Type I interferon contributes to CD4+ T cell depletion induced by infection with HIV-1 in the human thymus

Identification of the shared hub gene signatures and molecular mechanisms between HIV-1 and pulmonary arterial hypertension

The close link between HIV-1 infection and the occurrence of pulmonary arterial hypertension (PAH). However, the underlying molecular mechanisms of their interrelation remain unclear. The microarray data of HIV-1 and PAH were downloaded from GEO database. We utilized WGCNA to identify shared genes between HIV-1 and PAH, followed by conducting GO and pathway enrichment analyses. Subsequently, differentially genes analysis was performed using external validation datasets to further filter hub genes. Immunoinfiltration analysis was performed using CIBERSORT. Finally, hub gene expression was validated using scRNA-seq data. We identified 109 shared genes through WGCNA, primarily enriched in type I interferon (IFN) pathways. By taking the intersection of WGCNA important module genes and DEGs, ISG15 and IFI27 were identified as pivotal hub genes. Immunoinfiltration analysis and scRNA-seq results indicated the significant role of monocytes in the shared molecular mechanisms of HIV-1 and PAH. In summary, our study illustrated the possible mechanism of PAH secondary to HIV-1 and showed that the heightened IFN response in HIV-1 might be a crucial susceptibility factor for PAH, with monocytes being pivotal cells involved in the type I IFN response pathway. This provides potential new insights for further investigating the molecular mechanisms connecting HIV-1 and PAH.

Primary role of type I interferons for the induction of functionally optimal antigen-specific CD8+ T cells in HIV infection

BACKGROUND

CD8⁺ T cells equipped with a full arsenal of antiviral effector functions are critical for effective immune control of HIV-1. It has nonetheless remained unclear how best to elicit such potent cellular immune responses in the context of immunotherapy or vaccination. HIV-2 has been associated with milder disease manifestations and more commonly elicits functionally replete virus-specific CD8⁺ T cell responses compared with HIV-1. We aimed to learn from this immunological dichotomy and to develop informed strategies that could enhance the induction of robust CD8⁺ T cell responses against HIV-1.

METHODS

We developed an unbiased in vitro system to compare the de novo induction of antigen-specific CD8⁺ T cell responses after exposure to HIV-1 or HIV-2. The functional properties of primed CD8⁺ T cells were assessed using flow cytometry and molecular analyses of gene transcription.

FINDINGS

HIV-2 primed functionally optimal antigen-specific CD8⁺ T cells with enhanced survival properties more effectively than HIV-1. This superior induction process was dependent on type I interferons (IFNs) and could be mimicked via the adjuvant delivery of cyclic GMP-AMP (cGAMP), a known agonist of the stimulator of interferon genes (STING). CD8⁺ T cells elicited in the presence of cGAMP were polyfunctional and highly sensitive to antigen stimulation, even after priming from people living with HIV-1.

INTERPRETATION

HIV-2 primes CD8⁺ T cells with potent antiviral functionality by activating the cyclic GMP-AMP synthase (cGAS)/STING pathway, which results in the production of type I IFNs. This process may be amenable to therapeutic development via the use of cGAMP or other STING agonists to bolster CD8⁺ T cell-mediated immunity against HIV-1.

FUNDING

This work was funded by INSERM, the Institut Curie, and the University of Bordeaux (Senior IdEx Chair) and by grants from Sidaction (17-1-AAE-11097, 17-1-FJC-11199, VIH2016126002, 20-2-AEQ-12822-2, and 22-2-AEQ-13411), the Agence Nationale de la Recherche sur le SIDA (ECTZ36691, ECTZ25472, ECTZ71745, and ECTZ118797), and the Fondation pour la Recherche Médicale (EQ U202103012774). D.A.P. was supported by a Wellcome Trust Senior Investigator Award (100326/Z/12/Z).

Comparative Transcriptional Analysis Identified Characteristic Genes and Patterns in HIV-Infected Immunological Non-Responders

Purpose

The incomplete immune reconstitution is a complex phenomenon among human immunodeficiency virus (HIV)-infected patients despite the fact that they have achieved persistent viral suppression under the combined antiretroviral therapy. This study aims to screen and verify the immunological characteristics and underlying mechanisms of immunological non-responders (INRs).

Methods

The RNA-seq and the differentially expressed genes (DEGs) analysis were used to explore potential characteristics among INRs. Gene Ontology (GO) enrichment, ingenuity pathway analysis (IPA) analysis, Gene set enrichment analysis (GSEA) analysis, and the weighted gene co-expression network analysis (WGCNA) were used to explore the potential mechanism. The transcriptional meta-analysis was used to analyze the external efficiency.

Results

The RNA-seq identified 316 DEGs among INRs. The interferon signaling pathway was enriched via GO and IPA analysis among DEGs. The combined GSEA and WGCNA analysis confirmed that the IFN response was more correlated with INR. Furthermore, IFI27 (IFN-α Inducible Protein 27, also known as ISG12) was chosen based on combined DEG analysis, WGCNA analysis, and the transcriptional meta-analysis conducted on other published datasets about INRs. The expression of IFI27 was significantly negatively correlated with the CD4+ T-cell counts of PLWH, and the predictive efficiency of IFI27 level in distinguishing PLWH with poor immune recovery was also with significant power (AUC = 0.848).

Conclusion

The enhanced expression of IFI27 and the IFN response pathway are among the important immunological characteristics of INRs and exhibited promising efficiency as biomarkers for CD4⁺ T-cell recovery.

Distinct effects of treatment with two different interferon-alpha subtypes on HIV-1-associated T-cell activation and dysfunction in humanized mice

OBJECTIVE

Interferon-alpha (IFN-α) has been associated with excessive immune activation and dysfunction during HIV-1 infection. However, evidence suggests specific IFN-α subtypes may be beneficial rather than detrimental. This study compared the effects of treatment with two different IFN-α subtypes on indicators of T-cell activation and dysfunction during HIV-1 infection.

DESIGN

Humanized mice were infected with HIV-1 for 5 weeks and then treated with two different IFN-α subtypes for an additional 3 weeks. Splenic T cells were assessed both immediately posttreatment and again 6 weeks after treatment cessation.

METHODS

HIV-1 infected triple-knockout bone marrow-liver-thymus mice received daily intraperitoneal injections of either IFN-α14 or the clinically approved subtype, IFN-α2. T cells were analysed directly ex vivo for indicators of activation and dysfunction or stimulated to determine their proliferative capacity and ability to produce functional mediators.

RESULTS

Unlike IFN-α2, IFN-α14 treatment reduced viremia and resulted in less activated CD4+ T cells and a lower naïve to effector CD8+ T-cell ratio. Despite exhibiting a reduced proliferative response, the frequency of CD8+ T cells from IFN-α14 treated mice that produced functional mediators and expressed markers of dysfunction was more similar to healthy controls than untreated and IFN-α2 treated mice. Frequencies of exhaustion marker expression remained higher in untreated and IFN-α2 treated mice 6 weeks posttreatment despite similar viral loads between groups at this timepoint.

CONCLUSIONS

Treatment with different IFN-α subtypes had distinctive effects on T cells during HIV-1 infection. IFN-α14 was associated with fewer indicators of T-cell dysfunction whereas IFN-α2 treatment had little impact.

Phenotypic and Functional Study of Human Plasmacytoid Dendritic Cells

Plasmacytoid dendritic cells (pDCs) are a distinct lineage of bone-marrow-derived cells that reside mainly in blood and lymphoid organs in the steady state but are also present in sites of infection, inflammation, and cancer. The protocols in this article describes (1) detection and quantification of human pDCs in peripheral blood; (2) isolation of human pDCs by magnetic-activated cell sorting (MACS) and fluorescence-activated cell sorting (FACS); (3) evaluation of human pDC function by stimulation with TLR7 or TLR9 agonists; (4) detection of human pDCs in lymphoid tissues of humanized mice (hu-mice) by flow cytometry; (5) functional study of human pDC in hu-mice in vivo; and (6) specific depletion of human pDCs in vivo in hu-mice using monoclonal antibody targeting human pDCs. These assays thus provide comprehensive methods for phenotypic and functional studies in vitro and for the investigation of human plasmacytoid dendritic cells in hu-mice in vivo. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Analysis of pDCs in human peripheral blood mononuclear cells Basic Protocol 2: pDC separation using MACS beads Alternate Protocol 1: pDC sorting using flow cytometer Basic Protocol 3: Evaluation of human pDC function by stimulation with TLR agonists in vitro Alternate Protocol 2: Intracellular staining of cytokines in pDCs Basic Protocol 4: Phenotypic analysis of human pDCs from lymphoid organs in humanized mice Basic Protocol 5: Functional study of human pDCs in humanized mice during HIV infection Basic Protocol 6: pDC depletion and assessment of pDC depletion in acute HIV-infected in humanized mice.

Qualitative Differences Between the IFNα subtypes and IFNβ Influence Chronic Mucosal HIV-1 Pathogenesis

The Type I Interferons (IFN-Is) are innate antiviral cytokines that include 12 different IFNα subtypes and IFNβ that signal through the IFN-I receptor (IFNAR), inducing hundreds of IFN-stimulated genes (ISGs) that comprise the 'interferome'. Quantitative differences in IFNAR binding correlate with antiviral activity, but whether IFN-Is exhibit qualitative differences remains controversial. Moreover, the IFN-I response is protective during acute HIV-1 infection, but likely pathogenic during the chronic stages. To gain a deeper understanding of the IFN-I response, we compared the interferomes of IFNα subtypes dominantly-expressed in HIV-1-exposed plasmacytoid dendritic cells (1, 2, 5, 8 and 14) and IFNβ in the earliest cellular targets of HIV-1 infection. Primary gut CD4 T cells from 3 donors were treated for 18 hours ex vivo with individual IFN-Is normalized for IFNAR signaling strength. Of 1,969 IFN-regulated genes, 246 'core ISGs' were induced by all IFN-Is tested. However, many IFN-regulated genes were not shared between the IFNα subtypes despite similar induction of canonical antiviral ISGs such as ISG15, RSAD2 and MX1, formally demonstrating qualitative differences between the IFNα subtypes. Notably, IFNβ induced a broader interferome than the individual IFNα subtypes. Since IFNβ, and not IFNα, is upregulated during chronic HIV-1 infection in the gut, we compared core ISGs and IFNβ-specific ISGs from colon pinch biopsies of HIV-1-uninfected (n = 13) versus age- and gender-matched, antiretroviral-therapy naïve persons with HIV-1 (PWH; n = 19). Core ISGs linked to inflammation, T cell activation and immune exhaustion were elevated in PWH, positively correlated with plasma lipopolysaccharide (LPS) levels and gut IFNβ levels, and negatively correlated with gut CD4 T cell frequencies. In sharp contrast, IFNβ-specific ISGs linked to protein translation and anti-inflammatory responses were significantly downregulated in PWH, negatively correlated with gut IFNβ and LPS, and positively correlated with plasma IL6 and gut CD4 T cell frequencies. Our findings reveal qualitative differences in interferome induction by diverse IFN-Is and suggest potential mechanisms for how IFNβ may drive HIV-1 pathogenesis in the gut.

In ovo administration of Toll-like receptor ligands encapsulated in PLGA nanoparticles impede tumor development in chickens infected with Marek's disease virus

One of the economically important diseases in the poultry industry is Marek's disease (MD) which is caused by Marek's disease virus (MDV). The use of current vaccines provides protection against clinical signs of MD in chickens. However, these vaccines do not prevent the transmission of MDV to susceptible hosts, hence they may promote the development of new virulent strains of MDV. This issue persuaded us to explore alternative approaches to control MD in chickens. Induction of innate responses at the early stage of life in the chicken may help to prevent or reduce MDV infection. Further, prophylactic use of Toll-like receptor ligands (TLR-Ls) has been shown to generate host immunity against infectious diseases. In this regard, encapsulation of TLR-Ls in Poly(d, l-lactic-co-glycolic acid) (PLGA) may further enhance host responses by controlled release of TLR-Ls for an extended period. Hence, in the current study, protective effects of encapsulated TLR4 and TLR21 ligands, LPS and CpG, respectively, were investigated against MD. Results indicated that administration of encapsulated CpG and LPS first at embryonic day (ED) 18, followed by post-hatch at 14 days-post infection (dpi) intramuscularly, diminished tumor incidence by 60% and 42.8%, respectively at 21dpi compared to the MDV only group. In addition, analysis of cytokine gene profiles of interferon (IFN)-α, IFN-β, IFN-γ, inducible nitric oxide synthase (iNOS), interleukin (IL)-1β, IL-18 and IL-10 in spleen and bursa of Fabricius at different time points suggests that TLR-Ls possibly triggered host responses through the expression of IL-1β and IL-18 to reduce tumor formation. However, further studies are needed to explore the role of these pro-inflammatory cytokines and other influencing elements like lymphocytes in the hindrance of tumor development by TLR-Ls treatment in chickens.

IFN- protects primary macrophages against HIV infection

IFN-ε is a unique type I IFN that is not induced by pattern recognition response elements. IFN-ε is constitutively expressed in mucosal tissues, including the female genital mucosa. Although the direct antiviral activity of IFN-ε was thought to be weak compared with IFN-α, IFN-ε controls Chlamydia muridarum and herpes simplex virus 2 in mice, possibly through modulation of immune response. We show here that IFN-ε induces an antiviral state in human macrophages that blocks HIV-1 replication. IFN-ε had little or no protective effect in activated CD4⁺ T cells or transformed cell lines unless activated CD4⁺ T cells were infected with replication-competent HIV-1 at a low MOI. The block to HIV infection of macrophages was maximal after 24 hours of treatment and was reversible. IFN-ε acted on early stages of the HIV life cycle, including viral entry, reverse transcription, and nuclear import. The protection did not appear to operate through known type I IFN-induced HIV host restriction factors, such as APOBEC3A and SAMHD1. IFN-ε-stimulated immune mediators and pathways had the signature of type I IFNs but were distinct from IFN-α in macrophages. IFN-ε induced significant phagocytosis and ROS, which contributed to the block to HIV replication. These findings indicate that IFN-ε induces an antiviral state in macrophages that is mediated by different factors than those induced by IFN-α. Understanding the mechanism of IFN-ε-mediated HIV inhibition through immune modulation has implications for prevention.

CCR5 interaction with HIV-1 Env contributes to Env-induced depletion of CD4 T cells in vitro and in vivo

BACKGROUND

CD4 T cell depletion during HIV-1 infection is associated with AIDS disease progression, and the HIV-1 Env protein plays an important role in the process. Together with CXCR4, CCR5 is one of the two co-receptors that interact with Env during virus entry, but the role of CCR5 in Env-induced pathogenesis is not clearly defined. We have investigated CD4 T cell depletion mechanisms caused by the Env of a highly pathogenic CXCR4/CCR5 dual-tropic HIV-1 isolate R3A.

RESULTS

We report here that R3A infection induced depletion of both infected and uninfected "bystander" CD4 T cells, and treatment with CCR5 antagonist TAK-779 inhibited R3A-induced bystander CD4 T cell depletion without affecting virus replication. To further define the role of Env-CCR5 interaction, we utilized an Env-mutant of R3A, termed R3A-5/6AA, which has lost CCR5 binding capability. Importantly, R3A-5/6AA replicated to the same level as wild type R3A by using CXCR4 for viral infection. We found the loss of CCR5 interaction resulted in a significant reduction of bystander CD4 T cells death during R3A-5/6AA infection, whereas stimulation of CCR5 with MIP1-β increased bystander pathogenesis induced by R3A-5/6AA. We confirmed our findings using a humanized mouse model, where we observed similarly reduced pathogenicity of the mutant R3A-5/6AA in various lymphoid organs in vivo.

CONCLUSION

We provide the first evidence that shows CCR5 interaction with a dual-tropic HIV-1 Env played a significant role in Env-induced depletion of CD4 T cells.

HIV-1 Env and Nef Cooperatively Contribute to Plasmacytoid Dendritic Cell Activation via CD4-Dependent Mechanisms

Plasmacytoid dendritic cells (pDCs) are the major source of type I IFN (IFN-I) in response to human immunodeficiency virus type 1 (HIV-1) infection. pDCs are rapidly activated during HIV-1 infection and are implicated in reducing the early viral load, as well as contributing to HIV-1-induced pathogenesis. However, most cell-free HIV-1 isolates are inefficient in activating human pDCs, and the mechanisms of HIV-1 recognition by pDCs and pDC activation are not clearly defined. In this study, we report that two genetically similar HIV-1 variants (R3A and R3B) isolated from a rapid progressor differentially activated pDCs to produce alpha interferon (IFN-α). The highly pathogenic R3A efficiently activated pDCs to induce robust IFN-α production, while the less pathogenic R3B did not. The viral determinant for efficient pDC activation was mapped to the V1V2 region of R3A Env, which also correlated with enhanced CD4 binding activity. Furthermore, we showed that the Nef protein was also required for the activation of pDCs by R3A. Analysis of a panel of R3A Nef functional mutants demonstrated that Nef domains involved in CD4 downregulation were necessary for R3A to activate pDCs. Our data indicate that R3A-induced pDC activation depends on (i) the high affinity of R3A Env for binding the CD4 receptor and (ii) Nef activity, which is involved in CD4 downregulation. Our findings provide new insights into the mechanism by which HIV-1 induces IFN-α in pDCs, which contributes to pathogenesis.

IMPORTANCE

Plasmacytoid dendritic cells (pDCs) are the major type I interferon (IFN-I)-producing cells, and IFN-I actually contributes to pathogenesis during chronic viral infections. How HIV-1 activates pDCs and the roles of pDCs/IFN-I in HIV-1 pathogenesis remain unclear. We report here that the highly pathogenic HIV R3A efficiently activated pDCs to induce IFN-α production, while most HIV-1 isolates are inefficient in activating pDCs. We have discovered that R3A-induced pDC activation depends on (i) the high affinity of R3A Env for binding the CD4 receptor and (ii) Nef activity, which is involved in CD4 downregulation. Our findings thus provide new insights into the mechanism by which HIV-1 induces IFN-α in pDCs and contributes to HIV-1 pathogenesis. These novel findings will be of great interest to those working on the roles of IFN and pDCs in HIV-1 pathogenesis in general and on the interaction of HIV-1 with pDCs in particular.

Differential partial activation phenotype and production of tumour necrosis factor-α by conventional dendritic cells in response to lipopolysaccharide in HIV+ viraemic subjects and HIV+ controllers

HIV(+) subjects are reported to have increased soluble CD14 (sCD14) in plasma, an indicator of microbial translocation. We evaluated if microbial translocation has a differential impact on the activation and function of conventional dendritic cells (cDC) from viraemic HIV(+) subjects and HIV(+) controllers (CTs). The HIV(+) subjects were classified into two groups according to their plasma viral load (pVL): CT and viraemic. Subjects without HIV were included as controls (HIV(-) ). The frequencies and phenotypes of cDC from these subjects were evaluated by multi-parameter flow cytometry. In addition, peripheral blood mononuclear cells (PBMCs) were stimulated with lipopolysaccharide (LPS) or single-stranded RNA40 (ssRNA40), the phenotype of the cDC and the intracellular production of tumour necrosis factor (TNF)-α by the cDC were evaluated by flow cytometry. We observed a partial activation phenotype for the cDC in the viraemic subjects and CTs ex vivo and after LPS activation, which showed differences in the expression of CD40 and CD86. Furthermore, in response to LPS the cDC from the viraemic subjects produced more TNF-α compared to the cDC from CTs. Interestingly, the percentage of TNF-α(+) cDC was found to be correlated positively with the pVL. The partial activation of cDC and the over-production of TNF-α in response to LPS in viraemic HIV(+) subjects might be related to the increased chronic activation observed in these subjects. In contrast, cDC from CTs seem to have a regulated response to LPS, indicating that they respond differently to chronic immune activation. These results may have implications in the development of HIV therapies and vaccines using DC.

IFN-stimulated gene LY6E in monocytes regulates the CD14/TLR4 pathway but inadequately restrains the hyperactivation of monocytes during chronic HIV-1 infection

Owing to ongoing recognition of pathogen-associated molecular patterns, immune activation and upregulation of IFN-stimulated genes (ISGs) are sustained in the chronically infected host. Albeit most ISGs are important effectors for containing viral replication, some might exert compensatory immune suppression to limit pathological dysfunctions, although the mechanisms are not fully understood. In this study, we report that the ISG lymphocyte Ag 6 complex, locus E (LY6E) is a negative immune regulator of monocytes. LY6E in monocytes negatively modulated CD14 expression and subsequently dampened the responsiveness to LPS stimulation in vitro. In the setting of chronic HIV infection, the upregulation of LY6E was correlated with reduced CD14 level on monocytes; however, the immunosuppressive effect of LY6E was not adequate to remedy the hyperresponsiveness of activated monocytes. Taken together, the regulatory LY6E pathway in monocytes represents one of negative feedback mechanisms that counterbalance monocyte activation, which might be caused by LPS translocation through the compromised gastrointestinal tract during persistent HIV-1 infection and may serve as a potential target for immune intervention.

The impact of CSFV on the immune response to control infection

The severity of the acute form of CSF is responsible for the high mortality rate and has been the subject of many studies. Nevertheless, some animals are likely to develop a mild, chronic, or unapparent form of the disease. Paradoxically, this clinical form of the disease has not been well studied, especially regarding its pathogenesis. In this study, we investigated the infection in domestic pigs that is caused by the CSFV Cat01 strain, which is responsible for the 2001-2002 CSFV outbreak in Catalonia, Spain, and which caused mild and nonspecific clinical signs compared to the infection that is caused by another CSFV strain that is responsible for inducing severe clinical symptoms of disease. We assessed the impact of the CSFV infection in the immune system of domestic pigs, mainly on the kinetics of different cytokines, such as IFN-α (innate immunity) and IFN-γ (adaptive immune response), during the first weeks after infection. In addition, we evaluated the impact on the induction of the humoral response and its relation to the course of infection and the RNA CSFV viral load. The IFN-α levels in the serum samples from the pigs that developed a milder form of the CSF disease (infected with Cat01 strain) were lower than those that were detected in the pig with severe clinical CSF signs (Margarita strain). After infection with Cat01 strain, the IFN-γ levels in response to CSFV were detected in addition to the humoral response. Interestingly, in the serum samples of these animals, we detected the lowest load of CSFV RNA. Similarly, the lowest viral load levels were detected in the tonsils of these pigs. Both the T cells and the humoral response that were generated in most of the pigs that were infected with strain Cat01 may be related to the protection in the symptom progression of CSF against this viral strain. These results explain the antiviral role of IFN-γ in the absence of an antibody response. Likewise, these results corroborate the relevance and relationship that exists between the intensity of the T cell response and the protection against CSFV replication. Additionally, these results also explain how the failure to induce optimal levels of humoral and cellular responses after CSFV infection promotes the spread and persistence of the virus.

Modulation of inflammasome-mediated pulmonary immune activation by type I IFNs protects bone marrow homeostasis during systemic responses to Pneumocystis lung infection

Although acquired bone marrow failure (BMF) is considered a T cell-mediated autoimmune disease, possible innate immune defects as a cause for systemic immune deviations in response to otherwise innocuous infections have not been extensively explored. In this regard, we recently demonstrated an important role of type I IFNs in protecting hematopoiesis during systemic stress responses to the opportunistic fungal pathogen Pneumocystis in lymphocyte-deficient mice. Mice deficient in both lymphocytes and type I IFN receptor (IFrag(-/-) mice) develop rapidly progressing BMF due to accelerated bone marrow (BM) cell apoptosis associated with innate immune deviations in the BM in response to Pneumocystis lung infection. However, the communication pathway between lung and BM eliciting the induction of BMF in response to this strictly pulmonary infection has been unclear. In this study, we report that absence of an intact type I IFN system during Pneumocystis lung infection not only causes BMF in lymphocyte-deficient mice but also transient BM stress in lymphocyte-competent mice. This is associated with an exuberant systemic IFN-γ response. IFN-γ neutralization prevented Pneumocystis lung infection-induced BM depression in type I IFN receptor-deficient mice and prolonged neutrophil survival time in BM from IFrag(-/-) mice. IL-1β and upstream regulators of IFN-γ, IL-12, and IL-18 were also upregulated in lung and serum of IFrag(-/-) mice. In conjunction, there was exuberant inflammasome-mediated caspase-1 activation in pulmonary innate immune cells required for processing of IL-18 and IL-1β. Thus, absence of type I IFN signaling during Pneumocystis lung infection may result in deregulation of inflammasome-mediated pulmonary immune activation, causing systemic immune deviations triggering BMF in this model.

Type-I interferon is critical for FasL expression on lung cells to determine the severity of influenza

Infection of influenza A virus in mammals induces hyper lung pneumonia, which often causes lethal diseases. FasL is a specific ligand of Fas, which is a type-I transmembrane protein to induce cell death. Previously, it has been reported that the hyper induction of gene expression associated with Fas signal is observed in lethal influenza A virus infection. More importantly, it was also reported that functional mutation of the FasL gene protects the host against influenza A virus infection. These observations suggest that induction of FasL signal is functionally associated with the severity of influenza. However, regulation of the induction of FasL or Fas by influenza A virus infection is still unknown. Here, we demonstrated that FasL is induced after the viral infection, and inhibition of the Fas/FasL signal by treatment with a recombinant decoy receptor for FasL (Fas-Fc) increases the survival rate of mice after lethal infection of influenza A virus as well as functional mutation of the FasL gene in gld/gld mice. In addition, the induction level of FasL gene expression in the lung was correlated with the severity of influenza. We also showed that a variety of types of cells in the lung express FasL after the viral infection. Furthermore, type-I interferon induced by the viral infection was shown to be critical for induction of FasL protein expression in the lung. These findings suggested that expression of FasL protein induced by type-I IFN on the lung cell surface is critical to determine the severity of influenza.

Characteristics of plasmacytoid dendritic cell and CD4+ T cell in HIV elite controllers

Despite variability, the majority of HIV-1-infected individuals progress to AIDS characterized by high viral load and massive CD4+ T-cell depletion. However, there is a subset of HIV-1-positive individuals that does not progress and spontaneously maintains an undetectable viral load. This infrequent patient population is defined as HIV-1 controllers (HIV controllers), and represents less than 1% of HIV-1-infected patients. HIV-1-specific CD4+ T cells and the pool of central memory CD4+ T cells are also preserved despite immune activation due to HIV-1 infection. The majority of HIV controllers are also defined by the absence of massive CD4+ T-cell depletion, even after 10 years of infection. However, the mechanisms involved in protection against HIV-1 disease progression have not been elucidated yet. Controllers represent a heterogeneous population; we describe in this paper some common characteristics concerning innate immune response and CD4+ T cells of HIV controllers.

Alpha interferon and HIV infection cause activation of human T cells in NSG-BLT mice

The development of small animal models for the study of HIV transmission is important for evaluation of HIV prophylaxis and disease pathogenesis. In humanized bone marrow-liver-thymus (BLT) mice, hematopoiesis is reconstituted by implantation of human fetal liver and thymus tissue (Thy/Liv) plus intravenous injection of autologous liver-derived hematopoietic stem progenitor cells (HSPC). This results in reconstitution of human leukocytes in the mouse peripheral blood, lymphoid organs, and mucosal sites. NOD-scid interleukin-2 receptor-negative (IL-2Rγ(-/-)) (NSG)-BLT mice were inoculated intravaginally with HIV and were monitored for plasma viremia by a branched DNA assay 4 weeks later. T-cell activation was determined by expression of CD38 and HLA-DR on human CD4(+) and CD8(+) T cells in mouse peripheral blood at the time of inoculation and 4 weeks later. Additional BLT mice were treated with human alpha interferon 2b (IFN-α2b) (intron A) and assessed for T-cell activation. Productive HIV infection in BLT mice was associated with T-cell activation (increases in CD38 mean fluorescence intensity and both the frequency and absolute number of CD38(+) HLA-DR(+) T cells) that correlated strongly with plasma viral load and was most pronounced in the CD8(+) T-cell compartment. This T-cell activation phenotype was recapitulated in NSG-BLT mice treated with intron A. HIV susceptibility correlated with the number of HSPC injected, yet a number of mice receiving the Thy/Liv implant alone, with no HSPC injection, were also susceptible to intravaginal HIV. These results are consistent with studies linking T-cell activation to progressive disease in humans and lend support for the use of NSG-BLT mice in studies of HIV pathogenesis.