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Viral vector-mediated gene transfer to the postnatal respiratory epithelium has, in general, been of low efficiency due to physical and immunological barriers, non-apical location of cellular receptors critical for viral uptake and limited transduction of resident stem/progenitor cells. These obstacles may be overcome using a prenatal strategy. In this study, HIV-1-based lentiviral vectors (LVs) pseudotyped with the envelope glycoproteins of Jaagsiekte sheep retrovirus (JSRV-LV), baculovirus GP64 (GP64-LV), Ebola Zaire-LV or vesicular stomatitis virus (VSVg-LV) and the adeno-associated virus-2/6.2 (AAV2/6.2) were compared for in utero transfer of a green fluorescent protein (GFP) reporter gene to ovine lung epithelium between days 65 and 78 of gestation. GFP expression was examined on day 85 or 136 of gestation (term is B145 days). The percentage of the respiratory epithelial cells expressing GFP in fetal sheep that received the JSRV-LV (3.18Â10 8 -6.85Â10 9 viral particles per fetus) was 24.6 ± 0.9% at 3 weeks postinjection (day 85) and 29.9±4.8% at 10 weeks postinjection (day 136). Expression was limited to the surface epithelium lining fetal airways o100 mm internal diameter. Fetal airways were amenable to VSVg-LV transduction, although the percentage of epithelial expression was low (6.6 ± 0.6%) at 1 week postinjection. GP64-LV, Ebola Zaire-LV and AAV2/6.2 failed to transduce the fetal ovine lung under these conditions. These data demonstrate that prenatal lung gene transfer with LV engineered to target apical surface receptors can provide sustained and high levels of transgene expression and support the therapeutic potential of prenatal gene transfer for the treatment of congenital lung diseases.

Purpose Successful in utero or perinatal gene therapy for congenital lung diseases, like cystic fibrosis and surfactant protein deficiency, requires identifying clinically relevant viral vectors that efficiently transduce airway epithelial cells. The purpose of the current preclinical large animal study was to evaluate lung epithelium transduction of adeno-associated viral vector (AAV) serotypes following intratracheal delivery. Methods Six different AAV serotypes (AAV1, AAV5, AAV6, AAV8, AAV9, AAVrh10) expressing the green fluorescent protein (GFP) as the transgene were injected into the right upper lobe (RUL) of perinatal sheep via bronchoscopy. At one-week samples were harvested, analyzed by fluorescent stereomicroscopy and immunohistochemistry, and quantified using a radial grid and quantitative real time PCR. Results Fluorescent stereomicroscopy demonstrated GFP expression in the RUL following injection of all AAV serotypes assessed except AAV5. Immunohistochemistry analysis confirmed GFP expression in small and medium sized airways following intratracheal injection of AAV1,6,8,9, and rh10, however; only AAV8 and AAVrh10 resulted in transgene expression in large airways. These results were confirmed by qPCR, yet, after 40-cycles AAV1 did not show GFP gene amplification. Conclusion AAV serotypes 6,8,9, and rh10 demonstrated efficient GFP transgene expression at early time points and AAV8 demonstrated efficient transduction of all airway sizes with high pulmonary GFP expression tested using qPCR.

Gene transfer to long-term repopulating hematopoietic stem cells (HSCs) using integrating viral vectors is an important goal in gene therapy. The SLAM (signaling lymphocyte activation molecule)-family receptors have recently been used for the isolation of highly enriched murine HSCs. This HSC enrichment protocol is relatively simple, and results in an HSC population with comparable repopulating capacity to c-kit + lin À Sca-1 + (KSL) HSCs. The capacity to withstand genetic manipulation and, most importantly, to maintain long-term repopulating capacity of SLAM-enriched HSC populations has not been reported. In this study, SLAMenriched HSCs were assessed for transduction efficiency and in vivo long-term repopulating capacity after lentiviral transduction using an abbreviated transduction protocol and KSL-enriched HSCs as a reference population. SLAM-and KSL-enriched HSCs were efficiently transduced by lentiviral vector using a simple protocol that involves minimal in vitro manipulation and no pre-stimulation. SLAM-HSCs are at least equal to KSL-HSCs with respect to efficiency of transduction and maintenance of long-term repopulating capacity. Although there was a reduction in repopulating capacity related to enrichment and culture manipulations relative to freshly isolated bone marrow (BM) cells, no detrimental effects were identified on long-term competitive capacity related to transduction, as transduced cells maintained stable levels of chimerism in competition with nontransduced cells and freshly isolated BM cells. These results support the SLAM-HSC enrichment protocol as a simple and efficient method for HSC enrichment for gene transfer studies.

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Introduction: Adenoviral gene transfer of Angiopoietin‐1 (AdAng1) recruits endothelial progenitor cells (EPCs) and improves diabetic wound healing. A suggested mechanism for EPC mobilization from the bone marrow (BM) is mediated through MMP‐9 and stem cell factor (SCF). We hypothesize that Ang‐1 recruits EPCs to diabetic wounds via an MMP‐9 dependent mechanism. 
Methods: Lethally irradiated mice were reconstituted with BM from transgenic TIE‐2/LacZ mice. After engraftment, diabetes was induced with steptozotocin. 8 mm wounds were created in BM transplanted (BMT)(n = 12) or MMP‐9 knockout (KO)(n = 12) mice and treated with 1 × 108 PFU of AdAng1, AdGFP or PBS. At 7 days wounds were analyzed for epithelial gap, vessel density, and EPCs. Serum levels of VEGF, proMMP9 and SCF were assessed. Data are expressed as mean ± SEM 
Results: In diabetic BMT wounds, AdAng1 results in improved reepithelialization (Ang1 2.3 ± .2 mm; GFP 3.9 ± .2; PBS 4.0 ± .1 p < .0001) neovascularization (Ang1 6.8 ± .3Caps/Hpf; GFP 3.0 ± .4; PBS 2.9 ± .3 p < .0001) and EPC recruitment (Ang1 5.3 ± .4 EPCs/Hpf; GFP 2.1 ± .3; PBS 2.2 ± .3 p < .0001). AdAng1 treatment results in increased levels of proMMP‐9 (Ang1 9.7 ± .8 ng/ml; GFP 6.3 ± .9; PBS 6.4 ± .4 p < .01) and SCF (Ang1 265 ± 28 pg/ml; GFP 119 ± 16; PBS159 ± 12 p < .001). In MMP9 KO mice, AdAng1 accelerates reepithelialization (Ang1 3.2 ± .1 mm; GFP 4.1 ± .2; PBS 3.8 ± .2; p<.) but has no significant effect on neovascularization (Ang1 4.1 ± .5 Caps/HPF; GFP 3.9 ± .4; PBS 3.9 ± .6), EPC recruitment (Ang1 2 ± .3 EPC/Hpf; GFP 1.5 ± .3; PBS 1.6 ± .2) or SCF levels (Ang1 83 ± 5 pg/ml; GFP 83 ± 2; PBS 88 ± 6). 
Conclusions: The effects of Ang‐1 on EPC recruitment and neovascularization are dependent on MMP‐9. Our data support the hypothesis that MMP‐9 enables SCF to permit mobilization of EPCs.

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