Respiratory Syncytial Virus Infects Regulatory B Cells in Human Neonates via Chemokine Receptor CX3CR1 and Promotes Lung Disease Severity.

Respiratory syncytial virus (RSV) is the major cause of lower respiratory tract infections in infants and is characterized by pulmonary infiltration of B cells in fatal cases. We analyzed the B cell compartment in human newborns and identified a population of neonatal regulatory B lymphocytes (nBreg cells) that produced interleukin 10 (IL-10) in response to RSV infection. The polyreactive B cell receptor of nBreg cells interacted with RSV protein F and induced upregulation of chemokine receptor CX3CR1. CX3CR1 interacted with RSV glycoprotein G, leading to nBreg cell infection and IL-10 production that dampened T helper 1 (Th1) cytokine production. In the respiratory tract of neonates with severe RSV-induced acute bronchiolitis, RSV-infected nBreg cell frequencies correlated with increased viral load and decreased blood memory Th1 cell frequencies. Thus, the frequency of nBreg cells is predictive of the severity of acute bronchiolitis disease and nBreg cell activity may constitute an early-life host response that favors microbial pathogenesis.

Epicutaneous immunotherapy protects cashew-sensitized mice from anaphylaxis.

BACKGROUND: The prevalence of tree nut allergy has increased worldwide, and cashew has become one of the most common food allergens. More critically, cashew allergy is frequently associated with severe anaphylaxis. Despite the high medical need, no approved treatment is available and strict avoidance and preparedness for prompt treatment of allergic reactions are considered dual standard of care. In the meantime, Phase III study results suggest investigational epicutaneous immunotherapy (EPIT) may be a relevant and safe treatment for peanut allergy and may improve the quality of life for many peanut allergic children. OBJECTIVE: We aimed to evaluate the capacity of EPIT to provide protection against cashew-induced anaphylaxis in a relevant mouse model. METHODS: The efficacy of EPIT was evaluated by applying patches containing cashew allergens to cashew-sensitized mice. As negative control, sham mice received patches containing excipient. Following treatment, mice were challenged orally to cashew and anaphylactic symptoms, as well as plasmatic levels of mast-cell proteases (mMCP)-1/7, were quantified. RESULTS: Of 16 weeks of EPIT significantly protects against anaphylaxis by promoting a faster recovery of challenged mice. This protection was characterized by a significant reduction of temperature drop and clinical symptoms, 60 minutes after challenge. This was associated with a decrease in mast-cell reactivity as attested by the reduction of mMCP-1/7 in plasma, suggesting that EPIT specifically decrease IgE-mediated anaphylaxis. CONCLUSION: We demonstrate that EPIT markedly reduced IgE-mediated allergic reactions in a mouse model of cashew allergy, which suggests that EPIT may be a relevant approach to treating cashew allergy.

Broad responses to chemical adducts shape the natural antibody repertoire in early infancy.

Natural antibodies are an integral part of innate humoral immunity yet their development and polyreactive nature are still enigmatic. Here, we show that characteristic monoclonal natural antibodies recognize common chemical moieties or adducts, supporting the view that polyreactive antibodies may often correspond to anti-adduct antibodies. We next examined the development of immunoglobulin M (IgM) and IgG to 81 ubiquitous adducts from birth to old age. Newborn IgM only reacted to a limited number of consensus determinants. This highly restricted neonatal repertoire abruptly diversified around 6 months of age through the development of antibodies to environmental antigens and age-driven epigenetic modifications. In contrast, the IgG repertoire was diverse across the entire life span. Our studies reveal an unrecognized component of humoral immunity directed to common adducts. These findings set the ground for further investigations into the role of anti-adduct B cell responses in homeostatic functions and pathological conditions.

Interspecies comparison of the early transcriptomic changes associated with hepatitis B virus exposure in human and macaque immune cell populations.

Background and aims: Hepatitis B virus (HBV) infection affects 300 million individuals worldwide, representing a major factor for the development of hepatic complications. Although existing antivirals are effective in suppressing replication, eradication of HBV is not achieved. Therefore, a multi-faceted approach involving antivirals and immunomodulatory agents is required. Non-human primates are widely used in pre-clinical studies due to their close evolutionary relationship to humans. Nonetheless, it is fundamental to identify the differences in immune response between humans and these models. Thus, we performed a transcriptomic characterization and interspecies comparison of the early immune responses to HBV in human and cynomolgus macaques. Methods: We characterized early transcriptomic changes in human and cynomolgus B cells, T cells, myeloid and plasmacytoid dendritic cells (pDC) exposed to HBV ex vivo for 2 hours. Differentially-expressed genes were further compared to the profiles of HBV-infected patients using publicly-available single-cell data. Results: HBV induced a wide variety of transcriptional changes in all cell types, with common genes between species representing only a small proportion. In particular, interferon gamma signaling was repressed in human pDCs. At the gene level, interferon gamma inducible protein 16 (IFI16) was upregulated in macaque pDCs, while downregulated in humans. Moreover, IFI16 expression in pDCs from chronic HBV-infected patients anti-paralleled serum HBsAg levels. Conclusion: Our characterization of early transcriptomic changes induced by HBV in humans and cynomolgus macaques represents a useful resource for the identification of shared and divergent host responses, as well as potential immune targets against HBV.

EAAT expression by macrophages and microglia: still more questions than answers.

Glutamate is the main excitatory amino acid, but its presence in the extracellular milieu has deleterious consequences. It may induce excitotoxicity and also compete with cystine for the use of the cystine-glutamate exchanger, blocking glutathione neosynthesis and inducing an oxidative stress-induced cell death. Both mechanisms are critical in the brain where up to 20% of total body oxygen consumption occurs. In normal conditions, the astrocytes ensure that extracellular concentration of glutamate is kept in the micromolar range, thanks to their coexpression of high-affinity glutamate transporters (EAATs) and glutamine synthetase (GS). Their protective function is nevertheless sensitive to situations such as oxidative stress or inflammatory processes. On the other hand, macrophages and microglia do not express EAATs and GS in physiological conditions and are the principal effector cells of brain inflammation. Since the late 1990s, a number of studies have now shown that both microglia and macrophages display inducible EAAT and GS expression, but the precise significance of this still remains poorly understood. Brain macrophages and microglia are sister cells but yet display differences. Both are highly sensitive to their microenvironment and can perform a variety of functions that may oppose each other. However, in the very particular environment of the healthy brain, they are maintained in a repressed state. The aim of this review is to present the current state of knowledge on brain macrophages and microglial cells activation, in order to help clarify their role in the regulation of glutamate under pathological conditions as well as its outcome.

Combined CD4+ donor lymphocyte infusion and low-dose recombinant IL-2 expand FOXP3+ regulatory T cells following allogeneic hematopoietic stem cell transplantation.

CD4(+)CD25(+)FOXP3(+) regulatory T cells (Treg) successfully control graft-versus-host-disease (GVHD) in animal models. In humans, incomplete reconstitution of Treg after allogeneic hematopoietic stem cell transplantation (HSCT) has been associated with chronic GVHD (cGVHD). Recent studies have demonstrated that interleukin (IL)-2 infusions expand Treg in vivo. However, the effectiveness of this therapy depends on the number of cells capable of responding to IL-2. We examined the effect of low-dose IL-2 infusions on Treg populations after HSCT in patients who also received infusions of donor CD4(+) lymphocytes. Utilizing FOXP3 as a Treg marker, we found that patients who received CD4+DLI concomitantly with IL-2 had greater expansion of Treg compared to patients who received IL-2 (P = .03) or CD4(+)DLI alone (P = .001). FOXP3 expression correlated with absolute CD4(+)CD25(+) cell counts. Moreover, expanded CD4(+)CD25(+) T cells displayed normal suppressive function and treatment with CD4(+)DLI and IL-2 was not associated with GVHD. This study suggests that administration of low-dose IL-2 combined with adoptive CD4(+) cellular therapy may provide a mechanism to expand Treg in vivo.

Nerve growth factor stimulation promotes CXCL-12 attraction of monocytes but decreases human immunodeficiency virus replication in attracted population.

The neurotrophins nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and neurotrophin-4 (NT-4) are key molecules in the central nervous system development, which also exert specific effects on cells of the immune system. With regard to the latter, in vitro as well as in vivo data suggested that neurotrophins may play a role in human immunodeficiency virus (HIV) infection, especially in perivascular spaces where infiltrated macrophages express NGF. In the present study, we examined the expression of neurotrophins and their receptors in human monocyte-derived macrophages (MDMs) during infection by the R5 prototype HIV1/Ba-L strain. We then assessed to what extent neurotrophins themselves modulate infected macrophage survival and the level of virus production. The data show that neurotrophins and neurotrophin receptors are not modulated during HIV replication. Likewise, exogenous neurotrophins, or alternatively the blocking of neurotrophin receptors, neither modulated MDM sensitivity to HIV infection and replication nor altered their viability. In contrast, NGF clearly increased CD184 expression in macrophages, but this did not sensitize them to the X4 isolate HIV-1/Lai infection. Nevertheless, NGF enhanced monocyte chemotactic response to low CXCL-12 concentration regardless of infection. Surprisingly, CXCL-12-attracted monocytes from NGF-stimulated, HIV-infected cultures produced decreased amounts of virus progeny than their non-NGF-stimulated counterparts. This suggests a preferential effect on uninfected monocytes. Together these findings suggest a role for NGF in the continuous attraction of activated monocytes to the perivascular spaces, contributing to the chronic inflammatory state rather than neuroinvasion by HIV.

The glutamate-glutamine cycle as an inducible, protective face of macrophage activation.

Neuronal damage in HIV infection results mainly from chronic activation of brain tissue and involves inflammation, oxidative stress, and glutamate-related neurotoxicity. Glutamate toxicity acts via two distinct pathways: an excitotoxic one, in which glutamate receptors are hyperactivated, and an oxidative one, in which cystine uptake is inhibited, resulting in glutathione depletion, oxidative stress, and cell degeneration. A number of studies have shown that astrocytes normally take up glutamate, keeping extracellular glutamate concentration low in the brain and preventing excitotoxicity. They, in turn, provide the trophic amino acid glutamine via their expression of glutamine synthetase. These protective and trophic actions are inhibited in HIV infection, probably as a result of the effects of inflammatory mediators and viral proteins. In vitro and in vivo studies have demonstrated that activated microglia and brain macrophages (AMM) express the transporters and enzymes of the glutamate cycle. This suggests that in addition to their recognized neurotoxic properties in HIV infection, these cells exhibit some neuroprotective properties, which may partly compensate for the inhibited astrocytic function. This hypothesis might explain the discrepancy between microglial activation, which occurs early in the disease, and neuronal apoptosis and neuronal loss, which are late events. In this review, we discuss the possible neuroprotective and neurotrophic roles of AMM and their relationships with inflammation and oxidative stress.

Dynamics of B Cell Recovery In Kidney/Bone Marrow Transplant Recipients.

BACKGROUND: Previous studies identified B cell gene signatures and predominance of specific B cell subsets as a marker of operational tolerance after kidney transplantation. These findings suggested a role for B cells in the establishment or maintenance of tolerance. Here we analyzed B cell recovery in 4 subjects, 3 of whom achieved tolerance after combined kidney/bone marrow transplantation. METHODS: Peripheral B cell subsets were examined longitudinally by flow cytometry. Immunoglobulin heavy chain repertoire analysis was performed using next-generation sequencing. Lastly, the patients' serum reactivity to HLA was assessed by Luminex. RESULTS: B cell counts recovered approximately 1 year posttransplant except for 1 subject who experienced delayed reconstitution. This subject resumed immunosuppression for acute rejection at 10 months posttransplant and underwent preemptive retransplantation at 3 years for chronic rejection. B cell recovery was accompanied by a high frequency of CD20 + CD24CD38 transitional B cells and a diversified clonal repertoire. However, all 4 subjects showed prevalence of CD20 + CD27+ memory B cells around 6 months posttransplant when B cell counts were still low and the clonal B cell repertoire very limited. The predominance of memory B cells was also associated with high levels of somatically mutated immunoglobulin heavy chain variable sequences and transient serum reactivity to HLA. CONCLUSIONS: Our observations reveal the presence of memory B cells early posttransplant that likely escaped the preparative regimen at a time consistent with the establishment of tolerance. Further studies are warranted to characterize the functional properties of these persisting memory cells and evaluate their potential contribution to tolerance induction.

Type I interferon-mediated autoinflammation due to DNase II deficiency.

Microbial nucleic acid recognition serves as the major stimulus to an antiviral response, implying a requirement to limit the misrepresentation of self nucleic acids as non-self and the induction of autoinflammation. By systematic screening using a panel of interferon-stimulated genes we identify two siblings and a singleton variably demonstrating severe neonatal anemia, membranoproliferative glomerulonephritis, liver fibrosis, deforming arthropathy and increased anti-DNA antibodies. In both families we identify biallelic mutations in DNASE2, associated with a loss of DNase II endonuclease activity. We record increased interferon alpha protein levels using digital ELISA, enhanced interferon signaling by RNA-Seq analysis and constitutive upregulation of phosphorylated STAT1 and STAT3 in patient lymphocytes and monocytes. A hematological disease transcriptomic signature and increased numbers of erythroblasts are recorded in patient peripheral blood, suggesting that interferon might have a particular effect on hematopoiesis. These data define a type I interferonopathy due to DNase II deficiency in humans.

Evidence to Support a Contribution of Polyreactive Antibodies to HLA Serum Reactivity.

BACKGROUND: Assessing the serum reactivity to HLA is essential for the evaluation of transplant candidates and the follow-up of allograft recipients. In this study, we look for evidence at the clonal level that polyreactive antibodies cross-reactive to apoptotic cells and multiple autoantigens can also react to HLA and contribute to the overall serum reactivity. METHODS: We immortalized B cell clones from the blood of 2 kidney transplant recipients and characterized their reactivity to self-antigens, apoptotic cells as well as native, denatured, and cryptic HLA determinants using enzyme-linked immunosorbent assay (ELISA), immunofluorescence, flow cytometry and Luminex assays. We also assessed the reactivity of 300 pretransplant serum specimens to HLA and apoptotic cells. RESULTS: We report here 4 distinct B cell clones cross-reactive to self and HLA class I. All 4 clones reacted to numerous HLA class I alleles but did not appear to target canonical "shared" epitopes. In parallel experiments, we observed a strong correlation between IgG reactivity to HLA and apoptotic cells in pretransplant serum samples collected from 300 kidney transplant recipients. Further analysis revealed that samples with higher reactivity to apoptotic cells displayed significantly higher class I percent panel-reactive antibodies compared to samples with low reactivity to apoptotic cells. CONCLUSIONS: We provide here (1) proof of principle at the clonal level that human polyreactive antibodies can cross-react to HLA, multiple self-antigens and apoptotic cells and (2) supportive evidence that polyreactive antibodies contribute to overall HLA reactivity in the serum of patients awaiting kidney transplant.

Regulated expression of sodium-dependent glutamate transporters and synthetase: a neuroprotective role for activated microglia and macrophages in HIV infection?

It is now widely accepted that neuronal damage in HIV infection results mainly from microglial activation and involves apoptosis, oxidative stress and glutamate-mediated neurotoxicity. Glutamate toxicity acts via 2 distinct pathways: an excitotoxic one in which glutamate receptors are hyperactivated, and an oxidative one in which cystine uptake is inhibited, resulting in glutathione depletion and oxidative stress. A number of studies show that astrocytes normally take up glutamate, keeping extracellular glutamate concentration low in the brain and preventing excitotoxicity. This action is inhibited in HIV infection, probably due to the effects of inflammatory mediators and viral proteins. Other in vitro studies as well as in vivo experiments in rodents following mechanical stimulation, show that activated microglia and brain macrophages express high affinity glutamate transporters. These data have been confirmed in chronic inflammation of the brain, particularly in SIV infection, where activated microglia and brain macrophages also express glutamine synthetase. Recent studies in humans with HIV infection show that activated microglia and brain macrophages express the glutamate transporter EAAT-1 and that expression varies according to the disease stage. This suggests that, besides their recognized neurotoxic properties in HIV infection, these cells also have a neuroprotective function, and may partly make up for the inhibited astrocytic function, at least temporarily. This hypothesis might explain the discrepancy between microglial activation which occurs early in the disease, and neuronal apoptosis and neuronal loss which is a late event. In this review article, we discuss the possible neuroprotective and neurotrophic roles of activated microglia and macrophages that may be generated by the expression of high affinity glutamate transporters and glutamine synthetase, 2 major effectors of glial glutamate metabolism, and the implications for HIV-induced neuronal dysfunction, the underlying cause of HIV dementia.

ATP binding cassette multidrug transporters limit the anti-HIV activity of zidovudine and indinavir in infected human macrophages.

OBJECTIVES: To investigate whether P-glycoprotein (P-gp) and multidrug resistance proteins (MRPs), which limit the bioavailability of HIV protease inhibitors (PIs) and nucleoside reverse transcriptase inhibitors (NRTIs), modulate the anti-HIV activity of NRTIs, non-NRTIs and PIs in vitro. DESIGN: We used primary cultures of major HIV target cells: human monocyte-derived macrophages (MDMs) and lymphocytes. METHODS: P-gp and MRP expression in response to long-term zidovudine (3'-azido-3'-deoxythymidine; AZT) or indinavir treatment was quantified by RT-PCR. MDM and lymphocytes were infected in vitro with HIV-1/Ba-L and HIV-1-LAI, respectively, and treated with antiretroviral drugs. We evaluated the activity of these drugs in combination with PSC833, a P-gp inhibitor, and/or probenecid, an MRP1 inhibitor. Intracellular AZT triphosphate derivative (AZT-TP) was quantified by HPLC-MSMS. P-gp ATPase activity was measured with inside-out native membrane vesicles enriched in P-gp. RESULTS: Levels of MDR1, mrp4 and mrp5 mRNA were high following AZT treatment. In infected MDM, PSC833 and probenecid increased the anti-HIV activity of AZT and indinavir. AZT (5 nM) decreased HIV replication by 34% alone and by 72% in combination with P-gp/MRP inhibitors. Indinavir (10 nM) gave 14% inhibition alone and 81% in combination. The increase in anti-HIV activity of AZT was correlated with an increase in intracellular AZT-TP concentration. However, unlike PIs, neither AZT nor its metabolites interacted with P-gp. CONCLUSION: AZT increases the expression of multidrug transporters, thereby decreasing its pharmacological activity. The cellular efflux of AZT probably involves MRP4 or MRP5. In contrast, increases in indinavir anti-HIV activity require the inhibition of both P-gp and MRP1.

Expansion and somatic hypermutation of B-cell clones in rejected human kidney grafts.

BACKGROUND: B-cell infiltrates are common in rejected kidney allografts, yet their composition is still unclear. The aim of our study was to characterize the clonal composition of B-cell infiltrates of rejected human kidney grafts. METHODS: We used a molecular approach to characterize the partial B-cell repertoires of 5 failed human kidney grafts with detectable B-cell infiltrates. A comparison between the intragraft and blood repertoire was also conducted for 1 case. RESULTS: Redundant sequences were observed in both blood and graft, although the level of clonal amplification was significantly higher for the graft. Somatic hypermutations (SHMs) were also more frequent in sequences found in the graft compared to the blood. The rate of nonsilent mutations was significantly higher in complementarity determining regions (CDRs) compared to framework regions in blood sequences as well as in graft sequences found at low frequency. In contrast, this preferential distribution was lost in sequences found at high frequency in the graft, suggesting a lack of affinity maturation in situ. Lastly, follicular dendritic cells were undetectable in CD20 infiltrates in all samples examined. CONCLUSIONS: We provide here evidence that B-cell clones expand and undergo SHMs in situ. However, the even distribution of nonsilent SHM in high-frequency graft sequences together with the absence of follicular dendritic cells do not support the view that infiltrating B cells are part of functional germinal centers.

Combined CD4 T-cell and antibody response to human minor histocompatibility antigen DBY after allogeneic stem-cell transplantation.

BACKGROUND: Antibody responses to HY antigens in male recipients are frequent after transplantation of stem cells from female donors (Miklos et al., Blood 2005; 105: 2973; Miklos et al., Blood 2004; 103: 353). However, evidence that this B-cell immunity is accompanied by T-cell responses to the cognate antigens is scarce. Here, we examined T- and B-cell responses to DBY antigen in a male patient who received hematopoietic stem cells from a human leukocyte antigen-identical female sibling. MATERIALS AND METHODS: We used 93 overlapping peptides representing the entire DBY protein to detect and characterize T-cell and antibody responses to DBY by enzyme-linked immunosorbent spot (ELISPOT) and enzyme-linked immunosorbent assay. RESULTS: High frequency CD4+ T cells specific for a unique DBY peptide were detected in the patient blood. We isolated the corresponding T-cell clone and characterized the recognized epitope as an 18-mer peptide restricted by human leukocyte antigen-DRB1*0101. Upon stimulation, this clone produced cytokines with no evidence of Th1 or Th2 polarization. Remarkably, this clone also recognized the DBX homologue peptide and responded to female donor dendritic cells stimulated with poly I/C or lipopolysaccharide, indicating that the peptide was endogenously processed in these cells. High titer DBY-specific antibodies were also found in the patient serum which, in contrast to the T-cell response, did not cross-react with DBX. CONCLUSION: We show here the development of a coordinated B and T-cell response to DBY in a recipient of sex mismatched allogeneic hematopoietic stem-cell transplantation. Our findings support a role for CD4+ T cells in the development of humoral immunity to minor histocompatibility antigens.

Chronic humoral rejection of human kidney allografts associates with broad autoantibody responses.

BACKGROUND: Chronic humoral rejection (CHR) is a major complication after kidney transplantation. The cause of CHR is currently unknown. Autoantibodies have often been reported in kidney transplant recipients alongside antidonor human leukocyte antigen antibodies. Yet, the lack of comprehensive studies has limited our understanding of this autoimmune component in the pathophysiology of CHR. METHODS: By using a series of ELISA and immunocytochemistry assays, we assessed the development of autoantibodies in 25 kidney transplant recipients with CHR and 25 patients with stable graft function. We also compared the reactivity of five CHR and five non-CHR patient sera with 8027 recombinant human proteins using protein microarrays. RESULTS: We observed that a majority of CHR patients, but not non-CHR control patients, had developed antibody responses to one or several autoantigens at the time of rejection. Protein microarray assays revealed a burst of autoimmunity at the time of CHR. Remarkably, microarray analysis showed minimal overlap between profiles, indicating that each CHR patient had developed autoantibodies to a unique set of antigenic targets. CONCLUSION: The breadth of autoantibody responses, together with the absence of consensual targets, suggests that these antibody responses result from systemic B-cell deregulation.

Modulation of indoleamine-2,3-dioxygenase expression and activity by HIV-1 in human macrophages.

Human immunodeficiency virus (HIV) infection is often complicated by the development of acquired immunodeficiency syndrome (AIDS) dementia complex (ADC). Implications of kynurenine pathway (KP) are suggested in ADC and other inflammatories brain diseases. The first and regulatory enzyme of the KP is the indoleamine-2,3-dioxygenase (IDO). IDO activation is known to contribute to the modulation of the immune response during various infectious diseases particularly in AIDS. HIV and viral proteins can activate IDO in immune cells leading to an increase catabolism of tryptophan through the KP; the consequence being the production of immuno-modulative and neuroactive metabolites. This mechanism is likely to favour HIV persistence. The present study analysed concomitantly several parameters involved in IDO regulation and activity associated with HIV-1-infection. We investigated relevant intracellular and extracellular mechanisms involved in the regulation of IDO expression and activity during the HIV infection and replication in human monocyte-derived macrophages (MdM). Using a complementary set of in vitro experiments, we found that HIV-1/Ba-L infection induces IDO expression and increases its activity in MdM. We also showed that IDO activation by HIV-1 is likely to be a direct effect of the infection and seems to be independent of IFN-gamma production.

Differential epitope mapping of antibodies to PDC-E2 in patients with hematologic malignancies after allogeneic hematopoietic stem cell transplantation and primary biliary cirrhosis.

A unique characteristic of the autoimmune liver disease primary biliary cirrhosis (PBC) is the presence of high-titer and extremely specific autoantibodies to the E2 component of the pyruvate dehydrogenase complex (PDC-E2). Autoantibodies to PDC-E2 antigen have only been detected in patients with disease or in those who subsequently develop PBC. One exception has been a subgroup of patients with multiple myeloma (MM) who underwent allogeneic hematopoietic stem cell transplantation (HSCT) and received donor lymphocyte infusions (DLIs) after transplantation. These patients developed high-titer antibodies to a variety of myeloma-associated antigens, including PDC-E2, coincident with rejection of myeloma cells in vivo. To examine the specificity of autoantibodies to PDC in these patients, we screened sera from patients with MM, chronic leukemias, monoclonal gammopathy of unknown significance (MGUS), PBC, and healthy donors. Three of 11 patients with MM (27%) and 2 of 6 patients with chronic leukemias (33%) developed anti-PDC-E2 antibodies in association with DLI response; 2 of 12 (17%) patients in the MGUS pretreatment control population also had detectable anti-PDC responses. Interestingly, the epitope specificity of these PDC-E2 autoantibodies was distinctive, suggesting that the mechanisms leading to loss of tolerance in the transplantation patients are distinct from PBC.

Characterization of human monocyte-derived microglia-like cells.

Microglial cells are central to brain immunity and intervene in many human neurological diseases. The aim of this study was to develop a convenient cellular model for human microglial cells, suitable for HIV studies. Microglia derive from the hematogenous myelomonocytic lineage, possibly as a distinct subpopulation but in any case able to invade the CNS, proliferate, and differentiate into ameboid and then ramified microglia in the adult life. We thus attempted to derive microglia-like cells from human monocytes. When cultured with astrocyte-conditioned medium (ACM), monocytes acquired a ramified morphology, typical of microglia. They overexpressed substance P and the calcium binding protein Iba-1 and dimly expressed class II MHC, three characteristics of microglial cells. Moreover, they also expressed a potassium inward rectifier current, another microglia-specific feature. These monocyte-derived microglia-like cells (MDMi) were CD4(+)/CD14(+), evocative of an activated microglia phenotype. When treated with lipopolysaccharide (LPS), MDMi lost their overexpression of substance P, which returned to untreated monocyte-derived macrophage (MDM) level. Compared with MDM, MDMi expressed higher CD4 but lower CCR5 levels; they could be infected by HIV-1(BaL), but produced less virus progeny than MDM did. This model of human microglia may be an interesting alternative to primary microglia for large scale in vitro HIV studies and may help to better understand HIV-associated microgliosis and chronic inflammation in the brain.

Glutamate metabolism in HIV-infected macrophages: implications for the CNS.

Central nervous system disorders are still a common complication of human immunodeficiency virus (HIV) infection and can lead to dementia and death. They are mostly the consequences of an inflammatory macrophagic activation and relate to glutamate-mediated excitotoxicity. However, recent studies also suggest neuroprotective aspects of macrophage activation through the expression of glutamate transporters and glutamine synthetase. We thus aimed to study whether HIV infection or activation of macrophages could modulate glutamate metabolism in these cells. We assessed the effect of HIV infection on glutamate transporter expression as well as on glutamate uptake by macrophages and showed that glutamate transport was partially decreased in the course of virus replication, whereas excitatory amino acid transporter-2 (EAAT-2) gene expression was dramatically increased. The consequences of HIV infection on glutamine synthetase were also measured and for the first time we show the functional expression of this key enzyme in macrophages. This expression was repressed during virus production. We then quantified EAAT-1 and EAAT-2 gene expression as well as glutamate uptake in differentially activated macrophages and show that the effects of HIV are not directly related to pro- or anti-inflammatory mediators. Finally, this study shows that glutamate transport by macrophages is less affected than what has been described in astrocytes. Macrophages may thus play a role in neuroprotection against glutamate in the infected brain, through their expression of both EAATs and glutamine synthetase. Because glutamate metabolism by activated macrophages is sensitive to both HIV infection and inflammation, it may thus be of potential interest as a therapeutic target in HIV encephalitis.