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Christina Nilsson

Publications and source records attributed to Christina Nilsson.

12 recordsLinked to original sources
PubMed2006

An enzymatic ruler modulates Lewis antigen glycosylation of Helicobacter pylori LPS during persistent infection.

Helicobacter pylori persistently colonizes about half the human population and contributes to the development of peptic ulcer disease and gastric cancer. This organism has evolved means to structurally alter its surface characteristics to evade innate and adaptive immune responses. H. pylori produces LPS O-antigen units that can be posttranslationally fucosylated to generate Lewis antigens, structures also found on human epithelial cells. We demonstrate an extensive diversity of Lewis x and Lewis y expression in LPS O-antigen units, occurring over time and in different regions of the human stomach. Lewis expression patterns were correlated with the on/off status of the three fucosyltransferases (FucT), FutA, FutB, and FutC, which are regulated via slipped-strand mispairing in intragenic polyC tract regions of the corresponding genes. The alpha1,3-FucT, FutA and FutB, each contain a C-terminal heptad repeat region, consisting of a variable number of DD/NLRV/INY tandem repeats. Variations in the number of heptad repeats correlated to the sizes of O-antigen polymers to become decorated by fucose residues. Our data support a molecular ruler mechanism for how H. pylori varies its LPS fucosylation pattern, where one heptad repeat in the enzyme corresponds to one N-acetyl-beta-lactosamine unit in the O-antigen polysaccharide.

Amino Acid Sequence↗
PubMed2006

Myeloablative and immunosuppressive properties of treosulfan in mice.

OBJECTIVE: Treosulfan is a prodrug with a specific clinical activity in ovarian carcinoma and other solid tumors. Due to its myeloablative and immunosuppressive effects, its use in conditioning regimens prior to allogeneic stem cell treatment (SCT) has been proposed. In the present preclinical study, myeloablative as well as immunosuppressive properties of treosulfan were compared with those of busulfan and cyclophosphamide. METHODS: Three groups of BALB/c mice were treated with treosulfan, cyclophosphamide, or busulfan at sublethal doses that maintained survival without bone marrow support. The control group was left untreated. At different intervals, colony-forming unit granulocyte macrophage assay was performed on marrow cells. Additionally, immunological analyses were performed using spleen cells. RESULTS: We found that treosulfan and busulfan induced a high and persisting degree of myeloablation, as compared with cyclophosphamide. Moreover, treosulfan was more effective in depletion of splenic B and T cells in comparison with busulfan and cyclophosphamide. Furthermore, T cells isolated from the spleens of treosulfan- or busulfan-treated mice were not responsive to allogeneic cells compared with that observed in controls and cyclophosphamide-treated mice. Treatment with treosulfan induced only interleukin-2 production in spleen cells for a short time and had no significant effect on synthesis of tumor necrosis factor-alpha and/or interferon-gamma as compared with that observed in splenic T cells isolated from mice treated with either busulfan or cyclophosphamide. CONCLUSION: Our findings suggest that treosulfan possesses both myeloablative and immunosuppressive properties and may be used as a single agent for conditioning prior to bone marrow transplantation.

Animals↗
PubMed2005

Stability, pKa and plasma protein binding of roscovitine.

In the present investigation, the binding of roscovitine (100, 500 and 1500 ng/mL) to plasma proteins was studied at 25 and 37 degrees C by ultrafiltration and equilibrium dialysis methods. Drug stability in plasma was assessed during a 48 h at 4, 25 and 37 degrees C. The effect of thawing and freezing on drug stability was studied. The pKa of roscovitine was measured using capillary electrophoresis coupled with mass spectrometry. Roscovitine was quantified utilizing liquid chromatography and tandem mass spectrometry. Roscovitine is highly bound to plasma proteins (90%). Binding of roscovitine to human serum albumin was constant (about 90%) within concentration range studied while the binding to alpha1-acid glycoprotein decreased with increasing drug concentration indicating that albumin is more important in clinical settings. However, alpha1-acid glycoprotein might be important when plasma proteins change with disease. Protein binding was higher at 25 degrees C compared to 37 degrees C. The results obtained by equilibrium dialysis were in good agreement with those obtained by ultrafiltration. Roscovitine was stable at all temperatures studied during 48 h. Roscovitine has a pKa of 4.4 showing that the drug mainly acts like a weak mono-base. The results obtained in our studies are important prior to clinical trials and to perform pharmacokinetic studies.

Blood Proteins↗
PubMed2005

Effect of altering administration order of busulphan and cyclophosphamide on the myeloablative and immunosuppressive properties of the conditioning regimen in mice.

OBJECTIVE: The present study was designed to investigate the influence of the administration sequence of busulphan (Bu) and cyclophosphamide (Cy) during conditioning regimen on myeloablative and immunosuppressive effects and on engraftment. METHODS: Female Balb/C mice were treated with either Bu-Cy or Cy-Bu (assigned order of administration). Bu was administered as 8.75 mg/kg/day x 4 and Cy as 100 mg/kg/day x 2. The control consisted of untreated animals. Bone marrow and spleen were harvested during the conditioning regimen and for up to 19 days after treatment. Colony-forming unit granulocyte macrophage assay was performed on marrow cells. Immunological analyses were performed using spleen cells. Liver status was determined using aspartate amino transferase (AST), alanine amino transferase (ALT), and bilirubin. Animals assigned for engraftment study were conditioned as above and transplanted using sca-1 cells from male Balb/C donors. Engraftment was followed using fluorescence in situ hybridization up to 30 days posttransplantation. RESULTS: No significant difference in myeloablative effect was observed between treatments. Immunosuppressive activity expressed as CD3+/CD19+ and CD4+/CD8+ was also similar. Levels of cytokines interleukin 2, tumor necrosis factor alpha, and interferon gamma at the end of the conditioning regimen were lower in the Cy-Bu group, while liver enzymes were higher after the Bu-Cy regimen. Engraftment in bone marrow was reached faster within the first 20 days after conditioning with Cy-Bu compared to Bu-Cy. However, no difference in chimerism was observed at 30 days. CONCLUSION: Cy-Bu treatment resulted in lower levels of cytokines, faster bone marrow engraftment, and lower values of liver enzymes compared to Bu-Cy regimen, which may benefit stem cell transplantation outcomes.

Animals↗
PubMed2004

Comparative analysis of the complete cag pathogenicity island sequence in four Helicobacter pylori isolates.

The cytotoxin-associated gene (cag) pathogenicity island (PAI) is important for the virulence of Helicobacter pylori. In this study, we have compared the complete nucleotide sequence of the cag PAI in four clinical isolates. These isolates were selected from patients matched for age and sex from the same geographical region. The patients suffered from either gastric cancer (Ca52 and Ca73) or duodenal ulcer (Du23:2 and Du52:2). All four strains induced an interleukin (IL)-8 response in AGS cells and translocated CagA into host cells where the protein was tyrosine phosphorylated, and thus harboured a functional type IV secretion system encoded by the cag PAI. The cagA gene contains a variable region close to its 3' end. Different compositions of this region has been proposed to exert various degrees of morphological changes in cultured gastric epithelial cells, and there are indications that the structure of the repetitive region is connected to the severity of disease. One of the studied strains (Du23:2) possessed five Western-type repeat regions while the other three strains harboured one Western-type repeat. Strain Du23:2 also contained a major rearrangement or large insertion/duplication in the intergenic region between HP0546 and HP0547 (cagA). Sequence similar to that of genes HP0510 and HP0509 was found in the 5' end of this region. The 3' end was similar to the corresponding region of strain ATCC 43504, including a mini IS605 element and a duplication of the 3' end of the cag PAI. Finally, a novel gene was identified in the cag PAI in three of the sequenced strains at the position of HP0521. This gene, HP0521B, is present in approximately half of Swedish H. pylori isolates.

Antigens, Bacterial↗
PubMed2003

Gastric mucosal recognition of Helicobacter pylori is independent of Toll-like receptor 4.

Little is known about the interactions between Helicobacter pylori, which specializes in colonizing the mucin layer that covers the gastric mucosa, and primary gastric epithelial cells. The expression pattern of Toll-like receptors (TLRs) in primary gastric epithelial cells and cell lines was compared. Primary cells did not express TLR4, whereas all cell lines expressed a nonsignaling form of TLR4. Because other cells within the mucosa expressed TLR4, it was next investigated whether H. pylori can be recognized by TLR4--they cannot. Moreover, H. pylori infection of primary cells induced a regulated production of interleukin (IL)-6, IL-8, and tumor necrosis factor-alpha, whereas infection of cell lines only resulted in IL-8 production. The cytokine production in all cell types was strictly cag dependent. These findings indicate that, although the epithelium is important in directing the immune response against H. pylori infections, the response is independent of TLR4.

Adolescent↗
PubMed2003

The NudA protein in the gastric pathogen Helicobacter pylori is an ubiquitous and constitutively expressed dinucleoside polyphosphate hydrolase.

The gastric pathogen Helicobacter pylori harbors one Nudix hydrolase, NudA, that belongs to the nucleoside polyphosphate hydrolase subgroup. In this work, the enzymatic activity of purified recombinant NudA protein was analyzed on a number of nucleoside polyphosphates. This predicted 18.6-kDa protein preferably hydrolyzes diadenosine tetraphosphate, Ap(4)A at a k(cat) of 0.15 s(-1) and a K(m) of 80 microm, resulting in an asymmetrical cleavage of the molecule into ATP and AMP. To study the biological role of this enzyme in H. pylori, an insertion mutant was constructed. There was a 2-7-fold decrease in survival of the mutant as compared with the wild type after hydrogen peroxide exposure but no difference in survival after heat shock or in spontaneous mutation frequency. Western blot analyses revealed that NudA is constitutively expressed in H. pylori at different growth stages and during stress, which would indicate that this protein has a housekeeping function. Given that H. pylori is a diverse species and that all the H. pylori strains tested in this study harbor the nudA gene and show protein expression, we consider NudA to be an important enzyme in this bacterium.

Bacterial Proteins↗
PubMed2003

Persistent infection with Helicobacter pylori and the development of gastric cancer.

Gastric malignancies have been closely linked to infection of the gastric mucosa with Helicobacter pylori, but the individual factors involved in the multistage process of tumor development are still poorly understood. H. pylori evades the host defense system and causes persistent infection and chronic inflammation. Immune activation leads to DNA damage by the release of oxygen and nitrogen radicals. Ongoing tissue repair mechanisms and the secretion of cytokines and growth factors, as well as bacterial effector molecules, cause disturbances in the balance between epithelial cell proliferation and apoptosis, promote the accumulation of potential oncogenic mutations, and support neovascularization and tumor growth. In addition, H. pylori might hamper the development of an efficient antitumor immunity and provoke immune-mediated pathology. This review summarizes the recent progress in the understanding of the intimate bacteria-host relationship and the mechanisms by which H. pylori may promote the process of tumor development.

Apoptosis↗
PubMed2003

Correlation between cag pathogenicity island composition and Helicobacter pylori-associated gastroduodenal disease.

Helicobacter pylori infection is associated with a variety of outcomes ranging from seemingly asymptomatic coexistence to peptic ulcer disease and gastric cancer. The cag pathogenicity island (PAI) contains genes associated with a more aggressive phenotype and has been suggested to be a determinant of severe disease outcome. The cagA gene has served as a marker for the cag PAI. However, the presence of this single gene does not necessarily indicate the presence of a complete set of cag PAI genes. We have analyzed the composition of the cag PAI in 66 clinical isolates obtained from patients with duodenal ulcer, gastric cancer, and nonulcer dyspepsia. Hybridization of DNA to microarrays containing all the genes of the cag PAI showed that 76 and 9% of the strains contained all or none of the cag PAI genes, respectively. Partial deletions of the cag PAI were found in 10 isolates (15%), of which 3 were cagA negative. The ability to induce interleukin-8 (IL-8) production in AGS cells was correlated to the presence of a complete cag PAI. Strains carrying only parts of the island induced IL-8 at levels significantly lower than those induced by cag PAI-positive isolates. The presence of an intact cag PAI correlates with development of more severe pathology, and such strains were found more frequently in patients with severe gastroduodenal disease (odds ratio, 5.13; 95% confidence interval, 1.5 to 17.4). Partial deletions of the cag PAI appear to be sufficient to render the organism less pathogenic.

Antibodies, Bacterial↗
PubMed2002

Colonization of germ-free transgenic mice with genotyped Helicobacter pylori strains from a case-control study of gastric cancer reveals a correlation between host responses and HsdS components of type I restriction-modification systems.

Helicobacter pylori infects the stomachs of half of all humans. It has a relatively benign relationship with most hosts but produces severe pathology, including gastric cancer, in others. Identifying the relative contributions of host, microbial, and environmental factors to the outcome of infection has been challenging. Here we describe one approach for identifying microbial genes that affect the magnitude of host responses to infection. Single colony purified H. pylori isolates were obtained from 25 cases and 71 controls in a Swedish case-control study of gastric cancer. Strains were first phenotyped based on their ability to produce adhesins that recognize two classes of human gastric epithelial receptors. Thirteen binding strains and two non-binding controls were then subjected to whole genome genotyping using H. pylori DNA microarrays. A cohort of "variable" genes was identified based on a microarray-determined call of "absent" in at least one member of the strain panel. Each strain was subsequently introduced into two types of germ-free transgenic mice, each programmed to express a different host factor postulated to pose increased risk for development of severe pathology. Expression of biomarkers of host defense was quantitated 4 weeks after inoculation, and the magnitude of the response correlated with bacterial genotype. The proportion of genes encoding HsdS homologs (specificity subunit of hetero-oligomeric type I restriction-modification systems) was significantly higher in the pool of 18 variable genes whose presence directly correlated with a robust host response than their proportion in the remaining 352 members of the variable gene pool. This suggests that the functions of these HsdS homologs may include control of expression of microbial determinants that affect the extent of gastric responses to this potentially virulent pathogen.

Animals↗