Cervical duct cannulation in sheep for collection of afferent lymph dendritic cells from head tissues

Characterisation of dendritic cell frequency and phenotype in bovine afferent lymph reveals kinetic changes in costimulatory molecule expression

The bovine afferent lymphatic cannulation model allows collection of large volumes of afferent lymph and provides an opportunity to study lymphatic cells trafficking from the periphery directly ex-vivo. The technique requires surgical intervention, but influence of the procedure or time post-surgery on cells trafficking in the lymph has not been well documented. Here, we measured the volume of lymph and number of cells/mL collected daily over a two week time-course. Animal to animal variability was demonstrated but no consistent changes in lymph volume or cell density were observed in relation to time post-cannulation. Cell populations (dendritic cells, αβ T-cells, γδ T-cells and NK cells) were analysed by flow cytometry at 1, 3 and 10 days post-cannulation (DPC) and a reduced percentage of γδ T-cells in afferent lymph was observed at 1 DPC. In addition, cell surface molecule expression by afferent lymphatic dendritic cells (ALDC) was assessed due to the key role of these cells in initiating an adaptive immune response. Co-stimulatory molecules CD80 and CD86 were upregulated by CD172a+ve ALDC early in the time-course, suggesting that the cannulation procedure and duration of experiment may impact the activation state of DCs in the naïve host. This should be considered when analysing the response of these cells to vaccines or pathogens.

Lymphatic cannulation models in sheep: Recent advances for immunological and biomedical research

Lymphatic cannulation models are useful tools for studying the immunobiology of the lymphatic system and the immunopathology of specific tissues in diseases. Sheep cannulations have been used extensively, as models for human physiology, fetal and neonatal development, human diseases, and for studies of ruminant pathobiology. The development of new and improved cannulation techniques in recent years has meant that difficult to access sites, such as mucosal associated tissues, are now more readily available to researchers. This review highlights the new approaches to cannulation and how these, in combination with advanced omics technologies, will direct future research using the sheep model.

Frequency and phenotype of natural killer cells and natural killer cell subsets in bovine lymphoid compartments and blood

Natural killer (NK) cells are widely distributed in lymphoid and non‐lymphoid tissues, but little is known about the recirculation of NK cells between blood and tissues. This is relevant to understanding recirculation in the steady‐state and also for determining the roles for NK cells in vaccine‐induced immunity and responses to infection. Therefore, the percentage of NK cells and their phenotype across peripheral blood, afferent lymph and lymph nodes in steady‐state conditions was investigated in cattle using the pseudo‐afferent lymphatic cannulation model. CD2⁺ CD25^lo NK cells were the predominant subset of NK cells within the blood. In contrast, CD2⁻ CD25^hi NK cells were the main subset present within the skin‐draining afferent lymphatic vessels and lymph nodes, indicating that CD2⁻ NK cells are the principal NK cell subset trafficking to lymph nodes via the afferent lymphatic vessel. Furthermore, a low percentage of NK cells were present in efferent lymph, which were predominantly of the CD2⁻ subset, indicating that NK cells can egress from lymph nodes and return to circulation in steady‐state conditions. These compartmentalization data indicate that NK cells represent a population of recirculating lymphocytes in steady‐state conditions and therefore may be important during immune responses to vaccination or infection.

Development of an ovine efferent mammary lymphatic cannulation model with minimal tissue damage

Background

Two mammary lymphatic cannulation models in sheep have been described with minimal use in the past 50 years. The purpose of this study was to investigate a new surgical technique to allow long term monitoring of mammary lymph flow and composition from the mammary glands, with rapid ewe recovery and minimal complications post-surgery.

Results

We developed a modified methodology for cannulating the efferent mammary lymphatic from the mammary lymph node with minimum tissue damage. Compared to the previous models, our method required only a small incision on the aponeurosis of the external abdominal oblique muscles and thus reduced the difficulties in suturing the aponeurosis. It allowed for lymph collection and assessment for at least one week post-surgery with concurrent milk collection.

Conclusion

This method allows for good ewe recovery post-surgery and in vivo sampling of efferent mammary lymph from the mammary lymph nodes in real-time and comparison with milk parameters.

Techniques for thoracic duct cannulation without thoracotomy in piglets

Background

Pigs are the natural hosts of many zoonotic pathogens such as influenza viruses and Staphylococcus aureus and thus have advantages over non-natural hosts when studying these zoonotic diseases. In addition, pulmonary infections are a key issue in the pig industry, for example: porcine reproductive and respiratory syndrome virus infection. Exploration of the pathogenesis of swine pulmonary infections, in particular at the onset of disease, will provide valuable information for the development of vaccines against these diseases. Therefore, there is need to develop a methodology that allows for in vivo sampling of efferent pulmonary lymph with minimum damage to the target tissues for studying the pathogenesis of swine pulmonary infections.

Results

We introduce the surgical procedures for cannulating the thoracic duct at its point of entry into the external jugular vein cranial to the first rib on the left in pigs. Using this methodology, we monitored the amounts of triglyceride and cholesterol in the lymph collected from the thoracic duct following 30 h fasting and at multiple time points after meals. It was found that the levels of triglyceride rather than cholesterol corresponded to the milky appearance of the lymph samples.

Conclusions

Our techniques provide a strategy for collecting lymph including pulmonary lymph from the thoracic duct without thoracotomy. A pig model for collecting in vivo, in situ efferent lymph draining the lower respiratory tract and its local lymph nodes in real-time with minimal tissue damage to the target tissues opens a new door for studying disease processes in pulmonary infections. Techniques described here are the key to this door.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-016-0808-3) contains supplementary material, which is available to authorized users.

Transient Migration of Large Numbers of CD14(++) CD16(+) Monocytes to the Draining Lymph Node after Onset of Inflammation

The dynamics of skin-draining cells following infection or vaccination provide important insight into the initiation of immune responses. In this study, the local recruitment and activation of immune cells in draining lymph nodes (LNs) was studied in calves in an adjuvant-induced inflammation. A transient but remarkably strong recruitment of monocytes was demonstrated after onset of inflammation, constituting up to 41% of live cells in the draining LNs after 24 h. Numerous CD14(+) cells were visualized in subcutaneous tissues and draining LNs, and the majority of these cells did not express dendritic cell-associated markers CD205 and CD11c. In the LNs, recruited cells were predominately of a CD14(++) and CD16(+) phenotype, consistent with an intermediate monocyte subset characterized to possess a high inflammatory potential. Moreover, monocytes from the draining LN showed a high expression of genes coding for pro-inflammatory cytokines, including IL-1β, IL-6, TNFa, and TGFβ. Shortly after their appearance in the LN cortical areas, the monocytes had moved into the medulla followed by an increase in peripheral blood. In conclusion, this study provides novel information on in vivo monocyte recruitment and migration after onset of inflammation.

Transduction of skin-migrating dendritic cells by human adenovirus 5 occurs via an actin-dependent phagocytic pathway

Dendritic cells (DC) are central to the initiation of immune responses, and various approaches have been used to target vaccines to DC in order to improve immunogenicity. Cannulation of lymphatic vessels allows for the collection of DC that migrate from the skin. These migrating DC are involved in antigen uptake and presentation following vaccination. Human replication-deficient adenovirus (AdV) 5 is a promising vaccine vector for delivery of recombinant antigens. Although the mechanism of AdV attachment and penetration has been extensively studied in permissive cell lines, few studies have addressed the interaction of AdV with DC. In this study, we investigated the interaction of bovine skin-migrating DC and replication-deficient AdV-based vaccine vectors. We found that, despite lack of expression of Coxsackie B–Adenovirus Receptor and other known adenovirus receptors, AdV readily enters skin-draining DC via an actin-dependent endocytosis. Virus exit from endosomes was pH independent, and neutralizing antibodies did not prevent virus entry but did prevent virus translocation to the nucleus. We also show that combining adenovirus with adjuvant increases the absolute number of intracellular virus particles per DC but not the number of DC containing intracellular virus. This results in increased trans-gene expression and antigen presentation. We propose that, in the absence of Coxsackie B–Adenovirus Receptor and other known receptors, AdV5-based vectors enter skin-migrating DC using actin-dependent endocytosis which occurs in skin-migrating DC, and its relevance to vaccination strategies and vaccine vector targeting is discussed.

Exploring local immune responses to vaccines using efferent lymphatic cannulation

The early stages of the induction of a primary immune response to a vaccine can shape the overall quality of the immune memory generated and hence affect the success of the vaccine. This early interaction between a vaccine and the immune system occurs first at the site of vaccination and can be explored using afferent cannulation. Subsequently, the vaccine and adjuvant activates the local draining lymph node. These interactions can be studied in real time in vivo using efferent lymphatic duct cannulation in large animal models and are the subject of this review. Depending on how the vaccine is delivered, the draining lymph nodes of different organs can be accessed, facilitating the testing of tissue-specific vaccinations. The efferent lymphatic cannulation model provides an avenue to study the effect of both adjuvants and antigen on the local immune system, and hence opens a pathway toward developing more effective ways of inducing immunity.

Immunology of bovine respiratory syncytial virus in calves

Bovine respiratory syncytial virus (BRSV) is an important cause of respiratory disease in young calves. The virus is genetically and antigenically closely related to human (H)RSV, which is a major cause of respiratory disease in young infants. As a natural pathogen of calves, BRSV infection recapitulates the pathogenesis of respiratory disease in man more faithfully than semi-permissive, animal models of HRSV infection. With the increasing availability of immunological reagents, the calf can be used to dissect the pathogenesis of and mechanisms of immunity to RSV infection, to analyse the ways in which the virus proteins interact with components of the innate response, and to evaluate RSV vaccine strategies. Passively transferred, neutralising bovine monoclonal antibodies, which recognise the same epitopes in the HRSV and BRSV fusion (F) protein, can protect calves against BRSV infection, and depletion of different T cells subsets in calves has highlighted the importance of CD8(+) T cells in viral clearance. Calves can be used to model maternal-antibody mediated suppression of RSV vaccine efficacy, and to increase understanding of the mechanisms responsible for RSV vaccine-enhanced respiratory disease.

Natural Killer Cells in Afferent Lymph Express an Activated Phenotype and Readily Produce IFN-γ

Natural killer (NK) cells are motile cells that migrate between peripheral blood (PB), lymph nodes (LNs), and various organs. Domestic animals have frequently been used to study cellular migration, and offer unique opportunities for such studies. The aim of this study was to characterize the phenotype and cytokine producing capacity of NK cells in bovine skin-draining lymph. NKp46/NCR1⁺ CD3⁻ cells constituted 2–11% of mononuclear cells in afferent lymph (AL), a majority of cells were CD16⁺, CD8α⁺, and CD2^−/low, and elevated CD25 and CD44 expression indicated an activated phenotype. Interestingly, significantly fewer AL NK cells expressed the early activation marker CD69 compared to PB NK cells. A large proportion of lymph and blood NK cells produced interferon (IFN)-γ following stimulation with IL-2 and IL-12. Notably, in AL, but not blood, a similar amount of IFN-γ⁺ NK cells was observed when cells were stimulated with IL-12 alone. Overall, AL NK cells were more similar to LN-residing NK cells than those circulating in PB. We conclude that AL appears to be an important migration route for tissue-activated NK cells, and may represent an alternative route for NK cell traffic to LNs. These findings may have important implications in the development of adjuvant strategies that aim to target NK cells in a vaccine response.

Dendritic cell subtypes from lymph nodes and blood show contrasted gene expression programs upon Bluetongue virus infection

Human and animal hemorrhagic viruses initially target dendritic cells (DCs). It has been proposed, but not documented, that both plasmacytoid DCs (pDCs) and conventional DCs (cDCs) may participate in the cytokine storm encountered in these infections. In order to evaluate the contribution of DCs in hemorrhagic virus pathogenesis, we performed a genome-wide expression analysis during infection by Bluetongue virus (BTV), a double-stranded RNA virus that induces hemorrhagic fever in sheep and initially infects cDCs. Both pDCs and cDCs accumulated in regional lymph nodes and spleen during BTV infection. The gene response profiles were performed at the onset of the disease and markedly differed with the DC subtypes and their lymphoid organ location. An integrative knowledge-based analysis revealed that blood pDCs displayed a gene signature related to activation of systemic inflammation and permeability of vasculature. In contrast, the gene profile of pDCs and cDCs in lymph nodes was oriented to inhibition of inflammation, whereas spleen cDCs did not show a clear functional orientation. These analyses indicate that tissue location and DC subtype affect the functional gene expression program induced by BTV and suggest the involvement of blood pDCs in the inflammation and plasma leakage/hemorrhage during BTV infection in the real natural host of the virus. These findings open the avenue to target DCs for therapeutic interventions in viral hemorrhagic diseases.

Canine recombinant adenovirus vector induces an immunogenicity-related gene expression profile in skin-migrated CD11b⁺ -type DCs

Gene expression profiling of the blood cell response induced early after vaccination has previously been demonstrated to predict the immunogenicity of vaccines. In this study, we evaluated whether the analysis of the gene expression profile of skin-migrated dendritic cells (DCs) could be informative for the in vitro prediction of immunogenicity of vaccine, using canine adenovirus serotype 2 (CAV2) as vaccine vector. CAV2 has been shown to induce immunity to transgenes in several species including sheep and is an interesting alternative to human adenovirus-based vectors, based on the safety records of the parental strain in dogs and the lack of pre-existing immunity in non-host species. Skin-migrated DCs were collected from pseudo-afferent lymph in sheep. Both the CD11b(+) -type and CD103(+) -type skin-migrated DCs were transduced by CAV2. An analysis of the global gene response to CAV2 in the two skin DC subsets showed that the gene response in CD11b(+) -type DCs was far higher and broader than in the CD103(+) -type DCs. A newly released integrative analytic tool from Ingenuity systems revealed that the CAV2-modulated genes in the CD11b(+) -type DCs clustered in several activated immunogenicity-related functions, such as immune response, immune cell trafficking and inflammation. Thus gene profiling in skin-migrated DC in vitro indicates that the CD11b(+) DC type is more responsive to CAV2 than the CD103(+) DC type, and provides valuable information to help in evaluating and possibly improving viral vector vaccine effectiveness.

Lymph node dissection--understanding the immunological function of lymph nodes

Lymph nodes (LN) are one of the important sites in the body where immune responses to pathogenic antigens are initiated. This immunological function induced by cells within the LN is an extensive area of research. To clarify the general function of LN, to identify cell populations within the lymphatic system and to describe the regeneration of the lymph vessels, the experimental surgical technique of LN dissection has been established in various animal models. In this review different research areas in which LN dissection is used as an experimental tool will be highlighted. These include regeneration studies, immunological analysis and studies with clinical questions. LN were dissected in order to analyse the different cell subsets of the incoming lymph in detail. Furthermore, LN were identified as the place where the induction of an antigen-specific response occurs and, more significantly, where this immune response is regulated. During bacterial infection LN, as a filter of the lymph system, play a life-saving role. In addition, LN are essential for the induction of tolerance against harmless antigens, because tolerance could not be induced in LN-resected animals. Thus, the technique of LN dissection is an excellent and simple method to identify the important role of LN in immune responses, tolerance and infection.

Modified vaccinia virus Ankara-based vaccine vectors induce apoptosis in dendritic cells draining from the skin via both the extrinsic and intrinsic caspase pathways, preventing efficient antigen presentation

Dendritic cells (DC) are potent antigen-presenting cells and central to the induction of immune responses following infection or vaccination. The collection of DC migrating from peripheral tissues by cannulation of the afferent lymphatic vessels provides DC which can be used directly ex vivo without extensive in vitro manipulations. We have previously used bovine migrating DC to show that recombinant human adenovirus 5 vectors efficiently transduce afferent lymph migrating DEC-205(+) CD11c(+) CD8(-) DC (ALDC). We have also shown that recombinant modified vaccinia virus Ankara (MVA) infects ALDC in vitro, causing downregulation of costimulatory molecules, apoptosis, and cell death. We now show that in the bovine system, modified vaccinia virus Ankara-induced apoptosis in DC draining from the skin occurs soon after virus binding via the caspase 8 pathway and is not associated with viral gene expression. We also show that after virus entry, the caspase 9 pathway cascade is initiated. The magnitude of T cell responses to mycobacterial antigen 85A (Ag85A) expressed by recombinant MVA-infected ALDC is increased by blocking caspase-induced apoptosis. Apoptotic bodies generated by recombinant MVA (rMVA)-Ag85A-infected ALDC and containing Ag85A were phagocytosed by noninfected migrating ALDC expressing SIRPα via actin-dependent phagocytosis, and these ALDC in turn presented antigen. However, the addition of fresh ALDC to MVA-infected cultures did not improve on the magnitude of the T cell responses; in contrast, these noninfected DC showed downregulation of major histocompatibility complex class II (MHC-II), CD40, CD80, and CD86. We also observed that MVA-infected ALDC promoted migration of DEC-205(+) SIRPα(+) CD21(+) DC as well as CD4(+) and CD8(+) T cells independently of caspase activation. These in vitro studies show that induction of apoptosis in DC by MVA vectors is detrimental to the subsequent induction of T cell responses.

The double-stranded RNA bluetongue virus induces type I interferon in plasmacytoid dendritic cells via a MYD88-dependent TLR7/8-independent signaling pathway

Dendritic cells (DCs), especially plasmacytoid DCs (pDCs), produce large amounts of alpha/beta interferon (IFN-α/β) upon infection with DNA or RNA viruses, which has impacts on the physiopathology of the viral infections and on the quality of the adaptive immunity. However, little is known about the IFN-α/β production by DCs during infections by double-stranded RNA (dsRNA) viruses. We present here novel information about the production of IFN-α/β induced by bluetongue virus (BTV), a vector-borne dsRNA Orbivirus of ruminants, in sheep primary DCs. We found that BTV induced IFN-α/β in skin lymph and in blood in vivo. Although BTV replicated in a substantial fraction of the conventional DCs (cDCs) and pDCs in vitro, only pDCs responded to BTV by producing a significant amount of IFN-α/β. BTV replication in pDCs was not mandatory for IFN-α/β production since it was still induced by UV-inactivated BTV (UV-BTV). Other inflammatory cytokines, including tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), and IL-12p40, were also induced by UV-BTV in primary pDCs. The induction of IFN-α/β required endo-/lysosomal acidification and maturation. However, despite being an RNA virus, UV-BTV did not signal through Toll-like receptor 7 (TLR7) for IFN-α/β induction. In contrast, pathways involving the MyD88 adaptor and kinases dsRNA-activated protein kinase (PKR) and stress-activated protein kinase (SAPK)/Jun N-terminal protein kinase (JNK) were implicated. This work highlights the importance of pDCs for the production of innate immunity cytokines induced by a dsRNA virus, and it shows that a dsRNA virus can induce IFN-α/β in pDCs via a novel TLR-independent and Myd88-dependent pathway. These findings have implications for the design of efficient vaccines against dsRNA viruses.

Capacities of migrating CD1b+ lymph dendritic cells to present Salmonella antigens to naive T cells

Dendritic cells (DCs) are well known as professional antigen-presenting cells (APC) able to initiate specific T-cell responses to pathogens in lymph nodes (LN) draining the site of infection. However, the respective contribution of migratory and LN-resident DCs in this process remains unclear. As DC subsets represent important targets for vaccination strategies, more precise knowledge of DC subsets able to present vaccine antigens to T cells efficiently is required. To investigate the capacities of DCs migrating in the lymph (L-DCs) to initiate a specific T-cell response, we used physiologically generated DCs collected from a pseudoafferent lymphatic cannulation model in sheep. The CD1b⁺ L-DCs were assessed for presenting antigens from the vaccine attenuated strain of Salmonella enterica serovar Abortusovis. CD1b⁺ L-DCs were able to phagocytose, process and to present efficiently Salmonella antigens to effector/memory T cells in vitro. They were shown to be efficient APC for the priming of allogeneic naive T cells associated with inducing both IFN-γ and IL-4 responses. They were also efficient in presenting Salmonella antigens to autologous naive T cells associated with inducing both IFN-γ and IL-10 responses. The capacities of L-DCs to process and present Salmonella antigens to T cells were investigated in vivo after conjunctival inoculation of Salmonella. The CD1b⁺ L-DCs collected after inoculation were able to induce the proliferative response of CD4⁺ T cells suggesting the in vivo capture of Salmonella antigens by the CD1b⁺ L-DCs, and their potential to present them directly to CD4⁺ T cells. In this study, CD1b⁺ L-DCs present potential characteristics of APC to initiate by themselves T cell priming in the LN. They could be used as target cells for driving immune activation in vaccinal strategies.

Unraveling features of the natural MHC class II peptidome of skin-migrated dendritic cells

Dendritic cells (DCs) migrating from peripheral tissues at steady state are considered the most efficient antigen-presenting cells (APCs) involved in the induction of peripheral T-cell tolerance via self-antigen presentation on MHC class II molecules. However, difficulties in obtaining sufficient numbers of such DCs have precluded previous analyses of their natural MHC class II peptidome in laboratory animals or humans. Here, we overcome this difficulty by collecting the large quantities of sheep DCs that migrate from the skin via the afferent lymphatics at steady state to the draining lymph node. We compared the repertoire of MHC class II-bound peptides from afferent lymph DCs with autologous APCs derived from peripheral blood. A large fraction of the MHC class II peptidome from skin DCs was derived from membrane-recycling proteins (59%) and from proteins of the antigen presentation machinery (50%), whereas these types of peptides constituted a more limited fraction in blood APCs (21 and 11%, respectively). One sheep cytokeratin peptide was identified in the skin DC peptidome indicating active processing of epithelium-derived antigens. Conversely, peptides derived from cytosolic and soluble antigens of the extracellular milieu were more represented in blood APCs than skin DCs. The biased peptidome of skin-migrated DCs indicates that these cells express a peptide repertoire for the generation of self-reactive and/or regulatory T cells mainly directed toward DC molecules from internal and external membranes and to a lesser extent toward antigens of the extracellular milieu, including some tissue-specific peptides.

Exploiting mucosal surfaces for the development of mucosal vaccines

Mucosal immunity covers a variety of mucosal surfaces susceptible to different pathogens. This review highlights the diversity of mucosal tissues and the unique microenvironments in which an immune response is generated. It argues that tissue-specific factors present throughout mucosal tissues and lymph nodes determine the differentiation into IgA-producing B cells, which in turn determines their migration patterns. Mucosal immunity can therefore be induced when antigen is delivered at any mucosal tissue without the need for specific 'mucosal adjuvants' or targeting to specialised lymphoid structures. Non-oral vaccination strategies directed at alternative and more accessible mucosal tissue sites, may provide new avenues for both mucosal and systemic immunization, and will be greatly facilitated by the use of large animal models.

Classical swine fever virus N(pro) limits type I interferon induction in plasmacytoid dendritic cells by interacting with interferon regulatory factor 7

Viruses are detected by different classes of pattern recognition receptors that lead to the activation of interferon regulatory factors (IRF) and consequently to the induction of alpha/beta interferon (IFN-α/β). In turn, efficient viral strategies to escape the type I IFN-induced antiviral mechanisms have evolved. Previous studies established that pestivirus N(pro) antagonizes the early innate immune response by targeting the transcription factor IRF3 for proteasomal degradation. Here, we report that N(pro) of classical swine fever virus (CSFV) interacts also with IRF7, another mediator of type I IFN induction. We demonstrate that the Zn-binding domain of N(pro) is essential for the interaction of N(pro) with IRF7. For IRF3 and IRF7, the DNA-binding domain, the central region, and most of the regulatory domain are required for the interaction with N(pro). Importantly, the induction of IRF7-dependent type I IFN responses in plasmacytoid dendritic cells (pDC) is reduced after wild-type CSFV infection compared with infection with virus mutants unable to interact with IRF7. This is associated with lower levels of IRF7 in pDC. Consequently, wild-type but not N(pro) mutant CSFV-infected pDC show reduced responses to other stimuli. Taken together, the results of this study show that CSFV N(pro) is capable of manipulating the function of IRF7 in pDC and provides the virus with an additional strategy to circumvent the innate defense.

Mucosal vaccination: lung versus nose

The induction of potent mucosal immune responses able to prevent the establishment of infection at the onset of mucosal pathogen colonisation represents a desirable but challenging goal for vaccine development. Here we compare nasal vaccine delivery with intra-pulmonary vaccination using a sheep lymphatic cannulation model. Our results demonstrate that nasal delivery of a non-infective ISCOMATRIX(®) influenza vaccine does not induce primary immune responses in the lymph draining the nasal lymph nodes, suggesting that local immune responses in the lymph nodes draining the nasal cavity are relatively weak. However, this mode of delivery can boost existing immunity in the nasal lymph. Using the same adjuvant we were able to induce very potent immune responses in both blood and bronchoalveolar lavage (BAL), following intra-pulmonary delivery of ISCOMATRIX(®) influenza vaccine, even when very small doses of antigen were employed. Lung delivery could also induce comparable immune responses against other recombinant antigens mixed with ISCOMATRIX(®) adjuvant and could therefore become a method of choice for the induction of immunity to mucosal pathogens infecting the lower respiratory tract.

The XC chemokine receptor 1 is a conserved selective marker of mammalian cells homologous to mouse CD8alpha+ dendritic cells

Human BDCA3⁺ dendritic cells (DCs) were suggested to be homologous to mouse CD8α⁺ DCs. We demonstrate that human BDCA3⁺ DCs are more efficient than their BDCA1⁺ counterparts or plasmacytoid DCs (pDCs) in cross-presenting antigen and activating CD8⁺ T cells, which is similar to mouse CD8α⁺ DCs as compared with CD11b⁺ DCs or pDCs, although with more moderate differences between human DC subsets. Yet, no specific marker was known to be shared between homologous DC subsets across species. We found that XC chemokine receptor 1 (XCR1) is specifically expressed and active in mouse CD8α⁺, human BDCA3⁺, and sheep CD26⁺ DCs and is conserved across species. The mRNA encoding the XCR1 ligand chemokine (C motif) ligand 1 (XCL1) is selectively expressed in natural killer (NK) and CD8⁺ T lymphocytes at steady-state and is enhanced upon activation. Moreover, the Xcl1 mRNA is selectively expressed at high levels in central memory compared with naive CD8⁺ T lymphocytes. Finally, XCR1^−/− mice have decreased early CD8⁺ T cell responses to Listeria monocytogenes infection, which is associated with higher bacterial loads early in infection. Therefore, XCR1 constitutes the first conserved specific marker for cell subsets homologous to mouse CD8α⁺ DCs in higher vertebrates and promotes their ability to activate early CD8⁺ T cell defenses against an intracellular pathogenic bacteria.

The role of dendritic cells in alphaherpesvirus infections: archetypes and paradigms

Dendritic cells (DCs) play a critical role in orchestrating both innate and adaptive components of the immune system and are therefore of pivotal importance in the initiation of immune responses to control and eliminate viral infections. A major focus of this review is to give an overview on the recent findings that point out the importance of DCs in controlling alphaherpesvirus infections, but also indicate that these viruses have evolved several strategies to inhibit and/or exploit DC functions to delay or escape elimination by the immune system. In addition, we point out the common features and interspecies differences between DCs from man and animal, and discuss the potential use of animal alphaherpesvirus homologues to gain further insights into the interaction between alphaherpesviruses and DCs in their natural virus-host environment. Finally, recent knowledge on the potential of alphaherpesviruses as vectors for DC stimulation and their use for immunotherapy is presented.

Bluetongue virus targets conventional dendritic cells in skin lymph

Bluetongue virus (BTV) is the etiological agent of bluetongue, a hemorrhagic disease of ruminants (particularly sheep), which causes important economic losses around the world. BTV is transmitted primarily via the bites of infected midges, which inject the virus into the ruminant's skin during blood feeding. The virus initially replicates in the draining lymph node and then disseminates to secondary organs where it induces edema, hemorrhages, and necrosis. In this study, we show that ovine conventional dendritic cells (cDCs) are the primary targets of BTV that contribute to the primary dissemination of BTV from the skin to draining lymph nodes. Lymph cDCs support BTV RNA and protein synthesis, as well as the production of infectious virus belonging to several different BTV serotypes, regardless of their level of attenuation. Afferent lymph cell subsets, other than cDCs, showed only marginal levels of BTV protein expression. BTV infection provoked a massive recruitment of cDCs to the sheep skin and afferent lymph, providing cellular targets for infection. Although BTV productively infects cDCs, no negative impact on their physiology was detected. Indeed, BTV infection and protein expression in cDCs enhanced their survival rate. Several serotypes of BTV stimulated the surface expression of the CD80 and CD86 costimulatory molecules on cDCs as well as the mRNA synthesis of cytokines involved in inflammation and immunity, i.e., interleukin-12 (IL-12), IL-1beta, and IL-6. BTV-infected cDCs stimulated antigen-specific CD4 and CD8 proliferation as well as gamma interferon production. BTV initially targets cDCs while preserving their functional properties, reflecting the optimal adaptation of the virus to its host cells for its first spread.

Ontogeny and phagocytic function of baboon lung dendritic cells

Dendritic cells (DCs) are the most potent antigen-presenting cells, but the ontogeny and functions of lung DCs are not known during prenatal period. Here, we isolated lung DC population from fetal (125 −175dGA) and adult baboons. The cells were stained with fluorochrome-conjugated-HLA-DP, DQ, DR, CD1a, CD11c, CD14, CD40, CD80, CD86, CD209, CMKLR1, ILT7-specific antibodies, and staining was analyzed by Flow-cytometry. The phagocytic function was investigated by incubating the cells with fluorescent-labeled Escherichia coli bioparticles and analyzed by Flow-cytometry and fluorescence microscopy. The fetal baboon lung DCs expressed low levels of HLA-DP, DQ, DR, CD11c and CD86 as compared to adult baboon lung DCs and showed distinct DC morphology. The fetal lung DCs were also less capable of phagocytosing E. coli as compared to the adult lung DCs (p<0.05). In conclusion, the fetal lung DCs are not only phenotypically immature, but also less efficient in phagocytosing E. coli.

Plasmacytoid dendritic cells migrate in afferent skin lymph

Conventional dendritic cells enter lymph nodes by migrating from peripheral tissues via the lymphatic route, whereas plasmacytoid dendritic cells (pDC), also called IFN-producing cells (IPC), are described to gain nodes from blood via the high endothelial venules. We demonstrate here that IPC/pDC migrate in the afferent lymph of two large mammals. In sheep, injection of type A CpG oligodinucleotide (ODN) induced lymph cells to produce type I IFN. Furthermore, low-density lymph cells collected at steady state produced type I IFN after stimulation with type A CpG ODN and enveloped viruses. Sheep lymph IPC were found within a minor B(neg)CD11c(neg) subset expressing CD45RB. They presented a plasmacytoid morphology, expressed high levels of TLR-7, TLR-9, and IFN regulatory factor 7 mRNA, induced IFN-gamma production in allogeneic CD4(pos) T cells, and differentiated into dendritic cell-like cells under viral stimulation, thus fulfilling criteria of bona fide pDC. In mini-pig, a CD4(pos)SIRP(pos) subset in afferent lymph cells, corresponding to pDC homologs, produced type I IFN after type A CpG-ODN triggering. Thus, pDC can link innate and acquired immunity by migrating from tissue to draining node via lymph, similarly to conventional dendritic cells.

De l’utilité des animaux domestiques pour la recherche en immunologie

Les recherches en immunologie des animaux domestiques fournissent des données complémentaires à celles menées chez la souris, du fait des « opportunités » qu’offrent ces espèces. Certaines d’entre elles font l’objet de cette communication: approche chirurgicale du fonctionnement in vivo des organes lymphoïdes, interventions in utero pour l’étude de l’ontogénèse du système immunitaire, pertinence de l’étude physiopathologique des infections sur espèces cibles.