Human immunodeficiency virus replication in human brain cells

Summary Human immunodeficiency virus (HIV), the etiologic agent of AIDS, was found to infect and replicate in human brain cells. The extent of HIV replication was minimal in human brain-derived cells in comparison to T4 lymphoid cells. These results suggest that direct infection of glial/neuronal cells by HIV may contribute to the CNS dysfunction frequently observed in HIV infected individuals.     

A DNA ligase gene in the Copenhagen strain of vaccinia virus is nonessential for viral replication and recombination

Biochemical and genetic analyses have been conducted to determine whether a vaccinia virus open reading frame (orf) with extensive homology to the Saccharomyces cerevisiae DNA ligase gene encodes a functional ligase activity. This orf in HindIII A, designated A50R, is capable of encoding a 552-amino-acid, 63.4-kDa polypeptide. Full-length A50R mRNA produced in vitro directed the synthesis of a polypeptide with an apparent molecular weight of 57 kDa. Significantly, translation reactions programmed with A50R mRNA were capable of ligating a 3-kb Notl restriction fragment into multimers. DNA ligase activity was not detectable when either truncated sense or full-length antisense mRNA was translated in vitro. In extracts prepared from cells infected with wt vaccinia virus, DNA ligase activity was detected as assayed by the formation of a 57 kDa ligase-AMP adduct which was expressed early in the viral replication cycle. In cells infected with a DNA ligase deletion mutant no equivalent AMP-labeled adduct was detected. Relative to wt virus, the DNA ligase deletion mutant exhibited no significant differences in homologous recombination. These results indicate that the vaccinia orf A50R encodes a functional DNA ligase expressed early in infection, but this DNA ligase is nonessential for either recombination or viral replication.     

Preferential targeting of vesicular stomatitis virus to breast cancer cells

Vesicular stomatitis virus (VSV) is a candidate for development for cancer therapy. We created a recombinant replicating VSV (rrVSV) with an altered surface protein that targeted preferentially to breast cancer cells. The rrVSV genome contained a single glycoprotein (gp) gene derived from Sindbis virus. This gene expressed a chimeric Sindbis E2 binding gp and the native Sindbis E1 fusion gp. The chimeric E2 binding gp, called Sindbis-SCA-erbb2, was modified to reduce its native binding function and to contain a single chain antibody (SCA) with specificity for the human epidermal growth factor receptor Her2/neu protein, erbb2. These viruses selectively infected, replicated in and killed cells expressing erbb2. The titer of rrVSV on SKBR3 cells, a human breast cancer cell line which highly expresses erbb2 was 3.1 x 10(7)/ml compared with a titer of 7.3 x 10(5)/ml on 143 cells, a human osteosarcoma cell line which does not express erbb2. The titer of rrVSV on D2F2/E2 cells, a mouse mammary cancer cell line stably transfected to express human erbb2 was 2.46 x 10(6)/ml compared with a titer of 5 x 10(4)/ml on the parent D2F2 cells which do not express erbb2. When titered on erbb2-negative cells, non-replicating pseudotype VSV coated with Sindbis-SCA-erbb2 had <3% the titer of pseudotype VSV coated with wild type Sindbis gp indicating that the chimeric Sindbis gp had severely impaired binding to the natural receptor. Analysis of the protein composition of the rrVSV found low expression of the modified Sindbis gp on the virus.     

The highly attenuated vaccinia virus strain modified virus Ankara induces apoptosis in melanoma cells and allows bystander dendritic cells to generate a potent anti-tumoral immunity

Vaccinia virus (VV) has been tested as oncolytic virus against malignant melanoma in clinical trials for more than 40 years. Until now, mainly strains comparable to viral strains used for smallpox vaccination have been probed for anti-tumoral therapy. We have shown recently that the wild-type strain Western Reserve (WR) can interfere with crucial functions of monocyte-derived dendritic cells (DCs). Our aim was to examine whether viral immune evasion mechanisms might be responsible for the ineffectiveness of WR-based vaccination strategies and whether the highly attenuated strain modified virus Ankara (MVA) differs from WR with respect to its possible immunostimulatory capacity after intratumoral injection. Using in vitro experiments, we compared the effect of both strains on melanoma cells and on local bystander DCs. We found that both VV-strains infected melanoma cells efficiently and caused disintegration of the actin cytoskeleton, as shown by fluorescence microscopy. In addition, both VV-strains caused apoptotic cell death in melanoma cells after infection. In contrast to MVA, WR underwent a complete viral replication cycle in melanoma cells. Bystander DCs were consecutively infected by newly generated WR virions and lost their capacity to induce allogeneic T cell proliferation. DCs in contact with MVA-infected melanoma cells retained their capacity to induce T cell proliferation. Immature DCs were capable of phagocytosing MVA-infected melanoma cells. Priming of autologous CD8(+) T cells by DCs that had phagocytosed MVA-infected, MelanA positive melanoma cells resulted in the induction of T cell clones specifically reactive against the model antigen MelanA as shown by enzyme-linked immunospot (ELISPOT) analysis. We conclude that the clinical trials with oncolytic wild-type VV failed probably because of suppression of bystander DCs and consecutive suppression of T cell-mediated anti-melanoma immunity. The attenuated VV-strain MVA facilitates the generation of tumour associated antigen (TAA)-specific T cell response as it is oncolytic for melanoma cells, but non-toxic for DC, and should be a promising candidate for intralesional metastatic melanoma therapy.     

Ability of small animal cells to support the postintegration phase of human immunodeficiency virus type-1 replication

We examine the potential for a broad range of small animal cells, including rodent, mink, and avian cells, from multiple tissues to support postintegration steps of HIV-1 replication. These cells were engineered so as to support a stable expression of human cyclin T1 and were further transduced with HIV-1 gag and pol genes. Viral gene expression was activated by the presence of human cyclin T1, but, with the exception of mink cells, was not at the level seen in human cells. Furthermore, there were considerable defects in p24 CA release, in particular in the case of rodent cells. Fractionation of Gag proteins by sucrose floatation revealed that the Gag in human cells trafficked to membrane fractions and was processed to p24 CA and p17 MA efficiently. Confocal imaging demonstrated that Gag was localized in a punctate pattern at the plasma membrane as well as intracellular membrane trans-Golgi cisternae in these cells. In contrast, the majority of Gag in rodent cells was largely present in cytosolic complexes and remained unprocessed. Labeling with [9,10(n)-(3)H]myristic acid showed a similar degree of N-myristoylated Pr55(gag) in rodent and human cells, indicating that while N-myristoylation of Gag was essential for membrane binding, it was not sufficient to confer membrane targeting specificity. Remarkably, despite the reduced level of intracellular Gag processing, mink Mv.1.Lu cells did not appear to differ significantly from human cells in support of virion assembly and release. Analysis of reciprocal heterokaryons suggested that the cellular factor(s) required for efficient assembly and release of infectious virions is lacking in murine cells but appears to be functionally present in mink as well as human cells. Our findings confirm and extend previous reports of multiple blocks to HIV replication in nonhuman cells that are most profound in murine cells. They also raise the possibility that other small animals, such as mink, could serve as novel model systems for studying HIV-1 infection and disease.     

Myxoma and vaccinia viruses exploit different mechanisms to enter and infect human cancer cells

Myxoma (MYXV) and vaccinia (VACV) viruses have recently emerged as potential oncolytic agents that can infect and kill different human cancer cells. Although both are structurally similar, it is unknown whether the pathway(s) used by these poxviruses to enter and cause oncolysis in cancer cells are mechanistically similar. Here, we compared the entry of MYXV and VACV-WR into various human cancer cells and observed significant differences: 1 — low-pH treatment accelerates fusion-mediated entry of VACV but not MYXV, 2 — the tyrosine kinase inhibitor genistein inhibits entry of VACV, but not MYXV, 3 — knockdown of PAK1 revealed that it is required for a late stage event downstream of MYXV entry into cancer cells, whereas PAK1 is required for VACV entry into the same target cells. These results suggest that VACV and MYXV exploit different mechanisms to enter into human cancer cells, thus providing some rationale for their divergent cancer cell tropisms.     

The in vivo antitumor effect of the apoptin-producing recombinant vaccinia virus strain is associated with blockage of mitotic division of cancer cells

Vaccinia virus (VACV) possesses a natural oncolytic activity, for the enhancement of which genes encoding various effector molecules, for example, those inducing apoptotic death of tumor cells, are introduced into the virus genome. One such transgene is the gene encoding apoptin protein. The aim of the current work was to study antitumor activity of the apoptin-producing recombinant VACV strain VVdGF-ApoS24/2 in a syngenic murine tumor model. An Ehrlich carcinoma was implanted subcutaneously or intraperitoneally into C57B1 line mice. After tumor development, mice were intratumorally injected with 10⁷ PFU/mouse of VVdGF-ApoS24/2 virus in a single dose, while control mice received 0.9% NaCl solution. Animals were sacrificed at different times after VACV injection. Tumor samples and ascetic fluid cells were fixed in 4% paraformaldehyde and further studied by light microscopy, immunohistochemistry, and electron microscopy. Virus titers in tumor cells were determined by the PFU method. VVdGF-ApoS24/2 VACV strain caused a significant reduction in the volumes of both solid and ascites Ehrlich carcinomas compared to the tumors in the control group of mice, although the virus reproduction rate in the tumor cells was rather low. The antitumor effect of VVdGF-ApoS24/2 could neither be attributed to virus-induced destruction, necrosis, or apoptosis of tumor cells nor to accumulation of the immune-effector cells in the tumors. A decrease in the number of tumor cells undergoing mitosis was observed when examining carcinoma sections, while counting Ki-67 and PCNA positive cells and analysis of their numbers showed that VVdGF-ApoS24/2 strain arrests cell cycle in the S-phase, thereby blocking tumor-cell division and slowing down tumor growth. The obtained results indicate that the insertion of the gene encoding apoptin into the genome of the original L-IVP VACV strain improved the ability of the virus to arrest the cell cycle in Ehrlich carcinoma cells.     

Differential susceptibility of nonmalignant human breast epithelial cells and breast cancer cells to thiol antioxidant-induced G(1)-delay

Reactive oxygen species (ROS) and ROS signaling have been implicated in a variety of human pathophysiological conditions that involve aberrant cellular proliferation, particularly cancer. We hypothesize that intracellular redox state differentially affects cell-cycle progression in nonmalignant versus malignant cells. The thiol antioxidant, N-acetyl-L-cysteine (NAC), was used to alter intracellular redox state in nonmalignant human breast epithelial (MCF-10A) and breast cancer cells (MCF-7 and MDA-MB-231). Treatment of cells with NAC resulted in significant augmentation of intracellular small-molecular-weight thiols, glutathione and cysteine. In addition, NAC treatment decreased oxidation of a prooxidant-sensitive dye in MCF-10A cells, but not in MDA-MB-231 and MCF-7 cells. NAC-induced shifts in intracellular redox state toward a more reducing environment caused G(1) delays in MCF-10A cells without causing any significant changes in MCF-7 and MDA-MB-231 cell-cycle progression. NAC treatment of MCF-10A (but not MCF-7 and MDA-MB-231) was accompanied by a decrease in cyclin D1 and an increase in p27 protein levels, which correlated with increased retinoblastoma protein hypophosphorylation. These results show differential redox control of progression from G(1) to S in nonmalignant versus malignant cells and support the hypothesis that loss of a redox control of the cell cycle could contribute to aberrant proliferation seen in cancer cells.     

Changes in cell gene expression in human leukemic cells persistently infected with vaccinia virus

Persistent viral infections in vitro are useful systems to study the coevolution of virus and cell populations. Persistent infection of mouse Friend erythroleukemic cells (FEL) with vaccinia virus results in profound changes of the virus as well as of the cells. To investigate phenotypic changes of other cell types, we have established a persistent infection with vaccinia virus in a human leukemic cell line (K562). This cell line can be induced to differentiate along the erythroid pathway synthesizing embryonic and fetal globins, thus providing a system in which specific genes can be stimulated. After serial passage, the persistently infected cells (K562vac) became spontaneously differentiated, as shown by the increase in the number of cells producing hemoglobin (benzidine positive cells), and resistant to superinfection. These phenotypic changes of the cells were not accompanied by changes in the viral population. Hybridization of cellular RNA with cloned embryonic and fetal globin genes indicated that uninduced K562 cells do not express these genes, whereas cells induced by hemin or butyrate express G gamma (fetal globin) epsilon and zeta (embryonic globins) genes. By contrast vaccinia infected cells spontaneously express the G gamma gene. These results demonstrate that persistent infection with vaccinia virus elicited phenotypic changes in the infected cell population; in this case the constitutive expression of fetal hemoglobin.     

载紫杉醇PLGA/F68纳米粒逆转多药耐药用于乳腺癌的治疗

目的载紫杉醇聚乳酸聚羟基乙酸共聚物（PLGA）/F68纳米粒逆转耐紫杉醇人乳腺癌细胞MCF-7/Taxol细胞多药耐药的可行性研究。方法使用超声乳化溶剂挥发法分别制备载紫杉醇PLGA和载紫杉醇PLGA/F68纳米粒（10%）,并对载紫杉醇纳米粒进行表征。载紫杉醇纳米粒的体外释放研究使用高效液相色谱进行分析。最后研究载紫杉醇纳米粒在耐紫杉醇人乳腺癌细胞MCF-7/Taxol细胞的细胞摄取和细胞毒性（PLGA/F68组、PLGA组和泰素组）。结果纳米粒呈球形,表面粗糙多孔,平均粒径250 nm左右,粒径分布比较窄,体外药物释放呈双相释放模型。载紫杉醇PLGA/F68纳米粒能够被耐紫杉醇人乳腺癌细胞MCF-7/Taxol细胞摄取。载紫杉醇PLGA/F68纳米粒比载紫杉醇PLGA纳米粒（P〈0.05）和泰素（TaxolR）（P〈0.05）有更高的细胞毒性。结论载紫杉醇PLGA/F68纳米粒能够逆转耐紫杉醇人乳腺癌细胞MCF-7/Taxol细胞的多药耐药,药用辅料Pluronic F68在乳腺癌治疗中具有潜在的应用前景。     

Mycophenolate mofetil inhibits hepatitis C virus replication in human hepatic cells

Hepatitis C virus (HCV) infection is the most common indication for liver transplantation and the major cause of graft failure. A widely used immunosuppressant, cyclosporine A (CsA), for people who receive organ transplantation, has been recognized to have the ability to inhibit HCV replication both in vivo and in vitro. In this study, we investigated the effects of several other immunosuppressants, including mycophenolate mofetil (MMF), rapamycin and FK506, on HCV replication in human hepatic cells. MMF treatment of hepatic cells before or during HCV infection significantly suppressed full cycle viral replication, as evidenced by decreased expression of HCV RNA, protein and production of infectious virus. In contrast, rapamycin and FK506 had little effect on HCV replication. Investigation of the mechanism(s) disclosed that the inhibition of HCV replication by MMF was mainly due to its depletion of guanosine, a purine nucleoside crucial for synthesis of guanosine triphosphate, which is required for HCV RNA replication. The supplement of exogenous guanosine could reverse most of anti-HCV effect of mycophenolate mofetil. These data indicate that MMF, through the depletion of guanosine, inhibits full cycle HCV JFH-1 replication in human hepatic cells. It is of interest to further determine whether MMF is indeed beneficial for HCV-infected transplant recipients in future clinical studies.     

Effect of aldosterone on the amplification of oncolytic vaccinia virus in human cancer lines

Background/Aims

JX-594 is an oncolytic virus derived from the Wyeth vaccinia strain that causes replication-dependent cytolysis and antitumor immunity. Starting with a cross-examination of clinical-trial samples from advanced hepatocellular carcinoma patients having high levels of aldosterone and virus amplification in JX-594 treatment, we investigated the association between virus amplification and aldosterone in human cancer cell lines.

Methods

Cell proliferation was determined by a cell-counting-kit-based colorimetric assay, and vaccinia virus quantitation was performed by quantitative polymerase chain reaction (qPCR) and a viral plaque assay. Also, the intracellular pH was measured using a pH-sensitive dye.

Results

Simultaneous treatment with JX-594 and aldosterone significantly increased viral replication in A2780, PC-3, and HepG2 cell lines, but not in U2OS cell lines. Furthermore, the aldosterone treatment time altered the JX-594 replication according to the cell line. The JX-594 replication peaked after 48 and 24 hours of treatment in PC-3 and HepG2 cells, respectively. qPCR showed that JX-594 entry across the plasma membrane was increased, however, the changes are not significant by the treatment. This was inhibited by treatment with spironolactone (an aldosterone-receptor inhibitor). JX-594 entry was significantly decreased by treatment with EIPA [5-(N-ethyl-N-isopropyl)amiloride; a Na⁺/H⁺-exchange inhibitor], but aldosterone significantly restored JX-594 entry even in the presence of EIPA. Intracellular alkalization was observed after aldosterone treatment but was acidified by EIPA treatment.

Conclusions

Aldosterone stimulates JX-594 amplification via increased virus entry by affecting the H⁺ gradient.     

痘苗病毒VGF细胞膜外结构域在真核及原核细胞中的表达

目的为了进一步探索ＶＧＦ的生物学功能方法分别构建了痘苗病毒天坛株生长因子（Ｖａｃｃｉｎｉａｇｒｏｗｔｈｆａｃｔｏｒ，ＶＧＦ）基因细胞膜外结构域（ＶＧＦｓｌ）的真核及原核表达系统，在相应的细胞中获得了单独表达（真核）和融合表达（原核）。结果初步纯化的ＶＧＦｓｌ表达产物能够与上皮生长因子（ＥＧＦ）的受体结合，并刺激受体中酪氨酸残基发生磷酸化反应。与ＥＧＦ相比，ＶＧＦｓｌ表达产物刺激ＥＧＦ受体自身磷酸化的能力更强。结论上述结果为ＶＧＦ在病毒感染过程中的作用以及ＶＧＦ作为新型多肽类药物的研究提供了有价值的线索。     

芪三酚与人乳腺癌MDC1基因关系的研究

目的探讨芪三酚（Res）对人乳腺癌MDA—MB-231细胞增殖抑制的相关效应及其与MDCl基因的关系。方法以人乳腺癌MDA—MB-231细胞株为研究对象,采用MTS方法测定细胞增殖,应用吖啶橙荧光染色观察Res对乳腺癌MDA—MB-231细胞的影响,用RT-PCR与免疫印迹方法测定MDCl基因与蛋白表达水平,用小RNA干扰MDCl基因后,用流式细胞仪检测细胞的凋亡并观察其对Res的敏感性影响。结果40μmol／L以上的Res可显著抑制乳腺癌MDA—MB-231细胞的增殖（P〈0．05）,给予0、60、120μmol／LRes能明显降低MDCl基因和蛋白的表达（P〈0．05）。用小RNA干扰MDC1基因后,流式细胞术分析显示,实验组（MDCl．siRNA）的细胞凋亡率[（45．13±6．2）％]较阴性对照组[（24．34±2．6）％]和未处理组[（17．69±4．9）％]明显上升（P〈0．05）,MTS结果显示MDCl基因干扰后细胞对Res的敏感性增加。结论40μmol／L以上的Res可以抑制MDA-MB-231细胞的增殖,Res可以有效降低MDC基因和蛋白的表达并促进细胞的凋亡。用小RNA干扰MDCl基因（MDCl-siRNA）后,MDA-MB-231细胞对Res的敏感性增加。     

紫杉醇对乳腺癌细胞紫杉醇耐药基因Txr1表达的影响

目的应用人乳腺癌细胞制备紫杉醇耐药细胞模型,探讨紫杉醇对乳腺癌细胞中紫杉醇耐药基因Txr1表达的影响。方法比较紫杉醇预处理前后不同浓度紫杉醇对乳腺癌细胞的增殖和细胞周期的改变;用RT-PCR方法检测Txr1、TSP1和MDR1的mRNA水平变化;用Western blot检测Txr1和TSP1的蛋白质水平的变化。结果紫杉醇预处理后,紫杉醇抑制乳腺癌细胞(MCF-7细胞)的生长作用明显减弱。流式细胞仪分析表明,MCF-7细胞经过紫杉醇作用后被阻滞于细胞周期的G2M期。紫杉醇作用于MCF-7细胞后,Txr1的mRNA水平上调,TSP1下调,而MDR1表达无明显改变。类似的结果在蛋白的水平被Western blot进一步证实。结论紫杉醇可能通过Txr1上调抑制TSP1的表达从而诱导肿瘤细胞的耐药性。