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Host responses to infection with the malaria parasite Plasmodium falciparum vary among individuals for reasons that are poorly understood. Here we reveal metabolic perturbations as a consequence of malaria infection in children and identify an immunosuppressive role of endogenous steroid production in the context of P. falciparum infection. We perform metabolomics on matched samples from children from two ethnic groups in West Africa, before and after infection with seasonal malaria. Analysing 306 global metabolomes, we identify 92 parasitaemia-associated metabolites with impact on the host adaptive immune response. Integrative metabolomic and transcriptomic analyses, and causal mediation and moderation analyses, reveal an infection-driven immunosuppressive role of parasitaemia-associated pregnenolone steroids on lymphocyte function and the expression of key immunoregulatory lymphocyte genes in the Gouin ethnic group. In children from the less malaria-susceptible Fulani ethnic group, we observe opposing responses following infection, consistent with the immunosuppressive role of endogenous steroids in malaria. These findings advance our understanding of P. falciparum pathogenesis in humans and identify potential new targets for antimalarial therapeutic interventions.

Aim: The present study aimed to evaluate the Plasmodium falciparum genetic diversity according to the host hemoglobin and G6PD genetic variants during the course of malaria in infected children aged from 2 to 10 years and living in endemic area in Burkina Faso. Study Design: The study was designed as a longitudinal follow up conducted between May 2015 and February 2016 in Banfora health district, Burkina Faso. Methodology: We included 136 subjects (73 males and 63 females; age range from 2-10 years). Blood thick and thin film was done by capillary blood. Venous blood was collected for DNA extraction. Malaria diagnosis was done by microscopy. Human and parasite DNA were extracted based on Qiagen kit procedure. Then, hemoglobin and G6PD were genotyped by RLFP-PCR while the msp1, msp2 and eba175 genes were typed by a nested PCR. All PCR products were analyzed by electrophoresis on a 1.5-2% agarose gel and alleles categorized according to the molecular weight. Results: The prevalence of hemoglobin type was 19.11% for abnormal hemoglobin and 80.9% for normal hemoglobin carriage. The prevalence of G6PD type was 91.18% for normal and 8.82% for G6PD deficiency carriage, respectively. The prevalence of msp1 allelic families was 81.60%, 80.80% and 67.20% for k1, ro33 and mad20 respectively while for msp2 gene, fc27 and 3D7 allelic family the prevalence was 70.53% and 69.64% respectively. The eba175 allelic families’ distribution showed 77.31% and 40.21% for fcr3 and Camp respectively. There was no difference in multiplicity of infection (MOI) according to hemoglobin genotypes and G6PD types. We found that k1 was the predominant allelic family of msp1 in normal hemoglobin genotype (AA) and normal G6PD type. The mixed infection of eba175 was statistically higher in abnormal hemoglobin (p=0.04). There was no statistical difference between fcr3 and camp prevalence excepted in G6PD deficient type. The polymorphism results showed that the prevalence of 450 bp in fc27 was statistically significantly higher in normal hemoglobin variant carriers (AA) than abnormal hemoglobin carriers (p=2.10 -4)). However, the prevalence of 350 bp in fc27 was statistically higher in normal G6PD than deficient G6PD carriers (p=0.034). Conclusion: Our result showed that the distribution of msp1 and eba75 polymorphism could be influenced by hemoglobin and G6PD variants. These results suggest that hemoglobin and G6PD could influence P. falciparum genetic diversity.

Aims: The aim of this study was to assess the impact of hemoglobin polymorphisms and G6PD deficiency on the course of uncomplicated malaria infection in children aged from 2 to 10 years in Burkina Faso. Study Design: The study was conducted as a longitudinal study in Banfora health district. A total of 150 children aged from 2 to 10 years was enrolled and followed up between May 2015 and February 2016. Blood samples were collected at four different time points: before infection (Visit 1), during asymptomatic parasitemia (Visit 2), during symptomatic parasitemia (Visit 3) and three weeks after treatment (Visit 4). Clinical examination, hematology parameters and malaria diagnosis using microscopy were performed. Hemoglobin and G6PD typing were done using PCR-RFLP. Hemoglobin AA genotypes were defined as normal hemoglobin while Hemoglobin AC, AS and SS were defined as abnormal hemoglobin (hb non-AA). Results: The prevalence of hemoglobin (hb) genotypes was 81.21% for AA while hb non-AA genotypes were estimated at 18.79% (12.08% for hbAC, 6.04% for hbAS and 0.67% for HbSC). The prevalence of G6PD genotypes was 89.26% and 10.74% for normal G6PDn and G6PD deficiency respectively. The prevalence of asymptomatic carriers of P. falciparum was not affected neither by the genotypes of Hemoglobin, nor by the G6PD deficiency. Conversely, the risks of developing uncomplicated malaria in G6PD deficiency (G202A) group, was significantly lower (p = 0.04). The results showed a significant difference (p˂0.0001) in the means of P. falciparum parasite densities between asymptomatic and symptomatic phase in Hemoglobin AA genotypes carriers while the means of parasite density was comparable in non-Hemoglobin AA carriers. Conclusion: Our study showed that G6PD deficiency protects against clinical malaria while P. falciparum parasite density increasing was correlated with carrying hemoglobin genotypes AA.

A major challenge in controlling the COVID-19 pandemic is the high false-negative rate of the commonly used RT-PCR methods for SARS-CoV-2 detection in clinical samples. Accurate detection is particularly challenging in samples with low viral loads that are below the limit of detection (LoD) of standard one- or two-step RT-PCR methods. In this study, we implemented a three-step approach for SARS-CoV-2 detection and quantification that employs reverse transcription, targeted cDNA preamplification, and nano-scale qPCR based on a commercially available microfluidic chip. Using SARS-CoV-2 synthetic RNA and plasmid controls, we demonstrate that the addition of a preamplification step enhances the LoD of this microfluidic RT-qPCR by 1000-fold, enabling detection below 1 copy/&micro, L. We applied this method to analyze 182 clinical NP swab samples previously diagnosed using a standard RT-qPCR protocol (91 positive, 91 negative) and demonstrate reproducible and quantitative detection of SARS-CoV-2 over five orders of magnitude (&lt, 1 to 106 viral copies/&micro, L). Crucially, we detect SARS-CoV-2 with relatively low viral load estimates (&lt, 1 to 40 viral copies/&micro, L) in 17 samples with negative clinical diagnosis, indicating a potential false-negative rate of 18.7% by clinical diagnostic procedures. In summary, this three-step nano-scale RT-qPCR method can robustly detect SARS-CoV-2 in samples with relatively low viral loads (&lt, 1 viral copy/&micro, L) and has the potential to reduce the false-negative rate of standard RT-PCR-based diagnostic tests for SARS-CoV-2 and other viral infections.

Host responses to infection with the malaria parasite Plasmodium falciparum vary among individuals for reasons that are poorly understood. Here we reveal metabolic perturbations as a consequence of malaria infection in children and identify an immunosuppressive role of endogenous steroid production in the context of P. falciparum infection. We perform metabolomics on matched samples from children from two ethnic groups in West Africa, before and after infection with seasonal malaria. Analysing 306 global metabolomes, we identify 92 parasitaemia-associated metabolites with impact on the host adaptive immune response. Integrative metabolomic and transcriptomic analyses, and causal mediation and moderation analyses, reveal an infection-driven immunosuppressive role of parasitaemia-associated pregnenolone steroids on lymphocyte function and the expression of key immunoregulatory lymphocyte genes in the Gouin ethnic group. In children from the less malaria-susceptible Fulani ethnic group, we observe opposing responses following infection, consistent with the immunosuppressive role of endogenous steroids in malaria. These findings advance our understanding of P. falciparum pathogenesis in humans and identify potential new targets for antimalarial therapeutic interventions.

BackgroundA major challenge in controlling the COVID-19 pandemic is the high false-negative rate of the commonly used standard RT-PCR methods for SARS-CoV-2 detection in clinical samples. Accurate detection is particularly challenging in samples with low viral loads that are below the limit of detection (LoD) of standard one- or two-step RT-PCR methods.MethodsWe implement a three-step approach for SARS-CoV-2 detection and quantification that employs reverse transcription, targeted cDNA preamplification and nano-scale qPCR based on the Fluidigm 192.24 microfluidic chip. We validate the method using both positive controls and nasopharyngeal swab samples.ResultsUsing SARS-CoV-2 synthetic RNA and plasmid controls, we demonstrate that the addition of a preamplification step enhances the LoD of the Fluidigm method by 1,000-fold, enabling detection below 1 copy/μl. We applied this method to analyze 182 clinical NP swab samples previously diagnosed using a standard RT-qPCR protocol (91 positive, 91 negative) and demonstrate reproducible detection of SARS-CoV-2 over five orders of magnitude (< 1 to 106viral copies/μl). Crucially, we detect SARS-CoV-2 with relatively low viral load estimates (ConclusionThe three-step nano-scale RT-qPCR method can robustly detect SARS-CoV-2 in samples with relatively low viral loads (< 1 viral copy/μl) and has the potential to reduce the false negative rate of standard RT-PCR-based diagnostic tests for SARS-CoV-2 and other viral infections.SummaryWe test, implement and report the results of a microfluidic RT-qPCR assay system involving sequential RT, preamplification and nano-scale qPCR that can robustly detect SARS-CoV-2 in clinical samples with viral loads less than 1 copy/ul.

Soil salinity is an increasing threat to global food production systems. As such, there is a need for salt tolerant plant model systems in order to understand salt stress regulation and response. Salicornia bigelovii, a succulent obligatory halophyte, is one of the most salt tolerant plant species in the world. It possesses distinctive characteristics that make it a candidate plant model for studying salt stress regulation and tolerance, showing promise as an economical non-crop species that can be used for saline land remediation and for large-scale biofuel production. However, available S. bigelovii genomic and transcriptomic data are insufficient to reveal its molecular mechanism of salt tolerance. We performed transcriptome analysis of S. bigelovii flowers, roots, seeds and shoots tissues cultivated under desert conditions and irrigated with saline aquaculture effluent. We identified a unique set of tissue specific transcripts present in this non-model crop. A total of 66,943 transcripts (72.63%) were successfully annotated through the GO database with 18,321 transcripts (27.38%) having no matches to known transcripts. Excluding non-plant transcripts, differential expression analysis of 49,914 annotated transcripts revealed differentially expressed transcripts (DETs) between the four tissues and identified shoots and flowers as the most transcriptionally similar tissues relative to roots and seeds. The DETs between above and below ground tissues, with the exclusion of seeds, were primarily involved in osmotic regulation and ion transportation. We identified DETs between shoots and roots implicated in salt tolerance including SbSOS1, SbNHX, SbHKT6 upregulated in shoots relative to roots, while aquaporins (AQPs) were up regulated in roots. We also noted that DETs implicated in osmolyte regulation exhibit a different profile among shoots and roots. Our study provides the first report of a highly upregulated HKT6 from S. bigelovii shoot tissue. Furthermore, we identified two BADH transcripts with divergent sequence and tissue specific expression pattern. Overall, expression of the ion transport transcripts suggests Na+ accumulation in S. bigelovii shoots. Our data led to novel insights into transcriptional regulation across the four tissues and identified a core set of salt stress-related transcripts in S. bigelovii.

Following the entry into the host cell, SARS‐CoV‐2 replication is mediated by the replication transcription complex (RTC) assembled through a number of nonstructural proteins (Nsps). A monomeric form of Nsp9 is particularly important for RTC assembly and function. In the present study, 136 unique nanobodies targeting Nsp9 are generated. Several nanobodies belonging to different B‐cell lineages are expressed, purified, and characterized. Results from immunoassays applied to purified Nsp9 and neat saliva from coronavirus disease (COVID‐19) patients show that these nanobodies effectively and specifically recognize both recombinant and endogenous Nsp9. Nuclear magnetic resonance analyses supported by molecular dynamics reveal a composite Nsp9 oligomerization pattern and demonstrate that both nanobodies stabilize the tetrameric form of wild‐type Nsp9 also identifying the epitopes on the tetrameric assembly. These results can have important implications in the potential use of these nanobodies to combat viral replication., New nanobodies targeting Nsp9, a nonstructural protein required for Sars‐CoV‐2 replication, are generated. These nanobodies specifically recognize Nsp9 in saliva samples from COVID‐19 patients and stabilize a tetrameric form of Nsp9, not compatible with its role in facilitating viral replication. These results potentially identify novel diagnostic and therapeutic antiviral strategies to combat Sar‐CoV‐2 and, therefore, COVID‐19.

Human mesenchymal stromal cells (MSC) have been shown to dampen immune response and promote tissue repair, but the underlying mechanisms are still under investigation. Herein, we demonstrate that umbilical cord-derived MSC (UC-MSC) alter the phenotype and function of monocyte-derived dendritic cells (DC) through lactate-mediated metabolic reprogramming. UC-MSC can secrete large quantities of lactate and, when present during monocyte-to-DC differentiation, induce instead the acquisition of M2-macrophage features in terms of morphology, surface markers, migratory properties and antigen presentation capacity. Microarray expression profiling indicates that UC-MSC modify the expression of metabolic-related genes and induce a M2-macrophage expression signature. Importantly, monocyte-derived DC obtained in presence of UC-MSC, polarize naive allogeneic CD4+ T-cells into Th2 cells. Treatment of UC-MSC with an inhibitor of lactate dehydrogenase strongly decreases lactate concentration in culture supernatant and abrogates the effect on monocyte-to-DC differentiation. Metabolic analysis further revealed that UC-MSC decrease oxidative phosphorylation in differentiating monocytes while strongly increasing the spare respiratory capacity proportional to the amount of secreted lactate. Because both MSC and monocytes are recruited in vivo at the site of tissue damage and inflammation, we propose the local increase of lactate concentration induced by UC-MSC and the consequent enrichment in M2-macrophage generation as a mechanism to achieve immunomodulation.

Understanding the patterns of genetic diversity of fish species is essential for marine conservation and management. This is particularly important in the Arabian Gulf where marine life is subject to extreme environmental conditions that could impact genetic diversity. Here we assess genetic diversity of the most commercially important fish in the United Arab Emirates; groupers (Epinephelus spp.). Sequencing of 973 bp mitochondrial DNA from 140 tissue samples collected in four main fish markets revealed 58 haplotypes clustered within three groups. Data analysis revealed the presence of three distinct Epinephelus species being marketed as one species (hammour): Epinephelus coioides, Epinephelus areolatus and Epinephelus bleekeri. We report species-specific genetic markers and demonstrate that all three species exhibit relatively low levels of genetic variation, reflecting the effect of overfishing and environmental pressures. In light of the genetic evidence presented here, conservation and management of groupers in the UAE warrant the implementation of species-specific measures.

Although clinical studies have yet to demonstrate clearly the use of intravenous immunoglobulin (IVIG) for prevention of graft-versus-host disease (GVHD), their effective use in a xenogeneic mouse model has been demonstrated. We aimed to determine the mechanism of action by which IVIG contributes to GVHD prevention in a xenogeneic mouse model. NOD/LtSz-scidIL2rg−/− (NSG) mice were used for our xenogeneic mouse model of GVHD. Sublethally irradiated NSG mice were injected with human peripheral blood mononuclear cells (huPBMCs) and treated weekly with PBS or 50 mg IVIG. Incidence of GVHD and survival were noted, along with analysis of cell subsets proliferation in the peripheral blood. Weekly IVIG treatment resulted in a robust and consistent proliferation of human natural killer cells that were activated, as demonstrated by their cytotoxicity against K562 target cells. IVIG treatment did not inhibit GVHD when huPBMCs were depleted in natural killer (NK) cells, strongly suggesting that this NK cell expansion was required for the IVIG-mediated prevention of GVHD in our mouse model. Moreover, inhibition of T cell activation by either cyclosporine A (CsA) or monoclonal antihuman CD3 antibodies abolished the IVIG-induced NK cell expansion. In conclusion, IVIG treatment induces NK cell proliferation, which is essential for IVIG-mediated protection of GVHD in our mouse model. Furthermore, activated T cells are mandatory for effective IVIG-induced NK cell proliferation. These results shed light on a new mechanism of action of IVIG and could explain why the efficacy of IVIG in preventing GVHD in a clinical setting, where patients receive CsA, has never been undoubtedly demonstrated.

Climate change is affecting the trophic ecology of reef fishes through changes in reef-associated food availability and fish feeding behavior. The southern Arabian Gulf is a thermally extreme environment, providing an opportunity to study fish diets on reefs with summer temperatures representative of next-century conditions elsewhere. Using 18S metagenomic analyses of stomach contents, we provide the first description of the dietary composition of three abundant reef fishes (Pomacanthus maculosus, Pomacentrus aquilus, and Pomacentrus trichrourus) from the thermally extreme southern Arabian Gulf, with five sampling periods across 1 year used to assess seasonal variation in diet. In total, 146 stomach content samples were sequenced, resulting in 9.6 million filtered reads that aligned to 17 classes in 14 phyla. Corals (Cnidaria, Anthozoa) dominated stomach contents of all three fishes (overall mean: 74.6, 40.6, and 21.2% of stomach reads, respectively), suggesting coral consumption to be characteristic of reef fish diet in the region. Sanger sequencing validated the presence of corals in the stomach contents and identified two common genera in the region, Porites and Platygyra, as part of the diet. Other common phyla included sponges and annelid worms (P. maculosus: 14.9%, 4.1%; P. aquilus: 5.9%, 16.7%; P. trichrourus: 8.2%, 14.7%, respectively), with the remainder comprised of 11 other phyla. Algae were virtually absent in diets of all three species. The P. maculosus diet was consistently coral/sponge dominated across the year, but there was substantial seasonal variation in the damselfishes, with diets dominated by coral in the hottest month (August; P. aquilus: 89.4%, P. trichrourus: 51.5%) but broadest in spring (March, May) when corals became less common (16.4%). These results suggest that these fishes have developed a feeding ecology responsive to the fluctuating and extreme environmental conditions of their region. These results broaden our understanding of the diets of these three species and document the nature, complexity and temporal dynamics of reef fish diets in the most thermally extreme coral reef environment on earth.

Fas-mediated apoptosis is one of the mechanisms used by tumor cells to escape the cytotoxicity of tumor-infiltrating lymphocytes. It has been suggested that cytokine-induced killer (CIK) cells are resistant to Fas-mediated apoptosis, thereby rendering them more attractive for use in cellular immunotherapy. Unlike what was observed by others, here we show that CIK cells are sensitive to Fas-mediated apoptosis. We have observed an increase in Fas expression in the different CIK cell subpopulations (CD3(+)CD56(-), CD3(+)CD56(+), and CD3(-)CD56(+)) isolated from both cord blood (CB) and peripheral blood (PB). We also show that the bulk, as well as the CD3(+)CD56(-) and CD56(+) CB- and PB-CIK cell subpopulations were sensitive to Fas-mediated apoptosis induced by both CH11 and APO-1 antibodies, albeit with a weaker effect for the CH11 antibody on CB-CIK cells. In addition, in the presence of the APO-1 and CH11 inducers, Fas engagement inhibited the cytotoxic activity of CB- and PB-CIK cells. This new contradictory result may help explain the variable efficacy observed with CIK cells in the clinic.

Background aims. Cytokine-induced killer (CIK) cells may represent a promising immunotherapy for the treatment of children with relapsing B-lineage acute lymphoblastic leukemia (B-ALL) following hematopoietic stem cell transplantation (HSCT). Therefore, we investigated the possibility of combining adoptive immunotherapy with CIK cells and human interferon-alpha (hIFN- α ) in order to potentiate the cytotoxicity of CIK cells against B-ALL. Methods. Cord bloodderived CIK (CB-CIK) cells were differentiated, stimulated with phosphate-buffered saline (PBS) or hIFN- α , and tested for cytotoxic activity. We tested the anti-leukemic and graft-versus-host disease (GvHD) effects of CB-CIK cells in a human xenograft NOD/SCID/ γ c � (NSG) mouse model. Results. Bulk CB-CIK cells showed very moderate cytotoxic activity while the subpopulation of CD56 � CB-CIK cells showed signifi cant cytotoxic activity against B-ALL cells. hIFN- α signifi cantly augmented the cytotoxicity of CD56 � CB-CIK cells in vitro and induced signal transducer and activator of transcription-1 (STAT1) phosphorylation. In addition, CD56 � CB-CIK cells could delay mouse mortality signifi cantly in vivo , and this effect was enhanced signifi cantly by hIFN- α ( P � 0.022). Furthermore, unlike CB mononuclear cells or peripheral blood mononuclear cells (PBMC), CD56 � CB-CIK cells, alone or stimulated with hIFN- α , caused either no GvHD or mild GvHD, respectively, when injected into sublethally irradiated NSG mice. Conclusions. CD56 � CB-CIK cells are effective cytotoxic agents against human B-ALL cell lines in vitro and possess anti-leukemic activity that is potentiated by hIFN- α in an NSG mouse model in vivo. These pre-clinical data support the testing of this immunotherapeutic approach in the clinic for the treatment of B-ALL.

Human mesenchymal stromal cells (MSCs) have been successfully utilized for the treatment of refractory graft-versus-host disease (GvHD). Despite the large number of in vitro and in vivo models developed for clarifying their immunomodulatory properties, the mechanism of action of MSCs remains elusive and their efficacy controversial. Here, we tested the ability of cord blood-derived MSCs to alleviate the symptoms of GvHD induced by the injection of human peripheral blood mononuclear cells into NOD/SCID/γc(-) mice. In this in vivo xeno-GvHD model, we demonstrate that a single MSC injection is able to inhibit GvHD in terms of clinical signs and related mortality. We also show that in this model MSCs act by both immunomodulating T-cells and fostering recovery after irradiation. The translational impact of these findings could provide a reliable preclinical model for studying the efficacy, dosage, and time of administration of human MSCs for the prevention of acute GvHD.

BACKGROUND: Optimal conditions of cord blood (CB) storage, processing, cryopreservation, and thawing are critical for banking and transplantation. Nevertheless, standardized procedures are still awaited. STUDY DESIGN AND METHODS: We evaluated the impact of preprocessing storage and temperature on recovery, viability, and functional differentiation capacities of hematopoietic progenitor cells. We compared units stored at room temperature (RT) or at 4°C for 72 hours before cryopreservation to units processed shortly after collection (

Background aims Cytokine-induced killer (CIK) cells ex vivo –expanded from cord blood (CB) or peripheral blood (PB) have been shown to be cytotoxic against autologous and allogeneic tumor cells. We have previously shown that CD56 + CIK cells (CD3 + CD56 + and CD3 − CD56 + ) are capable of killing precursor B-cell acute lymphoblastic leukemia (B-ALL) cell lines. However, the lytic pathways used by CD56 + PB and CB-CIK cells to kill B-ALL cell lines have not been studied. Methods CB and PB-CIK cells were differentiated. CD56 + CB- and PB-CIK cells were compared for expression of different phenotypic markers and for the lytic pathways used to kill B-ALL cell lines. Results We found that cytotoxic granule proteins were expressed at higher levels in CD56 + PB-CIK than in CD56 + CB-CIK cells. However, CD56 + CB-CIK cells expressed more tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) compared with CD56 + PB-CIK cells. We observed that CD56 + CB-CIK cells used both the NKG2D and TRAIL cytotoxic pathways and were more effective at killing REH cells than CD56 + PB-CIK cells that used only the NKG2D pathway. In contrast, CD56 + PB-CIK cells used both NKG2D and TRAIL pathways to kill NALM6 cells, whereas CD56 + CB-CIK cells used only the NKG2D pathway. Conclusions Our results suggest that both the source of CIK and the type of B-ALL cell line have an impact on the intensity of the cytolytic activity and on the pathway used. These findings may have clinical implications with respect to optimizing therapeutic efficacy, which may be dependent on the source of the CIK cells and on the target tumor cells.

The mechanisms by which mesenchymal stromal cells (MSCs) induce immunomodulation are still poorly understood. In the current work, we show by a combination of polymerase chain reaction (PCR) array, flow cytometry, and multiplex cytokine data analysis that during the inhibition of an alloantigen-driven CD4+ T-cell response, MSCs induce a fraction of CD4+ T-cells to coexpress interferon-γ (IFNγ) and interleukin-10 (IL-10). This CD4+ IFNγ+ IL-10+ cell population shares properties with recently described T-cells originating from switched Th1 cells that start producing IL-10 and acquire a regulatory function. Here we report that IL-10-producing Th1 cells accumulated with time during T-cell stimulation in the presence of MSCs. Moreover, MSCs caused stimulated T-cells to downregulate the IFNγ receptor (IFNγR) without affecting IL-10 receptor expression. Further, the inhibitory effect of MSCs could be reversed by an anti-IFNγR-blocking antibody, indicating that IFNγ is one of the major players in MSC-induced T-cell suppression. Stimulated (and, to a lesser extent, resting) CD4+ T-cells treated with MSCs were able to inhibit the proliferation of autologous CD4+ T-cells, demonstrating their acquired regulatory properties. Altogether, our results suggest that the generation of IL-10-producing Th1 cells is one of the mechanisms by which MSCs can downmodulate an immune response.

The efficacy of IVIG in preventing GvHD has not been definitely demonstrated clinically. Using a xenogeneic model of GvHD in NOD/SCID/γc- (NSG) mice, we showed that weekly administration of IVIG significantly reduced the incidence and associated mortality of GvHD to a degree similar to CsA. Unlike CsA and OKT3, IVIG were not associated with inhibition of human T-cell proliferation in mice. Instead, IVIG significantly inhibited the secretion of human IL-17, IL-2, IFN-γ and IL-15 suggesting that IVIG prevented GvHD by immunomodulation. Furthermore, the pattern of modification of the human cytokine storm differed from that observed with CsA and OKT3. Finally, in a humanized mouse model of immune reconstitution, in which NSG mice were engrafted with human CD34(+) stem cells, IVIG transiently inhibited B-cell reconstitution, whereas peripheral T-cell reconstitution and thymopoiesis were unaffected. Together these in vivo data raise debate related to the appropriateness of IVIG in GvHD prophylaxis. In addition, this model provides an opportunity to further elucidate the precise mechanism(s) by which IVIG inhibit GvHD.

Background Vpu is a multifunctional accessory protein that enhances the release of HIV-1 by counteracting the entrapment of nascent virions on infected cell surface mediated by BST2/Tetherin. Vpu-mediated BST2 antagonism involves physical association with BST2 and subsequent mislocalization of the restriction factor to intracellular compartments followed by SCF(β-TrCP) E3 ligase-dependent lysosomal degradation. Apart from BST2 antagonism, Vpu also induces down regulation of several immune molecules, including CD4 and SLAMF6/NTB-A, to evade host immune responses and promote viral dissemination. However, it should be noted that the multiple functions of Vpu have been studied in cell-based assays, and thus it remains unclear how Vpu influences the dynamic of HIV-1 infection in in vivo conditions. Results Using a humanized mouse model of acute infection as well as CCR5-tropic HIV-1 that lack Vpu or encode WT Vpu or Vpu with mutations in the β-TrCP binding domain, we provide evidence that Vpu-mediated BST2 antagonism plays a crucial role in establishing early plasma viremia and viral dissemination. Interestingly, we also find that efficient HIV-1 release and dissemination are directly related to functional strength of Vpu in antagonizing BST2. Thus, reduced antagonism of BST2 due to β-TrCP binding domain mutations results in decreased plasma viremia and frequency of infected T cells, highlighting the importance of Vpu-mediated β-TrCP-dependent BST-2 degradation for optimal initial viral propagation. Conclusions Overall, our findings suggest that BST2 antagonism by Vpu is critical for efficient early viral expansion and dissemination during acute infection and as such is likely to confer HIV-1 increased transmission fitness.