Expression of functional factor VIII in primary human skin fibroblasts after retrovirus-mediated gene transfer

We have developed a retroviral-vector system for the transfer and expression of a cloned blood clotting factor VIII cDNA. Since inclusion of the complete cDNA into existing vectors is precluded by its large size, we deleted most codons for the B-domain, which is also excised during in vivo maturation of factor VIII. When inserted into the retroviral vector M5-neoR (Laker, C., Stocking, C., Bergholtz, V., Hess, N., DeLamarter, J. F., and Ostertag, W. (1987) Proc. Natl. Acad. Sci. U. S. A. 84, 8458-8462), the sequence was shown to be efficiently expressed in murine fibroblast cell lines, as well as in primary human skin fibroblasts. Upon infection of murine fibroblast cell lines, clones containing only a single copy of the integrated vector-provirus secreted up to 125 milliunits of factor VIII antigen/10(6) cells/day. Equivalent amounts were found in a factor VIII activity assay, which signifies that the factor VIII protein secreted by the infected fibroblasts is fully functional. Primary human skin fibroblasts infected with the vector virus secreted up to 30 milliunits/10(6) cells/day.     

Viral RNA Intermediates as Targets for Detection and Discovery of Novel and Emerging Mosquito-Borne Viruses

Mosquito-borne viruses encompass a range of virus families, comprising a number of significant human pathogens (e.g., dengue viruses, West Nile virus, Chikungunya virus). Virulent strains of these viruses are continually evolving and expanding their geographic range, thus rapid and sensitive screening assays are required to detect emerging viruses and monitor their prevalence and spread in mosquito populations. Double-stranded RNA (dsRNA) is produced during the replication of many of these viruses as either an intermediate in RNA replication (e.g., flaviviruses, togaviruses) or the double-stranded RNA genome (e.g., reoviruses). Detection and discovery of novel viruses from field and clinical samples usually relies on recognition of antigens or nucleotide sequences conserved within a virus genus or family. However, due to the wide antigenic and genetic variation within and between viral families, many novel or divergent species can be overlooked by these approaches. We have developed two monoclonal antibodies (mAbs) which show co-localised staining with proteins involved in viral RNA replication in immunofluorescence assay (IFA), suggesting specific reactivity to viral dsRNA. By assessing binding against a panel of synthetic dsRNA molecules, we have shown that these mAbs recognise dsRNA greater than 30 base pairs in length in a sequence-independent manner. IFA and enzyme-linked immunosorbent assay (ELISA) were employed to demonstrate detection of a panel of RNA viruses from several families, in a range of cell types. These mAbs, termed monoclonal antibodies to viral RNA intermediates in cells (MAVRIC), have now been incorporated into a high-throughput, economical ELISA-based screening system for the detection and discovery of viruses from mosquito populations. Our results have demonstrated that this simple system enables the efficient detection and isolation of a range of known and novel viruses in cells inoculated with field-caught mosquito samples, and represents a rapid, sequence-independent, and cost-effective approach to virus discovery.     

Efficient immortalization and morphological transformation of human fibroblasts by transfection with SV40 DNA linked to a dominant marker

Immortal cell lines are essential for genetic and biochemical studies. Unlike rodent cells, which will form continuously growing cultures either spontaneously or after infection with an oncogenic virus (e.g., Simian Virus 40 (SV40)), human cells fail to form continuous cell lines spontaneously and in only rare cases from cell lines after oncogenic virus infection. We have used a plasmid (pSV3gpt) containing both the SV40 early region encoding T antigen and the bacterial gene xanthine-guanine phosphoribosyl transferase (gpt) to achieve high efficiency morphological transformation and immortalization of primary human skin fibroblasts. Transfection of this plasmid into primary human skin fibroblasts derived from a normal individual, two Cockayne's syndrome patients, and an immuno-deficient patient and selection for the gpt gene resulted in an altered cell morphology and growth properties characteristic of previously described SV40-transformed cells. Transfected cultures subsequently senesced, entered crisis and in each case formed a rapidly growing culture. The high efficiency of immunortalization described here (four out of four cell strains) is in contrast to previously described procedures utilizing focal overgrowth. We suggest that the use of a dominant selectable marker linked to the SV40 early region increases the probability of establishing an immortal human cell line.     

Human cytomegalovirus entry into epithelial and endothelial cells depends on genes UL128 to UL150 and occurs by endocytosis and low-pH fusion

Human cytomegalovirus (HCMV) replication in epithelial and endothelial cells appears to be important in virus spread, disease, and persistence. It has been difficult to study infection of these cell types because HCMV laboratory strains (e.g., AD169 and Towne) have lost their ability to infect cultured epithelial and endothelial cells during extensive propagation in fibroblasts. Clinical strains of HCMV (e.g., TR and FIX) possess a cluster of genes (UL128 to UL150) that are largely mutated in laboratory strains, and recent studies have indicated that these genes facilitate replication in epithelial and endothelial cells. The mechanisms by which these genes promote infection of these two cell types are unclear. We derived an HCMV UL128-to-UL150 deletion mutant from strain TR, TRdelta4, and studied early events in HCMV infection of epithelial and endothelial cells, and the role of genes UL128 to UL150. Analysis of wild-type TR indicated that HCMV enters epithelial and endothelial cells by endocytosis followed by low-pH-dependent fusion, which is different from the pH-independent fusion with the plasma membrane observed with human fibroblasts. TRdelta4 displayed a number of defects in early infection processes. Adsorption and entry of TRdelta4 on epithelial cells were poor compared with those of TR, but these defects could be overcome with higher doses of virus and the use of polyethylene glycol (PEG) to promote fusion between virion and cellular membranes. High multiplicity and PEG treatment did not promote infection of endothelial cells by TRdelta4, yet virus particles were internalized. Together, these data indicate that genes UL128 to UL150 are required for HCMV adsorption and penetration of epithelial cells and to promote some early stage of virus replication, subsequent to virus entry, in endothelial cells.     

Characterization of a Human Cytomegalovirus with Phosphorylation Site Mutations in the Immediate-Early 2 Protein

A human cytomegalovirus mutant (TNsubIE2P) was constructed with alanine substitutions of four residues (T27, S144, T233, and S234) previously shown to be phosphorylated in the immediate-early 2 (IE2) protein. This mutant grew as well as the wild type at both low and high multiplicities of infection. The mutant activated the major immediate-early, UL4, and UL44 promoters to similar levels, and with similar kinetics, as wild-type virus. However, the TNsubIE2P mutant virus transactivated an endogenous simian virus 40 early promoter 4 h earlier and to higher levels than the wild-type virus in infected human fibroblasts. The modification of the IE2 protein by SUMO-1 (i.e., its sumoylated state) was also examined.     

Transient assay, by [3H]guanine incorporation of Escherichia coli xanthine-guanine phosphoribosyl transferase (GPT) in transfected human fibroblasts

We have used [3H]guanine incorporation as a rapid and sensitive assay of xanthine-guanine phosphoribosyl transferase (GPT) activity in SV40 transformed human fibroblasts. The SV40 early promoter is more efficient than the Rous sarcoma virus long terminal repeat for transient expression of the gpt gene. The assay works well in a derivative of AT5BIVA which lacks hypoxanthine-guanine phosphoribosyl transferase (hprt-) and we show here how the assay has been adapted to work in the hprt+ AT5BIVA parent.     

Discovery of selective imidazole-based inhibitors of mammalian 15-lipoxygenase: highly potent against human enzyme within a cellular environment

A series of 2,4,5-tri-substituted imidazoles has proven to be highly potent in inhibiting mammalian 15-lipoxygenase (15-LO) with excellent selectivity over human isozymes 5- and P-12-LO. Non-symmetrical sulfamides (e.g., 21a-n) were found to be suitable replacements for the earlier arylsulfonamide-containing members of this series (e.g., 2, 14a-p). Several members of these series also demonstrated potent inhibition of human 15-LO in a cell-based assay.     

Postmitotic human dermal fibroblasts preserve intact feeder properties for epithelial cell growth after long-term cryopreservation

Summary In vitro, human dermal fibroblasts (HDF) differentiate through morphologically and biochemically identified compartments. In the course of this spontaneous differentiation through mitotic and postmitotic states, a tremendous increase in cellular and nuclear size occurs. Induction of postmitotic states can be accelerated by chemical (e.g., mitomycin C) or physical (e.g., x-ray) treatments. Such experimentally induced postmitotic HDF cells support very efficiently the growth of cutaneous epithelial cells, i.e. interfollicular keratinocytes and follicular outer root sheath cells, especially in primary cultures starting from very low cell seeding densities. The HDF feeder system provides more fundamental and also practical advantages, i.e. use of initially diploid human fibroblasts from known anatomic locations, easy handling and excellent reproducibility, and the possibility of long-term storage by incubation at 37°C. Conditions for the cryogenic storage of postmitotic HDF cells in liquid nitrogen are presented and related to the feeder capacity for epithelial cell growth. Because postmitotic HDF cells preserve intact feeder properties after long-term storage, the immediate availability of feeder cells and the possibility to repeat experiments with identical materials further substantiate the usefulness of this feeder system.     

Inhibition of protease-resistant prion protein formation in a transformed deer cell line infected with chronic wasting disease

Chronic wasting disease (CWD) is an emerging transmissible spongiform encephalopathy (prion disease) of North American cervids, i.e., mule deer, white-tailed deer, and elk (wapiti). To facilitate in vitro studies of CWD, we have developed a transformed deer cell line that is persistently infected with CWD. Primary cultures derived from uninfected mule deer brain tissue were transformed by transfection with a plasmid containing the simian virus 40 genome. A transformed cell line (MDB) was exposed to microsomes prepared from the brainstem of a CWD-affected mule deer. CWD-associated, protease-resistant prion protein (PrP(CWD)) was used as an indicator of CWD infection. Although no PrP(CWD) was detected in any of these cultures after two passes, dilution cloning of cells yielded one PrP(CWD)-positive clone out of 51. This clone, designated MDB(CWD), has maintained stable PrP(CWD) production through 32 serial passes thus far. A second round of dilution cloning yielded 20 PrP(CWD)-positive subclones out of 30, one of which was designated MDB(CWD2). The MDB(CWD2) cell line was positive for fibronectin and negative for microtubule-associated protein 2 (a neuronal marker) and glial fibrillary acidic protein (an activated astrocyte marker), consistent with derivation from brain fibroblasts (e.g., meningeal fibroblasts). Two inhibitors of rodent scrapie protease-resistant PrP accumulation, pentosan polysulfate and a porphyrin compound, indium (III) meso-tetra(4-sulfonatophenyl)porphine chloride, potently blocked PrP(CWD) accumulation in MDB(CWD) cells. This demonstrates the utility of these cells in a rapid in vitro screening assay for PrP(CWD) inhibitors and suggests that these compounds have potential to be active against CWD in vivo.     

Metabolism of homologous and heterologous lipoproteins by cultured rat and human skin fibroblasts

Rat fibroblasts degraded human low density lipoprotein (LDL) very slowly, one-tenth to one-fortieth the rates observed in human fibroblasts. In rat cells, human LDL caused only very small increases in cell cholesterol content and acylCoA:cholesterol acyltransferase (ACAT) activity and caused only small decreases in beta-hydroxy-beta-methylglutaryl CoA (HMG CoA) reductase activity; in human cells, however, human LDL induced very large changes in all three of these parameters, as expected. The binding of human LDL to rat fibroblasts was not reduced by previous incubation with human LDL or with 25-hydroxycholesterol. Thus, in rat fibroblasts there appear to be few, if any, regulated high-affinity receptors that recognize human LDL. Rat LDL fractions (d 1.02-1.05 g/ml), in contrast, were degraded more rapidly than human LDL by rat fibroblasts, caused a significant increase in cell cholesterol content, an increase in ACAT activity, and a significant decrease in HMG CoA reductase activity. Moreover, the degradation of this rat LDL fraction by rat fibroblasts as a function of concentration was biphasic, i.e., there appeared to be a high-affinity component of degradation. Thus, it appears that rat fibroblasts do have a receptor for homologous lipoproteins. However, because both apoprotein B and apoprotein E are present in these rat lipoprotein fractions, the observed effects may relate to recognition of either or both of these apoproteins. The metabolism and metabolic effects of the conventionally defined high density lipoprotein (HDL) fraction of the rat by rat or human fibroblasts resembled those of human LDL in human fibroblasts. It is suggested that rat HDL may, because of its apo E content and higher concentration in rat plasma relative to that of LDL, play an important role in cholesterol homeostasis in vivo.     

Human gamma interferon production by cytotoxic T lymphocytes sensitized during hepatitis A virus infection

The production of interferon (IFN) during a chromium-51 release assay with hepatitis A virus (HAV)-infected fibroblasts and autologous peripheral blood lymphocytes from patients with acute HAV infection was studied to determine whether IFN plays a role in immunopathogenesis of hepatitis A infection in humans. Skin fibroblasts of eight patients after acute HAV infection and from two control persons without history of current or past HAV infection were infected with HAV. Peripheral blood lymphocytes were collected at different times after the onset of icterus and tested in a chromium-51 release assay against autologous HAV-infected skin fibroblasts for their cytolytic and IFN-producing activity. The IFN produced during the assay was characterized and found to have the properties of human gamma IFN. Cytotoxicity and gamma IFN release were virus specific. The cell types responsible for both functions were characterized and found to be in the HLA-dependent T8+ lymphocyte subset. Considering that gamma IFN has an antiviral effect on persistent HAV infection in vitro and that it probably accounts for stimulation of HLA class I antigen expression on hepatocytes, our experimental results presented here demonstrate that human gamma IFN produced by HAV-specific T cells may participate in pathogenesis of hepatitis A infection in humans.     

PKC signaling prevents irradiation-induced apoptosis of primary human fibroblasts

Primary cells respond to irradiation by activation of the DNA damage response and cell cycle arrest, which eventually leads to senescence or apoptosis. It is not clear in detail which signaling pathways or networks regulate the induction of either apoptosis or senescence. Primary human fibroblasts are able to withstand high doses of irradiation and to prevent irradiation-induced apoptosis. However, the underlying regulatory basis for this phenotype is not well understood. Here, a kinetic network analysis based on reverse phase protein arrays (RPPAs) in combination with extensive western blot and cell culture analyses was employed to decipher the cytoplasmic and nuclear signaling networks and to identify possible antiapoptotic pathways. This analysis identified activation of known DNA damage response pathways (e.g., phosphorylation of MKK3/6, p38, MK2, Hsp27, p53 and Chk1) as well as of prosurvival (e.g., MEK-ERK, cAMP response element-binding protein (CREB), protein kinase C (PKC)) and antiapoptotic markers (e.g., Bad, Bcl-2). Interestingly, PKC family members were activated early upon irradiation, suggesting a regulatory function in the ionizing radiation (IR) response of these cells. Inhibition or downregulation of PKC in primary human fibroblasts caused IR-dependent downregulation of the identified prosurvival (CREB phosphorylation) and antiapoptotic (Bad phosphorylation, Bcl-2) markers and thus lead to a proliferation stop and to apoptosis. Taken together, our analysis suggests that cytoplasmic PKC signaling conditions IR-stressed MRC-5 and IMR-90 cells to prevent irradiation-induced apoptosis. These findings contribute to the understanding of the cellular and nuclear IR response and may thus eventually improve the efficacy of radiotherapy and help overcome tumor radioresistance.     

Host-cell reactivation of UV-irradiated and chemically-treated herpes simplex virus-1 by xeroderma pigmentosum, XP heterozygotes and normal skin fibroblasts

The host-cell reactivation of UV-irradiated and N-acetoxy-2-acetylamino-fluorene-treated herpes simplex virus type 1 strain MP was studied in normal and xeroderma pigmentosum human skin fibroblasts. Virus treated with either agent demonstrated lower survival in XP cells from complementation groups A, B, C and D than in normal fibroblasts. The relative reactivation ability of XP cells from the different genetic complementation groups was found to be the same for both irradiated and chemically treated virus. In addition, the inactivation kinetics for virus treated with either agent in the XP variant were comparable to that seen in normal skin fibroblasts. The addition of 2 or 4 mmoles caffeine to the post-infection assay medium had no effect on the inactivation kinetics of virus treated by either agent in the XP variant or in XP cells from the different genetic complementation groups. Treatment of the virus with nitrogen mustard resulted in equivalent survival in normal and XP genetic complementation group D cells. No apparent defect was observed in the ability of XP heterozygous skin fibroblasts to repair virus damaged with up to 100 μg N-acetoxy-2-acetylaminofluorene per ml. These findings indicate that the repair of UV-irradiated and N-acetoxy-2-acetylaminofluorene-treated virus is accomplished by the same pathway or different pathways sharing a common intermediate step and that the excision defect of XP cells plays little if any role in the reactivation of nitrogen mustard treated virus.     

Different biosynthetic transport routes to the plasma membrane in BHK and CHO cells

The question of how membrane proteins are delivered from the TGN to the cell surface in fibroblasts has received little attention. In this paper we have studied how their post-Golgi delivery routes compare with those in epithelia] cells. We have analyzed the transport of the vesicular stomatitis virus G protein, the Semliki Forest virus spike glycoprotein, both basolateral in MDCK cells, and the influenza virus hemagglutinin, apical in MDCK cells. In addition, we also have studied the transport of a hemagglutinin mutant (Cys543Tyr) which is basolateral in MDCK cells. Aluminum fluoride, a general activator of heterotrimeric G proteins, inhibited the transport of the basolateral cognate proteins, as well as of the hemagglutinin mutant, from the TGN to the cell surface in BHK and CHO cells, while having no effect on the surface delivery of the wild-type hemagglutinin. Only wild-type hemagglutinin became insoluble in the detergent CHAPS during transport through the BHK and CHO Golgi complexes, whereas the basolateral marker proteins remained CHAPS-soluble. We also have developed an in vitro assay using streptolysin O-permeabilized BHK cells, similar to the one we have previously used for analyzing polarized transport in MDCK cells (Pimplikar, S.W., E. Ikonen, and K. Simons. 1994. J. Cell Biol. 125:1025-1035). In this assay anti-NSF and rab-GDI inhibited transport of Semliki Forest virus spike glycoproteins from the TGN to the cell surface while having little effect on transport of the hemagglutinin. Altogether these data suggest that fibroblasts have apical and basolateral cognate routes from the TGN to the plasma membrane.     

Expression of baboon endogenous virus in exogenously infected baboon cells.

Strains of low-passage, fetal diploid, baboon (Papio cynocephalus) fibroblasts were susceptible to exogenous infection with three independent isolates of baboon endogenous virus, as measured by an immunofluorescence assay specific for viral p28. Infectivity of the M7 strain of baboon endogenous virus for baboon cells of fetal skin muscle origin was equivalent to that for human and dog cells in that similar, linear, single-hit titration patterns were obtained. The assay for supernatant RNA-dependent DNA polymerase, however, showed that baboon cells produced only low levels of virus after infection compared with the production by heterologous cells. The results showed that baboon endogenous virus was capable of penetrating baboon cells and that viral genes were expressed in infected cells. Replication of complete infectious virus was restricted, however, indicating that in this primate system homologous cells differentially regulated the expression of viral genes.     

Identification of human galactoprotein b3, an oncogenic transformation-induced membrane glycoprotein, as VLA-3 alpha subunit: the primary structure of human integrin alpha 3.

Galactoprotein b3 is one of the cell membrane glycoproteins of fibroblasts showing enhanced expression in association with oncogenic transformation. Analysis of cDNA for this glycoprotein from hamster fibroblasts indicated that the glycoprotein is a member of the integrin superfamily [Tsuji, T., Yamamoto, F., Miura, Y., Takio, K., Titani, K., Pawar, S., Osawa, T., & hakomori, S. (1990) J. Biol. Chem. 265, 7016-7021]. In the present study, we examined the change in the amounts of mRNA for the mouse and human counterparts in fibroblasts after oncogenic transformation by Northern blot analysis using hamster galactoprotein b3 cDNA as a probe. In both human and murine fibroblasts transformed with SV-40, the homologous mRNA to galactoprotein b3 was also found to increase as compared with the progenitor cells. The human homologue of galactoprotein b3 cDNA was cloned from human bladder carcinoma cell line (T24) cDNA library. The cDNA codes for a single polypeptide of which the N-terminal sequence (21 amino acids) is identical with that of human VLA-3 alpha subunit. Based on this sequence identity and the structural similarities (i.e. the positions of most cysteine residues, the presence of a transmembrane domain near the C-terminus and the presence of metal binding sequences) with other integrins so far cloned, we conclude that human galactoprotein b3 is an integrin alpha 3 subunit. The mature integrin alpha 3 polypeptide was composed of 1,019 amino acid residues, and the overall structure was quite similar to the hamster counterpart.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of human immunodeficiency virus-1 protease inhibitors on the toxicity of a variety of cells

Protease inhibitors in combination with other antiretroviral drugs have been shown to be efficacious in treating human immunodeficiency virus-1 (HIV-1) infection. The side effects of such a treatment usually involve perturbations of fat metabolism and insulin responsiveness. This has led to a number of studies on the adverse effects of these drugs in vitro. The concentrations of various protease inhibitors used in many of these studies were >20 microM. Although some investigators did address the toxicity of protease inhibitors, no overall effort was made to examine this effect during differentiation of fat or muscle. In this study, we assessed the toxicity of HIV-1 protease inhibitors over a range of concentrations (i.e., 0 to 100 microM) in nondifferentiating (e.g., human fibroblasts, 3T3-L1 preadipocytes, and L6 myoblasts) and differentiated cells (e.g., L6 myotubes). The most toxic protease inhibitor in all cell types was Saquinavir (sqv), whereas the least toxic protease inhibitor was Indinavir (idv). Ritonavir (rtv) and Amprenavir (apv) were more toxic than idv but not quite as toxic as sqv. In 3T3-L1 preadipocytes, treatment with sqv, rtv, and apv resulted in toxicity, whereas idv was not toxic even at the highest concentration used. Indinavir was not toxic to L6 myoblasts or L6 myotubes; however, sqv, rtv, and apv caused toxicity in L6 myoblasts. Saquinavir decreased L6 myotube viability in a dose-dependent manner. Human immunodeficiency virus-1 protease inhibitors were shown to be toxic in a variety of cell types. These effects on human fibroblasts and muscle cells have not been reported previously.     

Lipid metabolism in cultured cells. XVIII. Comparative uptake of low density and high density lipoproteins by normal, hypercholesterolemic and tumor virus-transformed human fibroblasts.

Serum lipoproteins control cell cholesterol content by regulating its uptake, biosynthesis, and excretion. Monolayers of cultured fibroblasts were used to study interactions with human high density (HDL) and low density (LDL) lipoproteins doubly labeled with [(3)H]cholesterol and (125)I in the apoprotein moiety. In the binding assay for LDL, the absence of specific LDL receptors in type II hypercholesterolemic fibroblasts was confirmed, whereas monolayers of virus-transformed human lung fibroblasts (VA-4) exhibited LDL binding characteristics essentially the same as normal lung fibroblasts. In the studies of HDL binding, specific HDL binding sites were demonstrated in normal and virus-transformed fibroblasts. In addition, type II hypercholesterolemic cells, despite the loss of LDL receptors, retained normal HDL binding sites. No significant competition was displayed between the two lipoprotein classes for their respective binding sites over a 5-fold concentration range. In VA-4 cells, the amount of lipoprotein required to saturate half the receptor sites was 3.5 micro g/ml (9 x 10(-9) M) for LDL and 9.1 micro g/ml (9 x 10(-8) M) for HDL. Pronase treatment reduced LDL binding by more than half but had no effect on HDL binding. Chloroquine, a lysomal enzyme inhibitor, stimulated net LDL uptake 3.5-fold by increasing internalized LDL but had essentially no effect on HDL uptake. Further experiments were conducted using doubly labeled lipoproteins to characterize the interaction of LDL and HDL with cells. While the cholesterol and protein moieties of LDL were incorporated into cells at similar rates, the uptake of the cholesterol moiety of HDL was 5 to 10 times more rapid than that of the protein component. Furthermore, the apoprotein component of LDL is extensively degraded following exposure, whereas the apoprotein moiety of HDL retains its macromolecular chromatographic characteristics. These results indicate that HDL and LDL bind to cultured cells at separate sites and that further processing of the two lipoprotein classes appears to take place by fundamentally different mechanisms.-Wu, J-D., J. Butler, and J. M. Bailey. Lipid metabolism in cultured cells XVIII. Comparative uptake of low density and high density lipoproteins by normal, hypercholesterolemic, and tumor virus-transformed human fibroblasts.