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C Speth

Publications and source records attributed to C Speth.

32 records · Page 2Linked to original sources
PubMed1999

Epstein-Barr virus infection of human astrocyte cell lines.

Epstein-Barr virus (EBV) is implicated in different central nervous system syndromes. The major cellular receptor for EBV, complement receptor type 2 (CR2) (CD21), is expressed by different astrocyte cell lines and human fetal astrocytes, suggesting their susceptibility to EBV infection. We demonstrated the infection of two astrocyte cell lines, T98 and CB193, at low levels. As infection was mediated by CR2, we used two stable CR2 transfectant astrocyte cell lines (T98CR2 and CB193CR2) to achieve a more efficient infection. We have monitored EBV gene expression for 2 months and observed the transient infection of T98 and T98CR2 cells and persistent infection of CB193 and CB193CR2 cells. The detection of BZLF1, BALF2, and BcLF1 mRNA expression suggests that the lytic cycle is initiated at early time points postinfection. At later time points the pattern of mRNA expressed (EBER1, EBNA1, EBNA2, and LMP1) differs from latency type III in the absence of LMP2A transcription and in the expression of BALF2 and BcLF1 but not BZLF1. A reactivation of the lytic cycle was achieved in CB193CR2 cells by the addition of phorbol esters. These studies identify astrocyte cell lines as targets for EBV infection and suggest that this infection might play a role in the pathology of EBV in the brain.

Astrocytes↗
PubMed1998

Antigenic characterization of HIV-1 gp41 binding proteins.

The envelope protein HIV-1 gp41 has been shown to exert various effects on human T-cells, B-cells and monocytes like inhibition of cell proliferation, modulation of MHC expression and cytokine production. In contrast to gpl20, where several receptor molecules have been identified, the receptor for gp41 is still unknown. Using a sepharose column, coupled with recombinant soluble gp41, (rsgp41; Env amino acids 539-684), five gp41-binding proteins of 37, 45, 50, 62 and 100 kDa had been isolated from lysates of the B-cell line Raji. Two mouse antiserums were generated against the proteins P45 and P62 and were tested against the binding specificity of both antiserums. In Western blot analysis the antiserums recognized two protein bands of 45 and 62 kDa in complete Raji cell lysates, as well as the purified proteins P45 and P62, respectively, but did not show any cross-reaction, indicating that the two proteins do not share any immunological epitopes. Besides, the polyclonal antiserums did not recognize the other gp41-binding proteins P37, P50 and P100. Using the P62 antiserum proteins of the same size as in Raji cell lysates were stained in the lysates of the monocytic cell line U937 and the T-cell line H9, demonstrating distribution of P62 in different blood cells. P45 seems not to be identical to HLA-C which had been shown to bind to gp41. These results indicate, that P45 and P62 are two separate gp41-binding proteins without homology to each other or to the other gp41-binding proteins.

Animals↗
PubMed1998

Urokinase plasminogen activator receptor (uPAR; CD87) expression on monocytic cells and T cells is modulated by HIV-1 infection.

The transmembranous urokinase-type plasminogen activator receptor (uPAR; CD87) focuses the formation of active plasmin at the cell surface, thus enhancing directional extracellular proteolysis. Since proteolysis is involved in processes like adhesion, chemotaxis and migration which are important for viral spreading, we investigated the expression of uPAR in HIV-infected cells. Expression of CD87 was upmodulated in U937 monocytic cells as well as in the T cell line H9 and in peripheral blood mononuclear cells (PBMC), both on protein and on mRNA level. This upmodulation was not caused by enhanced mRNA stability but by an enhanced transcriptional rate of the CD87 gene as shown by nuclear run-on analysis. To identify the HIV-responsive element in the CD87 promoter we investigated the promoter activity in U937 and H9 cells at different time points after HIV-infection. Although the transcription of the CD87 gene is higher in HIV-infected cells the promoter activity declines after infection, indicating the presence of an additional regulatory element located upstream of the known promoter sequence or in intron sequences.

Gene Expression Regulation↗
PubMed1998

gp41 envelope protein of human immunodeficiency virus induces interleukin (IL)-10 in monocytes, but not in B, T, or NK cells, leading to reduced IL-2 and interferon-gamma production.

The effect of extracellular domain of human immunodeficiency virus (HIV-1) transmembrane glycoprotein gp41 on interleukin (IL)-10, IL-2, interferon (IFN)-y, IL-4, and tumor necrosis factor-alpha production by human peripheral blood mononuclear cells (PBMC) was assessed by ELISA. Rapid gp41-induced increase of IL-10 production was detected in resting PBMC and isolated monocytes but not in B, T, or NK cells. Furthermore, gp41 also enhanced IL-10 production in staphylococcal enterotoxin B-stimulated PBMC, while synthesis of IL-2, IFN-gamma, and IL-4 in these cells was down-modulated. Kinetic studies revealed that increased IL-10 production preceded reduction of IL-2, indicating the possible IL-10 regulatory role in the gp41-induced down-modulation of this cytokine. Anti-IL-10 antibody reversed almost completely the gp41 inhibitory effect on IL-2 production. In this study, HIV-1 gp41 was a potent modulator of cytokine production by PBMC, in particular by increasing IL-10 secretion from normal monocytes/macrophages and consequently down-regulating IL-2 and IFN-gamma.

Antibodies, Blocking↗
PubMed1997

The immunosuppressive peptide of HIV-1 gp41 like human type I interferons up-regulates MHC class I expression on H9 and U937 cells.

Based on our findings that the immunosuppressive peptide (ISP, amino acids (aa) 583-599) of human immunodeficiency virus type 1 (HIV-1) gp41 shows sequence-similarity with human type I interferons (IFN-alpha and IFN-beta) and HIV-1 soluble gp41 (sgp41, aa 539-684) enhanced cell surface expression of major histocompatibility complex (MHC) class I molecule on human H9 (T cells), Raji (B cells) and U937 (monocytic cells) cells, we examined the effect of HIV-1 immunosuppressive peptide on the surface expression of MHC class I molecules on H9 and U937 cells. Flow cytometry analysis demonstrated that ISP-BSA (conjugate) could enhance MHC class I expression by about 40% on H9 cells and by about 45% on U937 cells, while monomer ISP (not conjugated) and EDCI-treated carrier protein (BSA-EDCI) did not increase the expression. By comparison, human type I interferons, IFN-alpha and IFN-beta, showed similar effects (enhanced the expression by about 40-60%) to ISP-BSA on the MHC class I expression on H9 and U937 cells. The results suggest that HIV-1 gp41 in a polymerized form by its immunosuppressive domain upregulates human MHC class I expression. The basis for this similar effect of HIV-1 gp41 and IFN-alpha and -beta, i.e. upregulation of MHC class I molecule expression, may be based on the sequence-similarity between these otherwise different molecules.

Amino Acid Sequence↗
PubMed1997

Complement receptors in HIV infection.

The complement system plays an important role in the antimicrobial defense of the organism. Its components recognize a large variety of pathogens and target them for destruction, either directly by formation of a membrane attack complex or indirectly by recruiting phagocytic cells. In addition, it has several functions in cell activation, clearance of immune complexes, control of inflammatory reactions, chemotaxis and autoimmunity. For mediation of all these tasks of the complement system, complement receptor molecules on the cell surface play a key role. Current knowledge on structure, function, signal transduction and associated molecules is briefly summarized here. The role of complement receptors for human immunodeficiency virus (HIV)-associated pathogenesis is ambiguous and varies depending on cell type. On the one hand, complement receptors support the infected host to manage HIV infection and to defend itself, at least partially, against viral spreading throughout the organism. Such complement receptor-mediated supporting mechanisms are activation of immune cells and lysis of viral particles and infected host cells. On the other hand, HIV employs complement receptors to intrude more easily into various cell types, to become localized into lymph follicles and to activate viral replication in latently infected cells. This review summarizes the complex interaction of virus and complement receptors in HIV infection for different cell types.

Animals↗
PubMed1995

Akv murine leukemia virus enhances lymphomagenesis in myc-kappa transgenic and in wild-type mice.

The contribution of endogenous retroviruses to the multistep process of lymphomagenesis was investigated in wild-type mice and in two different myc-kappa transgenic mouse lines by infection with Akv. This retrovirus is derived from the endogenous ecotropic provirus of the AKR mouse and was previously considered to be nonlymphomagenic. The mice of the two myc-k transgenic lines are predisposed to B-cell lymphomagenesis and were therefore considered to be more susceptible to Akv. For comparison, the same mouse strains were also infected with the exogenous Moloney murine leukemia virus (MoMuLV). Both MoMuLV and Akv increased the tumor incidence and shortened the tumor latency period in wild-type mice and in the transgenic mouse lines. The differences in pathogenicity, number of provirus integrations, and level of virus expression between MoMuLV and Akv indicate different mechanisms of lymphomagenesis: while MoMuLV induced tumors apparently by insertional mutagenesis involving common integration sites similar to previous reports, the enhancement of lymphomagenesis by Akv seems to be directed by other mechanisms.

AKR murine leukemia virus↗
PubMed1993

Expression of basement membrane proteins: evidence for complex post-transcriptional control mechanisms.

Differentiated murine teratocarcinoma cell lines have been widely used as sources for the basement membrane proteins laminin and collagen IV. In order to understand the control of their expression, we have measured the transcription rates of the corresponding genes in nuclear run-on assays. The ratios of transcripts obtained from the five different genes of interest (for laminins A, B1, and B2 and alpha 1(IV), alpha 2(IV)) are rather different from the ratios of the corresponding mRNAs, which are again different from the protein levels needed. The gene for alpha 2(IV) is transcribed at a higher rate than the one for alpha 1(IV) and, similarly, the gene for laminin A is transcribed at a higher rate than the other two laminin genes, respectively. However, the alpha 2(IV) and laminin A mRNA levels are lower than those for the other chains of the same molecule. The alpha 1(IV) mRNA is 3- to 15-fold more abundant than the alpha 2(IV) mRNA, depending on the cell line. At the protein level, the A chain seems to be limiting for the assembly of laminin, in accordance with its low mRNA level. The two collagen chains have variable pool sizes, but the triple helical molecules always seem to be composed of two alpha 1(IV) and one alpha 2(IV) chains. These results point to extensive control mechanisms at various stages of posttranscriptional events, some of which we could identify.

Animals↗
PubMed1992

Evaluation of mRNA steady-state and protein levels for basement membrane proteins in cultured murine cells.

We have determined the mRNA steady-state levels for the six constituent polypeptide chains of the basement membrane proteins collagen IV, laminin and nidogen in murine cell lines derived from a teratocarcinoma, and in some other cell lines of different origin in stationary cultures and during different growth phases. The mRNA and protein levels change in response to growth phase. The amounts of the mRNAs for the single chains do not agree with the ratios needed for the different peptide chains of collagen IV and laminin. While the mRNA and protein levels for laminin are in a similar range for the teratocarcinoma-derived cell lines, the mRNA and protein levels vary by at least a factor of 10 for collagen IV. These results point to complex posttranscriptional regulatory mechanisms for the biosynthesis of basement membrane proteins.

Animals↗
PubMed1991

DNA fingerprinting with oligonucleotides can differentiate cell lines derived from the same tumor.

Oligonucleotide fingerprinting was applied to investigate the relatedness of several cell lines that were established between 1973 and 1977 from a teratocarcinoma. We were able to distinguish cell lines derived at different times. In addition, sublines from one cell line (PYS-2) could be discriminated by using a combination of different probes. Therefore multilocus fingerprinting with oligonucleotides is a useful method for monitoring changes in cell lines kept in culture for many generations.

Animals↗
PubMed1990

Detection of RNA on northern blots by negative staining with aurintricarboxylic acid.

Aurintricarboxylic acid (ATA) is a well-known inhibitor of RNA and DNA modifying enzymes and was suggested as a potent RNase inhibitor for preparation of RNA (Hallick et al., 1977, Nucleic Acids Res. 4, 3055-3064). We show that ATA is a very useful stain for detecting RNA on Northern blots and slot blots although it did not fully protect purified RNA in concentrated solution against RNase A.

Animals↗