S100A9 protein is a novel ligand for the CD85j receptor and its interaction is implicated in the control of HIV-1 replication by NK cells

Background

The reportedly broad expression of CD85j across different immune cell types suggests an importance for this molecule in the human immune system. Previous reports have shown that this receptor interacts with several HLA class-I molecules, as well as with some viral proteins. We have demonstrated that the subset of CD85j + Natural Killer (NK) cells efficiently controls human immunodeficiency virus type 1 (HIV-1) replication in monocyte-derived dendritic cells (MDDC) in vitro and this led us to hypothesize that the CD85j + NK cell-mediated anti-HIV activity in MDDC is specifically dependent on the interaction between the CD85j receptor and unknown non-HLA class-I ligand(s).

Results

In this study, we focused our efforts on the identification of these non-described ligands for CD85j. We found that the CD85j receptor interacts with a calcium-binding proteins of the S100 family; namely, S100A9. We further demonstrated that HIV-1 infection of MDDC induces a modulation of S100A9 expression on surface of the MDDC, which potentially influences the anti-HIV-1 activity of human NK cells through a mechanism involving CD85j ligation. Additionally, we showed that stimulation of NK cells with exogenous S100A9 enhances the control of HIV-1 infection in CD4+ T cells.

Conclusions

Our data show that S100A9 protein, through ligation with CD85j, can stimulate the anti-HIV-1 activity of NK cells.

The Th17/Treg ratio, IL-1RA and sCD14 levels in primary HIV infection predict the T-cell activation set point in the absence of systemic microbial translocation

Impairment of the intestinal barrier and subsequent microbial translocation (MT) may be involved in chronic immune activation, which plays a central role in HIV pathogenesis. Th17 cells are critical to prevent MT. The aim of the study was to investigate, in patients with primary HIV infection (PHI), the early relationship between the Th17/Treg ratio, monocyte activation and MT and their impact on the T-cell activation set point, which is known to predict disease progression. 27 patients with early PHI were included in a prospective longitudinal study and followed-up for 6 months. At baseline, the Th17/Treg ratio strongly negatively correlated with the proportion of activated CD8 T cells expressing CD38/HLA-DR or Ki-67. Also, the Th17/Treg ratio was negatively related to viral load and plasma levels of sCD14 and IL-1RA, two markers of monocyte activation. In untreated patients, the Th17/Treg ratio at baseline negatively correlated with CD8 T-cell activation at month 6 defining the T-cell activation set point (% HLA-DR(+)CD38(+) and %Ki-67(+)). Soluble CD14 and IL-1RA plasma levels also predicted the T-cell activation set point. Levels of I-FABP, a marker of mucosal damages, were similar to healthy controls at baseline but increased at month 6. No decrease in anti-endotoxin core antibody (EndoCAb) and no peptidoglycan were detected during PHI. In addition, 16S rDNA was only detected at low levels in 2 out 27 patients at baseline and in one additional patient at M6. Altogether, data support the hypothesis that T-cell and monocyte activation in PHI are not primarily driven by systemic MT but rather by viral replication. Moreover, the "innate immune set point" defined by the early levels of sCD14 and IL-1RA might be powerful early surrogate markers for disease progression and should be considered for use in clinical practice.

High number of CD56(bright) NK-cells and persistently low CD4+ T-cells in a hemophiliac HIV/HCV co-infected patient without opportunistic infections

Background

Both the human immunodeficiency virus (HIV) and hepatitis C virus (HCV), either alone or as coinfections, persist in their hosts by destroying and/or escaping immune defenses, with high morbidity as consequence. In some cases, however, a balance between infection and immunity is reached, leading to prolonged asymptomatic periods. We report a case of such an indolent co-infection, which could be explained by the development of a peculiar subset of Natural Killer (NK) cells.

Results

Persistently high peripheral levels of CD56⁺ NK cells were observed in a peculiar hemophiliac HIV/HCV co-infected patient with low CD4 counts, almost undetectable HIV viral load and no opportunistic infections. Thorough analysis of NK-subsets allowed to identify a marked increase in the CD56^bright/dim cell ratio and low numbers of CD16⁺/CD56^- cells. These cells have high levels of natural cytotoxicity receptors but low NCR2 and CD69, and lack both CD57 and CD25 expression. The degranulation potential of NK-cells which correlates with target cytolysis was atypically mainly performed by CD56^bright NK-cells, whereas no production of interferon γ (IFN-γ) was observed following NK activation by K562 cells.

Conclusions

These data suggest that the expansion and lytic capacity of the CD56^bright NK subset may be involved in the protection of this « rare » HIV/HCV co-infected hemophiliac A patient from opportunistic infections and virus-related cancers despite very low CD4⁺ cell counts.

Molecular characterization of avian reovirus isolates in Tunisia

BACKGROUND

Genotype analyses of avian reoviruses isolated from organ samples collected from chickens with suspicious clinical symptoms, between 1997-2008, was based on sequences for both σC and σB genes and aligned with those published in the Genbank, making it possible to carry out studies of molecular classification and relationships.

METHODS

The full length of the known variable protein σC and part of the σB encoding genes, were amplified with RT-PCR, using conserved primers. PCR products were sequenced and the sequences were analyzed and aligned with avian reovirus sequences from the Genbank database.

RESULTS

The sequences of σC-encoding genes of all the isolated strains indicated their close relationship with the American, Chinese and Indian strains. Taking the American strain S1133 as a reference, the two Tunisian isolates 97.1 and 97.2 showed some nucleotide substitutions. For isolate 97.1, the substitution was silent whereas for strain 97.2 the mutation was at the first position of the corresponding codon and induced the substitution of the amino acid encoded. For the σB-encoding gene, the sequences of the Tunisian strains showed mutations at positions two or three of the corresponding codons, inducing substitutions of amino acids at these positions. The phylogenic trees based on σC and σB encoding genes indicated closer relationship between Tunisian, American and Taiwanese isolates of genotype I.

CONCLUSION

Our study describes the genotype of avian reoviruses that are not yet well characterized genetically. The characterization and classification of these viruses might be significant for understanding the epidemiology of malabsorption syndrome and viral arthritis, and improving our knowledge of the genotype of strains circulating in Tunisian flocks. Furthermore, the study of their variable pathogenicity could be extremely important in the choice of the appropriate vaccine strain to control disease.

Natural resistance to HIV infection: lessons learned from HIV‐exposed uninfected individuals

We explored potential mechanisms of resistance to human immunodeficiency virus type 1 (HIV‐1) infection in different groups of uninfected individuals exposed by systemic or mucosal routes: intravascular drug users in Vietnam and spouses of HIV‐infected individuals in Cambodia and Central African Republic. Our main findings were reduced susceptibility of peripheral blood mononuclear cells to HIV‐1 infection in vitro, associated with low levels of CD4+ T cell activation in vivo and/or cell restriction of viral replication, and enhanced natural killer cell activity, associated with increased ratios of activating to inhibitory natural killer cell receptors. These results support a contribution of innate responses to resistance against HIV‐1 infection. Scientific and ethical issues encountered during research in exposed uninfected subjects must be considered.

Changes to the natural killer cell repertoire after therapeutic hepatitis B DNA vaccination

BACKGROUND

Improvements to the outcome of adaptive immune responses could be achieved by inducing specific natural killer (NK) cell subsets which can cooperate with dendritic cells to select efficient T cell responses. We previously reported the induction or reactivation of T cell responses in chronic hepatitis B patients vaccinated with a DNA encoding hepatitis B envelope proteins during a phase I clinical trial.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, we examined changes in the peripheral NK cell populations occurring during this vaccine trial using flow cytometry analysis. Despite a constant number of NK cells in the periphery, a significant increase in the CD56(bright) population was observed after each vaccination and during the follow up. Among the 13 different NK cell markers studied by flow cytometry analysis, the expression of CD244 and NKG2D increased significantly in the CD56(bright) NK population. The ex vivo CD107a expression by CD56(bright) NK cells progressively increased in the vaccinated patients to reach levels that were significantly higher compared to chronically HBV-infected controls. Furthermore, modifications to the percentage of the CD56(bright) NK cell population were correlated with HBV-specific T cell responses detected by the ELISPOT assay.

CONCLUSIONS/SIGNIFICANCE

These changes in the CD56(bright) population may suggest a NK helper effect on T cell adaptive responses. Activation of the innate and adaptive arms of the immune system by DNA immunization may be of particular importance to the efficacy of therapeutic interventions in a context of chronic infections.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00988767.

MG132 proteasome inhibitor modulates proinflammatory cytokines production and expression of their receptors in U937 cells: involvement of nuclear factor-kappaB and activator protein-1

In response to inflammatory stimuli, monocytes/macrophages secrete greater quantities of the proinflammatory cytokines tumour necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and IL-6. The inflammatory process and the innate immune response are related to the activation of several transcription factors, such as nuclear factor kappaB (NF-kappaB) and activator protein 1 (AP-1). The proteasome is a multimeric protease complex, which plays a vital role in several cellular functions, including the regulation of transcription factors like NF-kappaB. In this study, we used the human monocyte cell line U937 stimulated with lipopolysaccharide (LPS) and phorbol 12-myristate 13-acetate (PMA) as a model to investigate the in vitro effects of MG132, a proteasome inhibitor, on the release of TNF-alpha, IL-1beta and IL-6 and on the expression of their membrane and soluble receptors TNF-R1, IL-1R1 and IL-6R. We also analysed the effects of MG132 on the activation of NF-kappaB and AP-1 and on the IkappaB molecule. MG132 significantly inhibited the secretion of those proinflammatory cytokines. MG132 increased the release of the soluble receptors TNF-R1 and IL-1R1 from U937 cells and decreased their cell-surface expression. MG132 also increased IL-6R cell-surface expression and decreased its release. Proteasome inhibition also led to an increase in LPS+PMA-induced AP-1 activation and the attenuation of LPS+PMA-induced IkappaB degradation, resulting in the abolition of NF-kappaB activation. Our experiments strongly suggest that the proteasome is an important factor in the regulation of proinflammatory cytokines and their receptors.

Antiinflammatory and Antiatherogenic Effects of the NF-κB Inhibitor Acetyl-11-Keto-β-Boswellic Acid in LPS-Challenged ApoE −/− Mice

Objective— In this article, we studied the effect of acetyl-11-keto-β-boswellic acid (AKβBA), a natural inhibitor of the proinflammatory transcription factor NF-κB on the development of atherosclerotic lesions in apolipoprotein E–deficient (apoE −/− ) mice.

Methods and Results— Atherosclerotic lesions were induced by weekly LPS injection in apoE −/− mice. LPS alone increased atherosclerotic lesion size by ≈100%, and treatment with AKβBA significantly reduced it by ≈50%. Moreover, the activity of NF-κB was also reduced in the atherosclerotic plaques of LPS-injected apoE −/− mice treated with AKβBA. As a consequence, AKβBA treatment led to a significant downregulation of several NF-κB–dependent genes such as MCP-1, MCP-3, IL-1α, MIP-2, VEGF, and TF. By contrast, AKβBA did not affect the plasma concentrations of triglycerides, total cholesterol, antioxidized LDL antibodies, and various subsets of lymphocyte-derived cytokines. Moreover, AKβBA potently inhibited the IκB kinase (IKK) activity immunoprecipitated from LPS-stimulated mouse macrophages and mononuclear cells leading to decreased phosphorylation of IκBα and inhibition of p65/NF-κB activation. Comparable AKβBA-mediated inhibition was also observed in LPS-stimulated human macrophages.

Conclusion— The inhibition of NF-κB activity by plant resins from species of the Boswellia family might represent an alternative for classical medicine treatments for chronic inflammatory diseases such as atherosclerosis. (Arterioscler Thromb Vasc Biol. 2008;28:272-277)

HIV-1 induced decrease of nitric oxide production and inducible nitric oxide synthase expression during in vivo and in vitro infection

Nitric oxide (*NO) has been implicated in immunopathogenesis of HIV-1 infection. Initial reports using low sensitive techniques showed elevated levels of *NO in sera and tissues from seropositive patients. These results were not further supported using similar experimental approaches. To gain insight on *NO deregulation during HIV-1 infection, we used recently described fluorescent probes with enhanced sensitivity to assess *NO levels combined with iNOS mRNA expression in peripheral blood mononuclear cells (PBMC) from HIV-infected patients or after in vitro HIV-1 infection of normal cells. We demonstrate that PBMC from HIV-infected patients display a significant decrease of *NO production and iNOS mRNA expression. Results from in vitro infection showed that HIV-1 induces a significant decrease in *NO production and iNOS mRNA expression. Since *NO could play a role in some key processes like apoptosis, regulation of immune responses and viral replication, these results could help in elucidating HIV-1 immunopathogenesis.

Distinctive NK-cell receptor repertoires sustain high-level constitutive NK-cell activation in HIV-exposed uninfected individuals

We have previously associated high natural killer (NK)–cell activity and protection against HIV-1 infection in Vietnamese exposed uninfected intravascular drug users (EUs). Considering that activating and inhibitory signals sensed by NK-cell receptors regulate NK-cell activation, we performed phenotypic and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) transcript analyses of the NK-cell receptor (NKR) repertoire in 25 EUs, 19 HIV+ intravenous drug users, and 26 uninfected blood donors. Although NK-cell activation was not linked to a unique NKR repertoire in EUs, various patterns consistent with NK-cell activation were detected in EUs: high KIR3DS1/KIR3DL1 ratio associated with down-regulated KIR3DL1 transcript levels, KIR2DL3+ low-affinity receptor expansion associated to group HLA-C1 ligand in 2DS2−/2DL2− EUs, enhanced NKG2C/NKG2A ratio, and increased CD69 expression. Remarkably, EUs exhibited high constitutive degranulation activity in the absence of exogenous stimulation, as shown by the CD107a assay. Furthermore, CD161 expression was increased within the CD107a+ NK-cell compartment. Our results suggest that in response to viral exposition, particular genetic or regulated features of the NKR repertoire of EUs contribute to their high constitutive NK-cell potential. This might allow NK cells to generate a more rapid and effective immune response to HIV-1, thereby contributing to prevention toward infection.

Persistent resistance to HIV-1 infection in CD4 T cells from exposed uninfected Vietnamese individuals is mediated by entry and post-entry blocks

BACKGROUND

We have previously reported that CD4 T cells from some exposed uninfected (EU) Vietnamese intravenous drug users are relatively resistant to HIV infection in vitro. Here, we further characterized the restriction of viral replication in CD4 T cells from five EUs and assessed its persistence in serial samples.

RESULTS

CD4 T cells and/or PBMC sampled during a period of between 2 and 6 years were challenged with replication-competent HIV-1 and other retroviral particles pseudotyped with envelope proteins of various tropisms. CCR5 expression and function in resistant CD4 T cells was evaluated. The step at which HIV-1 replication is restricted was investigated by real-time PCR quantification of HIV-1 reverse transcripts. We identified three patterns of durable HIV-1 restriction in EU CD4 T cells. CD4 T cells from four of the five EU subjects were resistant to HIV-1 R5 infection. In two cases this resistance was associated with low CCR5 surface expression, which was itself associated with heterozygous CCR5 mutations. In the other two cases, CD4 T cells were resistant to HIV-1 R5 infection despite normal CCR5 expression and signaling function, and normal beta-chemokine secretion upon CD4 T cell activation. Instead, restriction appeared to be due to enhanced CD4 T cell sensitivity to beta-chemokines in these two subjects. In the fifth EU subject the restriction involved post-entry steps of viral replication and affected not only HIV-1 but also other lentiviruses. The restriction was not overcome by a high viral inoculum, suggesting that it was not mediated by a saturable inhibitory factor.

CONCLUSION

Various constitutive mechanisms of CD4 T cell resistance to HIV-1 infection, affecting entry or post-entry steps of viral replication, are associated with resistance to HIV-1 in subjects who remain uninfected despite long-term high-risk behavior.

Poor recognition of HIV-1 Nef protein by CD8 T cells from HIV-1-infected children: impact of age

Recognition of various HIV proteins by CD8 T cells from HIV-infected children was determined by two functional assays. First, using an Elispot assay, we show that 80% of patients recognized Gag, 77% recognized Pol, 61% recognized Env, 44% recognized Nef and 29% recognized Vif. Frequencies of Gag-, Pol-, and Env-specific IFN-gamma producing CD8 T cells were higher than frequencies of Nef and Vif-specific CD8 T cells. The poor recognition of Nef by ex vivo CD8 T cells was confirmed by CTL assays performed in HAART naïve children: 25% of children had positive response against Nef versus 44, 63 and 62% for Env, Gag, and Pol, respectively. Memory Gag-specific CTL were positively correlated with age, whereas Nef-specific CTL were negatively correlated with age. The poor Nef-specific CD8 T cell response in HIV-infected children contrasts with dominance of Nef-specific responses in infected adults.

Reduced CD4 T cell activation and in vitro susceptibility to HIV-1 infection in exposed uninfected Central Africans

BACKGROUND

Environmentally driven immune activation was suggested to contribute to high rates of HIV-1 infection in Africa. We report here a study of immune activation markers and susceptibility to HIV-1 infection in vitro of forty-five highly exposed uninfected partners (EUs) of HIV-1 infected individuals in Central African Republic, in comparison with forty-four low-risk blood donors (UCs).

RESULTS

Analysis of T lymphocyte subsets and activation markers in whole blood showed that the absolute values and the percentage of HLA-DR+CD4 T cells and of CCR5+CD4 T cells were lower in the EUs than in the UCs (p = 0.0001). Mutations in the CCR5 coding region were not found in either group. Susceptibility to in vitro infection of unstimulated peripheral blood mononuclear cells, prior of PHA activation, was decreased in EUs compared to UCs, either using a CXCR4-tropic or a CCR5-tropic HIV-1 strain (p = 0.02 and p = 0.05, respectively). Levels of MIP-1beta, but not of MIP-1alpha or RANTES, in the supernatants of PHA-activated PBMC, were higher in the EUs than in the UCs (p = 0.007).

CONCLUSION

We found low levels of CD4 T cell activation and reduced PBMC susceptibility to HIV-1 infection in Central African EUs, indicating that both may contribute to the resistance to HIV-1 infection.

[Cryptococcal meningo-encephalitis in an apparently immunocompetent patient]

INTRODUCTION

Cryptococcal meningo-encephalitis is a rare disease occurring more frequently in immunocompromised hosts.

CASE REPORT

We report the case of an apparently immunocompetent patient who developed a recurrent neurological deficit with lymphocytic meningitis. The time from the first symptoms to diagnosis was 8 months. We noted mild CD4+ lymphocytopenia (500 cells/mm3) without HIV infection. CD4+ lymphocytes were not reactive for a panel of antigens.

CONCLUSION

This case illustrates the usefulness of cerebrospinal fluid Cryptococcus Neoformans antigen test in patients with an unexplained neurological syndrome with a lymphocytic meningitis together with quantification of circulating lymphocytes clusters and analyse of their function in opportunistic infections.

In vivo and in vitro sensitization of leukemic cells to adriamycin-induced apoptosis by pentoxifyllineInvolvement of caspase cascades and IκBα phosphorylation

The aim of this work was to investigate whether in vivo and in vitro pentoxifylline (PTX) sensitizes hematological tumor cells to adriamycin (ADM)-induced apoptosis, and to investigate the involvement of caspase cascades and phosphorylated forms of IkappaBalpha. Balb/c mice inoculated intraperitoneally with L5178-Y murine lymphoma cells were used for in vivo experiments and for survival studies. The U937 human monocytic cell line was used for in vitro experiments. Both cell lines were treated under similar experimental conditions with PTX and/or ADM to assess their effects on apoptosis. Apoptosis was evaluated by fluorescence microscopy with ethidium bromide and acridine orange staining and confirmed by electrophoretic DNA analysis. Caspase inhibitors Z-VAD-fmk, Z-DEVD-fmk, and Z-LEHD-fmk were used to investigate the involvement of caspase cascades. C-terminally and Ser32 phosphorylated forms of IkappaBalpha were evaluated in cytoplasmic extracts in the absence or presence of TNFalpha.

RESULTS

In vivo, PTX (50 mg/kg) with ADM (5 mg/kg) increased the apoptotic index relative to PTX or ADM administered alone, time- and dose-dependently. DNA laddering appeared in lymphoma cells treated with PTX+ADM at 24 h, whereas neither untreated control, PTX-, nor ADM-treated cells showed DNA fragmentation. All (100%) tumor-bearing mice treated with PTX (25 mg/kg)+ADM (2.5 mg/kg) survived for 1 year, whereas the mortality rates of mice treated with either PTX or ADM alone at the same doses were similar to that of untreated tumor-bearing mice (28+/-3 days). Caspase inhibitors inhibited apoptosis more efficiently in PTX- or ADM-treated cultures than in PTX+ADM-treated cultures. Pretreatment with TNFalpha (10 ng/mL) increased apoptosis in PTX- or ADM-treated U937 cells. However, the apoptotic index of PTX+ADM-treated cultures was significantly reduced and the expression of C-terminally and Ser32 phosphorylated IkappaBalpha was reduced. PTX sensitizes hematological malignancies to ADR-induced apoptosis. An independent caspase pathway is involved in PTX+ADM-induced apoptosis. The phosphorylation status of IkappaBalpha is closely related via TNFalpha to the possible mechanisms of drug resistance.

Systemic immune activation in HIV-1-exposed uninfected Vietnamese intravascular drug users

To assess immunological parameters, including markers of immune activation, in highly HIV-1-exposed uninfected (EU) Vietnamese intravascular drug users (IDUs) in comparison with HIV-1-infected IDUs and HIVunexposed controls, we determined peripheral lymphocyte phenotypes in fresh whole blood samples from 32 EU IDUs, 28 HIV+ IDUs, and 26 blood donors. We found higher levels of activation markers (CD38, HLADR) on CD4+ and CD8+ T cells, lower percentages of naive CD4+ and CD8+ T cells, higher percentages of CD8+ T cells and of CD8+ T cells expressing CD25, and lower levels of CXCR4+CD4+ T cells in EU IDUs than in unexposed controls. Despite several differences in CD4+ and CD8+ T cell subset phenotypes, both EU and HIV+ IDUs exhibited a pattern of peripheral immune activation. Lymphocyte activation in EU IDUs may reflect immune stimulation driven by viral infections other than HIV-1 and/or allogeneic stimulation associated with needle sharing. Our results suggest that immune activation does not necessarily favor HIV-1 transmission, but, on the contrary, may alter the susceptibility of EUs to HIV-1 infection and contribute to their resistance.

Differential susceptibility of human thymic dendritic cell subsets to X4 and R5 HIV-1 infection

OBJECTIVES

Human thymus can be infected by HIV-1 with potential consequences on immune regeneration and homeostasis. We previously showed that CD4 thymocytes preferentially replicate CXCR4 tropic (X4) HIV-1 dependently on interleukin (IL)-7. Here we addressed the susceptibility of thymic dendritic cells (DC) to HIV-1 infection.

METHODS

We investigated the replication ability of CXCR4 or CCR5 (R5) tropic HIV-1 in thymic micro-explants as well as in isolated thymic CD11clowCD14- DC, CD11chighCD14+ DC and plasmacytoid DC subsets.

RESULTS

Thymic tissue was productively infected by both X4 and R5 viruses. However, X4 but not R5 HIV-1 replication was enhanced by IL-7 in thymic micro-explants, suggesting that R5 virus replication occurred in cells other than thymocytes. Indeed, we found that R5 HIV-1 replicated efficiently in DC isolated from thymic tissue. The replicative capacity of X4 and R5 viruses differed according to the different DC subsets. R5 but not X4 HIV-1 efficiently replicated in CD11chighCD14+ DC. In contrast, no HIV-1 replication was detected in CD11clowCD14- DC. Both X4 and R5 viruses efficiently replicated in plasmacytoid DC, which secreted interferon-alpha upon HIV-1 exposure. Productive HIV-1 infection also caused DC loss, consistent with different permissivity of each DC subset.

CONCLUSIONS

Thymic DC sustain high levels of HIV-1 replication. DC might thus be the first target for R5 HIV-1 infection of thymus, acting as a Trojan horse for HIV-1 spread to thymocytes. Furthermore, DC death induced by HIV-1 infection may affect thymopoiesis.