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Lentiviral vectors (LVs) are increasingly employed in gene and cell therapy. Standard laboratory production of LVs is not easily scalable, and research-grade LVs often contain contaminants that can interfere with downstream applications. Moreover, purified LV production pipelines have been developed mainly for costly, large-scale, clinical-grade settings. Therefore, a standardized and cost-effective process is still needed to obtain efficient, reproducible, and properly executed experimental studies and preclinical development of ex vivo and in vivo gene therapies, as high infectivity and limited adverse reactions are important factors potentially influencing experimental outcomes also in preclinical settings. We describe here an optimized laboratory-scale workflow whereby an LV-containing supernatant is purified and concentrated by sequential chromatographic steps, obtaining biologically active LVs with an infectious titer and specific activity in the order of 109 transducing unit (TU)/mL and 5 × 104 TU/ng of HIV Gag p24, respectively. The purification workflow removes >99% of the starting plasmid, DNA, and protein impurities, resulting in higher gene transfer and editing efficiency in severe combined immunodeficiency (SCID)-repopulating hematopoietic stem and progenitor cells (HSPCs) ex vivo, as well as reduced activation of inflammatory responses ex vivo and in vivo as compared to TU-matched, laboratory-grade vectors. Our results highlight the value of accessible purified LV production for experimental studies and preclinical testing., Graphical Abstract, Lentiviral vectors (LVs) are powerful gene-transfer tools routinely exploited for distinct research and clinical applications. LVs produced in most research laboratories contain contaminants that can generate confounding effects in experimental studies. Soldi et al. describe a laboratory-scale workflow for purified LV production, highlighting enhanced gene-editing efficiency and diminished inflammatory responses.

Aberrant induction of type I IFN is a hallmark of the inherited encephalopathy Aicardi-Goutières syndrome (AGS), but the mechanisms triggering disease in the human central nervous system (CNS) remain elusive. Here, we generated human models of AGS using genetically modified and patient-derived pluripotent stem cells harboring TREX1 or RNASEH2B loss-of-function alleles. Genome-wide transcriptomic analysis reveals that spontaneous proinflammatory activation in AGS astrocytes initiates signaling cascades impacting multiple CNS cell subsets analyzed at the single-cell level. We identify accumulating DNA damage, with elevated R-loop and micronuclei formation, as a driver of STING- and NLRP3-related inflammatory responses leading to the secretion of neurotoxic mediators. Importantly, pharmacological inhibition of proapoptotic or inflammatory cascades in AGS astrocytes prevents neurotoxicity without apparent impact on their increased type I IFN responses. Together, our work identifies DNA damage as a major driver of neurotoxic inflammation in AGS astrocytes, suggests a role for AGS gene products in R-loop homeostasis, and identifies common denominators of disease that can be targeted to prevent astrocyte-mediated neurotoxicity in AGS.

Long-range gene editing by homology-directed repair (HDR) in hematopoietic stem/progenitor cells (HSPCs) often relies on viral transduction with recombinant adeno-associated viral vector (AAV) for template delivery. Here, we uncover unexpected load and prolonged persistence of AAV genomes and their fragments, which trigger sustained p53-mediated DNA damage response (DDR) upon recruiting the MRE11-RAD50-NBS1 (MRN) complex on the AAV inverted terminal repeats (ITRs). Accrual of viral DNA in cell-cycle-arrested HSPCs led to its frequent integration, predominantly in the form of transcriptionally competent ITRs, at nuclease on- and off-target sites. Optimized delivery of integrase-defective lentiviral vector (IDLV) induced lower DNA load and less persistent DDR, improving clonogenic capacity and editing efficiency in long-term repopulating HSPCs. Because insertions of viral DNA fragments are less frequent with IDLV, its choice for template delivery mitigates the adverse impact and genotoxic burden of HDR editing and should facilitate its clinical translation in HSPC gene therapy.

The liver hosts an immune suppressive environment favouring metastatic seeding and proliferation of cancer cells. Pharmacological treatments, including immunotherapies, fail in the presence of liver metastases (LMS). Therefore, identifying new interventional tools and key targetable players involved in the immunosuppressive environment is of pivotal importance. We developed a lentiviral vector (LV)-based platform for selective genetic engineering of resident and tumour-associated macrophages enabling locally-sourced delivery of therapeutic molecules to LMS. Selective transgene expression is driven by a macrophage specific promoter and fine-tuned by microRNA target sequences. Upon systemic delivery of the LV, we observed enhanced transgene expression in macrophages located in areas surrounding LMS. We then equipped the LV with an IFNα-coding sequence, a cytokine with pleiotropic immune effects. Long term analysis in mice showed LV dose-dependent, sustained and well-tolerated IFNα expression. To investigate the therapeutic efficacy, we employed a colorectal cancer (CRC) organoid-based syngeneic mouse model of LMS containing molecular and histopathological hallmarks of the human disease. IFNα LV treatment significantly delayed LMS growth reaching a complete response in up to 50%. Single cell omics of LMS from IFNα LV-treated mice showed upregulation of IFNα-responsive genes, macrophage skewing to an antigen presenting (M1-like) polarization state, and expansion as well as reduced exhaustion of LMS-associated antigen specific CD8 T cells. Employing spatial transcriptomics, we found that the interface between LMS and liver parenchymal tissue was the major site of IFNα action, which was associated with enhanced immune activation and antigen presentation. Furthermore, we observed decreased angiogenesis and hypoxia in IFNα LV-treated LMS. When comparing LMS of treatment responsive to resistant mice, we found accumulation of activated CD8 T-cells in responsive whereas a high number of immunosuppressive T regulatory type 1 (TR1)-like cells in resistant mice. Molecular analyses suggest that TR1-like cell infiltration was associated with increased IL10 signaling in resistant mice. Furthermore, we found a positive correlation between IFNα and TR1-like cell signatures in human LMS and primary CRC thus supporting the link between IFNα activation and expansion of TR1-like cells in cancer. In summary, we developed an innovative gene-based platform that upon a single well-tolerated intravenous LV infusion rapidly promotes a protective therapeutic response against LMS through enabling immune activation. However, we also found that TR1-like cells might promote tumor immune evasion in presence of IFNα signaling in this setting, suggesting targeting of TR1-like cells when facing resistance to cancer immunotherapies that trigger IFNα signaling. Citation Format: Thomas Kerzel, Stefano Beretta, Eloise Scamardella, Chiara Balestrieri, Tamara Canu, Federica Pedica, Rossana Norata, Lucia Sergi Sergi, Marco Genua, Ostuni Renato, Anna Kajaste-Rudnitski, Antonio Esposito, Masanobu Oshima, Giovanni Tonon, Francesca Sanvito, Mario Leonardo Squadrito, Luigi Naldini. IFNalpha by in vivo-engineered macrophages abates liver metastases and triggers counter regulatory responses limiting efficacy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3297.

Trained immunity (TI) is a proinflammatory program induced in monocyte/macrophages upon sensing of specific pathogens and is characterized by immunometabolic and epigenetic changes that enhance cytokine production. Maladaptive activation of TI (ie, in the absence of infection) may result in detrimental inflammation and development of disease; however, the exact role and extent of inappropriate activation of TI in the pathogenesis of human diseases is undetermined. In this study, we uncovered the oncogene-induced, maladaptive induction of TI in the pathogenesis of a human inflammatory myeloid neoplasm (Erdheim-Chester disease, [ECD]), characterized by the BRAFV600E oncogenic mutation in monocyte/macrophages and excess cytokine production. Mechanistically, myeloid cells expressing BRAFV600E exhibit all molecular features of TI: activation of the AKT/mammalian target of rapamycin signaling axis; increased glycolysis, glutaminolysis, and cholesterol synthesis; epigenetic changes on promoters of genes encoding cytokines; and enhanced cytokine production leading to hyperinflammatory responses. In patients with ECD, effective therapeutic strategies combat this maladaptive TI phenotype; in addition, pharmacologic inhibition of immunometabolic changes underlying TI (ie, glycolysis) effectively dampens cytokine production by myeloid cells. This study revealed the deleterious potential of inappropriate activation of TI in the pathogenesis of human inflammatory myeloid neoplasms and the opportunity for inhibition of TI in conditions characterized by maladaptive myeloid-driven inflammation.

D-mannose is a monosaccharide approximately a hundred times less abundant than glucose in human blood. Previous studies demonstrated that supraphysiological levels of D-mannose inhibit tumour growth and stimulate regulatory T cell differentiation. It is not known whether D-mannose metabolism affects the function of non-proliferative cells, such as inflammatory macrophages. Here, we show that D-mannose suppresses LPS-induced macrophage activation by impairing IL-1β production. In vivo, mannose administration improves survival in a mouse model of LPS-induced endotoxemia as well as decreases progression in a mouse model of DSS-induced colitis. Phosphomannose isomerase controls response of LPS-activated macrophages to D-mannose, which impairs glucose metabolism by raising intracellular mannose-6-phosphate levels. Such alterations result in the suppression of succinate-mediated HIF-1α activation, imposing a consequent reduction of LPS-induced Il1b expression. Disclosing an unrecognized metabolic hijack of macrophage activation, our study points towards safe D-mannose utilization as an effective intervention against inflammatory conditions., Mannose is present at trace levels in blood and regulates cancer growth. Here the authors show that supraphysiological levels of mannose can also regulate macrophages, limiting their production of IL-1β and increasing resistance of mice to LPS-induced endotoxemia and DSS-induced colitis.

The prominent role of dendritic cells (DC) in promoting tolerance and the development of methods to generate clinical grade products allowed the clinical application of tolerogenic DC (tolDC)-based therapies for controlling unwanted immune responses. We established an efficient method to generate tolerogenic human DC, producing supra-physiological levels of IL-10, by genetically engineering monocyte-derived DC with a bidirectional Lentiviral Vector (bdLV) encoding for IL-10 and a marker gene. DCIL−10 are mature DC, modulate T cell responses, promote T regulatory cells, and are phenotypically and functionally stable upon stimulation. Adoptive transfer of human DCIL−10 in a humanized mouse model dampens allogeneic T cell recall responses, while murine DCIL−10 delays acute graft-vs.-host disease in mice. Our report outlines an efficient method to transduce human myeloid cells with large-size LV and shows that stable over-expression of IL-10 generates an effective cell product for future clinical applications in the contest of allogeneic transplantation.

Targeted gene editing in hematopoietic stem cells (HSCs) is a promising treatment for several diseases. However, the limited efficiency of homology-directed repair (HDR) in HSCs and the unknown impact of the procedure on clonal composition and dynamics of transplantation have hampered clinical translation. Here, we apply a barcoding strategy to clonal tracking of edited cells (BAR-Seq) and show that editing activates p53, which substantially shrinks the HSC clonal repertoire in hematochimeric mice, although engrafted edited clones preserve multilineage and self-renewing capacity. Transient p53 inhibition restored polyclonal graft composition. We increased HDR efficiency by forcing cell-cycle progression and upregulating components of the HDR machinery through transient expression of the adenovirus 5 E4orf6/7 protein, which recruits the cell-cycle controller E2F on its target genes. Combined E4orf6/7 expression and p53 inhibition resulted in HDR editing efficiencies of up to 50% in the long-term human graft, without perturbing repopulation and self-renewal of edited HSCs. This enhanced protocol should broaden applicability of HSC gene editing and pave its way to clinical translation. Transient p53 inhibition and induced cell-cycle progression increase clonal engraftment and homology-directed repair in hematopoietic stem cells.

The low gene manipulation efficiency of human hematopoietic stem and progenitor cells (HSPC) remains a major hurdle for sustainable and broad clinical application of innovative therapies for a wide range of disorders. Given that all current and emerging gene transfer and editing technologies are bound to expose HSPC to exogenous nucleic acids and most often also to viral vectors, we reason that host antiviral factors and nucleic acid sensors play a pivotal role in the efficacy of HSPC genetic manipulation. Here, we review recent progress in our understanding of vector–host interactions and innate immunity in HSPC upon gene engineering and discuss how dissecting this crosstalk can guide the development of more stealth and efficient gene therapy approaches in the future.

Improving hematopoietic stem and progenitor cell (HSPC) permissiveness to lentiviral vector (LV) transduction without compromising their biological properties remains critical for broad-range implementation of gene therapy as a treatment option for several inherited diseases. This study demonstrates that the use of one-hit ex vivo LV transduction protocols based on either cyclosporin A (CsA) or rapamycin enable as efficient gene transfer as the current two-hit clinical standard into bone marrow–derived CD34+ cells while better preserving their engraftment capacity in vivo. CsA was additive with another enhancer of transduction, prostaglandin E2, suggesting that tailored enhancer combinations may be applied to overcome multiple blocks to transduction simultaneously in HSPC. Interestingly, besides enhancing LV transduction, CsA also significantly reduced HSPC proliferation, preserving the quiescent G0 fraction and the more primitive multipotent progenitors, thereby yielding the highest engraftment levels in vivo. Importantly, no alterations in the vector integration profiles could be detected between CsA and control transduced HSPC. Overall, the present findings contribute to the development of more efficient and sustainable LV gene therapy protocols, underscoring the benefits of scaling down required vector doses, as well as shortening the HSPC ex vivo culture time.

Innate immune factors may restrict hematopoietic stem cell (HSC) genetic engineering and contribute to broad individual variability in gene therapy outcomes. Here, we show that HSCs harbor an early, constitutively active innate immune block to lentiviral transduction that can be efficiently overcome by cyclosporine H (CsH). CsH potently enhances gene transfer and editing in human long-term repopulating HSCs by inhibiting interferon-induced transmembrane protein 3 (IFITM3), which potently restricts VSV glycoprotein-mediated vector entry. Importantly, individual variability in endogenous IFITM3 levels correlated with permissiveness of HSCs to lentiviral transduction, suggesting that CsH treatment will be useful for improving ex vivo gene therapy and standardizing HSC transduction across patients. Overall, our work unravels the involvement of innate pathogen recognition molecules in immune blocks to gene correction in primary human HSCs and highlights how these roadblocks can be overcome to develop innovative cell and gene therapies.

Improving hematopoietic stem and progenitor cell (HSPC) permissiveness to HIV-derived lentiviral vectors (LVs) remains a challenge for the field of gene therapy as high vector doses and prolonged ex vivo culture are still required to achieve clinically relevant transduction levels. We report here that Cyclosporin A (CsA) and Rapamycin (Rapa) significantly improve LV gene transfer in human and murine HSPC. Both compounds increased LV but not gammaretroviral transduction and acted independently of calcineurin and autophagy. Improved gene transfer was achieved across all CD34(+) subpopulations, including in long-term SCID repopulating cells. Effects of CsA were specific of HSPC and opposite to its known impact on HIV replication. Mutating the Cyclophilin A binding pocket of the viral capsid (CA) further improved transduction in combination with CsA. Tracking of the LV genome fate revealed that CsA relieves a CA-dependent early block and increases integration, while Rapa acts early in LV infection independently of the viral CA. In agreement, only Rapa was able to improve transduction by an integrase-defective LV harboring wild-type CA. Overall, our findings pave the way for more efficient and sustainable LV gene therapy in human HSPCs and shed light on the multiple innate barriers specifically hampering LV transduction in these cells.

Influenza remains a serious health threat, with resistance to frontline drugs becoming more common, and new treatments urgently sought. One strategy for the inhibition of the attachment of influenza to host cells is to employ chemically modified heparins, capable of effectively competing with the multivalent interactions involved. In an assay of H5N1 influenza viral invasion comprising a H5 pseudotyped HIV system, selective removal of the sulfate groups from heparin (IC50 ~22 × 10−9 g mL−1) allowed the retention of inhibitory activity in the products (IC50 ~4 × 10−9 g mL−1) while significantly reducing their anticoagulant activities. Chemically modified anionic polysaccharides offer a potential source of effective inhibitors of viral attachment, which are suitable for further optimisation.

Summary Ex vivo gene therapy based on CD34+ hematopoietic stem cells (HSCs) has shown promising results in clinical trials, but genetic engineering to high levels and in large scale remains challenging. We devised a sorting strategy that captures more than 90% of HSC activity in less than 10% of mobilized peripheral blood (mPB) CD34+ cells, and modeled a transplantation protocol based on highly purified, genetically engineered HSCs co-infused with uncultured progenitor cells. Prostaglandin E2 stimulation allowed near-complete transduction of HSCs with lentiviral vectors during a culture time of less than 38 hr, mitigating the negative impact of standard culture on progenitor cell function. Exploiting the pyrimidoindole derivative UM171, we show that transduced mPB CD34+CD38− cells with repopulating potential could be expanded ex vivo. Implementing these findings in clinical gene therapy protocols will improve the efficacy, safety, and sustainability of gene therapy and generate new opportunities in the field of gene editing., Highlights • CD34+CD38− cells as an HSC-enriched starting population for ex vivo gene therapy • Reduced culture time (, In this article, Gentner and colleagues undertake a comprehensive strategy to advance ex vivo genetic engineering of HSCs for gene therapy. They experimentally define an optimal strategy to purify HSCs, which allows uncoupling long-term from short-term hematopoietic reconstitution, and implement ex vivo conditions that best preserve their biological properties applying novel transduction-enhancing compounds and pyrimidoindole derivatives to support HSC expansion.

Clinical application of lentiviral vector (LV)‐based hematopoietic stem and progenitor cells (HSPC) gene therapy is rapidly becoming a reality. Nevertheless, LV‐mediated signaling and its potential functional consequences on HSPC biology remain poorly understood. We unravel here a remarkably limited impact of LV on the HSPC transcriptional landscape. LV escaped innate immune sensing that instead led to robust IFN responses upon transduction with a gamma‐retroviral vector. However, reverse‐transcribed LV DNA did trigger p53 signaling, activated also by non‐integrating Adeno‐associated vector, ultimately leading to lower cell recovery ex vivo and engraftment in vivo . These effects were more pronounced in the short‐term repopulating cells while long‐term HSC frequencies remained unaffected. Blocking LV‐induced signaling partially rescued both apoptosis and engraftment, highlighting a novel strategy to further dampen the impact of ex vivo gene transfer on HSPC. Overall, our results shed light on viral vector sensing in HSPC and provide critical insight for the development of more stealth gene therapy strategies.

Intracellular defense proteins, also referred to as restriction factors, are capable of interfering with different steps of the viral life cycle. Among these, we have shown that Tripartite motif 22 (TRIM22) suppresses basal as well as phorbol ester-induced HIV-1 long terminal repeat (LTR)-mediated transcription, independently of its E3 ubiquitin ligase activity, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) binding to the U3 region and Tat interaction with the TAR region of the HIV-1 LTR. As basal HIV-1 transcription is driven by the transcription factor specificity protein 1 (Sp1), we have investigated whether TRIM22 could interfere with Sp1-driven transcriptional activation of the HIV-1 LTR., SCOPUS: ar.j, info:eu-repo/semantics/published

OBJECTIVE to determine the immunogenicity of the monovalent vaccine against 2009 pandemic influenza A/H1N1 in HIV-1-infected individuals. DESIGN a total of 192 participants, including 44 HIV-1-positive individuals and 148 HIV-1-negative healthy controls were enrolled to receive a single dose of MF59-adjuvanted 2009 A/H1N1v vaccine formulated to contain 7.5 microg of haemagglutin antigen. METHODS standard haemagglutination inhibition (HAI) assay was performed to evaluate seroconversion and seroprotecsion rates against the pandemic virus in serum samples collected at baseline (T0) and 3-5-week postvaccination (T28). Seroconversion to vaccination was defined by either prevaccination HAI titer less than 1: 10 with a postvaccination titer higher than 1: 40, or a prevaccination titer higher than 1: 10 and increase of at least four-fold or more after vaccination. Seroprotection was defined by HAI titers higher than 1: 40. RESULTS the vaccine induced specific antibody titers in HIV-1-positive individuals similar to those of HIV-1-negative controls [215.3, 95% confidence interval (CI) 150.4-308.1 vs. 275.9, 95% CI 232.6-327.3] with postvaccination seroprotection rates higher than 97%. In contrast, the seroconversion rate was lower in the HIV-1-positive individuals as compared with the HIV-1-negative controls (36.4 vs. 79.0%, P < 0.0001), likely as a consequence of their high HAI baseline titers. Multivariable logistic regression analysis showed that seroconversion was less likely in HIV-1-positive individuals [odds ratio (OR) = 0.237, 95% CI 0.104-0.539, P = 0.0006) and with increasing age (OR = 0.805, 95% CI 0.684-0.947, P = 0.009). CONCLUSIONS a single dose of MF59-adjuvanted 2009 influenza H1N1 vaccine induced an immune response against pandemic H1N1 virus in HIV-1-positive individuals reaching titers similar to those of HIV-1-negative individuals. The seroconversion rate was negatively associated with HIV infection and increasing age.

Previous studies identified clones of the U937 promonocytic cell line that were either permissive or nonpermissive for human immunodeficiency virus type 1 (HIV-1) replication. These clones were investigated further in the search for host restriction factors that could explain their differential capacity to support HIV-1 replication. Among known HIV-1 restriction factors screened, tri partite m otif-containing protein 22 (TRIM22) was the only factor constitutively expressed in nonpermissive and absent in permissive U937 cells. Stable TRIM22 knockdown (KD) rescued HIV-1 long-terminal-repeat (LTR)-driven transcription in KD-nonpermissive cells to the levels observed in permissive cells. Conversely, transduction-mediated expression of TRIM22 in permissive cells reduced LTR-driven luciferase expression by ∼7-fold, supporting a negative role of TRIM22 in HIV-1 transcription. This finding was further confirmed in the human T cell line A3.01 expressing TRIM22. Moreover, overexpression of TRIM22 in 293T cells significantly impaired basal and phorbol myristate acetate-ionomycin-induced HIV-1 LTR-driven gene expression, whereas inhibition of tumor necrosis factor alpha-induced viral transcription was a consequence of lower basal expression. In agreement, TRIM22 equally inhibited an LTR construct lacking the tandem NF-κB binding sites. In addition, TRIM22 did not affect Tat-mediated LTR transactivation. Finally, these effects were independent of TRIM22 E3 ubiquitin-ligase activity. In the context of replication-competent virus, significantly higher levels of HIV-1 production were observed in KD-nonpermissive versus control nonpermissive U937 cells after infection. In contrast, lower peak levels of HIV-1 replication characterized U937 and A3.01 cells expressing TRIM22 versus their control transduced counterpart. Thus, nuclear TRIM22 significantly impairs HIV-1 replication, likely by interfering with Tat- and NF-κB-independent LTR-driven transcription.

Viral tropism, replication, and pathogenesis are determined by multiple interactions between the pathogen and the host. In the case of retroviruses, and in particular, the human immunodeficiency virus, the specific interaction of the envelope protein with the host receptors and co-receptors is essential to gain entry in the cells. After entry, the success of retroviruses to complete their life cycle depends on a complex interplay between the virus and host proteins. Indeed, the cell environment is endowed with a number of factors that actively block distinct stage(s) in the microbial life cycle. Among these restriction factors, Tripartite Motif-5 alpha (TRIM5 alpha) has been extensively studied; however, other TRIM family members have been demonstrated to be anti-retroviral effector proteins. This article reviews, in particular, the current knowledge on the anti-retroviral effects of TRIM5 alpha and TRIM22.

Recent studies suggest that hematopoietic stem cells (HSC) can sense foreign nucleic acids and pathogen-associated molecular patterns (PAMPs). Exposure to lentiviral vectors (LV) upon gene transfer may thus trigger acute host responses in HSC that could potentially impact on their biological properties, although no comprehensive studies are available to date. We have performed a high throughput RNA-Seq analysis on human cord-blood (CB)-derived CD34+ hematopoietic stem and progenitor cells (HSPC) exposed to research- or clinical-grade VSV-g pseudotyped (SIN) LV at a high multiplicity of infection, matching current clinical vector dose requirements. As controls, cells were exposed to non-transducing Env-less, genome-less or heat inactivated control vectors or kept in culture untreated. RNA was extracted at different times early after transduction, processed and ran in Illumina HiSeq2000. Analysis of Differential Expression in Time Course was performed using LIMMA R/BioConductor library. Key pathways were assessed by Term Enrichment Analysis considering KEGG pathways and Gene Ontology Biological processes. Transduction with both research-and clinical-grade LV significantly triggered DNA damage and apoptosis-related responses. In particular, p53 signaling was among the most significantly altered pathways (p

Hematopoietic gene therapy has tremendous potential to treat human disease. Nevertheless, for gene therapy to be efficacious, effective gene transfer into target cells must be reached without inducing detrimental effects on their biological properties. This remains a great challenge for the field as high vector doses and prolonged ex vivo culture conditions are still required to reach significant transduction levels of clinically relevant human hematopoietic stem and progenitor cells (HSPCs), while other potential target cells such as primary macrophages can hardly be transduced. The reasons behind poor permissiveness of primary human hematopoietic cells to gene transfer partly reside in the retroviral origin of lentiviral vectors (LVs). In particular, host antiviral factors referred to as restriction factors targeting the retroviral life cycle can hamper LV transduction efficiency. Furthermore, LVs may activate innate immune sensors not only in differentiated hematopoietic cells but also in HSPCs, with potential consequences on transduction efficiency as well as their biological properties. Therefore, better understanding of the vector-host interactions in the context of hematopoietic gene transfer is important for the development of safer and more efficient gene therapy strategies. In this review, we briefly summarize the current knowledge regarding innate immune recognition of lentiviruses in primary human hematopoietic cells as well as discuss its relevance for LV-based ex vivo gene therapy approaches.

The 2',5'-oligoadenylate synthetase (OAS) proteins associated with endoribonuclease RNase L are components of the interferon-regulated OAS/RNase L system, which is an RNA decay pathway known to play an important role in the innate antiviral immunity. A large body of evidence suggests a critical role for the 1b isoform of the mouse Oas gene (Oas1b) in resistance to West Nile virus (WNV) infection in vivo. WNV is a positive, single-stranded RNA virus responsible for severe encephalitis in a large range of animal species and humans. To investigate the molecular basis for the sensitivity of WNV to the Oas1b antiviral pathway, we established a stable mouse fibroblastic cell clone that up-regulates Oas1b protein expression under the control of the Tet-Off expression system. We showed that murine cells respond to Oas1b expression by efficiently inhibiting WNV replication. The antiviral action of Oas1b was essentially restricted to the early stages in virus life cycle. We found that the inability of WNV to productively infect the Oas1b-expressing cells was attributable to a dramatic reduction in positive-stranded viral RNA level. Thus, Oas1b represents an antiviral pathway that exerts its inhibitory effect on WNV replication by preventing viral RNA accumulation inside infected cells.

Dengue fever and dengue hemorrhagic fever are mosquito-borne viral diseases. Dendritic cell–specific ICAM-3 grabbing nonintegrin (DC-SIGN1, encoded by CD209), an attachment receptor of dengue virus, is essential for productive infection of dendritic cells1,2. Here, we report strong association between a promoter variant of CD209, DCSIGN1-336, and risk of dengue fever compared with dengue hemorrhagic fever or population controls. The G allele of the variant DCSIGN1-336 was associated with strong protection against dengue fever in three independent cohorts from Thailand, with a carrier frequency of 4.7% in individuals with dengue fever compared with 22.4% in individuals with dengue hemorrhagic fever (odds ratio for risk of dengue hemorrhagic fever versus dengue fever: 5.84, P = 1.4 × 10−7) and 19.5% in controls (odds ratio for protection: 4.90, P = 2 × 10−6). This variant affects an Sp1-like binding site and transcriptional activity in vitro. These results indicate that CD209 has a crucial role in dengue pathogenesis, which discriminates between severe dengue fever and dengue hemorrhagic fever. This may have consequences for therapeutic and preventive strategies. Supplementary information The online version of this article (doi:10.1038/ng1550) contains supplementary material, which is available to authorized users.

Transplantation of genetically engineered, autologous hematopoietic stem and progenitor cells (HSPC) is becoming a promising alternative to allogeneic stem cell transplantation for curing genetic diseases, avoiding the risks of graft versus host disease and prolonged immunosuppression. Most clinical gene therapy protocols are based on CD34+ HSPC engineered during >2 days of ex vivo culture. By xenotransplanting mobilized peripheral blood (mPB) CD34+ HSPC, which were lentivirally (LV) marked with different fluorescent proteins according to CD38/CD90 expression levels allowing quantitative assessment of the contribution of CD38/CD90 subpopulations to hematopoietic reconstitution (n=48 NSG mice, 3 experiments), we identified 2 distinct waves of reconstitution: (1) short term repopulation (up to 2 months) mostly driven by CD34+CD38intCD90+/- cells and (2) long-term repopulation driven by CD34+CD38-CD90+ (70%) and CD34+CD38-CD90- cells (30%). Notably, an intermediate wave extending from 2 to 4 months driven by CD34+CD38low cells was selectively eliminated by prolonged ex vivo culture and could be rescued when culture time was reduced to 1 day. We therefore developed a novel LV transduction protocol able to provide curative levels of gene transfer during a single day of ex vivo culture. Stimulating CD34+ cells or CD34+CD38- cells with Prostaglandin E2 (PGE2) increased gene transfer with VSVg-pseudotyped LVs by 1.5-2 fold acting on early steps of transduction, an effect that was further potentiated by the late-acting compound Cyclosporin A. Using large-scale vector preparations for gene therapy of mucopolysaccharidosis type 1, chronic granulomatous disease or beta-thalassemia, we show by in vitro and xenotransplantation assays that a 1-day PGE2 protocol achieved similar transduction efficiencies into BM or MPB HSPC from healthy donors and patients as our 62h benchmark protocol. PGE2 treatment did not result in toxicity or skewed multi-lineage differentiation. However, shortening ex vivo culture increased engraftment levels in the NSG mouse model. To entirely avoid culturing progenitor cells, we explored the feasibility to limit ex vivo manipulation to HSC-enriched CD34+CD38- cells that may be co-transplanted with unmanipulated CD34+ progenitor cells devoid of long-term engraftment potential. This could further improve hematopoietic reconstitution, increase safety by reducing the LV integration load infused into the patient and downscale ex vivo manipulation making the process more efficient and economically sustainable. To this end, we optimized a sequential bead-based, GMP-compatible selection procedure to separate mPB into a CD34+CD38- stem and CD38+ progenitor cell fraction. We reached high purity (87+/-6.6% CD34+) and recovery of CD34+CD38- cells (37.3+/-8.7%), making their isolation clinically viable. Bead-selected CD34+CD38- cells showed higher engraftment potential than equivalent numbers of FACS-sorted cells. Co-infusion of unmanipulated (culture-sensitive) CD38+ supporter cells with genetically-engineered CD34+CD38- cells into NSG mice resulted in rapid engraftment followed by near-complete replacement of untransduced short-term repopulating progenitors by gene-marked HSPC deriving from CD34+CD38- cells after the 3rd month post-transplant. Finally, we explored ex vivo expansion of mPB CD34+CD38- cells with arylhydrocarbon receptor antagonists and/or pyrimido-indole-derivatives. These cells expanded 3-10 fold in a 7-14 d time-window, far less than seen for total CD34+ cells, thereby facilitating culture handling and reducing cost. Unlike CD34+ cells, expanded mPB CD34+CD38- cells largely maintained their SCID-repopulating potential providing proof-of-concept for the expansion of gene-modified HSC. This clinically applicable platform will improve the efficacy, safety and sustainability of ex vivo gene addition and open up new opportunities in the field of gene editing. Disclosures Ciceri: MolMed SpA: Consultancy.

"OBJECTIVE(S):. Tripartite motif-containing 22 (TRIM22) is an interferon-induced protein that inhibits HIV-1 transcription and replication in vitro. Two single nucleotide missense polymorphisms rs7935564A\/G (SNP-1) and rs1063303C\/G (SNP-2) characterize the coding sequence of human TRIM22 gene. We tested whether these variants affected the inhibitory effect of TRIM22 on HIV-1 replication and transcription and their potential association with HIV-1 disease.. DESIGN:. The allelic discrimination was determined in 182 HIV-1-negative and among HIV-1-positive individuals with advanced disease progression (advanced progressors; n = 57), normal progressors (n = 76), and long-term nonprogressors (LTNPs; n = 95).. METHODS:. Renilla luciferase activity was measured after infection of activated peripheral blood mononuclear cells (PBMCs) from an additional group of 61 blood donors with a recombinant HIV-1. HIV-1-long terminal repeat (LTR)-driven luciferase activity was tested in the presence of plasmid expressing TRIM22 variants in 293T cells. The SNP genotyping was determined by TaqMan assay.. RESULTS:. HIV-1 replication was more efficient in PBMCs from donors with SNP-1G and SNP-2G than from those with SNP-1A and SNP-2C alleles. Consistently, TRIM22-GG enhanced, whereas TRIM22-AC restricted basal HIV-1 LTR-driven transcription. In vivo, SNP-1G homozygotes and A\/G heterozygotes were more frequent in advanced progressors than in LTNPs [odds ratio (OR) = 2.072, P = 0.005] or in normal progressors (OR = 1.809, P = 0.022); in contrast, SNP-2 was not associated with any state of HIV-1 disease progression. Although SNP-2 distribution was similar among the groups, TRIM22-GG haplotype was found more frequently in advanced progressors than in LTNPs (P = 0.02).. CONCLUSION:. TRIM22 genetic diversity affects HIV-1 replication in vitro and it is a potentially novel determinant of HIV-1 disease severity."

Efficient delivery of nucleic acids into cells is a promising technique to modulate cellular gene expression for therapeutic and research applications. Cationic lipid-based liposomes represent one of the most intensively studied and employed nonviral vectors. They are positively charged at physiological pH and spontaneously self-assemble with polyanionic nucleic acids forming nanoscaled complexes named lipoplexes. Here, we draft a simple protocol for the development, characterization, optimization, and screening of liposomal formulations for in vitro gene delivery. In particular, we report as a practical example a quick method to formulate and extrude nanometer-sized unilamellar cationic vesicles composed of DOTAP as cationic lipid and DOPE as zwitterionic helper lipid at 1:1 molar ratio. The physico-chemical characterization of liposomes and lipoplexes involves the measurement of mean diameter and overall surface charge using Dynamic Light Scattering (DLS) and Laser Doppler Microelectrophoresis. The outlined transfection procedure takes into account several experimental parameters affecting the in vitro performance of gene delivery systems, paying special attention to the charge ratio (CR). Gene delivery effectiveness is evaluated both in terms of transfection efficiency and cytotoxicity of the vector to find the optimal transfection conditions. Importantly, the proposed protocol can be easily shifted to different types of nonviral vectors.

"Objective: Functional polarization of human monocyte-derived macrophages (MDMs) into M1 cells leads to inhibition of R5 HIV-1 replication and viral DNA synthesis in comparison to control, unpolarized cells together with CD4 downregulation from the cell surface and upregulation of CCR5-binding chemokine secretion. We here investigated whether a postentry restriction of virus replication is also induced by M1 polarization of MDM.. \t . . Design: MDM were first polarized to M1 cells by 18 h stimulation with interferon-[gamma] and tumor necrosis factor-[alpha]; the cytokines were then removed and the cells were infected with vesicular stomatitis virus G-protein pseudotyped enhanced green fluorescence protein HIV-1 (HIV-GFP) generating a single-round infection cycle.. \t . . Methods: HIV-1 expression was monitored in terms of eGFP expression by fluorescence activated cell sorter (FACS) analysis and real-time PCR analysis of total HIV-1 gag DNA, 2-long terminal repeat DNA, proviral DNA, and multiply spliced RNA transcripts. Expression of apolipopoprotein B mRNA-editing, enzyme-catalytic, polypeptide-like 3G (APOBEC3G), and APOBEC3A was tested by western blotting and FACS analysis.. \t . . Results: Inhibition of HIV-GFP expression was observed in M1-MDM along with impaired viral DNA synthesis, delayed proviral integration, and reduced proviral transcription. Although APOBEC3G levels were similar in M1 and unpolarized MDM, APOBEC 3A was selectively expressed only by M1 cells.. \t . . Conclusion: M1 polarization of in-vitro differentiated primary MDM determines a transient, but profound restriction of HIV-1 replication affecting multiple (entry and postentry) steps in the virus life cycle likely involving the upregulated expression of APOBEC3A."

Tripartite motif (TRIM) protein superfamily members are emerging as important effectors of the innate immune response against viral infections. In particular, TRIM22 was reported to exert antiviral activity against RNA viruses, such as hepatitis B virus (HBV), encephalomyocarditis virus (ECMV), and human immunodeficiency virus type 1 (HIV-1). We demonstrate here, for the first time, that TRIM22 is upregulated by influenza A virus (IAV) infection at both mRNA and protein levels in human alveolar epithelial A549 cells. Conversely, TRIM22 potently restricted IAV replication, in that prevention of TRIM22 expression by means of short hairpin RNA led to a 10-fold enhancement of IAV replication in these cells. Depletion of TRIM22 also reduced the anti-IAV activity of alpha interferon (IFN-α), suggesting that TRIM22 is an important IFN-stimulated gene that is required for maximal suppression of IAV by type I IFN. Furthermore, the IAV infectious titer decreased up to 100-fold in MDCK cells expressing exogenous human TRIM22. Restriction of IAV replication was accounted for by the interaction between TRIM22 and the viral nucleoprotein (NP), resulting in its polyubiquitination and degradation in a proteasome-dependent manner. Thus, TRIM22 represents a novel restriction factor upregulated upon IAV infection that curtails its replicative capacity in epithelial cells.

Efficient delivery of nucleic acids into cells is a promising technique to modulate cellular gene expression for therapeutic and research applications. Cationic lipid-based liposomes represent one of the most intensively studied and employed nonviral vectors. They are positively charged at physiological pH and spontaneously self-assemble with polyanionic nucleic acids forming nanoscaled complexes named lipoplexes. Here, we draft a simple protocol for the development, characterization, optimization, and screening of liposomal formulations for in vitro gene delivery. In particular, we report as a practical example a quick method to formulate and extrude nanometer-sized unilamellar cationic vesicles composed of DOTAP as cationic lipid and DOPE as zwitterionic helper lipid at 1:1 molar ratio. The physico-chemical characterization of liposomes and lipoplexes involves the measurement of mean diameter and overall surface charge using Dynamic Light Scattering (DLS) and Laser Doppler Microelectrophoresis. The outlined transfection procedure takes into account several experimental parameters affecting the in vitro performance of gene delivery systems, paying special attention to the charge ratio (CR). Gene delivery effectiveness is evaluated both in terms of transfection efficiency and cytotoxicity of the vector to find the optimal transfection conditions. Importantly, the proposed protocol can be easily shifted to different types of nonviral vectors.

The development in an extremely short time of an efficacious and safe vaccine against the pandemi A/H1N1 virus was a challenge that involved the entire scientific community.To assess the immunological and clinical efficacy of the new H1N1v monovalent influenza vaccine (Focetria Novartis Vaccines, Siena, Italy) in a group of health care workers (HCWs).A total of 148 volunteer HCWs were enrolled between Mid-Novembre 2009 and December 2009. After measuring antibody titers, a single intramuscular dose of 7.5 microg of Focetria monovalent vaccine against A/H1N1/2009 influenza virus with MF59C.1 adjuvant was administered.Antibody titers (median value) before and after a single dose of vaccine, measured by means of standard beam-agglutination inhibition test (HAI), increased from 32 to 256 (p0.001). After vaccination, 79.7% of the subjects showed antibody seroconversion, and in 97.3% seroprotection was achieved. The ratio between the geometric means of antibody titers (GMTR) was 6.69. For the 3 subjects who reported symptoms of ILI (Influenza-like illness), a regular nasal-pharyngeal swab sample was taken to identify the virus type by RT-PCR, the laboratory results of tests performed on these samples were negative for pandemic A/H1N1/2009 virus. During the entire follow-up period of 6 months no severe adverse events occurred.The vaccine against pandemic A/H1N1/2009 virus provided protection against the virus and not only contributed to a significant immunization (according to EMEA criteria), but kept all 148 subjects under study free from A/H1N1/2009 influenza illness.

Phytohemagglutin-stimulated child and adult leukocytes equally supported CCR5-dependent (R5) and CXCR4-dependent (X4) HIV-1 replication. In contrast, when phytohemagglutin-stimulated leukocytes from either healthy or congenitally immunodeficient children were cultured on feeder cells, they well supported R5, but not X4 HIV-1 replication, whereas both viruses equally spread in adult cells maintained in similar conditions. Both child and adult cells showed similar levels of proliferation and surface expression of CD4, CCR5, CXCR4, CD25, CD69, and HLA-DR. Lack of X4 HIV-1 replication in child versus adult cells was not caused by a differential expression of several known HIV-1 restriction factors. Similar levels of HIV DNA synthesis occurred in child cells infected with R5 and X4 viruses up to 48 hours after infection when R5 HIV-1 showed a significantly superior capacity to spread in culture than X4 virus. Cultured child cells well supported single round vescicular stomatitis virus-G pseudotyped virus replication, whereas superinfection of R5-infected cells with X4 HIV-1 (or vice versa) rescued the replication of this latter virus. Thus, child cells exposed to feeder cell culture represent a novel model system in which the superior capacity of R5 versus X4 viruses to spread can be investigated in primary, untransformed CD4(+) cells. (Blood. 2012; 119(9): 2013-2023) Phytohemagglutin-stimulated child and adult leukocytes equally supported CCR5-dependent (R5) and CXCR4-dependent (X4) HIV-1 replication. In contrast, when phytohemagglutin-stimulated leukocytes from either healthy or congenitally immunodeficient children were cultured on feeder cells, they well supported R5, but not X4 HIV-1 replication, whereas both viruses equally spread in adult cells maintained in similar conditions. Both child and adult cells showed similar levels of proliferation and surface expression of CD4, CCR5, CXCR4, CD25, CD69, and HLA-DR. Lack of X4 HIV-1 replication in child versus adult cells was not caused by a differential expression of several known HIV-1 restriction factors. Similar levels of HIV DNA synthesis occurred in child cells infected with R5 and X4 viruses up to 48 hours after infection when R5 HIV-1 showed a significantly superior capacity to spread in culture than X4 virus. Cultured child cells well supported single round vescicular stomatitis virus-G pseudotyped virus replication, whereas superinfection of R5-infected cells with X4 HIV-1 (or vice versa) rescued the replication of this latter virus. Thus, child cells exposed to feeder cell culture represent a novel model system in which the superior capacity of R5 versus X4 viruses to spread can be investigated in primary, untransformed CD4(+) cells.

The interferon-inducible 2′,5′-oligoadenylate synthetase 1b (Oas1b) protein inhibits West Nile virus (WNV) infection by preventing viral RNA (vRNA) accumulation in infected cells. Serial passage of WNV in Oas1b-expressing mouse cells selected a virus variant with improved growth capacity. Two major amino acid substitutions were identified in this Oas1b-resistant WNV variant: NS3-S365G in the ATPase/helicase domain of NS3 and 2K-V9M in the C-terminal segment of NS4A. To assess their effect on antiviral activity of Oas1b, the NS3 and 2K mutations were engineered into an infectious WNV cDNA clone. The NS3 mutation alters requirement of ATP for ATPase activity and attenuates Oas1b-mediated suppression of vRNA accumulation. However, growth of NS3-mutant virus remains impaired in Oas1b-expressing cells. Only the 2K-V9M mutation efficiently rescued viral growth by promoting vRNA replication. Thus, WNV resistance to Oas1b antiviral action could be attributed to the 2K-V9M substitution with a potential role of NS3-S365G through rescue of vRNA accumulation. © 2009 Elsevier Inc. All rights reserved.

There are significant antigenic differences within subtypes that change over time as these viruses evolve, and this requires a semi-annual review and frequent update of vaccine strain candidates for human seasonal influenza vaccines. The degree of relatedness between the strains contained in the seasonal vaccine and the drifted strains that are isolated the following year is assessed through cross haemagglutination inhibition (HI) tests. If the results of these tests suggest that cross HI levels are low, the vaccine is updated to include the most recent strains. We reasoned that if a semi-annual review of the antigenic characteristics of human H1 and H3 viruses is necessary

Background Despite the use of currently optimized lipofection conditions, including transfection in serum-depleted media, the efficiency of gene transfer is low and high transfection rates often induce cytotoxicity. A lipid formulation with transfection efficiency not inhibited by serum would provide an advance towards in vivo applications. Methods We explored the ability of the cationic lipid SH-14 to dimerize upon DNA and form lipoplexes, and potentially release nucleic acids in the intracellular reducing milieu. We investigated the critical micelle-forming concentration of SH-14 and its intrinsic toxicity, size and Zeta potential measurements, the in vitro cytotoxicity of SH-14/plasmid DNA lipoplexes and their ability to transfect cells. Results Among all the charge ratios (CR, + /−) tested, lipoplexes at CR 10 with a mean diameter of 295 nm and a surface charge of + 20 mV, exhibited the best compromise between transfection efficiency and tolerability. SH-14 presented the same cytotoxicity level whether alone or complexed in lipoplexes. Lipofections carried out in serum-free medium shared a transfection efficiency, on average, of 40% and a cytotoxicity of 38%. An increase of 73% in transfection efficiency and 24% in cell viability were obtained, extending lipofection over 48 h in complete-medium. Moreover, when serum concentration was increased from 10% to 50%, a three-fold increase in plasmid dose led to more than 72% of cells being transfected with almost no sign of cytotoxicity. Conclusions Overall, SH-14 presents good potential as a novel transfection reagent to be used in the presence of serum. Copyright © 2008 John Wiley & Sons, Ltd.

Herpes simplex virus type 1 (HSV-1) and HSV-2 are neurotropic viruses and common human pathogens causing major public health problems such as genital herpes, a sexually transmitted disease also correlated with increased transmission and replication of human immunodeficiency virus type 1 (HIV-1). Therefore, compounds capable of blocking HIV-1, HSV-1, and HSV-2 transmission represent candidate microbicides with a potential added value over that of molecules acting selectively against either infection. We report here that sulfated derivatives of the Escherichia coli K5 polysaccharide, structurally highly similar to heparin and previously shown to inhibit HIV-1 entry and replication in vitro, also exert suppressive activities against both HSV-1 and HSV-2 infections. In particular, the N,O-sulfated [K5-N,OS(H)] and O-sulfated epimerized [Epi-K5-OS(H)] forms inhibited the infection of Vero cells by HSV-1 and -2, with 50% inhibitory concentrations (IC 50 ) between 3 ± 0.05 and 48 ± 27 nM, and were not toxic to the cells at concentrations as high as 5 μM. These compounds impaired the early steps of HSV-1 and HSV-2 virion attachment and entry into host cells and reduced the cell-to-cell spread of HSV-2. Since K5-N,OS(H) and Epi-K5-OS(H) also inhibit HIV-1 infection, they may represent valid candidates for development as topical microbicides preventing sexual transmission of HIV-1, HSV-1, and HSV-2.