Centrifugation facilitates transduction of green fluorescent protein in human monocytes and macrophages by adenovirus at low multiplicity of infection

The role of small leucine zipper protein in osteoclastogenesis and its involvement in bone remodeling

Bone remodeling is critical to maintain the quality of bone tissues and to heal bone tissue injury. Osteoclasts and osteoblasts are special types of cells involved in this event. In particular, the resorption activity of mature osteoclasts is required for the formation of new bones. Human small leucine zipper protein (sLZIP) is known to induce the osteoblast differentiation of mesenchymal stem cells. However, the roles of sLZIP in osteoclast differentiation and bone remodeling have not been explored. In this study, we investigated the roles of sLZIP in regulating osteoclast formation and in the bone remodeling process using sLZIP transgenic (TG) mice. Tibiae from sLZIP TG mice contained more osteoclasts than those from wild type (WT) mice. Bone marrow-derived macrophages (BMM) from sLZIP TG mice showed increased differentiation into osteoclasts compared with BMM from WT mice. sLZIP bound to the promotor and induced the expression of nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1) and its target osteoclastogenic genes. To understand the role of sLZIP in bone remodeling, a bone-defect model was generated. Results of micro-CT scanning and histologic analysis demonstrated that sLZIP TG mice have faster bone formation during healing compared with WT mice. Notably, the soft callus around the defect area was replaced faster by hard callus in sLZIP TG mice than in WT mice. These findings suggest that sLZIP promotes osteoclast differentiation and plays an important role in bone remodeling.

Preexisting Virus-Specific T Lymphocytes-Mediated Enhancement of Adenovirus Infections to Human Blood CD14+ Cells

Antigen-specific T lymphocytes play a critical role in controlling viral infections. However, we report here that preexisting virus-specific T cell responses also contribute to promoting adenovirus (Ad) infection. Previously, we found that CD14+ monocytes from Ad-seropositive individuals exhibited an increased susceptibility to Ad infection, when compared with that of Ad-seronegative individuals. But the underlying mechanisms for this enhancement of viral infection are not completely clarified. In this study, we found that the efficacy of Ad infection into CD14+ monocytes was significantly decreased after CD3+ T lymphocytes depletion from PBMC samples of Ad-seropositive individuals. In contrast, adding virus-specific CD3+ T lymphocytes into PBMC samples of Ad-seronegative individuals resulted in a significant increase of infection efficacy. CD3+ T lymphocytes in PBMC samples from Ad-seropositive individuals were more sensitive to be activated by adenovirus stimulus, characterized by upregulation of multiple cytokines and activation markers and also enhancement of cell proliferation. Further studies demonstrated that GM-CSF and IL-4 can promote Ad infection by up-regulating the expression of scavenger receptor 1 (SR-A) and integrins αVβ5 receptor of CD14+ cells. And taken together, these results suggest a novel role of virus-specific T cells in mediating enhancement of viral infection, and provide insights to understand the pathogenesis and complicated interactions between viruses and host immune cells.

Inhibition of porcine reproductive and respiratory syndrome virus infection by recombinant adenovirus- and/or exosome-delivered the artificial microRNAs targeting sialoadhesin and CD163 receptors

Background

The current vaccines failed to provide substantial protection against porcine reproductive and respiratory syndrome (PRRS) and the new vaccine development faces great challenges. Sialoadhesin (Sn) and CD163 are the two key receptors for PRRS virus (PRRSV) infection of porcine alveolar macrophages (PAMs), but the artificial microRNA (amiRNA) strategy targeting two viral receptors has not been described.

Methods

The candidate miRNAs targeting Sn or CD163 receptor were predicted using a web-based miRNA design tool and validated by transfection of cells with each amiRNA expression vector plus the reporter vector. The amiRNA-expressing recombinant adenoviruses (rAds) were generated using AdEasy Adenoviral Vector System. The rAd transduction efficiencies for pig cells were measured by flow cytometry and fluorescent microscopy. The expression and exosome-mediated secretion of amiRNAs were detected by RT-PCR. The knock-down of Sn or CD163 receptor by rAd- and/or exosome-delivered amiRNA was detected by quantitative RT-PCR and flow cytometry. The additive anti-PRRSV effect between the two amiRNAs was detected by quantitative RT-PCR and viral titration.

Results

All 18 amiRNAs validated were effective against Sn or CD163 receptor mRNA expression. Two rAds expressing Sn- or CD163-targeted amiRNA were generated for further study. The maximal rAd transduction efficiency was 62% for PAMs at MOI 800 or 100% for PK-15 cells at MOI 100. The sequence-specific amiRNAs were expressed efficiently in and secreted from the rAd-transduced cells via exosomes. The expression of Sn and CD163 receptors was inhibited significantly by rAd transduction and/or amiRNA-containing exosome treatment at mRNA and protein levels. Both PRRSV ORF7 copy number and viral titer were reduced significantly by transduction of PAMs with the two rAds and/or by treatment with the two amiRNA-containing exosomes. The additive anti-PRRSV effect between the two amiRNAs was relatively long-lasting (96 h) and effective against three different viral strains.

Conclusion

These results suggested that Sn- and CD163-targeted amiRNAs had an additive anti-PRRSV effect against different viral strains. Our findings provide new evidence supporting the hypothesis that exosomes can also serve as an efficient small RNA transfer vehicle for pig cells.

Novel ex vivo culture method for human monocytes uses shear flow to prevent total loss of transendothelial diapedesis function

Monocyte recruitment to inflammatory sites and their transendothelial migration into tissues are critical to homeostasis and pathogenesis of chronic inflammatory diseases. However, even short-term suspension culture of primary human monocytes leads to phenotypic changes. In this study, we characterize the functional effects of ex vivo monocyte culture on the steps involved in monocyte transendothelial migration. Our data demonstrate that monocyte diapedesis is impaired by as little as 4 h culture, and the locomotion step is subsequently compromised. After 16 h in culture, monocyte diapedesis is irreversibly reduced by ∼90%. However, maintenance of monocytes under conditions mimicking physiological flow (5-7.5 dyn/cm²) is sufficient to reduce diapedesis impairment significantly. Thus, through the application of shear during ex vivo culture of monocytes, our study establishes a novel protocol, allowing functional analyses of monocytes not currently possible under static culture conditions. These data further suggest that monocyte-based therapeutic applications may be measurably improved by alteration of ex vivo conditions before their use in patients.

Circumventing antivector immunity by using adenovirus-infected blood cells for repeated application of adenovirus-vectored vaccines: proof of concept in rhesus macaques

Adenovirus has been extensively exploited as a vector platform for delivering vaccines. However, preexisting antiadenovirus immunity is the major stumbling block for application of adenovirus-vectored vaccines. In this study, we found that freshly isolated peripheral blood mononuclear cells (PBMCs), mostly CD14(+) cells, from adenovirus serotype 5 (Ad5)-seropositive primates (humans and rhesus macaques) can be efficiently infected with Ad5 in vitro. On the basis of this observation, a novel strategy based on adenoviral vector-infected PBMC (AVIP) immunization was explored to circumvent antivector immunity. Autologous infusion of Ad5-SIVgag-infected PBMCs elicited a strong Gag-specific cellular immune response but induced weaker Ad5-neutralizing antibody (NAb) in Ad5-seronegative macaques than in macaques intramuscularly injected with Ad5-SIVgag. Moreover, Ad5-seropositive macaques receiving multiple AVIP immunizations with Ad5-SIVenv, Ad5-SIVgag, and Ad5-SIVpol vaccines elicited escalated Env-, Gag-, and Pol-specific immune responses after each immunization that were significantly greater than those in macaques intramuscularly injected with these Ad5-SIV vaccines. After challenged intravenously with a highly pathogenic SIVmac239 virus, macaques receiving AVIP immunization demonstrated a significant reduction in viral load at both the peak time and set-point period compared with macaques without Ad5-SIV vaccines. Our study warranted further research and development of the AVIP immunization as a platform for repeated applications of adenovirus-vectored vaccines.

Trafficking CD11b-positive blood cells deliver therapeutic genes to the brain of amyloid-depositing transgenic mice

A major question for gene therapy in brain concerns methods to administer therapeutic genes in a uniform manner over major portions of the brain. A second question in neuroimmunology concerns the extent to which monocytes migrate to the CNS in degenerative disorders. Here we show that CD11b+ cells (largely monocytes) isolated from the bone marrow of GFP (green fluorescent protein)-expressing donors spontaneously home to compacted amyloid plaques in the brain. Injections of these cells as a single pulse show a rapid clearance from circulation (90 min half-life) and tissue residence half-lives of approximately 3 d. The uptake into brain was minimal in nontransgenic mice. In transgenic mice containing amyloid deposits, uptake was dramatically increased and associated with a corresponding decrease in monocyte uptake into peripheral organs compared to nontransgenic littermates. Twice weekly infusions of the CD11b+ bone marrow cells transfected with a genetically engineered form of the protease neprilysin completely arrest amyloid deposition in an aggressively depositing transgenic model. Exploiting the natural homing properties of peripherally derived blood cells to deliver therapeutic genes has the advantages of access to the entire CNS, expression largely restricted to sites of injury, low risk of immune reactivity, and fading of expression if adverse reactions are encountered. These observations support the feasibility of testing autologous monocytes for application of therapeutic genes in human CNS disease. Moreover, these data support the results from bone marrow grafts that circulating CD11b+ cells can enter the CNS without requiring the use of lethal irradiation.

The anti-inflammatory effects of interleukin-4 are not mediated by suppressor of cytokine signalling-1 (SOCS1)

While it is known that the anti-inflammatory effects of interleukin (IL)-4 require new protein synthesis, the exact mechanisms by which IL-4 suppresses the production of pro-inflammatory cytokines by human monocytes and macrophages is unclear. IL-4 rapidly induced suppressor of cytokine signalling-1 (SOCS1) mRNA and protein, which peaked at 60 min, much earlier than lipopolysaccharide (LPS)-induced SOCS1 mRNA and protein which were consistently maximal 4 hr post-exposure. SOCS1 is a molecule generally considered to be induced for negative feedback of inflammatory processes. We investigated whether the early induction of SOCS1 by IL-4 was responsible for the suppression of LPS-induced tumour necrosis factor (TNF)-alpha production by IL-4. IL-4 suppressed LPS-induced TNF-alpha in freshly isolated monocytes at the level of transcription but acted by a different, possibly translational, mechanism in monocytes cultured overnight in macrophage colony-stimulating factor (M-CSF). Despite different modes of regulation by IL-4, the kinetics and magnitude of induction of SOCS1 mRNA and protein by IL-4 in the two cell types were identical. There was no significant difference in the suppression by IL-4 of LPS-induced TNF-alpha production by bone-marrow derived macrophages from wild-type mice, Ifngamma(-/-) mice and mice lacking SOCS1 (Socs1(-/-)Ifngamma(-/-)). These data suggest that SOCS1 is not involved in the suppression of LPS-induced TNF-alpha production by IL-4.

Inhibition of porcine reproductive and respiratory syndrome virus replication by adenovirus-mediated RNA interference both in porcine alveolar macrophages and swine

Porcine reproductive and respiratory syndrome virus (PRRSV) has been mainly responsible for the heavy economic losses in many swine-producing regions. Current vaccination strategies and antiviral drugs provide only limited protection. Consequently, there is a need to develop a new antiviral strategy. In this study, two recombinant adenoviruses expressing short-hairpin RNAs (shRNAs) directed against ORF1b of PRRSV S1 strain were constructed and the inhibition of PRRSV replication was determined. The results showed that pretreatment with these shRNAs delivered by recombinant adenovirus could induce a significant inhibition of viral RNA and protein level in Marc-145 cells infected with PRRSV S1 strains. One recombinant adenovirus (rAd-P2) was found to be also effective in inhibiting the replication of highly virulent PRRSV SY0608 strain in Marc-145 cells and porcine alveolar macrophages at both the protein and ORF1b mRNA level. The antiviral effect was dose-dependent and sustained for at least 96h. Twenty 6-week old piglets were assigned to four groups each with five piglets. Groups 1 and 2 were inoculated intramuscularly with rAd-P2 and mock construct rAd-mP2 individually. After 24h, groups 1, 2 and 3 were challenged intramuscularly with the SY0608 strain. Group 4 remained unchallenged but with PBS as mock. The results showed that the viral load of PRRSV in serum and lung tissue of swine was suppressed effectively by rAd-P2. The clinical signs and pathological lesions in the pigs inoculated with rAd-P2 were milder than those in rAd-mP2 negative and PRRSV control. These results indicated that shRNAs mediated by the adenovirus could inhibit PRRSV infection sufficiently in vitro as well as in vivo. RNAi mediated by recombinant adenovirus might be a potential new tool for controlling PRRSV infection. Of course, the protective efficiency of rAd-P2 should be made by using a large number of pigs in future.

The expression of exogenous genes in macrophages: obstacles and opportunities

Over the past three decades many techniques for expressing exogenous genes in a variety of cells and cell lines have been developed. Exogenous gene expression in macrophages has lagged behind that of other nonhematopioetic cells. There are many reasons for this, but most are due to technical difficulties associated with transfecting macrophages. As professional phagocytes, macrophages are endowed with many potent degradative enzymes that can disrupt nucleic acid integrity and make gene transfer into these cells an inefficient process. This is especially true of activated macrophages which undergo a dramatic change in their physiology following exposure to immune or inflammatory stimuli. Viral transduction of these cells has been hampered because macrophages are end-stage cells that generally do not divide; therefore, some of the vectors that depend on integration into a replicative genome have met with limited success. Furthermore, macrophages are quite responsive to "danger signals," and therefore several of the original viral vectors that were used for gene transfer induced potent anti-viral responses in these cells making these vectors inappropriate for gene delivery. Many of these difficulties have been largely overcome, and relatively high efficiency gene expression in primary human or murine macrophages is becoming more routine. In the present chapter we discuss some of the gene expression techniques that have met with success and review the advantages and disadvantages of each.

SOCS1 regulates the IFN but not NFkappaB pathway in TLR-stimulated human monocytes and macrophages

SOCS1 can regulate TLR-mediated signal transduction, yet mechanistic studies in murine macrophages have been confusing and contradictory. This study has used an adenoviral transfection system to determine the role of SOCS1 in the regulation of TNF-alpha production by activated human monocytes. Monocytes were infected with AdV-SOCS1 or with an empty vector control, AdV-GFP, for 24 h before activation with the TLR4 ligand, LPS. SOCS1 did not regulate TNF-alpha mRNA or protein production within the first two hours of TLR4 activation. However, SOCS1 suppressed the sustained production of TNF-alpha by primary human monocytes and synovial fluid macrophages ex vivo. In addition, SOCS1 regulated the production of IL-6, but not IL-10, by monocytes. Analysis of the early signaling pathway downstream of TLR4 demonstrated that SOCS1 had no regulatory effect on the activation or on the DNA binding capacity of NFkappaB. The late effects of LPS are mediated in part through the MyD88-independent pathway activating IRF3 and initiating the production of IFN-beta. In response to adenoviral infection and before LPS exposure, monocytes expressed enhanced levels of IFN-beta and Myxovirus A mRNA, an anti-viral molecule characterizing IFN-beta activity. These two genes were reduced in AdV-SOCS1-infected cells. Further, SOCS1 regulated IFN-dependent pathways in LPS-activated cells as evidenced by reduced IFN-beta production and STAT1 phosphorylation. Using AdV-infection to dissect SOCS1 control of IFN-dependent pathways, this study suggests that SOCS1-regulation of the IFN-dependent component of the LPS-induced TLR4 signaling pathway may contribute to the down-regulation of inflammatory cytokine production by AdV-SOCS1-infected human monocytes.

Suppressor of cytokine signalling-3 at pathological levels does not regulate lipopolysaccharide or interleukin-10 control of tumour necrosis factor-alpha production by human monocytes

Interleukin-10 (IL-10) is a potent anti-inflammatory cytokine that suppresses the production of tumour necrosis factor-alpha (TNF-alpha) by monocytes and macrophages. Suppressor of cytokine signalling-3 (SOCS3), a negative regulator of the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway, is induced following IL-10 exposure but recent studies in mice suggest that SOCS3 only targets gp-130-dependent signal transduction pathways. Understanding the signalling pathways responsible for IL-10-mediated effects in primary human monocytes is relevant to human inflammatory disease and necessary for the identification of potential therapeutic targets. An adenoviral transfection system was used to express different levels of SOCS3 (quantified experimentally with its tag green fluorescent protein (GFP)) with the aim of investigating the role of SOCS3 in LPS-induced and IL-10-mediated suppression of TNF-alpha production by non-transformed human monocytes. SOCS3 over-expression had no effect on TNF-alpha mRNA levels induced by LPS or LPS plus IL-10, or on IL-10 phosphorylation of STAT3, STAT1 and ERK1/2. When data from all donors were combined, adenoviral overexpression of SOCS3 significantly reversed the suppressive effects of IL-10 on LPS-induced TNF-alpha production after 2 hr. However, there was a direct correlation between mean GFP intensity (extent of viral infection) and extent of reversal of IL-10's inhibitory effects. Physiological levels of SOCS3 detected in IL-10-exposed human monocytes had no effect on LPS-induced TNF-alpha production. Although overexpression of SOCS3 to supraphysiological levels transiently antagonized the regulatory properties of IL-10 by a post-transcriptional mechanism, these findings suggest that under pathological conditions SOCS3 does not control LPS-activation or the anti-inflammatory properties of IL-10 in primary human monocytes.

Activated signal transducer and activator of transcription-3 (STAT3) is a poor regulator of tumour necrosis factor-alpha production by human monocytes

Signal transducer and activator of transcription-3 (STAT3) activation has been associated with suppressed inflammatory processes in experimental animals, murine myeloid cells and macrophage cell lines. Manipulation of STAT3 activity may therefore be a focus for pharmacological intervention of inflammatory diseases in humans. However, the ability of STAT3 to reduce the production of inflammatory mediators by activated human monocytes and macrophages has been characterized inadequately. To establish this, we used a recently optimized adenoviral approach to study the effect of overexpressed STAT3 or a transcriptionally inactive mutant STAT3 in lipopolysaccharide (LPS)-stimulated human monocytes. STAT3 activated by LPS did not directly regulate inhibitor of kappa B alpha (IkappaBalpha) activation or tumour necrosis factor (TNF)-alpha production, a process dependent on the transcriptional activity of nuclear factor kappa B (NFkappaB), although the transcriptional activity of STAT3 contributed to the mechanism by which interleukin (IL)-10 suppressed LPS-induced TNF-alpha levels. This contrasted with the efficient block in IL-10 induction of suppressor of cytokine signalling-3 (SOCS3) in monocytes infected with an adenovirus expressing mutant STAT3. These results indicate that STAT3 activation cannot directly regulate LPS-signalling in human monocytes and represents only part of the mechanism by which IL-10 suppresses TNF-alpha production by activated human monocytes. This study concludes that pharmacological manipulation of STAT3 transcriptional activity alone would be insufficient to control NFkappaB-associated inflammation in humans.

The CD16+Monocyte Subset Is More Permissive to Infection and Preferentially Harbors HIV-1 In Vivo

HIV-1 persists in peripheral blood monocytes in individuals receiving highly active antiretroviral therapy (HAART) with viral suppression, despite these cells being poorly susceptible to infection in vitro. Because very few monocytes harbor HIV-1 in vivo, we considered whether a subset of monocytes might be more permissive to infection. We show that a minor CD16+ monocyte subset preferentially harbors HIV-1 in infected individuals on HAART when compared with the majority of monocytes (CD14highCD16-). We confirmed this by in vitro experiments showing that CD16+ monocytes were more susceptible to CCR5-using strains of HIV-1, a finding that is associated with higher CCR5 expression on these cells. CD16+ monocytes were also more permissive to infection with a vesicular stomatitis virus G protein-pseudotyped reporter strain of HIV-1 than the majority of monocytes, suggesting that they are better able to support HIV-1 replication after entry. Consistent with this observation, high molecular mass complexes of apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3G (APOBEC3G) were observed in CD16+ monocytes that were similar to those observed in highly permissive T cells. In contrast, CD14highCD16- monocytes contained low molecular mass active APOBEC3G, suggesting this is a mechanism of resistance to HIV-1 infection in these cells. Collectively, these data show that CD16+ monocytes are preferentially susceptible to HIV-1 entry, more permissive for replication, and constitute a continuing source of viral persistence during HAART.

Centrifugation enhances integrin-mediated transduction of dendritic cells by conventional and RGD-modified adenoviral vectors

The level of antigen loading can impact on the capacity for dendritic cells (DC) to activate T cell responses. Several different approaches to adenoviral (Ad)-based transduction were therefore assessed for their effect on both transgene expression and T cell activation. While a conventional E1(-)/E3Delta Ad vector (Ad/GFP) produced a concentration-dependent expression of GFP, a modified vector expressing Arginine-Glycine-Aspartic Acid (RGD) sequence on its fiber knob (Ad-RGD/GFP) enhanced transgene expression by 9-20-fold at each MOI. The addition of centrifugal force (2000xg) during DC transduction with Ad/GFP also increased expression up to 20-fold. However, combining centrifugation with the Ad-RGD/GFP vector produced no effect on transduction rate and only a 1.5- to 2-fold increase in GFP expression, suggesting overlapping mechanisms of action. Consistent with this, exogenous RGD peptide blocked transduction regardless of the vector used, or the addition of centrifugal force, and transduction was primarily limited to DC expressing the CD51 integrin receptor. Ad vectors expressing ovalbumin (OVA) were used to assess transduced DC for their capacity to activate OVA-specific T cells. We observed a significant relationship between transgene expression and the capacity for T cell activation regardless of whether transgene expression was increased by using a higher MOI, an RGD-modified vector, or by employing centrifugal force. Furthermore, combining these approaches produced synergistic effects on T cell activation. We conclude that RGD-modified vectors and centrifugation both enhance DC transduction by increasing entry via integrin receptors and that the capacity for T cell activation can be optimized by combining approaches to achieve the highest possible level of transgene expression.

Effectiveness of anti-folate receptor beta antibody conjugated with truncated Pseudomonas exotoxin in the targeting of rheumatoid arthritis synovial macrophages

OBJECTIVE

To define the distribution of folate receptor beta (FRbeta)-expressing cells in various tissues, including rheumatoid arthritis (RA) synovial tissues, and to verify the effects of an immunotoxin composed of an anti-FRbeta monoclonal antibody (mAb) and truncated Pseudomonas exotoxin A (PEA) on apoptosis and tumor necrosis factor alpha (TNFalpha) production by adherent synovial mononuclear cells from RA patients.

METHODS

Anti-FRbeta mAb were produced by immunizing mice with FRbeta-transfected murine pre-B cells. The distribution of the FRbeta antigen was examined by immunohistochemical analysis using anti-FRbeta mAb and macrophage-specific anti-CD163 mAb. Anti-FRbeta mAb was chemically crosslinked with truncated PEA. FRbeta-expressing macrophages were produced by the transfection of adenovirus vector containing the FRbeta gene. Apoptotic cells were detected by staining with propidium iodide. TNFalpha was measured by enzyme-linked immunosorbent assay.

RESULTS

FRbeta-expressing cells were not present in peripheral blood leukocytes and their activated cells. In all of the tissues examined, most FRbeta-expressing cells were CD163+. The immunotoxin significantly induced the apoptosis of FRbeta-transfected macrophages and adherent RA synovial mononuclear cells and inhibited TNFalpha production by adherent RA synovial mononuclear cells.

CONCLUSION

We demonstrated the limited distribution of FRbeta-expressing cells in various tissues. The immunotoxin targeting FRbeta-expressing cells will provide a therapeutic tool for rheumatoid synovitis.