Weitao Huang

Requirement of Interleukin-17A for Systemic Anti-Candida albicans Host Defense in Mice

T cells are required for normal host defense against fungal infection, and individuals with T cell-deficiency syndromes are highly susceptible to fungal pathogens. Interleukin (IL)-17A is a proinflammatory cytokine that interconnects myeloid and lymphoid host defense. The role of murine (m) IL-17A/mIL-17A receptor (R) interactions was evaluated in a murine model of systemic candidiasis. In response to systemic challenge with Candida albicans, expression of mIL-17A was induced, and IL-17AR knockout (IL-17AR(-/-)) mice had dose-dependent, substantially reduced survival. Fungal burden in the kidneys of IL-17AR(-/-) mice was dramatically increased (25-fold at 96 h). In IL-17AR(-/-) mice, both mobilization of peripheral neutrophils and their influx to infected organs were significantly impaired and delayed. In vivo expression of mIL-17A protected normal mice from a lethal dose of C. albicans (100% at day 7 and 65% at day 42). The data suggest that the mIL-17A/mIL-17AR system is required for normal fungal host defense in vivo. IL-17A could have potential as a therapeutic cytokine for systemic C. albicans infections in immunocompromised patients with cancer or advanced acquired immunodeficiency syndrome.

Requirement of endogenous stem cell factor and granulocyte-colony-stimulating factor for IL-17-mediated granulopoiesis.

IL-17 is a novel, CD4+ T cell-restricted cytokine. In vivo, it stimulates hematopoiesis and causes neutrophilia consisting of mature granulocytes. In this study, we show that IL-17-mediated granulopoiesis requires G-CSF release and the presence or induction of the transmembrane form of stem cell factor (SCF) for optimal granulopoiesis. However, IL-17 also protects mice from G-CSF neutralization-induced neutropenia. G-CSF neutralization completely reversed IL-17-induced BM progenitor expansion, whereas splenic CFU-GM/CFU-granulocyte-erythrocyte-megakaryocyte-monocyte was only reduced by 50% in both Sl/Sld and littermate control mice. Thus, there remained a significant SCF/G-CSF-independent effect of IL-17 on splenic granulopoiesis, resulting in a preservation of mature circulating granulocytes. IL-17 is a cytokine that potentially interconnects lymphocytic and myeloid host defense and may have potential for therapeutic development.

Requirement of IL-17 Receptor Signaling in Radiation-Resistant Cells in the Joint for Full Progression of Destructive Synovitis

IL-17 is a proinflammatory cytokine suspected to be involved in inflammatory and autoimmune diseases such as rheumatoid arthritis. In the present study, we report that IL-17R signaling is required in radiation-resistant cells in the joint for full progression of chronic synovitis and bone erosion. Repeated injections of Gram-positive bacterial cell wall fragments (streptococcal cell wall) directly into the knee joint of naive IL-17R-deficient (IL-17R−/−) mice had no effect on the acute phase of arthritis but prevented progression to chronic destructive synovitis as was noted in wild-type (wt) mice. Microarray analysis revealed significant down-regulation of leukocyte-specific chemokines, selectins, cytokines, and collagenase-3 in the synovium of IL-17R−/− mice. Bone marrow (BM) chimeric mice revealed the need for IL-17R expression on radiation-resistant joint cells for destructive inflammation. Chimeric mice of host wt and donor IL-17R−/− BM cells developed destructive synovitis in this chronic reactivated streptococcal cell wall arthritis model similar to wt→wt chimeras. In contrast, chimeric mice of host IL-17R−/− and donor wt BM cells were protected from chronic destructive arthritis similar as IL-17R−/−→IL-17R−/− chimeras. These data strongly indicate that IL-17R signaling in radiation-resistant cells in the joint is required for turning an acute macrophage-mediated inflammation into a chronic destructive synovitis.

IL-17 Mobilizes Peripheral Blood Stem Cells with Short- and Long-Term Repopulating Ability in Mice

Autologous and allogeneic bone marrow transplantations have evolved as important cancer therapy modalities. For both indications, peripheral blood has been shown to have distinct advantages over bone marrow as the stem cell source. Cytokine combinations for mobilization have enhanced stem cell yield and accelerated engraftment. However, novel mobilizing agents and strategies are needed to further improve clinical outcomes. Within the donor graft, the dynamic equilibrium between T cells and stem cells critically influences engraftment and transplantation results. IL-17 is a cytokine produced almost exclusively from activated T cells. IL-17 was expressed in vivo with adenovirus technology. Here, proof-of-principle studies demonstrate that IL-17 effectively mobilizes hemopoietic precursor cells (CFU-granulocyte-erythrocyte-macrophage-monocyte, CFU-high proliferative potential) and primitive hemopoietic stem cells (Lin−/lowc-kit+Sca1+). Moreover, mouse IL-17 adenovirus-mobilized peripheral blood stem cells rescued lethally irradiated mice. Bone marrow was found to be 45–75% of donor origin at 1 year. In secondary recipients, donor-derived bone marrow cells ranged from 45 to 95%. These data show that IL-17 mobilizes stem cells in mice with short- and long-term reconstituting capacity. Additional comparative studies are needed as well as studies in tumor models to refine distinct potential clinical applications for IL-17-mobilized peripheral blood stem cells.

IL-17F/IL-17R interaction stimulates granulopoiesis in mice

OBJECTIVE IL-17F, a member of the interleukin (IL)-17 cytokine family, most closely resembles IL-17A structurally. IL-17A is a potent stimulator of granulopoiesis; its expression is induced in response to microbial challenge. Although IL-17F is considered to be a weak IL-17A analog that is also mediating its effect via IL-17R, its exact role and in vivo functions are unknown. Our goal was to determine the in vivo activity of IL-17F on granulopoiesis as well as on release of granulopoiesis-stimulating downstream cytokines in mice and directly compare its effect to IL-17A. MATERIALS AND METHODS Murine IL-17A (mIL-17A) or IL-17F (mIL-17F) was expressed in vivo in C57BL6 mice using adenoviral gene transfer technology. Peripheral cell counts were assessed as well as hematopoietic precursors using colony-forming assays at set time points. Downstream cytokines were measured using enzyme-linked immunosorbent assay and reverse transcriptase polymerase chain reaction. RESULTS We found mIL-17F to have similar expression kinetics as mIL-17A in splenocytes in vitro and in vivo, following challenge with microbial agents. Overexpression of mIL-17F in vivo resulted in similar neutrophilia and only in slightly reduced myeloid progenitor expansion when compared to mIL-17A. In vivo, there was no difference in releases for granulocyte-macrophage colony-stimulating factor; regulated on activation, normal T expressed and secreted; interferon-inducible protein-10; IL-6; and monocyte chemotactic protein-1 between either cytokine. IL-1A, macrophage inflammatory protein -2 (MIP), KC, and granulocyte colony-stimulating factor expression was approximately half of that seen with mIL-17A. CONCLUSION Both IL-17A and IL-17F are induced by similar stimuli, have similar expression kinetics and despite only minimal in vitro activity for IL-17F, surprisingly they exert similar in vivo bioactivity. IL-17F bioactivity appears to be augmented in vivo through mechanisms that require further investigation.

Poly-l-lysine-Based Molecular Conjugate Vectors: A High Efficiency Gene Transfer System for Human Progenitor and Leukemia Cells

Background:Targeted, specific receptor mediated gene transfer is a major goal of gene therapy research to accomplish gene transfer exclusively to the desired cell population. Methods:First, the use of natural receptor for stem cell factor and transferrin receptor-targeted gene transfer using poly-l-lysine–based molecular conjugate vectors was evaluated in a panel of hematopoietic progenitor cell lines. Second, the ability of poly-l-lysine to enhance adenovirus mediated gene transfer efficiency was examined in different cell lines by using recombinant adenovirus-poly-l-lysine molecular conjugate conglomerates (recMCVEGFP). Results:Despite effective ligand internalization receptor, gene expression amplification in receptor positive cell lines was not uniformly observed. Therefore, using a poly-l-lysine–based, receptor-targeted vector, neither transferrin nor natural receptor for stem cell factor mediated gene transfer can be considered a universally applicable procedure that exclusively depends on the presence of receptors on the cell surface; rather, it is a cell specific phenomenon. In our model, poly-l-lysine is the major contributor for gene transfer to hematopoietic progenitor cells, mediating the initial vector-cell binding. Human progenitor cell lines are poorly transduceable with recombinant adenovirus vectors. This new poly-l-lysine–modified, adenovirus-based vector could overcome virus tropism restrictions and consistently achieve very high transduction efficiency (>90%) in cells otherwise refractory to adenovirus gene transfer. Conclusions:Polylysine-based adenovirus vectors may have promise for situations in which high-efficiency gene transfer with transient high level transgene expression in hematopoietic cells is needed, such as leukemia vaccine protocols or for purging strategies in leukemia cell contaminated stem cell preparations.

Efficient c-kit Receptor-Targeted Gene Transfer to Primary Human CD34-Selected Hematopoietic Stem Cells

ABSTRACT We have previously reported effective gene transfer with a targeted molecular conjugate adenovirus vector through the c-kit receptor in hematopoietic progenitor cell lines. However, a c-kit-targeted recombinant retroviral vector failed to transduce cells, indicating the existence of significant differences for c-kit target gene transfer between these two viruses. Here we demonstrate that conjugation of an adenovirus to a c-kit-retargeted retrovirus vector enables retroviral transduction. This finding suggests the requirement of endosomalysis for successful c-kit-targeted gene transfer. Furthermore, we show efficient gene transfer to, and high transgene expression (66%) in, CD34-selected, c-kit+ human peripheral blood stem cells using a c-kit-targeted adenovirus vector. These findings may have important implications for future vector development in c-kit-targeted stem cell gene transfer.

Flagellin Encoded in Gene-Based Vector Vaccines Is a Route-Dependent Immune Adjuvant

Flagellin has been tested as a protein-based vaccine adjuvant, with the majority of studies focused on antibody responses. Here, we evaluated the adjuvant activity of flagellin for both cellular and humoral immune responses in BALB/c mice in the setting of gene-based immunization, and have made several novel observations. DNA vaccines and adenovirus (Ad) vectors were engineered to encode mycobacterial protein Ag85B, with or without flagellin of Salmonella typhimurium (FliC). DNA-encoded flagellin given IM enhanced splenic CD4+ and CD8+ T cell responses to co-expressed vaccine antigen, including memory responses. Boosting either IM or intranasally with Ad vectors expressing Ag85B without flagellin led to durable enhancement of Ag85B-specific antibody and CD4+ and CD8+ T cell responses in both spleen and pulmonary tissues, correlating with significantly improved protection against challenge with pathogenic aerosolized M. tuberculosis. However, inclusion of flagellin in both DNA prime and Ad booster vaccines induced localized pulmonary inflammation and transient weight loss, with route-dependent effects on vaccine-induced T cell immunity. The latter included marked reductions in levels of mucosal CD4+ and CD8+ T cell responses following IM DNA/IN Ad mucosal prime-boosting, although antibody responses were not diminished. These findings indicate that flagellin has differential and route-dependent adjuvant activity when included as a component of systemic or mucosally-delivered gene-based prime-boost immunization. Clear adjuvant activity for both T and B cell responses was observed when flagellin was included in the DNA priming vaccine, but side effects occurred when given in an Ad boosting vector, particularly via the pulmonary route.

Gene-based neonatal immune priming potentiates a mucosal adenoviral vaccine encoding mycobacterial Ag85B

Tuberculosis remains a major public health hazard worldwide, with neonates and young infants potentially more susceptible to infection than adults. BCG, the only vaccine currently available, provides some protection against tuberculous meningitis in children but variable efficacy in adults, and is not safe to use in immune compromised individuals. A safe and effective vaccine that could be given early in life, and that could also potentiate subsequent booster immunization, would represent a significant advance. To test this proposition, we have generated gene-based vaccine vectors expressing Ag85B from Mycobacterium tuberculosis (Mtb) and designed experiments to test their immunogenicity and protective efficacy particularly when given in heterologous prime-boost combination, with the initial DNA vaccine component given soon after birth. Intradermal delivery of DNA vaccines elicited Th1-based immune responses against Ag85B in neonatal mice but did not protect them from subsequent aerosol challenge with virulent Mtb H37Rv. Recombinant adenovirus vectors encoding Ag85B, given via the intranasal route at six weeks of age, generated moderate immune responses and were poorly protective. However, neonatal DNA priming following by mucosal boosting with recombinant adenovirus generated strong immune responses, as evidenced by strong Ag85B-specific CD4+ and CD8+ T cell responses, both in the lung-associated lymph nodes and the spleen, by the quality of these responding cells (assessed by their capacity to secrete multiple antimicrobial factors), and by improved protection, as indicated by reduced bacterial burden in the lungs following pulmonary TB challenge. These results suggest that neonatal immunization with gene-based vaccines may create a favorable immunological environment that potentiates the pulmonary mucosal boosting effects of a subsequent heterologous vector vaccine encoding the same antigen. Our data indicate that immunization early in life with mycobacterial antigens in an appropriate vaccine setting can prime for protective immunity against Mtb.

Requirement of local synovial IL-17 receptor signaling in the progression of chronic synovitis and bone erosion in arthritis

IL-17 is a proinflammatory cytokine that is suspected to be involved in development of rheumatoid arthritis (RA). However, the role of IL-17–IL-17 receptor signaling in the effector phase of arthritis, including requirement of this signaling pathway in synoviocytes, is still not fully elucidated. Here we demonstrate, using IL-17 receptor deficient (IL-17R-/-) mice, a requirement for IL-17R signaling in immune reactivity and progression of synovitis and bone erosion in a T cell mediated mBSA arthritis model and chronic streptococcal cell wall arthritis. Of great interest, chimeric mice of host wild-type (wt) and donor IL-17R-/- bone marrow (BM) cells developed chronic synovitis similar to that in wt/wt chimeras. In contrast, chimeric mice of host IL-17R-/- and donor wt BM cells were protected from progressive synovitis similar to IL-17R-/-/ IL-17R-/- chimeras, suggesting a crucial role of resident synovial cells. Weakened mobilization of neutrophils into the joint and downregulation of synovial mRNA expression for leukocyte specific chemokines and selectins, and MMP-1 was found in IL-17R-/- mice. These data suggest that, in addition to the role played by IL-17–IL-17R signaling in development of immunity, synovial IL-17–IL-17R signaling plays a critical role in the effector phase of arthritis. Activation of IL-17R on fibroblast-like synoviocytes appears pivotal.