarkably efficient at driving naive CD4 T cell proliferation, yet DCIR2-induced responses failed to form germinal centers or undergo affinity maturation of serum Ab unless toll-like receptor (TLR) 7 or TLR9 agonists were included at the time of immunization. These results demonstrate DCIR2⁺ DCs have a unique capacity to initiate extrafollicular B cell responses to TD Ag, and thus define a novel division of labor among splenic DC subsets for B cell activation during humoral immune responses.

CD11c controls herpes simplex virus 1 responses to limit virus replication during primary infection

CD11c is expressed on the surface of dendritic cells (DCs) and is one of the main markers for identification of DCs. DCs are the effectors of central innate immune responses, but they also affect acquired immune responses to infection. However, how DCs influence the efficacy of adaptive immunity is poorly understood. Here, we show that CD11c(+) DCs negatively orchestrate both adaptive and innate immunity against herpes simplex virus type 1 (HSV-1) ocular infection. The effectiveness and quantity of virus-specific CD8(+) T cell responses are increased in CD11c-deficient animals. In addition, the levels of CD83, CD11b, alpha interferon (IFN-α), and IFN-β, but not IFN-γ, were significantly increased in CD11c-deficient animals. Higher levels of IFN-α, IFN-β, and CD8(+) T cells in the CD11c-deficient mice may have contributed to lower virus replication in the eye and trigeminal ganglia (TG) during the early period of infection than in wild-type mice. However, the absence of CD11c did not influence survival, severity of eye disease, or latency. Our studies provide for the first time evidence that CD11c expression may abrogate the ability to reduce primary virus replication in the eye and TG via higher activities of type 1 interferon and CD8(+) T cell responses.