Biomedical subjects

B Røsok

Publications and source records attributed to B Røsok.

8 recordsLinked to original sources

PubMed2000

Deregulation of the CD95/CD95L system in lymphocytes from patients with primary acute HIV infection.

OBJECTIVE: To analyze the role of CD95/CD95 ligand (CD95L) expression and functionality in peripheral blood lymphocytes (PBL) during primary, acute HIV syndrome (AHS) and in the subsequent period. PATIENTS: Twelve patients were studied during the acute phase of the viral infection and most were followed for some months. METHODS: Cell culture and cytotoxicity assays based upon 51Cr release and flow cytometry were used to evaluate cell killing via CD95 molecule, flow cytometry to assess surface antigens, enzyme-linked immunosorbent assay (ELISA) for the determination of soluble CD95 and CD95L plasma levels, quantitative competitive (QC) reverse transcription polymerase chain reaction (RT-PCR) with an original RNA competitor for the analysis of CD95L mRNA expression and QC RT-PCR for determining plasma viral load. RESULTS: The analysis of PBL during this phase revealed that almost all cells, including CD8 T cells with a virgin phenotype, B lymphocytes and natural killer cells displayed CD95 molecules on the plasma membrane. Activation of CD95 on the surface of isolated lymphocytes by anti-CD95 monoclonal antibodies or binding to CD95L induced rapid apoptosis. However, CD95L mRNA was not expressed in PBL from these patients and was poorly inducible. Soluble CD95 was found in the plasma of all patients, but only in a few at high levels, even some months after seroconversion. In contrast, soluble CD95L was detected in only one patient, this occurring after the symptomatic period. For 10 of the 12 patients, expression of CD95 on the cell membrane or in the plasma did not correlate with the plasma viral load, which varied widely from patient to patient. Further, plasma levels of soluble CD95 were not altered by decreased lymphocyte activation or by efficient antiretroviral therapy. CONCLUSIONS: In patients experiencing an acute, primary HIV infection, a prolonged deregulation of the CD95/CD95L system may exist, which is probably not entirely related to virus production but may contribute to the pathogenesis of the disease. The hypothesis can be put forward that a complex balance exists between proapoptotic events (increase in CD95 expression), probably triggered by the host as a method to limit viral production, and antiapoptotic events (decrease in CD95L expression) probably triggered by the virus as a way to increase its production and survival.

Apoptosis↗

PubMed1998

Subcellular localization of human immunodeficiency virus type 1 RNAs, Rev, and the splicing factor SC-35.

The HIV-1 protein Rev regulates the cytoplasmic levels of incompletely spliced HIV-1 mRNAs. The plasmid pSVc21, which contains a HIV-1 provirus, was introduced into COS cells by transient transfection. Simultaneous detection of HIV-1 RNAs and Rev proteins produced in transfected cells was then performed in order to determine the relative distribution of these two components. HIV-1 RNAs and the Rev protein localized to the same areas of the nucleoplasm, implying that these locations represent sites where Rev interacts with its target RNAs. Using a monoclonal antibody targeted to the splicing factor SC-35 it was demonstrated that the sites where HIV-1 mRNAs and Rev were detected often contained weak anti-SC-35 staining, whereas little RNA and Rev were found in strongly labeled SC-35-containing speckles. The same distribution of HIV-1 RNAs relative to SC-35 was also seen in transfected HeLa cells and in primary human lymphocytes infected with HIV-1 primary isolates. In addition, transiently expressed intron-containing beta-globin RNAs were shown to distribute to weak anti-SC-35 staining in a manner similar to that of HIV-1 RNAs. The findings suggest that Rev and HIV-1 RNAs interact at putative sites of mRNA transcription and splicing.

Animals↗

PubMed1997

CD8+ T cells from HIV type 1-seronegative individuals suppress virus replication in acutely infected cells.

CD8+ lymphocytes (CD8 cells) have been shown to inhibit replication of the human immunodeficiency virus (HIV) in vitro when cocultured with HIV-infected CD4+ lymphocytes (CD4 cells). This suppressive effect on HIV replication in experimentally infected CD4 cells has so far been demonstrated only for CD8 cells from HIV-seropositive individuals. In the present study we have investigated if CD8 cells from HIV-negative individuals can also suppress HIV replication in experimentally infected CD4 cells. Positively selected CD4 cells were infected with phenotypically different primary isolates of HIV type 1 and 2 (HIV-1 and HIV-2). Graded numbers of CD8 cells were added to the infected cultures. The T cells were activated by antibodies directed against the CD3 molecule or the T cell receptor. Culture supernatants were harvested for HIV p24 quantitation and the CD8 suppression of HIV replication was calculated by comparing p24 levels from parallel cultures in the presence or absence of CD8 cells from different donors. We show that CD8 cells from unexposed HIV-seronegative blood donors are able to control HIV-1 and HIV-2 replication in experimentally infected autologous CD4 cells. The antiviral activity of CD8 cells from and HIV-naive individual was reproducible over time and the suppressive effect was comparable to that seen with CD8 cells from HIV-positive individuals. The infected cells were not eliminated from the cultures. The suppressive effect of CD8 cells varied depending on the dose and biological phenotype of the virus used for infection. Thus, exposure to HIV in vivo is not a prerequisite for CD8 cells to exert a suppressive effect on HIV replication in acutely infected cells.

CD4-Positive T-Lymphocytes↗

PubMed1996

Dynamics of HIV-1 replication following influenza vaccination of HIV+ individuals.

Levels of HIV-1 have been reported to increase in peripheral blood after influenza vaccination of HIV+ individuals. In this study we have evaluated the dynamics of these changes. Ten HIV-1+ individuals classified in revised CDC clinical categories B and C as well as five seronegative healthy controls were vaccinated with the recommended influenza strains. HIV viral RNA and proviral DNA were sequentially quantified in serum and blood lymphocytes, respectively. Nine of the 10 HIV+ individuals had an increase in the frequency of infected CD4 cells 2 weeks after influenza vaccination. Individuals with low viral load had a rapid increase in viraemia and a small increase in frequency of infected cells in peripheral blood. In contrast, individuals with high viral load had a small drop in viraemia followed by a significant rise in the rate of infected cells. The observed change may resemble those taking place during intercurrent infections in HIV+ individuals. The effects of the relative increases in infectious virus after the transient viraemic phase should be further investigated to evaluate potential risks of vaccination.

CD4-Positive T-Lymphocytes↗

PubMed1995

Characterization of HIV type 1 from Romanian children: lack of correlation between V3 loop amino acid sequence and syncytium formation in MT-2 cells.

The biological properties and amino acid sequences of the third variable domain (V3 loop and flanking regions) of the env region of 34 HIV-1 isolates obtained from Romanian children were analyzed. Unambiguous nucleic acid sequences were obtained from 31 isolates. The derived V3 amino acid sequences were highly homologous (93-100%) and clustered with the HIV-1 subtype F Romanian consensus. Five of the 31 isolates presented a syncytium-inducing phenotype in MT-2 cells and established continuous viral replication in various CD4+ cell lines (rapid/high phenotype). The V3 sequence from one of these isolates showed a slightly lesser degree of homology with the consensus sequence. The presence of positively charged amino acids at positions 306 and 320 has been strongly associated with the ability to induce syncytia in MT-2 cells, whereas negatively or uncharged amino acids at these positions are present in non-syncytium-inducing isolates (slow/low phenotype). There was, however, no correlation between phenotype and amino acid sequence in the five syncytium-inducing isolates; negatively or uncharged amino acids were conserved at positions 306 and 320 for all 31 isolates in sequences obtained from PBMCs. A tendency toward a more positive net charge in the V3 loop of syncytium-inducing isolates was noted. These data confirm the recent observations that HIV-1 isolates from Romania not only cluster in subtype F, but also show a high degree of interpatient homogeneity in the V3 region.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1994

[Time for realism].

Explore the source record for details and available documents.

Acquired Immunodeficiency Syndrome↗

PubMed1993

Release of bicarbonate from damaged and restituted gastric mucosa in the cat.

BACKGROUND: Gastric mucosal damage leads to luminal alkalinization, but its dependence on mucosal blood flow and acid secretory state of the mucosa is not known. This study examined release of bicarbonate to the gastric lumen and mucosal blood flow in cats after mucosal damage caused by 2 mol/L NaCl and during 90 minutes of epithelial restitution. METHODS: Bicarbonate was calculated from measurements of pH and PCO2 in the luminal perfusate. Mucosal blood flow was measured with microspheres. RESULTS: Luminal bicarbonate increased more than twofold after damage in pharmacologically nontreated, pentagastrin-treated, and omeprazole-treated animals (P < 0.001). Luminal bicarbonate thereafter decreased completely to pre-damage level in pentagastrin-treated, partly in nontreated, but remained elevated in omeprazole-treated animals. Mucosal blood flow increased about 100% 15 minutes after damage (P < 0.001), irrespective of secretory state. Bicarbonate availability (arterial [HCO(3-)] x mucosal blood flow) was significantly related to luminal release of bicarbonate from the newly damaged (P < 0.01) but not from the restituted mucosa. CONCLUSIONS: (1) From the newly damaged mucosa, the luminal release of bicarbonate is related to availability of blood-borne bicarbonate. (2) From acid-stimulated restituted mucosa, the bicarbonate produced by the parietal cells is not released to the lumen, but either consumed within the mucosa by back-diffusing H+ or distributed to the systemic circulation.

Animals↗

PubMed1991

Gastric bicarbonate secretion, acid secretion, and mucosal blood flow during influence of pentagastrin and omeprazole in the cat.

In this study secretion of bicarbonate and acid and mucosal blood flow were determined simultaneously in cats. The gastric lumen of anesthetized cats was continuously perfused with isotonic saline. Secretion of HCO-3 and H+ was calculated from continuous measurements of pH and PCO2 in the perfusate. Mucosal blood was measured by means of radiolabeled microspheres. Under resting acid secretory conditions, bicarbonate secretion into the gastric lumen averaged 1.0 mumol/min. Somewhat surprising, both omeprazole (4 mg/kg as bolus) and pentagastrin (16 micrograms/kg.h intravenously) significantly reduced the HCO-3 secretion. Omeprazole did not influence mucosal blood flow, whereas corpus mucosal blood flow increased during pentagastrin stimulation. Under resting acid secretory conditions and during omeprazole treatment there was a close linear relationship between acid and bicarbonate secretion. No such relationship was found during pentagastrin stimulation of the mucosa. No consistent relationship was obtained between blood flow and bicarbonate secretion in normal gastric mucosa.

Animals↗