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Biomedical subjects

R Kurth

Publications and source records attributed to R Kurth.

At least 73 records · Page 4Linked to original sources
PubMed1997

Cerebral haemoglobin oxygenation during sustained visual stimulation--a near-infrared spectroscopy study.

Using near-infrared spectroscopy, we investigated the time-course of the concentrations of oxygenated haemoglobin, [oxy-Hb], and deoxygenated haemoglobin [deoxy-Hb], in the occipital cortex of healthy human adults during standard sustained visual stimulation. Within a few seconds after stimulation (by coloured dodecahedron), we observed a decrease in [deoxy-Hb], peaking after 13 s ('initial undershoot'). In the subsequent 1-2 min, in seven out of ten subjects, [deoxy-Hb] gradually returned to a plateau closer to the baseline level. After cessation of stimulation, there was a 'post-stimulus overshoot' in [deoxy-Hb]. There was a statistically significant correlation between the size of the 'initial undershoot' and the post-stimulus overshoot'. The concentration of oxyhaemoglobin increased upon functional activation. However, in the mean across all subjects there was no 'initial overshoot'. After approximately 19 s it reached a plateau and remained constantly elevated throughout the activation period. After cessation of activation there was a 'post-stimulus undershoot' of oxyhaemoglobin. It is important to consider the time-course of haemoglobin oxygenation when interpreting functional activation data, especially those data obtained with oxygenation-sensitive methods, such as BOLD-contrast fMRI.

Adult↗
PubMed1997

Molecular cloning, sequence, expression, and processing of the interleukin 16 precursor.

Interleukin 16 (IL-16) has been shown to function as chemoattractant factor, as a modulator of T-cell activation, and as an inhibitor of immunodeficiency virus replication. The recent identification of inconsistencies in published IL-16 cDNA nucleotide sequences led to the proposal that IL-16 is synthesized in the form of a large precursor protein (pro-IL-16). To identify the true transcriptional start of the IL-16 mRNA rapid amplification of cDNA ends methods were applied. The complete pro-IL-16 cDNA was subsequently molecularly cloned, sequenced, and expressed in COS-7 cells. We report here that pro-IL-16 is most likely synthesized as a 67-kDa protein and is encoded from a major 2.6-kb transcript. Recombinant pro-IL-16 polypeptides are specifically cleaved in lysates of CD8(+) cells, suggesting that the naturally secreted bioactive form of IL-16 is smaller than the originally published 130 amino acids fragment. Moreover, in contrast to other interleukins such as IL-15, IL-16 mRNA expression is almost exclusively limited to lymphatic tissues underlining the potential of IL-16 as an immune regulatory molecule.

Amino Acid Sequence↗
PubMed1997

Vaccine effect using a live attenuated nef-deficient simian immunodeficiency virus of African green monkeys in the absence of detectable vaccine virus replication in vivo.

Immunization of adult macaques with live attenuated simian immunodeficiency viruses (SIVs) lacking the nef genes has been shown to protect against challenge with full-length pathogenic SIV. To test live attenuated virus vaccines for the first time in a natural host we have constructed a mutant SIV from African green monkeys (SIVagm) with a deletion of 125 bp in the nef gene (SIVagm3 delta nef). This mutant showed moderately delayed in vitro replication in the T cell line MOLT-4/8 and in primary peripheral blood mononuclear cells from African green monkeys (Cercopithecus aetiops) and pig-tailed macaques (Macaca nemestrina) compared with cloned wild-type SIVagm3. In contrast, in vivo replication of SIVagm3 delta nef in African green monkeys was severely impaired or undetectable and did not induce seroconversion. After challenge with wild-type SIVagm3 the SIVagm3 delta nef preinoculated African green monkeys showed a memory antibody response that declined after week 2. In three of four African green monkeys the cell-associated virus load and in two of four African green monkeys the plasma virus load was dramatically decreased after the challenge compared with naive control animals. The remaining animal showed no evidence of productive challenge virus replication. This study demonstrates that a strong vaccine effect or protection in the SIVagm/African green monkey system is possible using a live attenuated vaccine in the absence of a productive infection and corresponding humoral immune response.

Animals↗
PubMed1997

Expression of human endogenous retrovirus type K envelope glycoprotein in insect and mammalian cells.

The human endogenous retrovirus type K (HERV-K) family codes for the human teratocarcinoma-derived retrovirus (HTDV) particles. The existence of the envelope protein (ENV) of HERV-K encoded by the subgenomic env mRNA has not yet been demonstrated. To study the genetic requirements for successful expression of ENV, we have constructed a series of recombinant HERV-K env expression vectors for infection and transfection experiments in insect cells and mammalian cells, respectively. Six baculovirus constructs bearing full-length or truncated HERV-K env with or without homologous or heterologous signal peptides were used for infections of insect cells. All recombinant baculoviruses yielded ENV proteins with the expected molecular masses. The full-length 80- to 90-kDa HERV-K ENV protein including the cORF leader sequence was glycosylated in insect cells. In addition, the 14-kDa cORF protein was expressed due to splicing of the full-length env mRNA. The ENV precursor protein is not cleaved to the surface (SU) and transmembrane (TM) glycoproteins; it does not appear on the surface of infected insect cells and is not secreted into the medium. For ENV expression in COS cells, plasmid vectors harboring the cytomegalovirus immediate-early promoter/intron A element and the tissue plasminogen activator (t-PA) signal peptide or the homologous HERV-K signal peptide upstream of the env gene were employed. Glycosylated and uncleaved ENV was expressed as in GH teratocarcinoma cells but at higher levels. The heterologous t-PA signal sequence was instrumental for expression of HERV-K ENV on the cell surface. Hence, we have shown for the first time that the HERV-K env gene has the potential to be expressed as a full-length envelope protein with appropriate glycosylation. In addition, our data provide explanations for the lack of infectivity of HERV-K/HTDV particles.

Animals↗
PubMed1997

Characterization of the antibody response specific for the human endogenous retrovirus HTDV/HERV-K.

Differentiated human teratocarcinoma cell lines produce the human teratocarcinoma-derived virus (HTDV) particles encoded by the human endogenous retrovirus sequence HERV-K. We screened almost 2,000 human sera for antibodies against this endogenous human retrovirus, HTDV/HERV-K. Specificity of the immunofluorescence reactions using particle producing teratocarcinoma cells was confirmed by immunoelectron microscopy of ultrathin frozen sections. Immunoblot analyses using lysates of HTDV-producing cells revealed a 80-kDa HERV-K Gag precursor and a 90-kDa putative viral Env protein after incubation with positive sera. No processed Gag protein could be observed. Virus-specific bands were not detected in lysates of nonproducing cells. High antibody titers were found in about 60% of male patients with germ cell tumors. Antibody reactivity declined after tumor removal. In healthy blood donors, anti-HTDV reactivity was found only at low titers in a small percentage (3.9%) of individuals. A slightly elevated but statistically significant percentage of HTDV positivity was also observed for sera of pregnant women, whereas human immunodeficiency virus-positive individuals exhibited no peculiarity compared to normal blood donors. Our results provide evidence that HTDV particles are expressed in vivo and that the immune reaction against HTDV/HERV-K is specific for defined viral proteins.

Antibodies, Viral↗
PubMed1997

Increased serum and mRNA levels of RANTES associated with elevated levels of activated CD8+CD38+ T cells in HIV-1 infected individuals.

The serum levels of the beta-chemokine RANTES and, albeit less, MIP-1 beta were found to be increased in 37 HIV-1 infected compared to seronegative individuals. In contrast the serum levels of IL-16 were only sporadically elevated in seropositives as well as in seronegatives. Concomitantly, the RANTES gene expression increased about tenfold in seropositives, whereas the MIP-1 beta and IL-16 mRNA levels were not elevated. No correlation between the increase of the MIP-1 beta and RANTES serum concentrations and the plasma virus load, the number of the peripheral CD4+ T cells or the therapy status of the patients was found. However, the increased proportion of activated CD8+CD38+ T cells in the peripheral blood of all seropositives paralleled the increased RANTES serum levels detected indicating that immune activation in HIV-1-infected individuals may contribute to increased RANTES serum levels.

ADP-ribosyl Cyclase↗
PubMed1997

Interleukin-16 for the gene therapy of HIV infection.

Interleukin 16 (IL-16) has been shown to function as chemoattractant factor, as a modulator of T-cell activation and as an inhibitor of human immunodeficiency virus (HIV) replication. It is now clear that IL-16 is synthesised as a large precursor molecule (pro-IL-16), from which as yet unidentified proteases release a bioactive carboxyterminal fragment. The mechanism for IL-16 secretion is still unknown, but it is likely that the secreted protein is smaller than the originally published 130 amino acids. Upon transfection of an IL-16 cDNA, human T-cells became virtually resistant against HIV infection. This system may well be helpful in studying the mechanism of HIV suppression by this lymphokine. In addition, this approach could potentially be important for the development of gene therapy against HIV.

Journal Article↗
PubMed1996

The immunosuppressive peptide of HIV-1 inhibits T and B lymphocyte stimulation.

The transmembrane glycoproteins of all retroviruses contain a conserved region composed of a leucine zipper, an immunosuppressive domain, and an immunodominant Cys-Cys loop. The amino acid sequence of the immunosuppressive domain of gp41 of human immunodeficiency virus type 1 (HIV-1; amino acids 583-599) is closely related, but not identical, to the immunosuppressive domains of type C and D retroviruses. A synthetic peptide corresponding to the immunosuppressive domain of HIV-1 (immunosuppressive peptide, ISU-peptide) inhibits mitogen and lymphokine stimulation of T lymphocytes. It is interspecies reactive and inhibits both human and mouse lymphocytes. The inhibitory effect is not based on direct cytotoxicity and the peptide is immunosuppressive only when conjugated to a carrier protein. The ISU-peptide of HIV-1 also inhibits B lymphocyte stimulation by the B cell mitogen lipopolysaccharide and by specific antibodies against delta and mu chains of cell surface immunoglobulins. These data suggest that the immunosuppressive domain of gp41 may play an important role in the immunopathogenesis of AIDS.

Amino Acid Sequence↗
PubMed1996

The viruses in all of us: characteristics and biological significance of human endogenous retrovirus sequences.

Human endogenous retroviruses (HERVs) are very likely footprints of ancient germ-cell infections. HERV sequences encompass about 1% of the human genome. HERVs have retained the potential of other retroelements to retrotranspose and thus to change genomic structure and function. The genomes of almost all HERV families are highly defective. Recent progress has allowed the identification of the biologically most active family, HTDV/HERV-K, which codes for viral proteins and particles and is highly expressed in germ-cell tumors. The demonstrable and potential roles of HTDV/HERV-K as well as of other human elements in disease and in maintaining genome plasticity are illustrated.

Antibody Formation↗
PubMed1996

Lack of dichotomy between virus load of peripheral blood and lymph nodes during long-term simian immunodeficiency virus infection of African green monkeys.

During the asymptomatic phase of human immunodeficiency virus 1 (HIV-1) infection the lymphatic tissues seem to function as a major reservoir of HIV. We have examined the viral load in peripheral blood mononuclear cells (PBMC) and lymph node mononuclear cells (LNMC) of 12 naturally and 4 experimentally long-term simian Immunodeficiency virus (SIV)-infected African green monkeys (AGM) to help explain the apathogenicity of the AGM isolates of SIV (SIVagm) in their natural host. The mean number of SIVagm producing cells determined by limiting dilution assay was found to be 1.7 +/- 2.2 and 2.1 +/- 3.3 per 10(5) PBMC or LNMC, respectively. Similarly, polymerase chain reaction analysis of serially diluted cells showed the mean provirus carrying cell number to be 2.8 +/- 3.7 per 10(5) PBMC and 4.0 +/- 5.5 per 10(5) LNMC. When normalized for CD4+ cells the provirus and infectious virus loads in the LNMC and PBMC were also similar. No trapping of virus particles could be detected by in situ hybridization or immunohistochemistry. The data demonstrate that in contrast to HIV-1-infected humans, the viral burden in the lymph nodes of long-term SIV(agm)-infected AGMs is comparable to that in the PBMC.

Animals↗
PubMed1996

Protection from pathogenic SIVmac challenge following short-term infection with a nef-deficient attenuated virus.

Infection of rhesus macaques with attenuated SIVmac is, at present, the only strategy which confers significant protection from challenge with wild-type SIVmac grown in monkey PBMC. However, initial results suggest that the protective mechanism does not develop until late after "vaccination" (approx 10 months). As part of a European study using the C8 variant of SIVmac251-32H (containing an in-frame 12-bp deletion in the nef gene), we wished to determine (a) if protection could be achieved against challenge with a "swarm" of SIVmac251-32H produced in monkey cells and (b) if protection could be demonstrated after a short period of infection with the attenuated virus. Eight Indian rhesus macaques were infected with C8 and four were challenged after 10 weeks with 50 MID50 of an uncloned stock of SIVmac251-32H grown in rhesus cells, and the other four were challenged after 20 weeks. Four animals served as naive controls. Three of the four monkeys challenged at 10 weeks and three of those challenged at 20 weeks were protected from productive superinfection. From one monkey in each group it was, however, possible to demonstrate the presence of the wild-type provirus in monkey PBMC by diagnostic PCR and anamnestic immune response. There was no apparent correlation between the levels of binding or neutralizing antibodies on the day of challenge and subsequent protection. Approximately 1 year after infection with the attenuated virus all monkeys were rechallenged with the heterologous SIVsm strain, first with 10-20 MID50 and then with 1000 MID50. Although not all of the SIVsm-inoculated naive controls became productively infected, PCR analysis failed to reveal any evidence for infection of the "immunized" monkeys.

Animals↗
PubMed1996

Induction of antibodies against SIV antigens after intramuscular nucleic acid inoculation using complex expression constructs.

By studying the infection of rhesus macaques with simian immunodeficiency virus (SIVmac) the potential of nucleic acid immunisation against AIDS can be evaluated. As a first step towards the development of suitable expression constructs, the levels and the durations of expression elicited by the house-keeping gene promoters of the murine phospho-glycerate kinase (PGK) gene and rat proto-ras 1Ha, a lentiviral LTR and the CMV-intron A promoter were tested in BALB/c mice intramuscularly inoculated with marker gene constructs encoding luciferase. The expression levels achieved by the CMV-intron A and the lentiviral promoter were comparably high, and also the PGK promoter induced a high level of expression for at least 64 days. Following the inoculation of plasmids comprising single or multiple genes of SIV, the induction of specific antibodies directed against SIV antigens was demonstrated. We previously showed in vitro that int- and nef-defective mutants of SIVmac were able to initiate a limited and self-abortive infection of permissive cells in the absence of chromosomal integration of the viral DNA. Intramuscular inoculations in monkeys using int-defective proviral DNA of SIV will show whether an increased immune response may be induced by expression of viruses undergoing a self-limited replication in vivo.

Animals↗
PubMed1996

Endogenous retroviral long terminal repeats of the HLA-DQ region are associated with susceptibility to insulin-dependent diabetes mellitus.

HLA-DQ genes are the main inherited factors predisposing to IDDM. This gene region harbors long terminal repeat (DQ LTR) elements of the human endogenous retrovirus HER V-K, which we analyzed for a possible association with disease. We first investigated whether LTR segregate with DQ alleles in families. Members (n = 110) of 29 families with at least one diabetic child, unrelated patients with IDDM (n = 159), and healthy controls (n = 173) were analyzed. Genomic DNA was amplified for DQ LTR3 by a nested primer approach as well as for DQA1 and DQB1 second exons, to assign DQA1 and DQB1 alleles. DQ LTR segregated in 24 families along with DQ alleles. Of the 29 families, 20 index patients were positive for DQ LTR. The DQ LTR was in all patients on the haplotype carrying the DQA1 *0301 and DQB1 *0302 alleles. A majority of patients had DQ LTR (62%) compared with controls (38%) (p < 1.3 x 10(-5)), even after matching for the high-risk alleles DQA1 *0501, DQB1 *0201-DQA1 *0301, and DQB1 *0302 (79% of patients and 48% of controls; p < 0.02). Subtyping for DRB1 *04 alleles in all DQB1 *0302+ individuals showed 56% DRB1 *0401, DQB1 *0302 [LTR' patients vs. 29% controls with the same haplotype (p < 0.002)]. In conclusion, these data demonstrate the segregation of DQ LTR with DQA1, DQB1 alleles on HLA haplotypes. Furthermore their presence on DRB1 *0401-, DQA1 *0301-, and DQB1 *0302-positive haplotypes suggest that they contribute to DQ-related susceptibility for IDDM.

Diabetes Mellitus, Type 1↗