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Biomedical subjects

A Vaheri

Publications and source records attributed to A Vaheri.

At least 73 records · Page 4Linked to original sources
PubMed1999

Phage-displayed peptides mimicking the discontinuous neutralization sites of puumala Hantavirus envelope glycoproteins.

We selected peptide ligands mimicking the surface structure of discontinuous binding sites of Puumala hantavirus-neutralizing monoclonal antibodies from a random 18-amino acid peptide library containing a disulfide bridge in a fixed position and displayed on a filamentous phage. The varying of selection conditions, either by shortening of the association time or by competitive elution with antigen, was crucial for the selection of peptide inserts that could be aligned with the primary sequences of the envelope glycoproteins G1 and G2. Correspondingly, when the envelope glycoprotein sequences were synthesized as overlapping peptides as spots on membrane, the same site in primary structure was found as with phage display, which corroborates the use of the two methods in mapping of conformational epitopes. Also, epitopes reactive with early-phase sera from Puumala virus infection were defined with the pepspot assay in the amino-terminal region of G1. Similarities of the selected phage clones to a monoclonal antibody-escape mutant site and to a linear early-phase epitope were found.

Amino Acid Sequence↗
PubMed1999

Puumala virus infections in Finland: increased occupational risk for farmers.

Puumala hantavirus, transmitted by bank voles (Clethrionomys glareolus), causes a mild-type hemorrhagic fever with renal syndrome. The disease is common in Finland and is considered an occupational hazard for farmers, but the actual risk has not been assessed by analytical studies. Data on 5,132 serologically confirmed Puumala virus infections during 1989-1994 were analyzed, and cases among farmers and the population living in similar conditions were compared. The farmers contracted the disease earlier and more often than did the comparison group. In the province of Mikkeli with the highest incidence (70/100,000), the risk ratio was 5.1 (95% confidence interval (CI) 3.0-8.4) for 20- to 29-year-old farmers; in the older age groups, the risk was still increased but the risk ratios were lower. The peak incidence in the comparison group was 10 years later (age group 30-39 years). For the whole country, the result was similar although less marked. The average risk ratio adjusted by age, sex, and geographic variation was 1.7 (95% CI 1.5-1.8) for the whole country and 1.9 (95% CI 1.5-2.3) for the Mikkeli province, where 80% of Puumala virus infections among young farmers could be estimated to be attributable to occupation.

Adult↗
PubMed1999

Tissue plasminogen activator gene expression in multiple sclerosis brain tissue.

Recent studies have implicated tissue-type plasminogen activator (tPA) in neurodegeneration. We studied multiple sclerosis (MS) brain tissue for tPA gene and protein expression in comparison with reference tissue, by in situ hybridisation and immunohistochemistry. MS is characterised by demyelination in the central nervous system. In this study, neuronal cell bodies in MS brain showed high expression of tPA mRNA and protein, while in reference brains, staining for protein and mRNA expression were very low in neurons and mostly restricted to blood vessel walls. In MS, there was an additional staining of mononuclear cells within perivascular cuffs and foamy macrophages within demyelinating plaques. In view of evidence that the final process of demyelination in MS is thought to be enzyme-mediated, our work suggests the involvement of tPA and by inference plasmin, in the demyelinating process. Blocking tPA or plasmin activity may be a potentially beneficial therapeutic approach in MS.

Blotting, Northern↗
PubMed1999

Analysis of puumala hantavirus genome in patients with nephropathia epidemica and rodent carriers from the sites of infection.

Reverse transcription-polymerase chain reaction (RT-PCR) followed by sequence and phylogenetic analyses were used to study specimens from nine Finnish nephropathia epidemica (NE) patients admitted to hospital during the epidemic in winter 1996-1997. Blood samples from six patients were found to be positive for the partial M- and/or S-segment sequences of Puumala hantavirus (PUUV). Analyses of these sequences (nt 2168-2610 for the M segment, and nt 819-1082 for the S segment) revealed six distinct PUUV strains showing highest similarity to previously described PUUV strains from Finland: 90-95% for the S segment, and 90-99% for the M segment. Accordingly, on the phylogenetic trees calculated for both viral segments, all six human strains were placed within the Finnish genetic lineage of PUUV. Attempts were made to trace five RT-PCR-positive patients to local bank voles (Clethrionomys glareolus) infected with wild-type PUUV, and for two patients a comparative analysis of human- and rodent-originated viral sequences was undertaken. Whereas in the first case the differences between the sequences were substantial (5. 7% for the S segment, and 10.8%, for the M segment), in the other case the M segment sequence recovered from the clinical specimen was 100% identical to three sequences recovered from rodent lungs, and the S sequences differed by one silent substitution only. This is the first finding of virtually identical PUUV sequences in an NE patient and a natural rodent host from the site of infection.

Adolescent↗
PubMed1999

Epidemiological study of nephropathia epidemica in Finland 1989-96.

This study presents data on 33,000 serum samples studied from July 1989 to June 1996 in Finland, with 6,701 serologically confirmed Puumala virus (PUU) infections. In addition, a PUU serosurvey of 8,000 sera from Finland is presented. On average, 957 PUU infections were detected annually, resulting in an incidence of 19/100,000; mortality was less than 0.1%. The infection was most common in the district of Ita-Savo with an incidence of 90/100,000. The seasonal peak was in November-December; however, the urban population had its incidence peak in August. Local epidemics mirrored bank vole densities, with 3-4-y cycles. Males contracted the disease at a mean age of 40 y, females at 44 y (male:female ratio 2:1). The disease was relatively rare in children and elderly people. The nationwide PUU antibody prevalence for women entering Finnish maternity clinics was 3%, suggesting 5% for the total population. The highest prevalences (7% for young women) were encountered in eastern Finland. In the district with the highest clinical alert, approximately 30% of all PUU infections were estimated to lead to clinical disease with serological confirmation.

Adolescent↗
PubMed1999

HLA-DQ alleles and human papillomavirus DNA in adult-onset laryngeal papillomatosis.

Sixty-two patients with histologically confirmed adult-onset laryngeal papilloma were clinically examined; their HLA class II DQA1 and DQB1 alleles and the presence and type of human papillomavirus (HPV) in their laryngeal papilloma biopsies were determined by polymerase chain reaction-based methods. No differences in the DQA1 or DQB1 frequencies appeared between the patients as a group and the reference population. When the patients were divided into groups according to number of laryngeal procedures performed, no HLA association was noticed with any group, nor did the presence of HPV-6 or HPV-11 DNA in the laryngeal specimen correlate with HLA type. A suggestive association was found between the DQB1 *0501 allele and the 16 patients whose laryngeal biopsy was HPV-negative, but because of the small series, additional patients need to be studied. Earlier, the DQB1 *0501 allele was reported to be protective against cervical cancer, another HPV-associated disease.

Adolescent↗
PubMed1999

Isolation and characterization of Dobrava hantavirus carried by the striped field mouse (Apodemus agrarius) in Estonia.

Dobrava hantavirus (DOB) was isolated from the striped field mouse (Apodemus agrarius) trapped on Saaremaa Island, Estonia, and its genetic and antigenic characteristics were subsequently analysed. Phylogenetic analysis showed that the Estonian DOB strain, together with several wild strains carried by Apodemus agrarius, forms a well-supported lineage within the DOB clade. The topography of the trees calculated for the S, M and L nucleotide sequences of the Estonian DOB suggests a similar evolutionary history for all three genes of this virus and, therefore, the absence of heterologous reassortment in its evolution. A cross-neutralization comparison of the Estonian virus with the prototype DOB, isolated from a yellow-necked mouse (A. flavicollis) in Slovenia, revealed 2- to 4-fold differences in the end-point titres of rabbit and human antisera. When studied with a panel of 25 monoclonal antibodies (MAbs), the Estonian and Slovenian DOB isolates showed similar antigenic patterns that could be distinguished by two MAbs. Genetic comparison showed sequence differences in all three genome segments of the two DOB isolates, including an additional N-glycosylation site in the deduced sequence of the G2 protein from the Estonian virus. Whether any of these mutations relates to the different rodent hosts rather than to the distant geographical origin of the two isolates remains to be resolved. Taken together, our observations suggest that A. agrarius, which is known to harbour Hantaan virus in Asia, carries another hantavirus, DOB, in north-east Europe.

Animals↗
PubMed1999

Plasminogen activation in human leukemia and in normal hematopoietic cells.

The active process of pericellular proteolysis is central in tumor invasion, and in particular the essential role of the urokinase-type plasminogen activator (uPA) is well established. uPA-mediated plasminogen activation facilitates cell migration and invasion through extracellular matrices by dissolving connective tissue components. uPA, its receptor (uPAR) and plasminogen activator inhibitor-1 (PAI-1) are enriched in several types of tumors. The importance of proteolysis and especially plasminogen activation is less clear in hematopoietic malignancies than in solid tumors. However, patients with leukemia have an increased tendency to bleeding, not always attributable to thrombocytopenia, and tissue infiltration by leukemic cells, processes in which plasminogen activation may be involved. Several studies have indicated that plasminogen activators (PAs) are highly expressed by cultured leukemia cells. Furthermore, differing from adherent tumor cells, leukemic cells have an enhanced capacity to activate pro-uPA and mainly the active form of uPA is released to culture medium. Ex vivo studies have shown that uPAR, uPA and its inhibitors can be found on the surface of normal blood cells and on the blast cell surfaces from patients with acute leukemia as well as from plasma samples. Elevated levels of PAs and their inhibitors have been detected in leukemic cell lysates. Few studies have tried to demonstrate a correlation between prognosis of leukemia and levels of plasminogen activators. More in vivo studies are needed to show, if any of the factors of the plasminogen activation process can be used as tools in subclassification or as markers for prognosis in leukemia. This review article will focus on the in vivo studies of plasminogen activation in leukemia and will present several in vitro findings on PAs in normal leukocytes and leukemic cell lines.

Blood Cells↗
PubMed1999

Recombination in Tula hantavirus evolution: analysis of genetic lineages from Slovakia.

To examine the evolution of Tula hantavirus (TUL), carried by the European common vole (Microtus arvalis and M. rossiaemeridionalis), we have analyzed genetic variants from Slovakia, the country where the virus is endemic. Phylogenetic analysis (PHYLIP) based on either partial (nucleotides [nt] 441 to 898) or complete N-protein-encoding sequences divided Slovakian TUL variants into two main lineages: (i) strains from eastern Slovakia, which clustered with Russian strains, and (ii) strains from western Slovakia situated closer to those from the Czech Republic. We found genetic diversity of 19% between the two groups and 4% within the western Slovakian TUL strains. Phylogenetic analysis of the 3' noncoding region (3'-NCR), however, placed the eastern Slovakian strains closer to those from western Slovakia and the Czech Republic, with a greater distance to the Russian strains, suggesting a recombinant nature of the S segment in the eastern Slovakian TUL lineage. A bootscan search of the S-segment sequences of TUL strains revealed at least two recombination points in the S sequences of eastern Slovakian TUL strains (nt 400 to 415 and around 1200) which agreed well with the pattern of amino acid substitutions in the N protein and deletions/insertions in the 3'-NCR of the S segment. These data suggest that homologous recombination events occurred in the evolution of hantaviruses.

3' Untranslated Regions↗
PubMed1999

Isolation and characterization of a hantavirus from Lemmus sibiricus: evidence for host switch during hantavirus evolution.

A novel hantavirus, first detected in Siberian lemmings (Lemmus sibiricus) collected near the Topografov River in the Taymyr Peninsula, Siberia (A. Plyusnin et al., Lancet 347:1835-1836, 1996), was isolated in Vero E6 cells and in laboratory-bred Norwegian lemmings (Lemmus lemmus). The virus, named Topografov virus (TOP), was most closely related to Khabarovsk virus (KBR) and Puumala viruses (PUU). In a cross focus reduction neutralization test, anti-TOP Lemmus antisera showed titers at least fourfold higher with TOP than with other hantaviruses; however, a rabbit anti-KBR antiserum neutralized TOP and KBR at the same titer. The TOP M segment showed 77% nucleotide and 88% amino acid identity with KBR and 76% nucleotide and 82% amino acid identity with PUU. However, the homology between TOP and the KBR S segment was disproportionately higher: 88% at the nucleotide level and 96% at the amino acid level. The 3' noncoding regions of KBR and the TOP S and M segments were alignable except for 113- and 58-nucleotide deletions in KBR. The phylogenetic relationships of TOP, KBR, and PUU and their respective rodent carriers suggest that an exceptional host switch took place during the evolution of these viruses; while TOP and KBR are monophyletic, the respective rodent host species are only distantly related.

Animals↗
PubMed1999

Transforming growth factor beta induces urokinase receptor expression in cultured retinal pigment epithelial cells.

The effect of transforming growth factor-beta1 (TGF-beta1) and interferon-gamma (IFN-gamma) was studied on urokinase receptor (uPAR) expression of cultured human retinal pigment epithelial (RPE) cells. Human RPE cells were incubated with 1, 5 or 10 ng/ml of TGF-beta1 or with 10, 100 or 1,000 IU/ml of IFN-gamma to measure total cellular uPAR protein and released uPAR by enzyme immunoassay. uPAR at cell surface was measured by flow cytometric analysis at 8, 12, 24 and 48 h. uPAR mRNA levels were assayed by Northern blotting at 2, 6, 12 and 24 h. The increase in uPAR gene expression in RPE cells exposed to TGF-beta1 paralleled enhanced uPAR level at the cell surface and in conditioned medium. TGF-beta appeared to induce also membrane-bound uPA activity and the release of active plasminogen activator inhibitor-1, indicating that TGF-beta has the potential to regulate plasminogen activation at the RPE cell surface. The increase in uPAR gene expression by IFN-gamma did not seem to translate into the protein level. We conclude that TGF-beta regulates the pericellular proteolysis in RPE cells by increasing uPAR expression.

Cell Membrane↗
PubMed1999

The association of the human herpesvirus-6 and MS.

Given the clinical and pathological nature of Multiple Sclerosis (MS), a viral infection has long been hypothesized as part of the etiology. In this study we investigated the possibility that the human herpesvirus-6 (HHV-6) is present in a dormant or active phase in the tissue of MS patients, specifically oligodendrocytes. Using PCR assays of MS and non-MS brain sections with primers prepared against the HHV-6 structural protein 101, the results demonstrated that 36% of MS brains were positive for the virus, while 13.5% of non-MS brains were positive. Antibody to the HHV-6 structural protein was also used in immunohistochemical experiments in brain tissue. 47% (7/15) of MS brains were positive for HHV-6, whereas 0/16 controls were positive. In addition, MS patients demonstrated high immune reactivity to this virus, even when compared to auto-immune diseases, which might cause polyclonal activation. Sera obtained from MS and control patients revealed that the IgM response to the HHV-6 virus was significantly elevated in 80% patients compared to 16% non-MS controls, P<.001. The above experiments strongly suggest that a significant number of MS brain samples contain HHV-6 antigens and genomic fragments in a dormant or active phase compared to control specimens and that MS patients mount a brisk, early IgM response.

Antibody Formation↗
PubMed1999

Homotypic and heterotypic interaction of the neurofibromatosis 2 tumor suppressor protein merlin and the ERM protein ezrin.

Ezrin, radixin and moesin (ERM) are homologous proteins, which are linkers between plasma membrane components and the actin-containing cytoskeleton. The ERM protein family members associate with each other in a homotypic and heterotypic manner. The neurofibromatosis 2 (NF2) tumor suppressor protein merlin (schwannomin) is structurally related to ERM members. Merlin is involved in tumorigenesis of NF2-associated and sporadic schwannomas and meningiomas, but the tumor suppressor mechanism is poorly understood. We have studied the ability of merlin to self-associate and bind ezrin. Ezrin was coimmunoprecipitated with merlin from lysates of human U251 glioma cells and from COS-1 cells transfected with cDNA encoding for merlin isoform I. The interaction was further studied and the association domains were mapped with the yeast two-hybrid system and with blot overlay and affinity precipitation experiments. The heterotypic binding of merlin and ezrin and the homotypic association of merlin involves interaction between the amino- and carboxy-termini. The amino-terminal association domain of merlin involves residues 1-339 and has similar features with the amino-terminal association domain of ezrin. The carboxy-terminal association domain cannot be mapped as precisely as in ezrin, but it requires residues 585-595 and a more amino-terminal segment. Unlike ezrin, merlin does not require activation for self-association but native merlin molecules can interact with each other. Heterodimerization between merlin and ezrin, however, occurs only following conformational alterations in both proteins. These results biochemically connect merlin to the cortical cytoskeleton and indicate differential regulation of merlin from ERM proteins.

Animals↗
PubMed1999

Blast cell-surface and plasma soluble urokinase receptor in acute leukemia patients: relationship to classification and response to therapy.

Plasminogen activation in leukemia has been less well characterized than in other malignancies. However, the increased tendency to bleeding and tissue infiltration by leukemic cells are processes in which plasminogen activation may be involved. We have examined plasma and the peripheral blood mononuclear cell fraction from 80 patients including 53 patients with newly diagnosed acute leukemia and 27 patients with other hematological disorders as well as 21 healthy controls. In 28 of 29 examined patients with acute myeloid leukemia (AML) and in two of three patients with hybrid leukemia we found urokinase receptor (uPAR) on the cell surface, while most (7/9) samples from patients with acute lymphoblastic leukemia (ALL) were negative for uPAR. The plasma mean value for soluble uPAR (suPAR) was significantly elevated in patients with AML and ALL. In AML the highest values were found in patients who had residual disease after several cycles of chemotherapy. Compared to controls the uPA antigen levels in patient plasmas were elevated and decreased along with uPAR during treatment. Our results suggest that cell surface uPAR may be a useful marker for leukemia classification and in our material a high level of plasma suPAR correlated with resistance to chemotherapy in AML.

Acute Disease↗
PubMed1998

Structure-function relationships in the ezrin family and the effect of tumor-associated point mutations in neurofibromatosis 2 protein.

Ezrin, radixin and moesin (ERM proteins) link cell adhesion molecules to the cytoskeleton, modulate cell morphology and cell growth and are involved in Rho-mediated signal transduction. Merlin, the tumor suppressor in neurofibromatosis 2, is a diverged member of the ezrin family, but its function is at least partially similar to the ERM proteins. In the N-domain, the ezrin family belongs to the band 4.1 superfamily. Secondary structure predictions made separately for the ezrin and band 4.1-tyrosine phosphatase families give a similar pattern for the homologous N-domains, indicating that both families have a similar binding site for the integral membrane proteins. The alpha-domain shows a strong coiled-coil prediction, that can be involved in the protein dimerization. The C-terminal actin-binding site in the ERM proteins and the actin-binding helix in the villin headpiece have a common amino acid motif. In merlin, the published tumor-associated single amino acid mutations in the N-domain are located in the conserved sites, and they affect mainly the predicted helices and strands, indicating that these mutations cause the disease primarily by disturbing the protein structure. In the alpha- and C-domains, some of the mutations break the helical structures. Some known mutations are observed at a site potentially interacting with cell adhesion molecules. We will also discuss the implications of the evolutionary information and the actin-binding models in the ezrin family.

Animals↗