Progress in gene transfer by germ cells in mammals

Use of germ cells as vectors for transgenesis in mammals has been well developed and offers exciting prospects for experimental and applied biology, agricultural and medical sciences. Such approach is referred to as either male germ cell mediated gene transfer （MGCMGT） or female germ cell mediated gene transfer （FGCMGT） technique. Sperm-mediated gene transfer （SMGT）, including its alternative method, testis-mediated gene transfer （TMGT）, becomes an established and reliable method for transgenesis. They have been extensively used for producing transgenic animals. The newly developed approach of FGCMGT, ovary-mediated gene transfer （OMGT） is also a novel and useful tool for efficient transgenesis. This review highlights an overview of the recent progress in germ cell mediated gene transfer techniques, methods developed and mechanisms of nucleic acid uptake by germ cells.

Adenoviral-mediated Hath1-EGFP gene transfer into guinea pig cochlea through intact round window membrane

Objective To study expression of adenoviral-mediated Hath1-EGFP gene in the guinea pig cochlea after transfer through intact round window membrane(RWM), and to assess its effects on hearing. Methods Twenty adult guinea pigs were used, of which: 12 were surgically inoculated with Ad-Hath1-EGFP in the bony groove of round window niche, and 8 with artificial perilymph. Auditory brainstem response(ABR) thresholds were determined in all animals before and 5 days after surgery. On post-surgery day 5 and day 14, animals were sacrificed and whole mounts of cochlea and frozen sections were examined. Results ABR tests showed no significant change of hearing after the surgery. Strong fluorescence staining in the cochleae was seen in Ad-Hath1-EGFP groups. The highest levels of gene expression were seen in the post-surgery day 5 group with little decrease on post-surgery day 14.The contralateral cochlea and those in the control groups were free of fluorescence staining. Conclusion The transgenic Hath1-EGFP can be effectively delivered into the inner ear through intact RWM, in an atraumatic manner.

Erythropoietin gene transfer into rat testes by in vivo electropo-ration may reduce the risk of germ cell loss caused by cryptorchidism

Aim： To investigate the effects of rat Erythropoietin （Epo） on spermatogenesis by transferring rat Epo gene into cryptorchid testes by means of in vivo electroporation. Methods： Sprague-Dawley rats with surgically-induced unilateral cryptorchidism were divided into three groups： the first group was given intratesticular injections of pCAGGS-Epo （pCAGGS-Epo group）, the second group was given intratesticular injections of pCAGGS （pCAGGS group）, and the third group were given intratesticular injections of phosphate-buffered saline （PBS group）. At the same time, square electric pulses of 30 V were applied six times with a time constant of 100 ms. One or two weeks after injection, each testis was weighed and the ratio of the total number of germ cells to that of Sertoli cells （G/S ratio） was calculated to evaluate the impairment of spermatogenesis. Ten testes taken from each of the three groups were examined at each time point. Results： The testicular weight after the injection of pCAGGS-Epo or pCAGGS control plasmid was （0.85 ± 0.08） g and （0.83 ± 0.03） g, respectively, at week 1 （P = 0.788） and （0.62 ± 0.06） g and （0.52 ± 0.02） g, respectively, at week 2 （P = 0.047）. At week 1, spermatids and sperm were more abundant in testes with pCAGGS-Epo than those in the control testes. At week 2, spermatids and sperm were hardly detected in either group. The G/S ratio was 23.27 ± 6.80 vs. 18.63 ± 5.30 at week 1 （P = 0.0078） and 7.16 ± 3.06 vs. 6.05 ± 1.58 at week 2 （P = 0.1471）, respectively. Conclusion： The transfer of Epo to rat testes by in vivo electroporation may reduce the risk of the germ cell loss caused by cryptorchidism.

Intrastriatal Gene Transfer of Vascular Endothelial Growth Factor Rescues Dopaminergic Neurons in a Rat Parkinson's Disease Model

To examine the ability of intrastriatal gene transfer of vascular endothelial growth factor 165 mediated by adenoviral vector to rescue dopaminergic neurons in a rat model of Parkinson＇s disease （PD）, we constructed recombinant replication-deficent adenoviral vectors carrying the gene of VEGF165 （Ad-VEGF）, and injected Ad-VEGF （or Ad-LacZ and PBS as controls） into the striatum of rats 7 days after the lesion by 6-hydroxydopamine. The rat rotational behavior analysis and tyrosine hydroxylase （TH） immunohistochemistry were performed to assess the change of dopaminergic neurons. Our results showed that the rats receiving Ad-VEGF injection displayed a significant improvement in apomorphine-induced rotational behavior and a significant preservation of TH-positive neurons and fibers compared with control animals, It is concluded that intrastriatal gene transfer by Ad-VEGF may rescue the dopaminergic neurons from degeneration in a rat model of PD.

Molecular Tissue Engineering: Applications for Modulation of Mesenchymal Stem Cells Proliferation by Transforming Growth Factor β_1 Gene Transfer

The effect of transforming growth factor β 1 (TGF β 1 ) gene transfection on the proliferation of bone marrow derived mesenchymal stem cells (MSC S ) and the mechanism was investigated to provide basis for accelerating articular cartilage repairing using molecular tissue engineering technology. TGF β 1 gene at different doses was transduced into the rat bone marrow derived MSCs to examine the effects of TGF β 1 gene transfection on MSCs DNA synthesis, cell cycle kinetics and the expression of proliferating cell nuclear antigen (PCNA). The results showed that 3 μl lipofectamine mediated 1 μg TGF β 1 gene transfection could effectively promote the proliferation of MSCs best; Under this condition (DNA/Lipofectamine=1μg/3μl), flow cytometry and immunohistochemical analyses revealed a significant increase in the 3 H incorporation, DNA content in S phase and the expression of PCNA. Transfection of gene encoding TGF β 1 could induce the cells at G0/G1 phase to S1 phase, modulate the replication of DNA through the enhancement of the PCNA expression, increase the content of DNA at S1 phase and promote the proliferation of MSCs. This new molecular tissue engineering approach could be of potential benefit to enhance the repair of damaged articular cartilage, especially those caused by degenerative joint diseases.

HIGH EFFICIENCY RETROVIRUS-MEDIATED GENE TRANSFERTO LEUKEMIA CELLS

Objective: To establish an efficient and safe gene transfer system mediated by retrovirus for gene marking and gene therapy of human leukemia. Method: The retroviral vector LXSN, containing the neomycin resistance (NeoR) gene, was transferred into amphotropic packaging cells GP+envAm12 by liposome transfection or by ecotropic retrovirus transduction. Amphotropic retrovirus in supernatants with higher titer was used to infect human leukemic cell lines NB4, U937, and THP-1. The efficiency of gene transfer was assayed on colonies formed by transduced K562 cells. Results: The titer of DOSPER directly transfected GP+envAm12 cells determined on NIH3T3 cells was 8.0×105 CFU/ml, while that of producer infected with retrovirus was 1.6×107 CFU/ml. Integration of NeoR gene into all leukemia cells was confirmed by polymerase chain reaction (PCR). Absence of replication-competent virus was proved by both nested PCR for env gene and marker gene rescue assay. Gene transfer with the efficiency as high as 93.3 to 100% in K562 cells was verified by seminested PCR for integrated NeoR gene on colonies after 7 days’ culture. Conclusion: The efficiency and safety of retrovirus mediated gene transfer system might provide an optimal system in gene therapy for leukemia or genetic diseases.

Gene transfer to human trabecular meshwork cells in vitro and ex vivo using HIV-based lentivirus

AIM: To investigate whether the enhanced green fluorescent protein(EGFP) reporter gene could be transferred into human trabecular meshwork(HTM) cells by a HIV-based lentivirus both in vitro and ex vivo.METHODS: The HIV-based lentivirus that contains an EF1-α promoter driving EGFP expression cassette was constructed following the standard molecular cloning methods. The cultured HTM cells were transduced at a range of multiplicity of infection(MOI) with HIV-based lentivirus. EGFP positive cell populations were detected by flow cytometry. Human anterior eye segments were cultured with perfusion culture system and transfected by HIV-based lentivirus with a 1 ×108transducing unit(TU) virus in perfusion liquid. The intraocular pressure was recorded every 8h for 21 d. The expression of EGFP in the anterior segment of the human eye was detected by fluorescence microscopy. Furthermore, the distribution of EGFP expression was confirmed by anti-EGFP immunohistochemical staining.RESULTS: The HIV-based lentivirus which contains an EF1-α promoter driving EGFP expression cassette was constructed successfully. After HTM cells were transduced with HIV-based lentivirus containing EGFP in vitro, the ratio of EGFP positive cells to the total cell number reached 92.3%, with the MOI of 15. After the lentivirus containing EGFP were used to transduce human anterior eye segments, the EGFP could be directly detected by fluorescence microscopy in vivo.Immunohistochemistry staining revealed that 88.19%EGFP-positive trabecular meshwork(TM) cells were observed in the human anterior segment. Nevertheless,the intraocular pressure in the lentivirus-transduced group kept constant when compared with control group(P 】0.05).CONCLUSION: EGFP gene could be efficiently transferred into HTM cells both in vitro and ex vivo by using HIV-based lentivirus.

Gene Transfer into Hematopoietic Cells of Mouse and Its in vivo Expression after Transplantation

We have shown previously that high-efficient gene transfer can be attained in primary hematopoietic cells using liposome-mediated gene transfer strategy. In order to examine the stability of gene expression mediated by this gene transduction protocol, we observed the expression of marker gene in vivo by using bone marrow transplantation (BMT) to engraft lethally irradiated mouse with the genetically modified hematopoietic cells. The results showed that the mouse transplanted with appropriated number of transduced cells remained alive andhealthy. The PCR analysis and G418 selection of the spleen colonies and bone marrow cells isolated from lethally irradiated animals 15 days and 30 days after injection of genetically modified bone marrow cells showed that the progeny cells of the transduced hematopoietic stem cells still contained and expressed the transduced genes, suggesting that the hematopoietic system is at least partially re-constructed by the stem cells with marker gene and that the stable expression of foreign genes in vivo can be attained by using this easy and harmless transduction protocol. These findings provide experimental basis for clinician to further investigate the biology of marrow reconstruction and the mechanism of leukemia relapse after BMT.

Fluorescence Tracking of Exogenous DNA in Genetic Transformation of the Chinese Oak Silkmoth Antheraea Pernyi via Sperm-Mediated Gene Transfer

Exogenous DNA expressing green fluorescent protein( GFP) and labeled with fluorescein isothiocyanate( FITC) was used to transform the Chinese oak silkmoth Antheraea pernyi( A. pernyi)via sperm-mediated gene transfer( SMGT). Sperms entry into the female reproductive system and eggs were observed using fluorescence microscopy. The ability of A. pernyi sperms to uptake exogenous DNA was confirmed,and transfer of the exogenous DNA was shown by GFP expression in the transgenic eggs. Our result suggested that SMGT could also be used to directly generate transgenic A. pernyi expressing functional genes of interest.

Direct Gene Transfer into Rabbit Peripheral Nerve in vivo

Exogenous gene suture was used to achieve peripheral nerve anastomoses to probe into the feasibility that the sites of anastomoses of nerves directly transfer gene and thus enable gene to be expressed at the sites of anastomoses under the condition that perfect nerve anastomoses are ensured. PCMVβ plasmid containing cytomegalovirus promoter (CMV promoter) and Escherichia coli (E.coli) β Galactosidase (β Gal) structural gene (lacZ gene) was conducted. A soaked medical 8 0nylon suture was used to perform epineurial repair of rabbit sciatic nerve. In the control group a suture soaked in sucrose PBS was used, while in the experimental group a suture soaked in PCMVβ plasmid solution was applied. The sites of anastomoses of nerves by stages were taken out, and β Gal histochemical staining was performed and β Gal enzyme activity was assayed with 5 bromo 4 chloro 3 indolyl β D galactoside. Results showed that the sites of anastomoses of nerves were taken out 2 days, 7 days, 14 days and 30 days respectively after the operation. The β Gal histochemical stains at the sites of anastomoses showed no indigo positive cells at different stages in the control group, whereas displayed indigo positive cells in the experimental group. In the control group, no β Gal enzyme activity was detected at different stages after operation, but in the experimental group, β Gal enzyme activity could be detected from the 3rd day to the 30th day after operation. It was concluded that by using exogenous gene suture, exogenous gene could be transferred to the sites of peripheral nerve and expressed the exogenous gene expression products with bioactivity, which provided the feasibility of using gene therapy to accelerate the recovery of nerve function.

Experiments on Gene Transferring to Primary Hematopoietic Cells by Liposome

Summary Liposomes have showed many advantages in mediating exogenous gene into many cell types in vitro and in vivo. But few data are available concerning gene transfer into hematopoietic cells. In this report, we described two-marker genes (Neo R and Lac Z) co-transferred into hematopoietic cells of human and mouse by using liposome in vitro. The efficiency of gene transfer was tested by X- gal staining and observation of colony formation. The X-gal blue staining rate of transduced cells was about (13. 33±2.68)% in human and about (16. 28±2. 95) % in mouse without G418 selection. After G418 selection, the blue cell rate was (46. 06±3. 47)% in human and (43. 45±4. 1)% in mouse, which were markedly higher than those before selection, suggesting that high-efficiency gene transfer and expression could be attained in primary hematopoietic cells using this easy and harmless transduction protocol. At the same time, this protocol provided experimental data for clinicians to in- vestigate the biology of marrow reconstitution and trace the origin of relapse after autologous bone marrow transplantation for the patients with leukemia.

Experimental Study of Plasmid TGF-β1 DNA Gene Transfer with Lipofectamine into Rabbit Corneal Epithelial Cells In Vitro

To investigate whether the TGF β1 plasmid DNA carried by lipofectamine could be introduced into cultured rabbit corneal epithelial cells, specific expression of the plasmid pMAM TGF β1 in the cultured corneal epithelial cells was studied. Two days after 12 h of transfection of pMAMTGF β1 mediated by lipofectamine into the cultured corneal epithelial cells, the TGF β1 protein expression specific for pMAMTGF β1 in the cells was detected by means of immunohistochemical staining and the positive rate was 23.37 %. The results suggested that foreign plasmid DNA could be effectively delivered into cultured rabbit corneal epithelial cells by means of lipofectamine, and this will provide a promising method of studying TGF β1 on the mechanism of physiology and pathology concerned with corneal epithelial cells.

Effects of kallikrein gene transfer on penumbral microvascular proliferation and on regional cerebral blood flow following cerebral ischemia/reperfusion injury

BACKGROUND： Recent findings have demonstrated that the kallikrein-kinin system （KKS） participates in the pathological process of cerebral ischemia/reperfusion injury. Kallikrein gene transfer exhibits neural protective effects following cerebral infarction. OBJECTIVE： To observe the effects of kallikrein gene transfer on vascular proliferation in the peripheral infarct focus and on regional cerebral blood flow （rCBF） following cerebral ischemia/reperfusion injury. DESIGN, TIME AND SETTING： The completely randomized, controlled experiment was performed at the Lin Baixin Laboratory Center, the Second Affiliated Hospital of Sun Yat-sun University between September 2007 and April 2008. MATERIALS： pUCI9-HTK plasmid was constructed and maintained in the Laboratory for Neurology, the Second Affiliated Hospital of Sun Yat-sen University, China. Mouse anti-human kallikrein 1 monoclonal antibody was purchased from R＆D Systems, USA. METHODS Ninety healthy, male, Sprague Dawley rats were used. Middle cerebral artery occlusion （MCAO） was established in all rats to induce cerebral ischemia/reperfusion injury. Following MCAO establishment, all rats were randomly divided into three groups （n = 30）： blank control, saline, and pAdCMV-HTK. The saline and pAdCMV-HTK groups were stereotactically micro-injected with 5μL of physiological saline or with pAdCMV-HTK [multiplicity of infection （MOI） = 20], respectively, into the ischemic penumbra. In the blank control group, only sham injection was performed. MAIN OUTCOME MEASURES： At 12, 24, and 72 hours after treatment, cerebral infarction volume was measured by 2, 3, 5-triphenyltetrazolium chloride （TTC） staining. Exogenous HTK expression, as well as regional vascular endothelial growth factor （VEGF） expression, was detected by immunohistochemistry. rCBF was examined by 14C-iodoantipyrine micro tracing. In addition, neurological severity score （NSS） was performed. Higher scores indicated more severe neurological deficits. RESULTS： NSS results demonstrated that compared with the saline and the blank control groups, the pAdCMV-HTK group exhibited lower NSSs 24 hours after pAdCMV-HTK injection （P 〈 0.05）. The NSSs were further decreased after 72 hours （P 〈 0.01）. Cerebral infarction volume at 24 hours, and in particular at 72 hours after treatment, was significantly reduced in the pAdCMV-HTK group compared with the blank control and saline groups （P 〈 0.05）. The rCBF in the area surrounding the infarction lesion was slightly decreased in all groups compared with the contralateral area. At 24 and 72 hours following treatment, the rCBF in the peripheral infarction lesion was significantly elevated in the pAdCMV-HTK group compared with the blank control and saline groups （P 〈 0.05）. Immunohistochemistry results revealed that VEGF-positive cells were primarily found in the cortex and in some white matter surrounding the cerebral infarction lesion. In addition, the expression of VEGF in the pAdCMV-HTK group was significantly higher compared with that in the blank control and saline groups at 12, 24, and 72 hours following treatment （P 〈 0.05）. CONCLUSION： Following cerebral ischemia/reperfusion, kallikrein gene transfer can promote vascular proliferation in the brain tissue surrounding the infarction lesion, improve rCBF, and reduce infarction volume, thereby exhibiting protective effects to attenuate neurological deficits.

Characterizing proteases in an Antarctic Janthinobacterium sp. isolate: Evidence of a protease horizontal gene transfer event

We report the isolation of a cold-adapted bacterium belonging to the genus Janthinobacterium （named AU 11）, from a water sample collected in Lake Uruguay （King George Island, South Shetlands）. AUI 1 （growth between 4℃ and 30℃） produces a single cold-active extracellular protease （ExPAU11）, differentially expressed at low temperature. ExPAU11 was identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry （MALDI-ToF MS） as an alkaline metallo-protease （70% coverage with an extracellular protease of Janthinobacterium sp. PI12）, and by protease-inhibitor screening identified as a serine-protease. To the best of our knowledge this is the first experimental evidence of a cold-active extracellular protease produced by Janthinobacterium. Furthermore, we identified a serine-protease gene （named JSP8A） showing 60% identity （98% query coverage） to subtilisin peptidases belonging to the $8 family （S8A subfamily） of many cyanobacteria. A phylogenetic analysis of the JSP8A protease, along with related bacterial protein sequences, confirms that JSP8A clusters with S8A subtilisin sequences from different cyanobacteria, and is clearly separated from SSA bacterial sequences of other phyla （including its own）. An analysis of the genomic organization around JSP8A suggests that this protease gene was acquired in an event that duplicated a racemase gene involved in transforming L- to D-amino acids. Our results suggest that AU11 probably acquired this subtilisin-like protease gene by horizontal gene transfer （HGT） from a cyanobacterittrn. We discuss the relevance of a bacterial protease-HGT in the Antarctic environment in light of this hypothesis.

Production of Transgenic Mice by Type-A Spermatogonia-Mediated Gene Transfer

Type-A spermatogonia first appear at between 3-7 d postnatally in mice and are the only immortalized diploid cells that reproduce in adulthood in these animals. In our current study, we explored the feasibility of producing stable transgenic mice using these cells. Enhanced pEGFP-N1 plasmids were suspended in ExGen500 transfection reagent and injected at different angles into the testes of 7-d-old male ICR mice. The resulting type-A spermatogonia-mediated gene transfer （TASMGT） mice were then mated with normal females at different stages of sexual maturity （6, 12, and 24 wk）. The integration and expression of the introduced EGFP gene was evaluated in the F1 transgenic offspring by PCR and Southern blotting analysis. The foreign gene integration rates for a low-dose group （15 μL gene suspension injected into each testis） and a high-dose group （30 μL suspensions injected） at the three stages of female sexual maturity tested were 11.76% （2/17）, 14.29% （3/21）, and 11.11% （2/18）, and 5% （1/20）, 5.56% （1/18）, and 0 （0/17）, respectively. The average integration rates for these two dose groups were 12.5% （7/56） and 3.64% （2/55）, respectively, which was a significant difference （P0.05）. Semi-quantitative RT-PCR analysis further showed that the introduced GFP gene was expressed in 3/9 integration mice. In addition, GFP expression was observed in the sperm cells from the TASMGT mice, and also in the embryos and F2 pups from the F1 generation transgenic mice. Hence, although the foreign gene integration rate for TASMGT is not high and the transgenic offspring show as yet unexplained defects, our results indicate that this method is a potentially feasible and reproducible new approach to creating transgenic mice.

Horizontal gene transfer of a syp homolog contributes to the virulence of Burkholderia glumae

Horizontal gene transfer(HGT)has been proved a major driving force in prokaryotic evolution.However,the molecular functions of these transferred genes in pathogenic bacteria especially plant pathogenic bacteria are still not fully investigated.In this study,the whole-genome in silico analysis was performed and found a syringopeptin synthetase(syp)homolog in Burkholderia glumae,which can cause bacterial panicle blight in rice,was predicted to be horizontally transferred from Pseudomonas ancestor with solid confidence by phylogenetic analysis.The comprehensive molecular experiments were performed to study the potential role of this gene in B.glumae.Inoculation of rice panicles with the syp mutant resulted in 60%lower disease index compared with the wild type(WT)parent strain,suggesting the requirement of syp for the full virulence of B.glumae.Chromatography analysis of exudates from B.glumae showed suppression of synthesis of metabolites analogous to syringopeptin in the mutants.All these data raise the possibility of HGT phenomenon in shaping the virulence and adaptation of B.glumae over evolutionary time.

SEQUENCE STUDY AND RETROVIRUS MEDIATED GENE TRANSFER IN MAMMALIAN CELL SYSTEMS OF HUMAN INTERLEUKIN 2 cDNA

Interleukin 2 (IL- 2) is a T cell growth factor. In the present study, human IL- 2 cDNA was cloned from total RNA of activated tonsillar mononuclear cells (TMNC) following reverse transcription and PCR amplification using a pair of synthesized primers. DNA sequence analysis demonstrated that the IL- 2 cDNA cloned from the Chinese tonsil donor is identical with the data reported so far, reflecting the high structural conservation of this gene. The human IL- 2 cDNA was inserted into XM6 to construct a recombinant retroviral expression vector XM6-IL2, having human IL-2 cDNA driven by the 5' LTR of MMLV. This vector was successfully passaged through ψ 2 and PA317 cells to yield high producer lines of ecotropic and amphotroplc infectious viruses. The murine myeloma cell line SP2/0 after being infected by retrovirus released from high titer PA317 constitutlvely secreted IL- 2 activity into the culture medium when assayed for T cell proliferative capacity. Activated human T cells are also exposed to the infectious retrovirus XM6- IL2. In sharp contrast to the parallel controls, the infected T cells with or without the furtheraddition of 500 units/ ml of exogenous IL- 2 proliferated and formed colonies of significant size under the selection pressure of G418. However, their growth in vitro could only be maintained for about 3 weeks. These facts demonstrated that gene transfer of human IL- 2 cDNA viaretrovirus is far from being sufficient to maintain the relatively long-termgrowth and clonal expansion of human T cell subpopulations in vitro.

Gene therapy for human colorectal carcinoma using human CEA promoter controlled bacterial ADP-ribosylating toxin genes:PEA and DTA gene transfer

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Gene transfer of huCTLA4-Ig to inhibit the acute rejection of liver allograft in rats

To observe the effect of gene transfer of huCTLA4-Ig to inhibit the acute rejection of liver allograft in rats.Methods With AdEasy vector system,the recombinant adenovirus containing huCTLA4-Ig gene was constructed.Using ex vivo gene transfer technique,exogenous gene was introduced to the liver graft during cold preservation and expressed locally in the graft.The effect of inhibition of acute rejection and inducing liver graft tolerance was observed.Results No recipients in group A (without any treatment,n=5) or group B (treated with Ad-GFP,n=4) died within 3 weeks after transplantation and severe acute rejection (massive periportal infiltration,endothelilitis,damage to biliary epithelium and severe tissue destruction) was confirmed pathologically in the graft.In contrast,all recipients in group C (treated with Ad-huCTLA4-Ig,n=5) achieved long-term liver allograft survival (>150 days).Histological examination of Ad-huCTLA4-Ig transduced allografts demonstrated a mild to moderate periportal inflammation and mild injury to liver graft on day 8 posttransplant.A mild mononuclear infiltration was observed;however,there was complete preservation of the bild ducts and no evidence of vascular injury on day 150 posttransplant.The mean IL-2 concentration in serum was (362.09±45.84) ng/L at day 1 pretransplant.In control animals (groups A and B),serum IL-2 concentration was elevated to a high level within 7 days posttransplant,which was about 1.5 to 2.5 times as much as that before transplant.In contrast,in huCTLA4-Ig-treated animals (groups C),IL-2 concentration in serum was maintained at a relative low level,which was near or less than that before transplant (P<0.01).Conclusion Using ex vivo gene transfer technique,huCTLA4-Ig gene can be introduced to the liver graft during cold preservation.The modified graft can express and excrete immunoregulatory protein locally,which can suppress acute alloimmune response and is responsible for prolongation of graft survival without using routine immunosuppressive drugs.These findings provide some experimental evidence that gene delivery of sequences encoding immunoregulatory proteins can be applied to clinical liver transplantation for inhibiting the acute alloimmune response and achieving graft tolerance.7 refs,2 tabs.