Productive HIV-1 infection of tissue macrophages by fusion with infected CD4+ T cells.

Macrophages are essential for HIV-1 pathogenesis and represent major viral reservoirs. Therefore, it is critical to understand macrophage infection, especially in tissue macrophages, which are widely infected in vivo, but poorly permissive to cell-free infection. Although cell-to-cell transmission of HIV-1 is a determinant mode of macrophage infection in vivo, how HIV-1 transfers toward macrophages remains elusive. Here, we demonstrate that fusion of infected CD4+ T lymphocytes with human macrophages leads to their efficient and productive infection. Importantly, several tissue macrophage populations undergo this heterotypic cell fusion, including synovial, placental, lung alveolar, and tonsil macrophages. We also find that this mode of infection is modulated by the macrophage polarization state. This fusion process engages a specific short-lived adhesion structure and is controlled by the CD81 tetraspanin, which activates RhoA/ROCK-dependent actomyosin contractility in macrophages. Our study provides important insights into the mechanisms underlying infection of tissue-resident macrophages, and establishment of persistent cellular reservoirs in patients.

Evidence for tmTNF reverse signaling in vivo: Implications for an arginase-1-mediated therapeutic effect of TNF inhibitors during inflammation.

In order to ascertain the significance of transmembrane tumor necrosis factor (tmTNF) reverse signaling in vivo, we generated a triple transgenic mouse model (3TG, TNFR1-/-, TNFR2-/-, and tmTNFKI/KI) in which all canonical tumor necrosis factor (TNF) signaling was abolished. In bone-marrow-derived macrophages harvested from these mice, various anti-TNF biologics induced the expression of genes characteristic of alternative macrophages and also inhibited the expression of pro-inflammatory cytokines mainly through the upregulation of arginase-1. Injections of TNF inhibitors during arthritis increased pro-resolutive markers in bone marrow precursors and joint cells leading to a decrease in arthritis score. These results demonstrate that the binding of anti-TNF biologics to tmTNF results in decreased arthritis severity. Collectively, our data provide evidence for the significance of tmTNF reverse signaling in the modulation of arthritis. They suggest a complementary interpretation of anti-TNF biologics effects in the treatment of inflammatory diseases and pave the way to studies focused on new arginase-1-dependent therapeutic targets.

The activation trajectory of plasmacytoid dendritic cells in vivo during a viral infection.

Plasmacytoid dendritic cells (pDCs) are a major source of type I interferon (IFN-I). What other functions pDCs exert in vivo during viral infections is controversial, and more studies are needed to understand their orchestration. In the present study, we characterize in depth and link pDC activation states in animals infected by mouse cytomegalovirus by combining Ifnb1 reporter mice with flow cytometry, single-cell RNA sequencing, confocal microscopy and a cognate CD4 T cell activation assay. We show that IFN-I production and T cell activation were performed by the same pDC, but these occurred sequentially in time and in different micro-anatomical locations. In addition, we show that pDC commitment to IFN-I production was marked early on by their downregulation of leukemia inhibitory factor receptor and was promoted by cell-intrinsic tumor necrosis factor signaling. We propose a new model for how individual pDCs are endowed to exert different functions in vivo during a viral infection, in a manner tightly orchestrated in time and space.

Inhibition of Osteoclastogenesis by the RNA-Binding Protein QKI5: a Novel Approach to Protect from Bone Resorption.

Increased osteoclastogenesis is a common feature of bone erosion, notably in osteoporosis but also in inflammatory diseases such as rheumatoid arthritis (RA) and osteoarticular infections. Human cytomegalovirus (HCMV) infection has been described to impair monocyte differentiation into macrophages and dendritic cells. However, its effect on monocyte-derived osteoclasts is yet to be determined. We showed here that in vitro HCMV infection is associated with an inhibition of osteoclastogenesis through decreased expression of colony stimulating factor 1 receptor (CSF-1R) and RANK in monocytes, which was mediated by an upregulation of quaking I-5 protein (QKI-5), a cellular RNA-interacting protein. We found that deliberate QKI5 overexpression in the absence of HCMV infection is able to decrease CSF-1R and RANK expression, leading to osteoclastogenesis inhibition. Finally, by using lentiviral vectors in a calvarial bone erosion mouse model, we showed that QKI5 inhibits bone degradation. This work identifies QKI5 as a strong inhibitor of bone resorption. Future research will point out whether QKI5 could be a target for bone pathologies. © 2019 American Society for Bone and Mineral Research.

Rheumatoid Synovial Fluids Regulate the Immunomodulatory Potential of Adipose-Derived Mesenchymal Stem Cells Through a TNF/NF-κB-Dependent Mechanism.

Introduction: Adipose-derived mesenchymal stem cells (ADSC) have been shown to have remarkable immune-modulating effects. However, their efficacy in clinical trials has yet to be fully demonstrated. This could be due to a lack of a proper inflammatory environment in vivo that primes ADSC. Here, we define how the articular microenvironment of rheumatoid arthritis (RA) patients modulates the therapeutic efficiency of ADSC. Methods: Synovial fluids (SF) were collected from 8 RA patients, 2 Spondyloarthritis patients and one control synovial fluid from a patient undergoing traumatic-related surgery. SF inflammatory status was determined by routine analysis and quantification of pro-inflammatory cytokines. ADSC were first treated with SF and ADSC proliferation and gene expression of immunomodulatory factors was evaluated. In order to determine the mechanisms underlying the effect of SF on ADSC, tumor necrosis factor (TNF), interleukin-6 (IL-6), and NF-κB neutralization assays were performed. To evaluate the effect of SF on ADSC functions, ADSC were pre-treated with SF and then co-cultured with either macrophages or T cells. The modulation of their phenotype was assessed by flow cytometry. Results: Pro-inflammatory RASF maintained the proliferative capacity of ADSC and upregulated the gene expression of cyclooxygenase-2 (COX2), indoleamine-1,2-dioxygenase (IDO), interleukin-6 (IL-6), tumor-necrosis factor stimulated gene 6 (TSG6), intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and programmed death-ligand 1 (PD-L1), all factors involved in ADSC immunomodulatory potential. The RASF-induced gene expression was mainly mediated by TNF alone or in combination with IL-6 and signaled through the NF-κB pathway. Conditioning ADSC with pro-inflammatory RASF enhanced their ability to induce CD4+Foxp3+CD25high regulatory T cells (Tregs) and inhibit pro-inflammatory markers CD40 and CD80 in activated macrophages. Conclusions: Inflammatory synovial fluids from RA patients had the capacity to modulate ADSC response, to induce Tregs and modulate the phenotype of macrophages. The clinical use of ADSC in affected joints should take into account the influence of the local articular environment on their potential. Having a sufficient pro-inflammatory microenvironment will determine whether optimal immunoregulatory response should be expected. Direct ADSC intra-articular delivery to patients could be a potential strategy to properly prime their immunomodulatory potential and enhance their clinical benefits.

Osteoclast-Derived Autotaxin, a Distinguishing Factor for Inflammatory Bone Loss.

OBJECTIVE: The severity of rheumatoid arthritis (RA) correlates directly with bone erosions arising from osteoclast (OC) hyperactivity. Despite the fact that inflammation may be controlled in patients with RA, those in a state of sustained clinical remission or low disease activity may continue to accrue erosions, which supports the need for treatments that would be suitable for long-lasting inhibition of OC activity without altering the physiologic function of OCs in bone remodeling. Autotaxin (ATX) contributes to inflammation, but its role in bone erosion is unknown. METHODS: ATX was targeted by inhibitory treatment with pharmacologic drugs and also by conditional inactivation of the ATX gene Ennp2 in murine OCs (ΔATXC tsk ). Arthritic and erosive diseases were studied in human tumor necrosis factor-transgenic (hTNF+/- ) mice and mice with K/BxN serum transfer-induced arthritis. Systemic bone loss was also analyzed in mice with lipopolysaccharide (LPS)-induced inflammation and estrogen deprivation. Joint inflammation and bone erosion were assessed by histology and micro-computed tomography. The role of ATX in RA was also examined in OC differentiation and activity assays. RESULTS: OCs present at sites of inflammation overexpressed ATX. Pharmacologic inhibition of ATX in hTNF+/- mice, as compared to vehicle-treated controls, significantly mitigated focal bone erosion (36% decrease; P < 0.05) and systemic bone loss (43% decrease; P < 0.05), without affecting synovial inflammation. OC-derived ATX was revealed to be instrumental in OC bone resorptive activity and was up-regulated by the inflammation elicited in the presence of TNF or LPS. Specific loss of ATX in OCs from mice subjected to ovariectomy significantly protected against the systemic bone loss and erosion that had been induced with LPS and K/BxN serum treatments (30% reversal of systemic bone loss [P < 0.01]; 55% reversal of erosion [P < 0.001]), without conferring bone-protective properties. CONCLUSION: Our results identify ATX as a novel OC factor that specifically controls inflammation-induced bone erosions and systemic bone loss. Therefore, ATX inhibition offers a novel therapeutic approach for potentially preventing bone erosion in patients with RA.

Polarization of Rheumatoid Macrophages by TNF Targeting Through an IL-10/STAT3 Mechanism.

Macrophages contribute to the pathogenesis of rheumatoid arthritis (RA). They can display different states of activation or "polarization," notably the so-called inflammatory "M1" and the various alternative "M2" polarizations, characterized by distinct functions. Data regarding the effects of RA anti-cytokine biological disease-modifying anti-rheumatic drugs (bDMARDs) on macrophage polarization are scarce. We aimed to assess in vitro modulation of macrophage polarization by bDMARDs targeting pro-inflammatory cytokines in RA. We generated monocyte derived macrophages using blood samples from 20 RA patients with active RA and 30 healthy controls. We evaluated in vitro the impact on M1 inflammatory macrophages of: etanercept (ETA), adalimumab (ADA), certolizumab (CZP), tocilizumab (TCZ), and rituximab (RTX). We assessed the impact on macrophage polarization using flow cytometry and RTqPCR to study the expression of surface markers and perform functional studies of cytokine production, phagocytosis, and negative feedback control of inflammation. Among evaluated bDMARDs, anti-TNF agents modulated the polarization of inflammatory macrophages by decreasing inflammatory surface markers (CD40, CD80) and favoring alternative markers (CD16, CD163, MerTK). Anti-TNF agents also induced alternative functions in macrophages activated in inflammatory condition with (i) the inhibition of inflammatory cytokines (TNF, IL-6, IL-12), (ii) an increase in phagocytosis. These findings were mechanistically related to an increase in early IL-10 production, responsible for higher negative feedback control of inflammation involving SOCS3 and Gas6. This IL-10 effect was STAT3-dependent. Anti-TNF agents not only inhibit in vitro inflammatory functions of macrophages, but also favor resolution of inflammation through polarization toward alternative features specifically involving the IL-10/STAT3 axis.

Modulation of T-cell responses by anti-tumor necrosis factor treatments in rheumatoid arthritis: a review.

Tumor necrosis factor (TNF) is a pleiotropic cytokine involved in many aspects of immune regulation. Anti-TNF biological therapy has been considered a breakthrough in the treatment of chronic autoimmune diseases, such as rheumatoid arthritis (RA). In this review, because of the major involvement of T cells in RA pathogenesis, we discuss the effects of anti-TNF biotherapy on T-cell responses in RA patients. We also outline the potential fields for future research in the area of anti-TNF therapy in RA.This could be useful to better understand the therapeutic efficiency and the side effects that are encountered in RA patients. Better targeting of T cells in RA could help set more specific anti-TNF strategies and develop prediction tools for response.

Anti-TNF certolizumab pegol induces antioxidant response in human monocytes via reverse signaling.

BACKGROUND: Anti TNF drugs have been widely used in rheumatoid arthritis (RA) but only 70 to 80 % of patients respond to this therapy. Exploring the mode of action of anti-TNF drugs remains important in order to improve the efficiency of the treatment and enhance our knowledge of inflammation. TNF-α exists as classical soluble cytokine as well as transmembrane protein (tmTNF-α). Evidence suggests that tmTNF-α can induce reverse signaling. In the present study, we have explored consequences of reverse signaling in human monocytes using certolizumab pegol (CZP). METHODS: Monocytes were purified from healthy blood donors and were incubated with CZP. Nuclear translocation of Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) was evaluated by wide-field microscopy and cell fractionation. Heme oxygenase 1 (HO-1) was assessed by RT-qPCR and western blot. Monocytes were stimulated with lipopolysaccharide (LPS). IL-1ß was quantitated by RT-qPCR. Reactive oxygen species (ROS) were evaluated by flow cytometry using the H2DCFDA fluorescent marker. RESULTS: CZP induced rapid minimal ROS production and Nrf2 nuclear translocation. This was followed by HO-1 mRNA and protein production. IL-1ß induction by LPS was inhibited at the mRNA and protein level. At a later time-point, CZP was able to counteract the strong production of ROS induced by LPS. Reverse signaling was suggested by short kinetics of Nrf2 translocation, extensive washing of CZP and the use of anti-TNF-Rs antibodies. CONCLUSION: Our data suggest a novel mechanism of ROS modulation by CZP. This observation sheds new light on the function of reverse signaling and on potential mechanisms of action of anti-TNF drugs.

Modulation of pro-inflammatory activation of monocytes and dendritic cells by aza-bis-phosphonate dendrimer as an experimental therapeutic agent.

INTRODUCTION: Our objective was to assess the capacity of dendrimer aza-bis-phosphonate (ABP) to modulate phenotype of monocytes (Mo) and monocytes derived dendritic cells (MoDC) activated in response to toll-like receptor 4 (TLR4) and interferon γ (IFN- γ) stimulation. METHODS: Mo (n = 12) and MoDC (n = 11) from peripheral blood of healthy donors were prepared. Cells were preincubated or not for 1 hour with dendrimer ABP, then incubated with lipopolysaccharide (LPS; as a TLR4 ligand) and (IFN-γ) for 38 hours. Secretion of tumor necrosis factor α (TNFα), interleukin (IL) -1, IL-6, IL-12, IL-10 and IL-23 in the culture medium was measured by enzyme-linked immunosorbent assay (ELISA) and Cytokine Bead Array. Differentiation and subsequent maturation of MoDC from nine donors in the presence of LPS were analyzed by flow cytometry using CD80, CD86, CD83 and CD1a surface expression as markers. RESULTS: Mo and MoDC were orientated to a pro-inflammatory state. In activated Mo, TNFα, IL-1ß and IL-23 levels were significantly lower after prior incubation with dendrimer ABP. In activated MoDC, dendrimer ABP promoted IL-10 secretion while decreasing dramatically the level of IL-12. TNFα and IL-6 secretion were significantly lower in the presence of dendrimer ABP. LPS driven maturation of MoDC was impaired by dendrimer ABP treatment, as attested by the significantly lower expression of CD80 and CD86. CONCLUSION: Our data indicate that dendrimer ABP possesses immunomodulatory properties on human Mo and MoDC, in TLR4 + IFN-γ stimulation model, by inducing M2 alternative activation of Mo and promoting tolerogenic MoDC.

Targeting monocytes/macrophages in the treatment of rheumatoid arthritis.

Biotherapies have revolutionized the treatment of RA. However, much work is needed to understand all the mechanisms of these biotherapies, and alternatives are needed to circumvent adverse effects and the high cost of these long-lasting treatments. In this article we outline some of the approaches we have used to target monocytes/macrophages as major components of inflammation and bone homeostasis. We also discuss how anti-TNF-α antibodies target monocytes/macrophages in the complex mechanisms contributing to inhibition of inflammation.

Link between traditional cardiovascular risk factors and inflammation in patients with early arthritis: results from a French multicenter cohort.

OBJECTIVE: To compare the characteristics of traditional cardiovascular risk factors for untreated patients with early arthritis (EA) and healthy subjects, and to look for a link between cardiovascular risk factors and inflammation in EA patients. METHODS: This multicenter case-control study enrolled 607 patients with EA (ESPOIR cohort) and 1,821 age- and sex-matched controls (World Health Organization MONICA survey). Lipid levels, blood pressure, glucose levels, and exposure to smoking were characterized in patients and controls. Systemic inflammation was quantified in EA patients. Traditional cardiovascular risk factor characteristics were compared between patients with EA and controls. The link between cardiovascular risk factors and inflammation was assessed in EA patients. RESULTS: Mean ± SEM total cholesterol (2.14 ± 0.022 versus 2.34 ± 0.017 gm/liter; P < 0.001), high-density lipoprotein (HDL) cholesterol (0.60 ± 0.011 versus 0.63 ± 0.007 gm/liter; P = 0.020), and low-density lipoprotein (LDL) cholesterol (1.28 ± 0.025 versus 1.51 ± 0.016 gm/liter; P < 0.001) were lower in EA patients than in controls. Triglycerides, triglycerides/HDL ratio, and pulse pressure were higher in patients with EA. Diastolic blood pressure and glucose levels were lower in EA patients. Former or current smokers were more frequent in patients with EA. Total and HDL cholesterol levels were negatively associated with C-reactive protein or serum interleukin-6 levels. CONCLUSION: Total, HDL, and LDL cholesterol, triglycerides, diastolic blood pressure, pulse pressure, glucose, and triglycerides/HDL ratio differ between patients with EA and controls. Some of these risk factors appear to be linked to systemic inflammation. Such initial differences could modulate the risk of cardiovascular events later in the course of arthritis.

A phosphorus-based dendrimer targets inflammation and osteoclastogenesis in experimental arthritis.

Dendrimers are highly branched "tree-like" polymers that have demonstrated therapeutic potential in drug delivery, medical imaging, and tissue engineering in recent years. In addition, we have shown that an azabisphosphonate (ABP)-capped dendrimer selectively targets monocytes and directs them toward anti-inflammatory activation. We explored this property to assess the therapeutic potential of dendrimer ABP in the treatment of an inflammatory disease, rheumatoid arthritis. Intravenous injections of dendrimer ABP inhibited the development of inflammatory arthritis in two animal models: IL-1ra(-/-) mice and mice undergoing K/BxN serum transfer. Suppression of disease was characterized by normal synovial membranes, reduced levels of inflammatory cytokines, and the absence of cartilage destruction and bone erosion. Dendrimer ABP also exhibited anti-osteoclastic activity on mouse and human cells, mediated by c-FMS (cellular-feline McDonough strain sarcoma virus oncogene homolog) inhibition. These preclinical demonstrations suggest the potential use of dendrimer ABP as a nanotherapeutic for rheumatoid arthritis.

Traditional cardiovascular risk factors in rheumatoid arthritis: a meta-analysis.

OBJECTIVE: Rheumatoid arthritis is associated with increased cardiovascular morbidity and mortality. We performed a systematic review of the literature and a meta-analysis to look for differences in the prevalence of traditional cardiovascular risk factor between RA patients and controls. METHODS: Medline database was searched to identify studies evaluating the prevalence of traditional cardiovascular risk factors in rheumatoid arthritis patients and controls. Studies were selected and reviewed by two investigators. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated and pooled using a random-effects model. Statistical heterogeneity was evaluated through the use of Chi2 and I2 statistics. RESULTS: Fifteen case-control studies with a total of 2956 patients and 3713 controls met the inclusion criteria. The prevalence of smoking was increased in RA patients in comparison with controls: OR (95%CI) 1.56 (1.35-1.80) (P < 0.00001). The prevalence of hypertension did not differ: OR (95% CI) 1.09 (0.91-1.31) (P = 0.35). The prevalence of diabetes mellitus was increased in RA: OR (95%CI) 1.74 (1.22-2.50) (P = 0.003). The prevalence of hypercholesterolemia did not differ: OR (95%CI) 0.84 (0.67-1.04) (P = 0.11). HDL cholesterol levels were lower in RA patients: weighted mean difference -17.72 mg/dl (-18.35 - -17.08) (P < 0.00001). Significant heterogeneity among studies was found for diabetes mellitus and HDL cholesterol levels. CONCLUSIONS: Some traditional cardiovascular risk factors, such as smoking, diabetes mellitus or lower HDL cholesterol levels, appear more prevalent in rheumatoid arthritis patients and could contribute to the increased cardiovascular morbidity and mortality observed in rheumatoid arthritis.

Maintenance of cytomegalovirus-specific CD4pos T-cell response in rheumatoid arthritis patients receiving anti-tumor necrosis factor treatments.

INTRODUCTION: Anti-tumor necrosis factor (TNF)-α biotherapies have considerably changed the treatment of rheumatoid arthritis (RA). However, serious infections are a major concern in patients with rheumatic diseases treated with anti-TNF-α. Little is known about viral, especially latent, infections in anti-TNF-α treatments. Infections by cytomegalovirus (CMV), a ß-herpes virus, are frequent and induce a strong CD4pos T-cell immunity, which participates in the control of infection. We thus have chosen to analyze the CD4pos T-cell response to CMV antigens as a model of antiviral response in RA patients treated with anti-TNF-α. CD28 expression was evaluated. METHODS: We have measured the CD4pos response to CMV antigens in RA patients, before and after initiation of treatment with an anti-TNF-α agent. The intracellular production of interferon (IFN)-γ in total and CD28neg CD4pos T cells in response to CMV antigens (Ags) was evaluated with flow cytometry. The proliferation of total CD4pos T cells in the presence of CMV antigens was measured with 3H-thymidine incorporation. RESULTS: Anti-TNF-α treatments impaired neither the anti-CD4pos anti-CMV IFN-γ response nor the proliferative response in patients. The percentage of CD28neg CD4pos cells remained constant. CONCLUSIONS: Our data suggest that the CD4pos T-cell response against CMV is not altered by anti-TNF-α treatments and that infection remains controlled in treated RA patients latently infected with CMV. Our observation brings new insight into the current knowledge of the risks of infection in patients treated with anti-TNF-α biotherapies.

Activities of Z-ajoene against tumour and viral spreading in vitro.

Z-ajoene is a garlic-derived compound with known anti-tumour properties. This report argues in favour of pro-apoptotic and cell cycle blockage activities of Z-ajoene on various cell lines involving activation of the p53-family gene products, p53, p63 and p73, at indicated doses. According to its known anti-proteasome activity, Z-ajoene induced a downregulation of MHC-class I expression at the surface of treated cells but did not impair their recognition by CD8+ T cells. We further demonstrated a new activity of Z-ajoene against human cytomegalovirus spreading in vitro that was mediated by an increased number of apoptotic cells after infection. Altogether our data point at the ubiquitous efficiency of Z-ajoene as a new compound to fight against cancers of various origins including those that put up viruses.

Tumor necrosis factor alpha and adalimumab differentially regulate CD36 expression in human monocytes.

In chronic inflammatory diseases, such as rheumatoid arthritis, inflammation acts as an independent cardiovascular risk factor and the use of anti-inflammatory drugs, such as anti-tumor necrosis factor alpha (anti-TNFalpha), may decrease this risk. The phagocytosis of oxidized low density lipoproteins (LDLs) accumulated in the subendothelium by mononuclear cells influences atherosclerosis and depends on CD36 expression. We investigated the role of TNFalpha and adalimumab, a human anti-TNFalpha monoclonal antibody widely used in human pathology, in CD36 expression in human monocytes. Human monocytes were prepared by adherence from whole-blood buffy-coat fractions from healthy donors. CD36 expression was assessed by RT-PCR and flow cytometry, with various TNFalpha or adalimumab concentrations. Implication of peroxisome proliferator-activated receptor (PPAR)gamma in the regulation of CD36 expression was assessed using specific inhibitor or gel shift assays. The impact of redox signaling was investigated using quantification of reactive oxygen species, antioxidant and a NADPH oxidase inhibitor. The F(ab')2 fragment of adalimumab was isolated and its effect was analyzed. TNFalpha inhibits both CD36 membrane expression and mRNA expression. This inhibition involves a reduction in PPARgamma activation. In contrast, adalimumab increases both CD36 membrane expression and mRNA expression. This induction is independent of the Fc portion of adalimumab and involves redox signaling via NADPH oxidase activation. CD36 expression on human monocytes is inhibited by TNFalpha and independently increased by adalimumab. These data highlight that pro-inflammatory cytokines and their specific neutralization influence the expression of cellular receptors implicated in atherosclerosis. Further studies are needed to investigate the clinical implications of these results in accelerated atherosclerosis observed in rheumatoid arthritis.

Macrophage cultures are susceptible to lytic productive infection by endothelial-cell-propagated human cytomegalovirus strains and present viral IE1 protein to CD4+ T cells despite late downregulation of MHC class II molecules.

The contribution of CD4(+) T cells to control of human cytomegalovirus (HCMV) has been shown and infected tissue macrophages might contribute to this response by antigen presentation. As shown previously, CD4(+) T cells recognize HCMV immediate-early antigen IE1 on glioblastoma cells manipulated to express MHC class II molecules. Here, the possible interference of virus-induced MHC class II downmodulation with the presentation of IE1 by natural target cells was analysed. The capacity of IE1-specific CD4(+) T-cell clones to recognize HCMV-infected monocyte-derived macrophages was tested. Various HCMV strains were used to achieve efficient infection of macrophages. Activation of CD4(+) T cells by infected macrophages was evaluated at different time points after infection. Endothelial-cell-adapted HCMV strains efficiently infected cultured human macrophages. However, the immediate-early and early phases of replication were prolonged. Infected cells entered the late replication phase only after 3 days of infection, which was associated with downmodulation of MHC class II molecules at the surface of infected cells. Strong stimulation of IE1-specific CD4(+) T cells resulted from endogenous de novo antigen production and presentation by infected macrophages during the first 3 days of virus replication, despite MHC class II downmodulation in the late replication phase. Therefore, infected macrophages are assumed to contribute to the antiviral immune response in infected organs.

Optimization of CD4+ T lymphocyte response to human cytomegalovirus nuclear IE1 protein through modifications of both size and cellular localization.

We have previously reported that the CD4+ T lymphocyte response against nuclear human CMV IE1 protein depends in part on endogenous MHC class II presentation. To optimize presentation by HLA-DR of the nuclear IE1 protein and increase the response by CD4+ T cells, we have constructed two different adenovirus vectors containing mutant versions of IE1, containing a HLA-DR3 epitope, fused to GFP. The first construct consisted of a sequence of 46 aa encoded by exon 4, called GFP-IE1 (86-131). The second construct consisted of the whole IE1 mutated on exon 4 nuclear localization signals, identified in this study, and deleted of already known exon 2 nuclear localization signals (GFP-IE1M). Both of these IE1 vectors expressed proteins with cytoplasmic localization, as evidenced by GFP expression, as opposed to control GFP-IE1, which was nuclear. GFP-IE1 (86-131) induced IE1-specific CD4+ T cell clone response that was >30-fold more potent than that against GFP-IE1 and GFP-IE1M. The CD4+ T cell response was due to endogenous presentation followed by exogenous presentation at later time points. Presentation was dependent on both proteasome and acidic compartments. GFP-IE1 (86-131) was rapidly degraded by the APC, which may account for better presentation. Our data show potentiation of the CD4+ T cell response to a specific epitope through shortening and relocation of an otherwise nuclear protein and suggest applications in vaccination.

Human cytomegalovirus-specific CD4(+) T-cell clones recognize cross-reactive peptides from the immediate early 1 protein.

Human cytomegalovirus (HCMV) is a beta-herpes virus that persists in a latent state in immunocompetent individuals. Both CD4(+) and CD8(+) T lymphocytes have been reported to be present at a high frequency in HCMV-seropositive individuals and are involved in the control of infection. How such frequencies are maintained is not completely understood. We have observed that the canonical HLA-DR8 epitope of the immediate early 1 protein (IE1) contained in the IE1 (156--175) sequence shares homologies with an IE1 sequence contained in part in the previously reported HLA-DR3 epitope, IE1 (91-110). We thus wondered whether such homology in a single protein would translate into recognition of the IE1 homolog sequence by HLA-DR8-restricted CD4(+) cells in addition to the canonical epitope. We found that established HLA-DR8-restricted T cell clones are also able to cross-recognize the IE1 (91--110) peptide, as well as a shorter 14-mer, IE1 (91--104). Moreover, the homolog peptide IE1 (91-110) was able to generate, from a seropositive blood donor, new IE1-specific, HLA-DR8-restricted CD4(+) T cell clones that were also cross-reactive. Those findings may provide clues to the formation and regulation of the T-cell repertoire and memory.