Dendritic cells induce the death of human papillomavirus-transformed keratinocytes

Origin and immunoescape of uterine cervical cancer

Human papillomavirus associated uterine cervical cancer is an important public health problem since it is classified as the fourth most common cancer in women worldwide with more than 500,000 recorded cases. This review is focused on where and why HPV infection induces cervical cancers and how this virus avoids the host immune response. Immunological therapeutic approaches are also addressed.

Tumoricidal activity of human dendritic cells

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Human DC subsets can exert tumoricidal activity.

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Killer DCs exploit several mechanisms for direct killing of target cells, including TRAIL and granzyme B.

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Antigen presentation and/or IFN production are important additional effector functions.

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Killer DCs are promising targets for immunotherapeutic strategies.

Dendritic cells (DCs) are a family of professional antigen-presenting cells (APCs) that are able to initiate innate and adaptive immune responses against pathogens and tumor cells. The DC family is heterogeneous and is classically divided into two main subsets, each with its unique phenotypic and functional characteristics: myeloid DCs (mDCs) and plasmacytoid DCs (pDCs). Recent results have provided intriguing evidence that both DC subsets can also function as direct cytotoxic effector cells; in particular, against cancer cells. In this review, we delve into this understudied function of human DCs and discuss why these so-called killer DCs might become important tools in future cancer immunotherapies.

Cytotoxic dendritic cells generated from cancer patients

Known for years as professional APCs, dendritic cells (DCs) are also endowed with tumoricidal activity. This dual role of DC as killers and messengers may have important implications for tumor immunotherapy. However, the tumoricidal activity of DCs has mainly been investigated in animal models. Cancer cells inhibit antitumor immune responses using numerous mechanisms, including the induction of immunosuppressive/ tolerogenic DCs that have lost their ability to present Ags in an immunogenic manner. In this study, we evaluated the possibility of generating tumor killer DCs from patients with advanced-stage cancers. We demonstrate that human monocyte-derived DCs are endowed with significant cytotoxic activity against tumor cells following activation with LPS. The mechanism of DC-mediated tumor cell killing primarily involves peroxynitrites. This observed cytotoxic activity is restricted to immature DCs. Additionally, after killing, these cytotoxic DCs are able to activate tumor Ag-specific T cells. These observations may open important new perspectives for the use of autologous cytotoxic DCs in cancer immunotherapy strategies.

The role of inflammation in HPV carcinogenesis

The role of inflammation in human papillomavirus (HPV) infection and disease is complex since it involves responses capable of preventing initial infections, clearing those ongoing as well as promoting persistence and progression of associated lesions. Avoiding the immune response has been considered a key aspect of HPV persistence which is the main factor leading to HPV-related neoplasia. HPVs have evolved different ways of targeting immune signaling pathways. Moreover, host inflammatory response may promote lesion progression and affect tumor fate by diverse mechanisms including the direct participation of inflammatory cells. In this review, we discuss the interplay between HPV oncogenic proteins and an array of inflammatory responses that ultimately may lead to cancer.

Local applications of GM-CSF induce the recruitment of immune cells in cervical low-grade squamous intraepithelial lesions

PROBLEM

Quantitative alterations of antigen-presenting cells (APC) in (pre)neoplastic lesions of the uterine cervix associated with human papillomavirus (HPV) infection suggest a diminished capacity to capture viral antigens and to induce a protective immune response.

METHOD OF STUDY

To test whether a cervical application of GM-CSF could restore an immune response against HPV in women with cervical low-grade squamous intraepithelial lesions (LSIL), we performed two clinical trials with 11 healthy women and 15 patients with LSIL.

RESULTS

GM-CSF applications were well tolerated in all enrolled women, and no difference in toxicity between the treated and placebo groups was observed during the follow-up (until 30 months). Interestingly, in the GM-CSF treated group, a significant increase of APC and cytotoxic T-lymphocyte infiltration was observed in the cervical biopsies with no change in regulatory T cell numbers. All the HPV16(+) patients exhibited an immune response against HPV16 after GM-CSF applications, as shown by NK and/or T cells producing IFN-gamma whereas no cellular immune response was observed before the treatment. Moreover, the anti-virus-like particles antibody titers also increased after the treatment.

CONCLUSION

These encouraging results obtained from a limited number of subjects justify further study on the therapeutic effect of APC in cervical (pre)neoplastic lesions.

Dendritic cells as killers: mechanistic aspects and potential roles

Dendritic cells (DC) are professional APC endowed with the unique capacity to activate naive T cells. DC also have important effector functions during the innate immune response, such as pathogen recognition and cytokine production. In fact, DC represent the crucial link between innate and adaptive immune responses. However, DC are quite heterogeneous and various subsets endowed with specific pathogen recognition mechanisms, locations, phenotypes, and functions have been described both in rodents and in humans. A series of studies indicated that rodent as well as human DC could also mediate another important innate function, i.e., cell-mediated cytotoxicity, mostly toward tumor cells. In this article, we will review the phenotypes of these so-called killer DC, their killing mechanism, and putative implication in the immune response.

Innate lymphocyte and dendritic cell cross-talk: a key factor in the regulation of the immune response

Dendritic cells (DC) are specialized in the presentation of antigens and the initiation of specific immune responses. They have been involved recently in supporting innate immunity by interacting with various innate lymphocytes, such as natural killer (NK), NK T or T cell receptor (TCR)-gammadelta cells. The functional links between innate lymphocytes and DC have been investigated widely and different studies demonstrated that reciprocal activations follow on from NK/DC interactions. The cross-talk between innate cells and DC which leads to innate lymphocyte activation and DC maturation was found to be multi-directional, involving not only cell-cell contacts but also soluble factors. The final outcome of these cellular interactions may have a dramatic impact on the quality and strength of the down-stream immune responses, mainly in the context of early responses to tumour cells and infectious agents. Interestingly, DC, NK and TCR-gammadelta cells also share similar functions, such as antigen uptake and presentation, as well as cytotoxic and tumoricidal activity. In addition, NK and NK T cells have the ability to kill DC. This review will focus upon the different aspects of the cross-talk between DC and innate lymphocytes and its key role in all the steps of the immune response. These cellular interactions may be particularly critical in situations where immune surveillance requires efficient early innate responses.

MIP3 alpha stimulates the migration of Langerhans cells in models of human papillomavirus (HPV)-associated (pre)neoplastic epithelium

Although human papillomavirus (HPV) DNA is detected in the majority of cervical cancers and their precursors (squamous intraepithelial lesions; SIL), the persistence or progression of cervical lesions could be associated with quantitative and functional alterations of dendritic/Langerhans cells (DC/LC). As LC abnormalities have been associated with a decreased expression of macrophage inflammatory protein 3alpha (MIP3alpha) in cervical SIL, we tested the effect of exogenous MIP3alpha on the migration of LC in a (pre)neoplastic epithelium formed in vitro. By using a Boyden chamber assay, we first showed that the migratory capacity of LC generated in vitro is significantly increased in the presence of MIP3alpha compared to control medium. We next demonstrated that MIP3alpha is able to increase the 3D infiltration of LC in organotypic cultures of HPV-transformed keratinocytes. This property to stimulate LC migration was not altered after inclusion of MIP3alpha in a bioadhesive polycarbophil gel. Moreover, the function of DC to exert cytostatic effects and to present alloantigens was not altered in the presence of MIP3alpha.

Defensins induce the recruitment of dendritic cells in cervical human papillomavirus-associated (pre)neoplastic lesions formed in vitro and transplanted in vivo

In addition to their direct antimicrobial activity, defensins might also influence adaptive immunity by attracting immature dendritic cells (DC). As these cells have been shown to be deficient in uterine cervix carcinogenesis, we evaluated the ability of alpha-defensin (HNP-2, human neutrophil defensin 2) and beta-defensin (HbetaD2, human beta defensin 2) to stimulate their migration in human papillomavirus (HPV)-associated (pre)cancers. We first observed, using RT-PCR and immunohistology, that HbetaD2 is absent in HPV-transformed keratinocytes and that it is weakly expressed in cervical (pre)neoplastic lesions in comparison with normal keratinocytes. We next demonstrated that defensins exert a chemotactic activity for DC in a Boyden Chamber assay and stimulate their infiltration in an in vitro-formed (pre)neoplastic epithelium (organotypic culture of HPV-transformed keratinocytes). To evaluate the ability of defensins also to recruit DC in vivo, we developed a model of immunodeficient mice grafted with organotypic cultures of HPV+ keratinocytes, which form an epithelium similar to a high-grade neoplastic lesion, with tumoral invasion and neovascularization. Intravenously injected human DC were able to infiltrate grafts of HPV+ keratinocytes after administration of HNP-2 in the transplantation chamber. Taken together, these results suggest that defensins could reverse a frequent immune alteration observed in cancer development.

Role of hormone cofactors in the human papillomavirus-induced carcinogenesis of the uterine cervix

If human papillomavirus (HPV) is necessary for the development of (pre)neoplastic lesions of the uterine cervix, it is not sufficient. Among the cofactors involved in the malignant transformation of cells infected by HPV, sex hormones may facilitate the cervical carcinogenesis by different mechanisms, including the induction of squamous metaplasia in the transformation zone of the cervix, interactions between steroid hormones and HPV gene expression and alterations of the local immune microenvironment.

Modulation of apoptosis by human papillomavirus (HPV) oncoproteins

The regulation of host-mediated apoptosis by the E6 and E7 oncoproteins has garnered attention because it is believed to be an important strategy employed by high-risk (HR)-human papillomaviruses (HPVs) to evade immune surveillance. Additionally, the revelation that E5 can protect cells from tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis suggests that it may also play a role in undermining host defense mechanisms. Cellular transformation is an unintended consequence of persistent infection by HR-HPVs, and it is therefore likely that the primary function of E5, E6 and E7 is to regulate cell survival throughout the normal viral life cycle in order to ensure viral replication and promote the spread of progeny. The purpose of this article is to review the literature on the regulation of host-mediated apoptosis by E5, E6 and E7 that describes the mechanisms employed by HR-HPVs to persist in the host and create the conditions necessary for cellular transformation.

Accelerated degradation of FADD and procaspase 8 in cells expressing human papilloma virus 16 E6 impairs TRAIL-mediated apoptosis

Viruses have developed sophisticated strategies to evade host defenses and facilitate the production and spread of progeny. In this study, we show that transfection of the human papillomavirus (HPV) 16 E6 oncogene into HCT116 cells provides protection from tumor necrosis factor-related apoptosis inducing ligand (TRAIL)-mediated apoptosis. Additionally, we demonstrate that the protection provided by E6 is dose-dependent because higher levels of E6 provide greater protection. The mechanism underlying this protection involves a rapid reduction in the protein levels of both Fas-associated death domain (FADD) and procaspase 8, which results in suppression of the activation of caspases 8, 3 and 2. Interestingly, E6 does not interfere with the mitochondrial apoptotic pathway even though HCT116 cells have been classified as type II cells with regard to TRAIL signaling. These findings demonstrate that E6 has a more generalized effect on signaling by death ligands than was previously thought and support the notion that E6 can utilize p53-independent mechanisms to modulate cell survival.

Functional tumor necrosis factor-related apoptosis-inducing ligand production by avian influenza virus-infected macrophages

Severe human disease associated with influenza A H5N1 virus was first detected in Hong Kong in 1997. Its recent reemergence in Asia and high associated mortality highlight the need to understand its pathogenesis. We investigated the roles of death receptor ligands (DRLs) in H5N1 infection. Significant up-regulation of tumor necrosis factor (TNF)–related apoptosis-inducing ligand (TRAIL) and TNF-α, but not Fas ligand (FasL) mRNA, was detected in human monocyte–derived macrophages (MDMs) infected with avian influenza viruses A/Hong Kong/483/97 (H5N1/97) or its precursor, A/Quail/Hong Kong/G1/97. H5N1/97-infected MDMs exhibited the strongest induction of apoptosis in Jurkat T cells, and it could be reduced by TRAIL–receptor 2 blocking antibody. Furthermore, influenza virus infection enhanced the sensitivity of Jurkat T cells to apoptosis induced by TNF-α, TRAIL, and FasL. Our data suggested that functional TRAIL produced by influenza virus–infected MDMs was related to their cytotoxicity and that the enhanced sensitization to DRL-induced apoptosis detected in avian influenza may contribute to disease pathogenesis

Relationship between HIV viral load and Langerhans cells of the cervical epithelium

AIM

To determine the relationship between the density of cervical mucosa Langerhans cells, cervical histology, and HIV viral load.

METHODS

Eighty-four HIV-infected and 17 women at high risk for HIV had cervical biopsies assessed for squamous intraepithelial lesions and Langerhans cell density. Langerhans cells were identified using the S-100 immunohistochemical stain and were counted manually. Polymerase chain reaction assays were used to detect cervical human papillomavirus (HPV)-DNA. T-cell subsets were determined using immunofluorescent flow cytometry. Plasma HIV RNA levels were measured using a nucleic acid sequence-based amplification technique. The associations between cervical Langerhans cell density, cervical histology, CD4 counts, HIV viral loads, HPV-DNA detection, and smoking status were assessed using multivariate statistical models.

RESULTS

In multivariate analysis among women infected with HIV, the mean Langerhans cell density per high-powered field was 4.00 among women with no detectable plasma HIV-RNA, and 1.92 among those with detectable HIV-RNA (P = 0.01). The mean cervical Langerhans cell density was increased in women with high-grade squamous intraepithelial lesions compared with those with low-grade squamous intraepithelial lesions and normal/metaplastic histology (3.87 vs 2.11; P = 0.05). Neither HPV-DNA detection, smoking status, nor CD4 count was significantly associated with Langerhans cell density.

CONCLUSIONS

The decrease in cervical Langerhans cell density in women with detectable HIV-RNA suggests an impaired mucosal immune response to local infections, such as HPV. Conversely, HPV infection resulting in high-grade dysplasia might be associated with an enhanced local immune response.

Immature CD4−CD103+Rat Dendritic Cells Induce Rapid Caspase-Independent Apoptosis-Like Cell Death in Various Tumor and Nontumor Cells and Phagocytose Their Victims

We previously reported the characterization of a MHC class II(low) CD4- CD103+ (CD4-) subset of dendritic cells (DC) in rat spleen that exhibit a Ca2+-, Fas ligand-, TRAIL- and TNF-alpha-independent cytotoxic activity against specific targets in vitro. In this study, we demonstrate that this DC subset was also found in lymph nodes. Freshly extracted and, therefore, immature CD4- DC exhibited a potent cytotoxic activity against a large panel of tumor cell lines as well as primary endothelial cells. The cytotoxic activity of immature CD4- DC required cell-to-cell contact and de novo protein expression. CD4- DC-mediated cell death resembled apoptosis, as evidenced by outer membrane phosphatidylserine exposure and nuclear fragmentation in target cells, but was caspase as well as Fas-associated death domain and receptor-interacting protein independent. Bcl-2 overexpression in target cells did not protect them against DC-mediated cell death. Immature CD4- DC phagocytosed efficiently apoptotic cells in vitro and, therefore, rapidly and specifically engulfed their victims following death induction. Maturation induced a dramatic down-regulation of the killing and phagocytic activities of CD4- DC. In contrast, CD4+ DC were both unable to kill target cells and to phagocytose apoptotic cells in vitro. Taken together, these data indicate that rat immature CD4- CD103+ DC mediate an unusual cytotoxic activity and can use this function to efficiently acquire Ag from live cells.

Immune response in cervical dysplasia induced by human papillomavirus: the influence of human immunodeficiency virus-1 co-infection - review

Human immunodeficiency virus (HIV-1) has become an important risk factor for human papillomavirus (HPV) infection and the development of HPV associated lesions in the female genital tract. HIV-1 may also increase the oncogenicity of high risk HPV types and the activation of low risk types. The Center for Disease Control and Prevention declared invasive cervical cancer an acquired immunodeficiency virus (AIDS) defining illness in HIV positive women. Furthermore, cervical cancer happens to be the second most common female cancer worldwide. The host's local immune response plays a critical factor in controlling these conditions, as well as in changes in the number of professional antigen-presenting cells, cytokine, and MHC molecules expression. Also, the production of cytokines may determine which arm of the immune response will be stimulated and may influence the magnitude of immune protection. Although there are many studies describing the inflammatory response in HPV infection, few data are available to demonstrate the influence of the HIV infection and several questions regarding the cervical immune response are still unknown. In this review we present a brief account of the current understanding of HIV/HPV co-infection, emphasizing cervical immune response.

Graft-versus-host disease of the skin: life and death on the epidermal edge

Despite impressive advances in the field of allogeneic hematopoietic transplantation, graft versus host disease (GVHD) remains a significant obstacle to be overcome; it would enhance the safety and efficacy of this life-saving therapy. This review provides a framework for understanding the molecular and cellular basis underlying GVHD. We propose a 3-phase model of GVHD that highlights the importance of the conditioning regimen on the recipient tissues administered prior to infusion of donor bone marrow inoculum. A novel skin explant model, designed to take into consideration the immunobiological consequences of conditioning regimens on resident host cells, is proposed to advance our understanding of GVHD and serve as a potential prognostic tool when allogeneic recipient/donor combinations are being contemplated in the clinic. Within this review, specific emphasis is placed on the importance of defining the apoptotic machinery engaged in epidermal keratinocytes triggered by both conditioning regimens, and by host resident and recruited immunocytes and soluble mediators produced at sites of injury. The review is completed with a working model for cutaneous GVHD. Although the skin is highlighted because of its accessibility for clinical observations and serial sampling opportunities, lessons learned from studies of cutaneous GVHD are likely to provide valuable insights into GVHD occurring in the gastrointestinal tract, lung, and liver. With new insights designed to better predict and prevent GVHD and novel agents designed to treat GVHD, overcoming this current impediment to successful bone marrow transplantation should become increasingly feasible.

Delivery of granulocyte-macrophage colony-stimulating factor in bioadhesive hydrogel stimulates migration of dendritic cells in models of human papillomavirus-associated (pre)neoplastic epithelial lesions

Because of the central role of dendritic cells and/or Langerhans cells(DC/LC) in the induction of cellular immune responses, pharmacological agents that modulate the recruitment of these cells might have a clinical interest. The present study was designed to evaluate the capacity of several pharmaceutical formulations to topically deliver granulocyte-macrophage colony-stimulating factor (GM-CSF) on human papillomavirus (HPV)-associated genital (pre)neoplastic lesions. The formulations were evaluated for their bioactivity and for their potential to recruit DC in organotypic cultures of HPV-transformed keratinocytes. We found that a bioadhesive polycarbophil gel (Noveon) at pH 5.5 is able to maintain the bioactivity of GM-CSF at 4 or 37 degrees C for at least 7 days, whereas a decreased activity of GM-CSF was observed when the molecule is included in other polymer gels. GM-CSF incorporated in the polycarbophil gel was also a potent factor in enhancing the colonization of DC into organotypic cultures of HPV-transformed keratinocytes since the infiltration of DC in the in vitro-formed (pre)neoplastic epithelium was very low under basal conditions and dramatically increased in the presence of GM-CSF gel. We next demonstrated that GM-CSF incorporated in polycarbophil gel induces the recruitment of human DC in a human (pre)neoplastic epithelium grafted into NOD/SCID mice. The efficacy of GM-CSF in this formulation was equivalent to that observed with liquid GM-CSF. These results suggest that GM-CSF incorporated in polycarbophil gel could play an important role in the recruitment of DC/LC in mucosal surfaces and be useful as a new immunotherapeutic approach for genital HPV-associated (pre)neoplastic lesions.

Progress in the Development of Immunotherapy of Cancer Using Ex Vivo-Generated Dendritic Cells Expressing Multiple Tumor Antigen Epitopes

Immunotherapy with tumor-associated antigen-pulsed, ex vivo-generated dendritic cells (DCs) is a promising approach for the treatment of cancer that has shown efficacy in animal models and is now being tested in the clinic. The majority of studies performed to date make use of a single tumor-associated epitope. However, because of the high rate of mutation in tumor cells allowing for loss of expression of a single antigen, it is likely that use of multiple antigenic epitopes will induce a broader, longer-lasting, and effective tumor-specific immune response. Multiple vehicles for loading DCs with multiple antigenic epitopes are under investigation to determine the most effective method for vaccination, with many of these methods showing promise. These loading methods, as well as other critical considerations for making DC vaccination as efficacious as possible, are discussed in this article.

Distinct mechanisms are involved in tumoristatic and tumoricidal activities of monocyte-derived dendritic cells

Monocyte-derived dendritic cells (DC) were found to inhibit proliferation of different tumor cell lines. LPS-induced maturation of DC strongly increased their capacity to inhibit tumor cell growth. We observed that tumoristatic activity of LPS-activated DC was independent of their cytotoxic potential. Indeed, LPS-activated DC were able to inhibit growth of caspase-8-deficient or Bcl-2-overexpressing Jurkat cells whereas they were not cytotoxic towards the same targets. On the other hand, we found that supernatant derived from LPS-activated DC exerted a significant anti-proliferative activity against Jurkat cells while it did not induce any cytotoxic effect. Tumor necrosis factor (TNF) was shown to critically contribute to tumor growth inhibition in this system.

HIV type 1-infected dendritic cells induce apoptotic death in infected and uninfected primary CD4 T lymphocytes

In addition to their essential role in adaptive immunity, dendritic cells (DCs) participate in innate immunity. In the context of measles virus (MV) or cytomegalovirus infections, they develop cytotoxic functions that may contribute in vivo to the elimination of virus-infected cells, but that also kill infected and noninfected T lymphocytes. Because the human immunodeficiency virus (HIV) induces T cell depletion through mechanisms that are still obscure, we investigated its ability to trigger DC cytotoxicity. When incubated with HIV, monocyte-derived DCs induced apoptosis in MDA-231 cells, which are sensitive to MV-induced DC cytotoxicity, and in uninfected as well as HIV-infected H9 CD4+ T cell lines. This apoptosis was inhibited by a mixture of FasL, TRAIL, TNF-alpha, and TWEAK inhibitors. Indeed, HIV infection induced or enhanced sensitivity to TRAIL, TNF-alpha, and TWEAK in H9 cells. Moreover, dendritic cells incubated with HIV-1 BAL or a wildtype HIV-1 isolate induced apoptosis in autologous primary CD4+ T lymphocytes, infected or not with a wild-type HIV-1 isolate. Therefore, induction of DC cytotoxicity by HIV may be relevant to in vivo HIV infection. Induction of cytotoxicity in DCs by HIV might contribute to HIV-associated T cell depletion through induction of apoptosis, especially in the early stages of infection. It may also contribute to elimination of infected cells in vivo, thereby enhancing cross-presentation of HIV by DCs. Therefore this new cytotoxic function of DCs may play an important role in innate and adaptive immunity during HIV infection.

Tracking death dealing by Fas and TRAIL in lymphatic neoplastic disorders: pathways, targets, and therapeutic tools

In the past decade, it was concluded from a number of investigations that death domain-containing members of the tumor necrosis factor-receptor (TNF-R) family and their ligands such as Fas/FasL and TNF-related apoptosis-inducing ligand (TRAIL)-R/TRAIL are essential for maintaining an intact immune system for surveillance against infection and cancer development and that nondeath domain-containing members such as CD30 or CD40 are involved in the fine tuning of this system during the selection process of the lymphatic system. In line with this conclusion are the observations that alterations in structure, function, and regulation of these molecules contribute to autoimmunity and cancer development of the lymphoid system. Besides controlling size and function of the lymphoid cell pool, Fas/FasL and TRAIL-R/TRAIL regulate myelopoiesis and the dendritic cell functions, and severe alterations of these lineages during the outgrowth and expansion of the lymphoid tumors have been reported. It is the aim of this review to summarize what is currently known about the complex role of these two death receptor/ligand systems in normal, disturbed, and neoplastic hemato-/lymphopoiesis and to point out how such knowledge can be used in developing novel, therapeutic options and the problems that will have to be faced along the way.

Dendritic cells and HCMV cross-presentation

The outcome of a viral infection is the result of an endless fight between the organism whose task is to mount an antiviral response and the virus that adapts strategies to circumvent the host response. Human cytomegalovirus (HCMV), a latent herpesvirus, can be considered as a spearhead in exploiting co-existence with the host to develop numerous immuno-evasion mechanisms. The ability of the organism to initiate a primary immune response against viruses such as HCMV is highly dependent on the capacity of professional antigen-presenting cells (APCs), namely dendritic cells (DCs), to prime and activate specific effector T cells. Recent findings emerging from the murine cytomegalovirus (MCMV) animal model demonstrated that infection of murine DCs with MCMV impaired their capacity to prime an effective T cell response. Even though data on interference of HCMV with DC functions are still limited, immunosuppressive effects identical to those reported for MCMV can be suspected and we may then ask how a cytotoxic T lymphocyte (CTL) response is generated in these unfavourable conditions. In response to this question, cross-presentation of HCMV antigens by uninfected DCs to CD8+ T cells could be considered a key process in initiating an immune response. In this chapter we discuss the mechanisms through which DCs could acquire HCMV antigens and how cross-presentation could be modulated throughout infection. Moreover, further knowledge of DC functions is key for the development of DC-based immunotherapy against HCMV.