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.

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In vivo demonstration of tmTNF reverses signaling existence

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tmTNF reverse signaling induces anti-oxidative stress response

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tmTNF reverse signaling induces an arginase-1-mediated anti-inflammatory response

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Reverse signaling is a complementary mechanism to TNF neutralization by anti-TNF

Cytomegalovirus infection: friend or foe in rheumatoid arthritis?

Human cytomegalovirus (HCMV) is a β-herpesvirus that causes inflammation and remains for life in a latent state in their host. HCMV has been at the center of many hypotheses regarding RA.

We have recently shown that HCMV infection impairs bone erosion through the induction of the mRNA-binding protein QKI5. Latently infected RA patients display a slower progression of bone erosion in patients from a national cohort. Our observations question the possible association between HCMV and the pathophysiology of RA. In this review, we examine the possibility that HCMV may be an aggravating factor of inflammation in RA while protecting from bone erosion. We also assess its relationship with other pathogens such as bacteria causing periodontitis and responsible for ACPA production.

This review thus considers whether HCMV can be regarded as a friend or a foe in the pathogenesis and the course of RA.

Glycerophosphodiesterase 3 (GDE3) is a lysophosphatidylinositol-specific ectophospholipase C acting as an endocannabinoid signaling switch

Endocannabinoid signaling plays a regulatory role in various (neuro)biological functions. 2-arachidonoylglycerol (2-AG) is the most abundant endocannabinoid, and although its canonical biosynthetic pathway involving phosphoinositide-specific phospholipase C and diacylglycerol lipase α is known, alternative pathways remain unsettled. Here, we characterize a noncanonical pathway implicating glycerophosphodiesterase 3 (GDE3, from GDPD2 gene). Human GDE3 expressed in HEK293T cell membranes catalyzed the conversion of lysophosphatidylinositol (LPI) into monoacylglycerol and inositol-1-phosphate. The enzyme was equally active against 1-acyl and 2-acyl LPI. When using 2-acyl LPI, where arachidonic acid is the predominant fatty acid, LC-MS analysis identified 2-AG as the main product of LPI hydrolysis by GDE3. Furthermore, inositol-1-phosphate release into the medium occurred upon addition of LPI to intact cells, suggesting that GDE3 is actually an ecto-lysophospholipase C. In cells expressing G-protein-coupled receptor GPR55, GDE3 abolished 1-acyl LPI-induced signaling. In contrast, upon simultaneous ex-pression of GDE3 and cannabinoid receptor CB2, 2-acyl LPI evoked the same signal as that induced by 2-AG. These data strongly suggest that, in addition to degrading the GPR55 LPI ligand, GDE3 can act as a switch between GPR55 and CB2 signaling. Coincident with a major expression of both GDE3 and CB2 in the spleen, spleens from transgenic mice lacking GDE3 displayed doubling of LPI content compared with WT mice. Decreased production of 2-AG in whole spleen was also observed, supporting the in vivo relevance of our findings. These data thus open a new research avenue in the field of endocannabinoid generation and reinforce the view of GPR55 and LPI being genuine actors of the endocannabinoid system.

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.

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 (ΔATX^{C 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.

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⁺CD25^high 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.

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.

Three-Dimensional Directionality Is a Pivotal Structural Feature for the Bioactivity of Azabisphosphonate-Capped Poly(PhosphorHydrazone) Nanodrug Dendrimers

Dendrimers are nanosized, nonlinear, hyperbranched polymers whose overall 3D shape is key for their biological activity. Poly(PhosphorHydrazone) (PPH) dendrimers capped with aza-bisphosphonate (ABP) end groups are known to have anti-inflammatory properties enabling the control of inflammatory diseases in different mouse models. Here we screen the anti-inflammatory activity of a series of PPH dendrimers bearing between 2 and 16 ABP end groups in a mouse model of arthritis and confront the biological results with atomistic simulations of the dendrimers. We show that only the PPH dendrimers capped with 10 and 12 ABP end groups can control the flare of the inflammatory disease. All-atom accelerated molecular dynamics simulations show that dendrimers with a low number of ABP end groups are directional but highly flexible/dynamic and have thereby limited efficiency in establishing multivalent interactions. The largest dendrimer appears as nondirectional, having 16 ABP end groups forming patches all over the dendrimer surface. Conversely, intermediate dendrimers having 10 or 12 ABP end groups reach the best compromise between the number of surface groups and their stable directional gathering, a real maximization of multivalency.

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-1β 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-1β 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-1β 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.

Activation of monocytes and dendritic cells through TLR4: modulation by dendrimer ABP as a potential therapeutic agent. (P5226)

Rheumatoid Arthritis (RA) is a chronic inflammatory autoimmune disease whose etiology is unknown. Monocytes (Mo) and dendritic cells (DC) are major mediators of inflammation and immune regulation. We have previously shown that aza-bisphosphonate (ABP) dendrimer targets Mo and reduces inflammation and bone erosion in mouse arthritis. However, the potential effect of ABP on inflammatory human Mo and DC is not well understood. We have used ABP to treat human Mo and DC that were stimulated in vitro with the TLR4 agonist LPS and with IFN-γ. Mo were purified from PBMC collected from healthy blood donors. DC were obtained by 6-day culture of purified Mo in the presence of GM-CSF and IL-4. Mo and DC were then preincubated alone or with 10µM ABP dendrimer for 1h, followed by LPS and IFN-γ. We quantitated the production of pro-inflammatory cytokines and IL-10, as well as markers of DC activation and maturation. ABP significantly decreased the production of TNF-α, IL-12 and IL-23. Furthermore, treated DC exhibited a tolerogenic profile, as suggested by an increase in IL-10, decrease in IL-12, and inhibition of maturation as assessed by inhibition of the costimulatory molecules CD80 and CD86 and of CD83. Our data extend our previous observations on the anti-inflammatory properties of ABP on human Mo and demonstrate the induction of a tolerogenic profile on DC. These observations should elucidate the in vivo response of the monocytic lineage to ABP as a novel compound for arthritis.

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.

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 β-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.

Inhibition of IFN-gamma-induced STAT1 tyrosine phosphorylation by human CMV is mediated by SHP2

Human CMV (HCMV) is a ubiquitous beta-herpesvirus which has developed several mechanisms of escape from the immune system. IFN-gamma-induced signaling relies on the integrity of the JAK/STAT pathway which is regulated by phosphorylation steps and leads to nuclear translocation of tyrosine-phosphorylated STAT1 (STAT1-P-Tyr), and its binding to IFN-gamma activation site sequences of IFN-gamma-inducible promoters. Activation of those promoters leads to the expression of genes involved in the immune response and in the antiviral effects of IFN-gamma. Src homology region 2 domain-containing phosphatase 2 (SHP2) is a ubiquitous phosphatase involved in the regulation of IFN-gamma-mediated tyrosine phosphorylation. Several mechanisms account for the inhibition IFN-gamma signaling pathway by HCMV. In this study, we have identified a new mechanism that involved the inhibition of STAT1 tyrosine phosphorylation within 12-24 h postinfection. This defect was dependent on HCMV transcription. Consequences were impaired nuclear translocation of STAT1-P-Tyr, inhibition of IFN-gamma activation site-STAT1 interaction, and inhibition of HLA-DR expression. Expression of indoleamine-2,3-dioxygenase which is involved in the antiviral effects of IFN-gamma was also inhibited. Treatment of cells with sodium orthovanadate rescued STAT1 tyrosine phosphorylation, suggesting that a tyrosine phosphatase was involved in this inhibition. Coimmunoprecipitation of STAT1 and SHP2 was induced by HCMV infection, and SHP2 small interfering RNA restored the expression of STAT1-P-Tyr. Our data suggest that SHP2 activation induced by HCMV infection is responsible for the down-regulation of IFN-gamma-induced STAT1 tyrosine phosphorylation.

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-TNFα), 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 TNFα and adalimumab, a human anti-TNFα 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 TNFα or adalimumab concentrations. Implication of peroxisome proliferator-activated receptor (PPAR)γ 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. TNFα inhibits both CD36 membrane expression and mRNA expression. This inhibition involves a reduction in PPARγ 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 TNFα 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.

Anti-IE1 CD4+ T-cell clones kill peptide-pulsed, but not human cytomegalovirus-infected, target cells

Cellular immunity plays a major role in the control of human cytomegalovirus (HCMV) infection. CD4(+) T lymphocytes have been shown to contribute to this function but their precise role is a matter of debate. Although CD4(+) T cells have been shown to kill target cells through the perforin/granzyme pathway, whether HCMV-specific CD4(+) T cells are capable of killing HCMV-infected targets has not yet been documented. In the present paper, we have taken advantage of well established cellular reagents to address this issue. Human CD4(+) T-cell clones specific for the major immediate-early protein IE1 were shown to perform perforin-based cytotoxicity against peptide-pulsed targets. However, when tested on infected anitgen presenting cell targets, cytotoxicity was not detectable, although gamma interferon (IFN-gamma) production was significant. Furthermore, cytotoxicity against peptide-pulsed targets was inhibited by HCMV infection, whereas IFN-gamma production was not modified, suggesting that antigen processing was not altered. Remarkably, degranulation of CD4(+) T cells in the presence of infected targets was significant. Together, our data suggest that impaired cytotoxicity is not due to failure to recognize infected targets but rather to a mechanism specifically related to cytotoxicity.

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.

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.

Human cytomegalovirus carries a cell-derived phospholipase A2 required for infectivity

Human cytomegalovirus (HCMV) is known to carry host cell-derived proteins and mRNAs whose role in cell infection is not understood. We have identified a phospholipase A2 (PLA2) activity borne by HCMV by using an assay based on the hydrolysis of fluorescent phosphatidylcholine. This activity was found in all virus strains analyzed and in purified strains. It was calcium dependent and was sensitive to inhibitors of cytosolic PLA2 (cPLA2) but not to inhibitors of soluble PLA2 or calcium-independent PLA2. No other phospholipase activity was detected in the virus. Purified virus was found to contain human cellular cPLA2alpha, as detected by monoclonal antibody. No homology with PLA2 was found in the genome of HCMV, indicating that HCMV does not code for a PLA2. Decreased de novo expression of immediate-early proteins 1 and 2 (IE1 and IE2), tegument phosphoprotein pp65, and virus production was observed when HCMV was treated with inhibitors of cPLA2. Cell entry of HCMV was not altered by those inhibitors, suggesting the action of cPLA2 was postentry. Together, our results indicate a selective sorting of a cell-derived cPLA2 during HCMV maturation, which is further required for infectivity.

Use of a lentiviral vector encoding a HCMV-Chimeric IE1-pp65 protein for epitope identification in HLA-Transgenic mice and for ex vivo stimulation and expansion of CD8+ cytotoxic T cells from human peripheral blood cells

H2-deleted, HLA-A2, or HLA-B7 transgenic mice were used to identify new human cytomegalovirus (HCMV)-derived major histocompatibility complex class I-restricted epitopes. Three different approaches for mice immunization were compared for their ability to induce a cytotoxic CD8(+) T cell (CTL) response: (1). inoculation of infectious HCMV, (2). injection of immunogenic synthetic peptides, and (3). infection with a newly designed HIV-derived central DNA flap positive lentiviral vector encoding the chimeric IE1-pp65 protein (Trip-IE1-pp65). Targets pulsed with either known immunogenic peptides or computer predicted ones were used to characterize CTL. Most of the mice immunized with the pp65 (495-NLVPMVATV-503) immunodominant peptide responded after one injection whereas only two of six mice responded to two successive inoculations with HCMV. Infection of mice with Trip-IE1-pp65 induced activation and expansion of CTL directed against peptides from both pp65 and IE1 and allowed identification of new epitopes. We further demonstrated the high capacity of monocyte-macrophage cells transduced with Trip-IE1-pp65 to activate and expand CTL directed against pp65 from peripheral blood mononuclear cells of HCMV-seropositive donors. Altogether these results suggest that Trip-IE1-pp65 is a powerful construct both to characterize new epitopes in combination with human leukocyte antigen-transgenic mice immunization and to provide an alternative to the use of known infectious and noninfectious approaches to expand effector T cells for adoptive immunotherapy.

Impaired killing of HCMV-infected retinal pigment epithelial cells by anti-pp65 CD8(+) cytotoxic T cells

PURPOSE

Host defense against infection by human cytomegalovirus (HCMV) is ensured in great part by cytotoxic CD8(+) T lymphocytes (CTLs) directed against the tegument protein pp65. The hyperimmediate release of incoming pp65 into the major histocompatibility complex (MHC) class I pathway after fusion of the virus with the cell membrane provides a very early mechanism of defense. In retinal pigment epithelial (RPE) cells HCMV is known to enter through endocytosis. This study was conducted to determine whether this means of penetration into the cells would allow the virus to elude immune surveillance.

METHODS

Infection of RPE cells with HCMV AD169 was performed for 6 hours, 48 hours, and 8 days. Expression of intracellular pp65 in RPE cells and in the astrocytoma reference cell line U373MG was evaluated by flow cytometry, fluorescence microscopy, and Western blot analysis. Killing of both HCMV-infected cell lines by HLA-A2-restricted CD8(+) CTLs directed against pp65 was monitored by (51)Cr-release assays.

RESULTS

RPE cells were not lysed by CTLs directed against incoming pp65, contrary to U373MG. Moreover, both cell lines were not killed by anti-pp65 CTLs later after infection, because of the MHC class-I-downregulating effect of HCMV unique short (US2-11) proteins.

CONCLUSIONS

In RPE cells, both HCMV entry through endocytosis and the immunosuppressive effect of US proteins could allow the virus to evade immune surveillance at any stage of infection, which could promote viral spreading within the retina.

Infection of APC by human cytomegalovirus controlled through recognition of endogenous nuclear immediate early protein 1 by specific CD4(+) T lymphocytes

Infections by human CMV are controlled by cellular immune responses. Professional APC such as monocytes and macrophages can be infected in vivo and are considered as a reservoir of virus. However, CMV-specific CD4(+) responses against infected APC have not been reported. To develop a model of CD4-infected APC interaction, we have transfected the U373MG astrocytoma cell line with the class II transactivator (CIITA). Confocal microscopy experiments showed that U373MG-CIITA cells expressed markers characteristic of APC. Functional assays demonstrated that infected U373MG-CIITA APC processed and presented both exogenous and endogenously neosynthesized nuclear immediate early (IE) protein 1 through the MHC class II pathway. More importantly, endogenous presentation of IE1 by infected APC lead to efficient control of CMV infection as revealed by decreased viral titer. Thus, these results describe the endogenous presentation of a nuclear viral protein by the MHC class II pathway and suggest that IE1-specific CD4(+) T cells may play an important role in CMV infection by directly acting against infected APC.

Ex vivo stimulation and expansion of both CD4(+) and CD8(+) T cells from peripheral blood mononuclear cells of human cytomegalovirus-seropositive blood donors by using a soluble recombinant chimeric protein, IE1-pp65

The transfer of anti-human cytomegalovirus (HCMV) effector T cells to allogeneic bone marrow recipients results in protection from HCMV disease associated with transplantation, suggesting the direct control of CMV replication by T cells. IE1 and pp65 proteins, both targets of CD4(+) and CD8(+) T cells, are considered the best candidates for immunotherapy and vaccine design against HCMV. In this report, we describe the purification of a 165-kDa chimeric protein, IE1-pp65, and its use for in vitro stimulation and expansion of anti-HCMV CD4(+) and CD8(+) T cells from peripheral blood mononuclear cells (PBMC) of HCMV-seropositive donors. We demonstrate that an important proportion of anti-HCMV CD4(+) T cells was directed against IE1-pp65 in HCMV-seropositive donors and that the protein induced activation of HLA-DR3-restricted anti-IE1 CD4(+) T-cell clones, as assessed by gamma interferon (IFN-gamma) secretion and cytotoxicity. Moreover, soluble IE1-pp65 stimulated and expanded anti-pp65 CD8(+) T cells from PBMC of HLA-A2, HLA-B35, and HLA-B7 HCMV-seropositive blood donors, as demonstrated by cytotoxicity, intracellular IFN-gamma labeling, and quantitation of peptide-specific CD8(+) cells using an HLA-A2-peptide tetramer and staining of intracellular IFN-gamma. These results suggest that soluble IE1-pp65 may provide an alternative to infectious viruses used in current adoptive strategies of immunotherapy.

Escape of human cytomegalovirus from HLA-DR-restricted CD4(+) T-cell response is mediated by repression of gamma interferon-induced class II transactivator expression

Human cytomegalovirus (HCMV), a betaherpesvirus, is a pathogen which escapes immune recognition through various mechanisms. In this paper, we show that HCMV down regulates gamma interferon (IFN-gamma)-induced HLA-DR expression in U373 MG astrocytoma cells due to a defect downstream of STAT1 phosphorylation and nuclear translocation. Repression of class II transactivator (CIITA) mRNA expression is detected within the first hours of IFN-gamma-HCMV coincubation and results in the absence of HLA-DR synthesis. This defect leads to the absence of presentation of the major immediate-early protein IE1 to specific CD4(+) T-cell clones when U373 MG cells, used as antigen-presenting cells, are treated with IFN-gamma plus HCMV. However, presentation of endogenously synthesized IE1 can be restored when U373 MG cells are transfected with CIITA prior to infection with HCMV. Altogether, the data indicate that the defect induced by HCMV resides in the activation of the IFN-gamma-responsive promoter of CIITA. This is the first demonstration of a viral inhibition of CIITA expression.

Distinct pathways for tumor necrosis factor alpha and ceramides in human cytomegalovirus infection

Human cytomegalovirus (HCMV) infection can be fatal to immunocompromised individuals. We have previously reported that gamma interferon and tumor necrosis factor alpha (TNF-alpha) synergistically inhibit HCMV replication in vitro. Ceramides have been described as second messengers induced by TNF-alpha. To investigate the mechanisms involved in the inhibition of HCMV by TNF-alpha, in the present study we have analyzed ceramide production by U373 MG astrocytoma cells and the effects of TNF-alpha versus ceramides on HCMV replication. Our results show that U373 MG cells did not produce ceramides upon incubation with TNF-alpha. Moreover, long-chain ceramides induced by treatment with exogenous bacterial sphingomyelinase inhibited HCMV replication in synergy with TNF-alpha. Surprisingly, short-chain permeant C6-ceramide increased viral replication. Our results show that the anti-HCMV activity of TNF-alpha is independent of ceramides. In addition, our results suggest that TNF-alpha and endogenous long-chain ceramides use separate pathways of cell signalling to inhibit HCMV replication, while permeant C6-ceramide appears to activate a third pathway leading to an opposite effect.

Characterization of an epitope of the human cytomegalovirus protein IE1 recognized by a CD4+ T cell clone

CD4+ T cells specific for human cytomegalovirus (HCMV) IE1 protein are potential effectors of the control of HCMV infection through cytokine production. Better knowledge of major histocompatibility complex (MHC)-peptide-T cell receptor (TcR) interactions in the CD4+ T cell response should result in a better design of immunizing peptides and is a prerequisite for the development of vaccines or anti-cytomegalovirus therapy. In this study, the recombinant protein comprising residues 86-491 encoded by exon 4 of IE1 (GST-e4) was cleaved by enzymatic digestion and analyzed by high pressure liquid chromatography-mass spectroscopy (HPLC-MS). We identified the 14-residue epitope 162-DKREMWMACIKELH-175 recognized by an HLA-DR8-restricted clone, BeA3. Synthetic elongated, truncated and di-Ala-substituted peptides of the 18-mer IE1 158-IVPEDKREMWMACIKELH-175 sequence were used to analyze the amino acid motifs involved in binding to HLA-DR8 and recognition by the BeA3 clone. Substitutions which abolished (MW --> AA), or decreased (RE --> AA and MA --> AA) T cell clone proliferation, cytokine production and cytotoxicity were identified. Loss of T cell function induced by the MW --> AA substitution was associated with poor HLA-DR8 binding. Decreased T cell function (RE --> AA and MA --> AA) was associated with good HLA-DR8 binding, which suggested that these motifs were involved in TcR binding. Other substitutions induced potentiation of the T cell clone response: the IV --> AA substitution induced stronger proliferation, but equivalent cytokine production, when compared with the reference peptide IE1 (158-175). CI --> AA substitution induced strong potentiation of HLA-DR8 binding, proliferation and interferon-gamma and interleukin-4 production, possibly due to the removal of negative effects of Cys, Ile, or both side chains. Cytotoxicity was not improved by any substitution. Our results show modulation of the CD4+ T cell response according to the peptide residues involved in the HLA-DR8-peptide-TcR interaction.

Anti-human cytomegalovirus activity of cytokines produced by CD4+ T-cell clones specifically activated by IE1 peptides in vitro

The control of latent cytomegalovirus (CMV) infections by the immune system is poorly understood. We have previously shown that CD4+ T cells specific for the human CMV major regulatory protein IE1 are frequent in latently infected healthy blood donors. In order to learn about the possible role of these cells, we have developed IE1-specific CD4+ T-cell clones and, in this study, analyzed their epitope specificity and function in vitro. We measured their cytokine production when stimulated with specific IE1 peptides or whole recombinant IE1 protein. Their cytokine profiles, as deduced from gamma interferon (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), and interleukin-4 (IL-4) and IL-6 production, were of the Th0- and Th1-like phenotypes. Supernatants from IE1-specific clones producing IFN-gamma and TNF-alpha were shown to inhibit CMV replication in U373 MG cells. This effect was due, as found by using cytokine-specific neutralizing antibodies, mostly to IFN-gamma, which was secreted at higher levels than TNF-alpha. To better assess the anti-CMV activity of cytokines, recombinant IFN-gamma and TNF-alpha were used and shown to have a synergistic effect on the inhibition of CMV replication and protein expression. Thus, IE1-specific CD4+ T cells display in vitro anti-CMV activity through cytokine secretion and may play a role in the control of in vivo latent infections.

Combination of human cytomegalovirus recombinant immediate-early protein (IE1) with 80 nm cationic biovectors: protection from proteolysis and potentiation of presentation to CD4+ T-cell clones in vitro

We have shown in a previous study that the proliferative CD4+ T-cell response to the regulatory immediate-early protein IE1 was a major component of the overall anti viral response in human cytomegalovirus (HCMV) seropositive blood donors. This viral antigen may be valuable in subunit vaccine design, since anti IE1 CD4+ T cells might provide help for production of antibodies and cytotoxic T lymphocytes (CTL) responses, and could take part in the control of viral infection. Preliminary to the elaboration of future vaccine formulations, we developed immunogenic complexes resulting from the combination of a purified recombinant protein derived from the fusion of Escherichia coli glutathione-S-transferase (GST) and a large C-terminal fragment (e4) of IE1, with new 80 nm cationic synthetic particles called Biovectors. We have shown that the antigen GST-e4 was stably complexed to vectors and that, contrary to the soluble form, it was protected from proteolysis in cell culture medium. By confocal microscopy we observed that the synthetic vectors were internalized by lymphoblastoid B cells, providing a significant enhancement of antigen delivery in antigen presenting cells (APC). Indeed, we demonstrated that the previous combination of antigen with particles, significantly enhanced the proliferation of specific CD4+ T-cell clones directed against IE1 in vitro, when either HLA-matched isolated peripheral blood mononuclear cells or EBV transformed B cell lines were used as APC. The relevance of these observations to the use of these new vectors for vaccine design against HCMV is discussed.

Analysis of the proliferative T cell response to human cytomegalovirus major immediate-early protein (IE1): phenotype, frequency and variability

Cellular immune responses are important in the recovery from human cytomegalovirus (HCMV) infection. However, little is known about the CD4+ T cell response and the target antigens (Ag) recognized. In this paper, we have analysed the proliferative T cell response of healthy HCMV seropositive (HCMV+) blood donors to recombinant immediate-early proteins expressed in transfected astrocytoma cells and to total HCMV Ags expressed in infected astrocytoma cells. We found that CD4+ T cells were the major cell population that proliferated in the presence of IE or total HCMV Ags. Among healthy HCMV seropositive blood donors with anti-HCMV specific proliferative response, 33-44% also responded to IE Ags. Moreover, in high responders, the precursor frequencies of cells which proliferated in the presence of total HCMV, IE, or IE1 Ags were high (1/103 to 1/255, 1/2785 to 1/7744 and 1/5190 to 1/13531, respectively). In some donors, the anti-IE response was variable over time, whereas the anti-total HCMV Ags response remained constant, which suggests regulation of the anti-IE response in immunocompetent subjects. Our results suggest that the CD4+ anti-IE1 response represents a significant part of the anti-HCMV proliferative response, both at the population level, and within individual immune systems.

Expression of human cytomegalovirus immediate early protein IE1 in insect cells: splicing of RNA and recognition by CD4+ T-cell clones

Recombinant baculoviruses containing the unspliced gene (Bac-IE1) and a truncated cDNA (Bac-EX4) of the immediate early protein 1 (IE1) of human cytomegalovirus (HCMV) were constructed. The recombinant proteins IE1 and EX4 were expressed in Sf 9 insect cells. Immunoblot analyses using a specific monoclonal antibody or human sera from HCMV seropositive subjects revealed that the IE1 protein had an apparent molecular mass of 71 kDa which was similar to that observed in both HCMV infected human fibroblasts and infected or transfected human astrocytoma cells. Furthermore, HCMV-specific CD4+ T cell clones proliferated in the presence of IE1 or of EX4 used as a control, and appropriate antigen presenting cells. Our data on the IE1 gene provide evidence that two introns can be properly spliced out in baculovirus infected insect cells. The expressed proteins should be useful in further studies on the immune response to the virus.

Overlap of the anti-Sm and anti-DNA responses of MRL/Mp-lpr/lpr mice

Autoantibodies specific for the Sm ribonucleoprotein are spontaneously produced in patients with SLE and in mice of the MRL mouse strains. We have previously reported the characterization of the clonality and V region gene use of 41 MRL/Mp-lpr/lpr (MRL/lpr)-derived B cell hybridomas selected for Sm binding. In this report, we show that many of the expressed V genes of these hybridomas are also expressed by anti-DNA hybridomas of MRL/lpr mice. Moreover, the anti-Sm hybridomas from nine clonal groups produce antibodies that bind ssDNA, and those of five clones produce antibodies that also bind dsDNA. Sm/DNA-specific hybridomas, but not Sm-only-specific hybridomas, have a higher than expected content of arginine residues in CDR3 of the H chain, similar to MRL/lpr hybridomas selected on the basis of DNA binding. One clone displays intraclonal differences in DNA binding, inasmuch as the most extensively mutated members produce antibodies that are able to bind dsDNA and have a higher affinity for ssDNA than the least mutated members of this clone. Thus, DNA appears to be a selecting Ag in this response. These data indicate an overlap in the anti-Sm and anti-DNA autoimmune responses in MRL mice that may have implications for the activation of anti-Sm B cells, and for defining the spectrum of Ag targeted in SLE.

V region gene analysis of anti-Sm hybridomas from MRL/Mp-lpr/lpr mice

Anti-Sm autoantibodies are unique to SLE, but are present in only 25% of patients with this disease. This response also occurs at a similar frequency in mice of the autoimmune MRL strains. Previous analyses of the anti-Sm response in these mice indicate that its occurrence is controlled by stochastic events, and suggest that Sm is the driving Ag. To further elucidate the role of Ag in this response, and to test the hypothesis that the 25% incidence is due to a requirement for particular Ig gene rearrangements or somatic mutations, we have analyzed the specificity and V-region gene sequences of 41 anti-Sm B cell hybridomas derived from nine anti-Sm-positive MRL/Mp-lpr/lpr mice. The majority of hybridomas are specific for the D peptide of the Sm particle. Hybridomas of independent origin express unique VH/V kappa combinations with diverse junctional sequences and are variable in the extent of somatic mutation. Thus, the response does not appear to be dependent upon the occurrence of a rare Ig gene rearrangement or specific somatic mutation. The response exhibits restriction in JH and VH gene use, and in individual mice is oligoclonal, suggestive of Ag selection. In the few B cells for which mutations can be identified, the evidence for selection of mutant B lymphocytes, based on patterns of mutation, is ambiguous. However, there is remarkably little intraclonal diversity, suggesting that the overall mutation rates in these clones are low.

Overlap of the anti-Sm and anti-DNA responses of MRL/Mp-lpr/lpr mice

Autoantibodies specific for the Sm ribonucleoprotein are spontaneously produced in patients with SLE and in mice of the MRL mouse strains. We have previously reported the characterization of the clonality and V region gene use of 41 MRL/Mp-lpr/lpr (MRL/lpr)-derived B cell hybridomas selected for Sm binding. In this report, we show that many of the expressed V genes of these hybridomas are also expressed by anti-DNA hybridomas of MRL/lpr mice. Moreover, the anti-Sm hybridomas from nine clonal groups produce antibodies that bind ssDNA, and those of five clones produce antibodies that also bind dsDNA. Sm/DNA-specific hybridomas, but not Sm-only-specific hybridomas, have a higher than expected content of arginine residues in CDR3 of the H chain, similar to MRL/lpr hybridomas selected on the basis of DNA binding. One clone displays intraclonal differences in DNA binding, inasmuch as the most extensively mutated members produce antibodies that are able to bind dsDNA and have a higher affinity for ssDNA than the least mutated members of this clone. Thus, DNA appears to be a selecting Ag in this response. These data indicate an overlap in the anti-Sm and anti-DNA autoimmune responses in MRL mice that may have implications for the activation of anti-Sm B cells, and for defining the spectrum of Ag targeted in SLE.

V region gene analysis of anti-Sm hybridomas from MRL/Mp-lpr/lpr mice

Anti-Sm autoantibodies are unique to SLE, but are present in only 25% of patients with this disease. This response also occurs at a similar frequency in mice of the autoimmune MRL strains. Previous analyses of the anti-Sm response in these mice indicate that its occurrence is controlled by stochastic events, and suggest that Sm is the driving Ag. To further elucidate the role of Ag in this response, and to test the hypothesis that the 25% incidence is due to a requirement for particular Ig gene rearrangements or somatic mutations, we have analyzed the specificity and V-region gene sequences of 41 anti-Sm B cell hybridomas derived from nine anti-Sm-positive MRL/Mp-lpr/lpr mice. The majority of hybridomas are specific for the D peptide of the Sm particle. Hybridomas of independent origin express unique VH/V kappa combinations with diverse junctional sequences and are variable in the extent of somatic mutation. Thus, the response does not appear to be dependent upon the occurrence of a rare Ig gene rearrangement or specific somatic mutation. The response exhibits restriction in JH and VH gene use, and in individual mice is oligoclonal, suggestive of Ag selection. In the few B cells for which mutations can be identified, the evidence for selection of mutant B lymphocytes, based on patterns of mutation, is ambiguous. However, there is remarkably little intraclonal diversity, suggesting that the overall mutation rates in these clones are low.

CD3 expression, modulation and signalling in T-cell subpopulations from MRL/Mp-lpr/lpr mice

The expanded T-cell population of MRL/Mp-lpr2lpr mice is abnormal from a variety of standpoints. We have already shown that T-cell receptor expression and modulation are aberrant in the predominant CD4- CD8 (DN) T cell population. To investigate these abnormalities further, we examined CD3 expression and modulation in subpopulations of +/+ and lpr T cells and measured mitogen-induced Ca++ mobilization in DN lpr T cells. We found that expression and modulation of CD3 in CD4hi and CD8hi lpr single positive (SP) T cells are similar to that in +/+ T cells. We have, however, identified additional lpr cell subsets that are CD4lo or CD8lo. Their expression and modulation of CD3 are intermediate, between that of SP and DN lpr T cells. These subpopulations may thus represent a transitional stage between the SP and DN populations. The rapid modulation of CD3 in the DN population does not appear to be merely related to the lack of expression of CD4 or CD8, and may in fact cause (rather than result from) low CD3 expression. In addition, we observed impairment of CA++ mobilization in DN lpr T cells in response to concanavalin A or anti-CD3 antibody. These findings further define the abnormalities of T cells from lpr mice.

Targeting of T-B interaction using heteroconjugate antibody

We have deliberately targeted collaboration between T cells and certain B cells by using a heteroconjugate (HETCONJ) antibody. This specific reagent was created by cross-linking the F(ab')2 portions of anti-I-Ab and anti-CD3 monoclonal antibodies. Spleen cells from B6 (I-Ab) but not bm12 (I-Abm12) mice proliferated in vitro in the presence of the HETCONJ. Similarly, T-cell dependent IgM secretion was induced in B cells from B6, yet only weakly in B cells from bm 12 mice. Using B cells from Igh allotype double congenic (B6.C20 Igha/I-Ab and bm12, Ighb/I-Abm12) mice in co-culture experiments, we have used the HETCONJ to study linked versus bystander T-B interaction. B-cell activation, mediated by HETCONJ, was 10 times greater in unseparated than in resting splenic B cells. T-B interaction through T-B contact was more efficient than activation through bystander effects both for unseparated and resting splenic B cells. Large, already activated B cells, in contrast, did not show a preference for linked recognition. Our reagent has mimicked some of the events involved in T-B collaboration and may be useful in studying the molecular basis of cellular interactions.

Immunological effects of recombinant interferon gamma in vivo in normal mice: failure to induce autoantibodies

We have investigated the effects on the immune system, and especially on the induction of autoimmunity, of treatment of mice with recombinant IFN-gamma in vivo by several protocols. Neither antichromatin nor Coombs autoantibody was observed. The spleens of the treated animals enlarged two fold, despite a dramatic decrease in numbers of Thy-1+ spleen cells and a smaller decrease in surface Ig+ spleen cells. This was correlated with a markedly diminished Con A response and moderately reduced LPS response. On the other hand, the numbers of IgG secreting cells were augmented in the spleens of treated mice. In addition, IFN-gamma-injected mice lost weight and became anemic. This study shows that, although IFN-gamma-injected in vivo leads to severe changes in the murine immune system, it is not responsible by itself for the induction of autoimmunity.

Diminished expression of the T cell receptor on the expanded lymphocyte population in MRL/Mp-lpr/lpr mice

MRL mice homozygous for the recessive lpr gene develop an accelerated autoimmune syndrome and massive lymphadenopathy. Because the function of the expanded lymph node population is unclear, we have studied the subunits of the T cell receptor for antigen (TcR). DNA and RNA were prepared from MRL/Mp-lpr/lpr (lpr) and congenic MRL/Mp(-)+/+ (+/+) mice by standard techniques and studied by Southern blot, northern blot, and dot blot analysis using the cDNAs TT11, specific for the TcR alpha chain; 86T5, specific for the TcR beta chain; and T3 delta; specific for the subunit of the T3 molecule. Surface protein was immunoprecipitated with antisera 8177, which recognizes TcR framework determinants, and resolved by diagonal SDS-PAGE. FACS analysis was performed with a monoclonal antibody to murine T3, and with the KJ16-133 and F23.1 monoclonal antibodies, which recognize determinants encoded by the V beta 8 subfamily of beta chain variable region genes. When compared with +/+ controls, surface TcR density as detected by immunofluorescence using all three antibodies was significantly diminished on lpr spleen and lymph node cells, as well as on lpr lymph node cells which had been depleted of L3T4+ and Ly2+ cells by negative selection. There appeared, however, to be selective expression of the genes encoding the epitopes binding F23.1. Southern blot analysis of DNA showed polyclonal rearrangements of the TcR beta chain genes. There were increased alpha, beta, and T3 delta RNA transcripts in the double negative lymph node cells. The paradoxical decrease in TcR surface expression in the setting of large quantities of full length transcript is yet to be explained.

Rapid T cell receptor modulation accompanies lack of in vitro mitogenic responsiveness of double negative T cells to anti-CD3 monoclonal antibody in MRL/Mp-lpr mice

The role of the CD8-, CD4- (double negative) (DN) T cells accumulating in MRL/Mp-lpr/lpr (lpr) mice is unclear. Although they bear the TCR/CD3, the lpr DN cells do not respond to Ag, and the specificity of TCR/CD3 on these cells is unknown. With the aid of monoclonal anti-murine CD3 epsilon (145-2C11), we have investigated the function of the CD3 molecule on the DN cells. 145-2C11 was not mitogenic for lpr DN lymph node cells (LNC), even in the presence of the phorbol ester 12-O-tetradecanoylphorbol 13-acetate, whereas MRL/Mp-+/+ (+/+) LNC responded strongly. Surprisingly, CD3 modulation induced by 145-2C11 was much more rapid for lpr DN than for +/+ LNC. For example, the modulation observed after 10 min in lpr DN LNC required at least 2 h in +/+ cells. This was not due solely to a property of the 145-2C11 antibody, because both TPA and the F23.1 anti-TCR mAb also provoked a faster modulation of the TCR in lpr DN LNC. Double-staining experiments showed that co-culturing +/+ and lpr DN LNC did not alter their respective rates of modulation, which suggests an intrinsic defect in the lpr DN cells. Moreover, in LNC from 6-wk-old lpr mice (before the appearance of DN cells), as well as in normal phenotype-bearing T cells (CD8+ or CD4+) from 6-mo-old lpr mice, the CD3 modulation was similar to that of +/+ LNC. After modulation, the CD3 molecule was reexpressed at the surface of both +/+ and lpr DN cells during subsequent incubation of the cells without 145-2C11. In addition, spontaneous recycling of CD3 was similar in +/+ and lpr DN LNC. The rapid modulation of the lpr DN TCR/CD3 is presumably related to the anergy of this cell population.

Rapid T cell receptor modulation accompanies lack of in vitro mitogenic responsiveness of double negative T cells to anti-CD3 monoclonal antibody in MRL/Mp-lpr mice

The role of the CD8-, CD4- (double negative) (DN) T cells accumulating in MRL/Mp-lpr/lpr (lpr) mice is unclear. Although they bear the TCR/CD3, the lpr DN cells do not respond to Ag, and the specificity of TCR/CD3 on these cells is unknown. With the aid of monoclonal anti-murine CD3 epsilon (145-2C11), we have investigated the function of the CD3 molecule on the DN cells. 145-2C11 was not mitogenic for lpr DN lymph node cells (LNC), even in the presence of the phorbol ester 12-O-tetradecanoylphorbol 13-acetate, whereas MRL/Mp-+/+ (+/+) LNC responded strongly. Surprisingly, CD3 modulation induced by 145-2C11 was much more rapid for lpr DN than for +/+ LNC. For example, the modulation observed after 10 min in lpr DN LNC required at least 2 h in +/+ cells. This was not due solely to a property of the 145-2C11 antibody, because both TPA and the F23.1 anti-TCR mAb also provoked a faster modulation of the TCR in lpr DN LNC. Double-staining experiments showed that co-culturing +/+ and lpr DN LNC did not alter their respective rates of modulation, which suggests an intrinsic defect in the lpr DN cells. Moreover, in LNC from 6-wk-old lpr mice (before the appearance of DN cells), as well as in normal phenotype-bearing T cells (CD8+ or CD4+) from 6-mo-old lpr mice, the CD3 modulation was similar to that of +/+ LNC. After modulation, the CD3 molecule was reexpressed at the surface of both +/+ and lpr DN cells during subsequent incubation of the cells without 145-2C11. In addition, spontaneous recycling of CD3 was similar in +/+ and lpr DN LNC. The rapid modulation of the lpr DN TCR/CD3 is presumably related to the anergy of this cell population.

Selective production of interleukin 3 (IL3) and granulocyte-macrophage colony-stimulating factor (GM-CSF) in vitro by murine L3T4+ T cells: lack of spontaneous IL3 and GM-CSF production by Ly-2-/L3T4- lpr subset

Murine spleen and lymph node L3T4+ T cells were found to spontaneously produce high levels of interleukin 3 (IL3) and granulocyte-macrophage colony-stimulating factor (GM-CSF) in cultures containing 10% fetal calf serum (FCS) in the absence of other stimulation. The IL3 and GM-CSF activities in culture supernatants peake between the fifth and seventh day of culture. The specificity of the bioassays was attested by the use of rabbit anti-IL3 and anti-GM-CSF antibodies, as well as by the detection of a maximal accumulation of IL3 and GM-CSF mRNA on the fourth day. In contrast, no significant activities of IL2, IL4 or interferon-gamma were detected in these culture supernatants. The markedly limited production of IL3 and GM-CSF in cultures performed in 1% autologous normal mouse serum and the inhibitory effect of anti-Ia or anti-L3T4 monoclonal antibody strongly suggest that the selective production of most, if not all IL3 and GM-CSF by L3T4+ T cells is a result of activation of L3T4+ T cells by fetal calf serum. All the strains of mice tested except athymic nude mice produced substantial amounts of IL3 and GM-CSF during the culture. This is in contrast to a previous report (Palacios, Eur. J. Immunol. 1984. 14: 599), indicating that only spleen cells of the MRL strain homozygous for the lpr gene spontaneously release IL3 in cultures. We found that spleen and lymph node cells from MRL/MpJ-lpr/lpr or C57BL/6J-lpr/lpr mice released, in fact, much less IL3 and GM-CSF in cultures. This was, however, due to the high proportion of the peculiar lpr Ly-2-/L3T4-T cells in spleen and lymph nodes, since after depletion of this lpr T cell subset, lymph node cells from C57BL/6J-lpr/lpr mice produced IL3 and GM-CSF at levels comparable to those in C57BL/6J-+/+ mice. These results further support the notion that the lpr Ly-2-/L3T4- T cell subset is immunologically nonfunctional and its accumulation dilutes functional L3T4+ T cells in mice bearing the lpr mutation.