PubMed Health⌕ Search

Biomedical subjects

M Sällberg

Publications and source records attributed to M Sällberg.

At least 37 records · Page 2Linked to original sources
PubMed1999

Limited humoral immunity in hepatitis C virus infection.

BACKGROUND & AIMS: The extremely high rate of chronicity to hepatitis C virus (HVC) infection suggests an inefficient immune response. The humoral immune response to HCV was evaluated in 60 patients with chronic HCV infection and in 12 patients acutely infected with HCV. METHODS: A number of recombinant HCV antigens including the core, envelope 2 (E2), nonstructural (NS) 3, NS4, and NS5 proteins, and NS4a and E2-HVR-1 peptides were used in enzyme-linked immunoassays. RESULTS: Immunoglobulin (Ig) G antibody responses to these viral antigens, except for the HCV core, were highly restricted to the IgG1 isotype. The prevalence of antibodies of the IgG1 isotype specific for the HCV core, E2, E2-HVR1, NS3 (helicase domain), NS4, and NS5 antigens was 97%, 98%, 28%, 88%, 33%, and 68%, respectively. Antibodies of the IgG3 isotype specific for E2, E2-HVR-1, NS3, NS4, and NS5 were detected in a minority of serum samples. The IgG2 and IgG4 isotypes were rarely if ever detected. Furthermore, antibody responses to HCV viral antigens were of relatively low titer and, with the exception of anti-HCV core, were delayed in appearance until the chronic phase of infection. CONCLUSIONS: The IgG1 restriction, low titer, and delayed appearance of antibody responses elicited during HCV infection suggest that the immunogenicity of HCV proteins is limited in the context of natural infection. Inasmuch as recombinant HCV viral antigens perform as relatively normal immunogens in small animals, we suggest that the defective humoral immune responses during HCV infection may be attributable to an "immune avoidance" strategy.

Acute Disease↗
PubMed1999

Metabolic fate of nociceptin/orphanin FQ in the rat spinal cord and biological activity of its released fragment.

Metabolism of orphanin FQ/nociceptin (OFQ/N) was studied in the spinal cord of rats. The heptadecapeptide was efficiently cleaved by a neutral serine endopeptidase, thus releasing the major metabolite, OFQ/N(1-11), further truncated to the final product, OFQ/N(1-6). Biologic activity of this latter fragment was tested in vivo, after intracerebroventricular and intrathecal injections. Hexapeptide exhibited a bi-phasic effect, causing antinociception up to 10 min after injection, followed by a hyperalgesia. The analgesic effect was blocked by naloxone and hyperalgesia was inhibited by NMDA--and NMDA/glycine site antagonists. The results indicate that shorter nociceptin fragments still possess their biologic activity though possibly acting via receptors other than ORL1.

Analgesics↗
PubMed1999

A high prevalence of serum GB virus C/hepatitis G virus RNA in children with and without liver disease.

The role of GB virus C/hepatitis G virus (GBV-C/HGV) in adult and pediatric liver disease is unclear. We detected serum GBV-C/HGV RNA by reverse transcriptase polymerase chain reaction in 1 (3%) of 38 cholestatic infants, in 4 (4%) of 95 children without liver disease, and in none of 30 children with autoimmune hepatitis. One cholestatic infant had antibodies, presumably maternal, to GBV-C/HGV. Sequence analysis of a nonstructural 3 region fragment suggested that mother-to-infant transmission was the route of infection for the cholestatic infant. The four infected children without liver disease had normal liver function test results and lacked risk factors for bloodborne infections. Thus, the detection of GBV-C/HGV RNA among children with and without liver disease suggests that chronic GBV-C/ HGV infections may be established early in life, possibly by mother-to-infant transmission. This may explain in part the high prevalence of serum GBV-C/HGV RNA and antibodies in healthy adults.

Adolescent↗
PubMed1999

Analysis of GB virus C markers in families over three generations.

GB virus C (GBV-C) markers were analyzed in two to three generations in three families with documented vertical transmission of GBV-C. None of the maternal grandparents had GBV-C markers, whereas the male spouses had GBV-C envelope 2 antibodies. Evidence was found for intrafamilial transmission but not for GBV-C transmission over three generations.

Adult↗
PubMed1999

Reappearance of founder virus sequence in human immunodeficiency virus type 1-infected patients.

Different patterns of temporal evolution in human immunodeficiency virus type 1 V3 and p17 regions are described for eight patients studied during the first years following primary infection. In samples from three patients, a rapid replacement of the major sequence occurred but the original sequence reappeared later simultaneously with clinical deterioration and increased plasma viral load.

Base Sequence↗
PubMed1999

Relation between GB virus C/hepatitis G virus and fulminant hepatic failure may be secondary to treatment with contaminated blood and/or blood products.

BACKGROUND: The role of the recently discovered GB virus C (GBV-C)/hepatitis G virus in fulminant hepatic failure (FHF) has been debated. Although GBV-C RNA has been detected in many cases of FHF, recent data suggest that the relation between GBV-C and FHF may be accidental. AIMS: To retrospectively investigate the possible relation between the presence of GBV-C markers (RNA or antibodies to the GBV-C envelope 2 (E2) glycoprotein) and FHF. METHODS: The presence of GBV-C RNA was determined in serum samples from 58 patients diagnosed with FHF using a reverse transcriptase polymerase chain reaction. Amplified genetic fragments were directly sequenced by the dideoxy chain termination method. Antibodies to GBV-C in serum samples were detected by enzyme immunoassay based on a recombinant GBV-C E2 protein. RESULTS: Nine (16%) patients with FHF had GBV-C RNA and 13 (22%) [corrected] had GBV-C E2 antibodies, which are higher frequencies than in healthy subjects (p<0.01 and p<0.05 respectively). Six of nine [corrected] patients with GBV-C markers during FHF tested negative for these markers before therapy with blood and/or blood products. Sequence analysis of the GBV-C NS3 region fragments of six FHF patients showed no common sequence pattern or motif. CONCLUSIONS: The frequencies of both GBV-C RNA and antibodies are higher in patients with FHF than in healthy subjects. However, these increased frequencies may in many cases be explained by the use of contaminated blood and/or blood products given as therapy.

Adolescent↗
PubMed1999

Nanospray mass spectrometry for identification of peptides. Application of a novel interface.

Electrospray ionization mass spectrometry is a powerful tool for identification of biomolecules such as peptides, proteins, oligosaccharides and neurotransmitters. Recent development of the nanospray techniques, applied at ultralow flow-rates, allowed a sensitive analysis of compounds at femto/attomolar level. Here, we present application of a novel nanospray device for the analysis and fragmentation of peptides with high sensitivity on a sector instrument. The lowest applied flow-rate of the mobile phase was maintained at 50 nl/min with a sample load of 90 fmol. Nanospray also provided a complete analysis of 500 nl of the sample for over 10 min, including sequencing of as little as 40 pmol of a substance. Such analysis provides full structural information necessary to identify the molecules.

Mass Spectrometry↗
PubMed1998

Coexisting members of HIV-1 p17 gene quasispecies represent proteins with distinct antigenicity and immunogenicity.

BACKGROUND: Despite the comparatively conserved nature of the HIV-1 gag gene, countless quasispecies of the p17 gene coexist in HIV-1-infected patients. It is not known if the minor genetic differences in quasispecies will affect immune recognition. OBJECTIVE: To characterize the antigenicity and immunogenicity of three different members of HIV-1 p17 quasispecies. METHODS: Three members of HIV-1 p17 gene quasispecies, one from patient A (clone 9; qsA9) and two from patient E (clones 5 and 8; qsE5 and qsE8), were expressed and purified from Escherichia coli. The antigenicity of the p17 proteins was analysed using sera from HIV-1-infected individuals, and the immunogenicity was evaluated using sera and lymphocytes from primed mice of three different haplotypes. RESULTS: The antigenicity of the qsE5 and qsE8 p17 recombinant proteins were distinct when tested for reactivity with human p17 antibodies. The qsE5 and qsE8 p17 were equally immunogenic in H-2d mice, but not in H-2b and H-2k mice. In H-2b mice the qsE8 protein induced higher levels of anti-p17 IgG2a, IgG2b and IgG3 than the qsE5 protein. Corroborating the IgG subclass pattern, H-2b-restricted qsE5-specific T cells produced higher in vitro levels of interferon-gamma, but not of interleukin (IL)-4, IL-5 and IL-6, than qsE8-specific T cells, suggesting a more pronounced T-helper (TH)1-like response. CONCLUSIONS: The p17 gene quasispecies coexisting in the same patient at the same time may represent antigenically and immunogenically distinct proteins despite sequence homologies of above 90%. Subsequently, subtle differences between two p17 protein quasispecies are enough to prime different TH1/TH2 subsets. These findings will have implications for therapeutic HIV-1 immunizations.

Amino Acid Sequence↗
PubMed1998

Genetic immunization of chimpanzees chronically infected with the hepatitis B virus, using a recombinant retroviral vector encoding the hepatitis B virus core antigen.

Cytotoxic T lymphocyte (CTL) activity and CD4+ helper T cell responses to the hepatitis B virus (HBV) core antigen (HBcAg) have been implicated in clearance of acute and chronic HBV infections. We showed that intramuscular injections of a novel recombinant retroviral vector expressing an HBcAg-neomycin phosphotransferase II (HBc-NEO) fusion protein induces HBc/eAg-specific antibodies and CD4+ and CD8+ T cell responses in mice and rhesus monkeys. We have now immunized three chronically infected chimpanzees, each with 10(10) CFU of nonreplicating retroviral vector particles expressing the HBc-NEO fusion protein. Of two immunized chimpanzees examined for CTL responses, one developed HBcAg-specific CTLs and showed marginal, transient elevations of alanine aminotransferase (ALT) levels following injection. However, both chimpanzees remained positive for serum HBeAg, negative for anti-HBe antibody by conventional assays, and displayed no change in HBV viral load throughout the study. In contrast, the third chimpanzee exhibited a traditional seroconversion evidenced by a loss of serum HBeAg and the subsequent emergence of anti-HBe antibodies within 24 weeks after the first injection. Simultaneously, two transient ALT flares and a significant decrease in the serum HBV DNA levels were noted. Despite its limitations, the present study demonstrates (1) the safety of treatment with high titers of retroviral vector in chimpanzees, (2) the capability of a retroviral vector expressing HBcAg to stimulate immune responses in HBV chronic carrier chimpanzees, and (3) that retroviral vector immunization may be therapeutically beneficial in the treatment of chronic HBV infection.

Amino Acid Sequence↗
PubMed1998

Identification of functional domains in Efb, a fibrinogen binding protein of Staphylococcus aureus.

Staphylococcus aureus produces and secretes a protein, Efb, that binds to fibrinogen, seems to be required for virulence, and may benefit the microorganism by delaying wound healing. Interactions of Efb with fibrinogen are influenced by divalent metal cations, including Ca2+. Increasing concentrations of Ca2+ increased the binding of fibrinogen to immobilized Efb, whereas binding of Efb to immobilized fibrinogen was decreased with increasing Ca2+ concentration. Studies with synthetic peptides showed that peptides from the carboxyl terminal half of Efb bound to soluble fibrinogen and enhanced the binding of fibrinogen to Efb. A peptide corresponding to a repeated sequence in the amino terminal half of the protein also bound fibrinogen and inhibited binding of fibrinogen to Efb. These results may provide clues to the biological function of Efb and aid in the rational design of agents to block the Efb fibrinogen interaction.

Amino Acid Sequence↗
PubMed1998

Nonsynonymous mutations within the human immunodeficiency virus type 1 p17 gene are clustered to sequences binding to the host human leukocyte antigen class I molecules.

We have analyzed the relation between intrapatient variabilities of the p17 gene and the location of known host p17 cytotoxic T lymphocyte (CTL) epitopes in five patients infected with human immunodeficiency virus type 1 (HIV-1). All patients were typed with respect to the human leukocyte antigen (HLA) class I type. One to seven previously fine-mapped p17 CTL epitopes corresponded to the HLA class I restriction elements of each patient. An average of 28+/-16% of the p17 gene of each patient encoded CTL epitopes corresponding to the HLA restriction elements of the host. Twenty full-length p17 gene clones were sequenced from each patient. The intrapatient homology between the p17 sequences ranged from 96.4 to 98.9%. The interpatient homology between the consensus sequences of each patient ranged from 83.1 to 91.6%. A total of 246 nucleotide differences within the 100 p17 clones was noted. Fifteen (16%) of 96 synonymous substitutions were found within host CTL epitopes, whereas 72 (48%) of 150 nonsynonymous nucleotide changes were found within CTL epitopes corresponding to the HLA restriction elements of the host (p < 0.0001; Fisher's exact test). Subsequently, variable residues indicating the evolution of at least two major p17 species (i.e., >20% of the clones) were determined to be more common at positions contained within these CTL epitopes (p < 0.01). The present data suggest that the evolution of the p17 gene is influenced by contact areas with the host HLA class I molecules.

Adult↗
PubMed1998

Human and murine antibody recognition is focused on the ATPase/helicase, but not the protease domain of the hepatitis C virus nonstructural 3 protein.

The hepatitis C virus (HCV) nonstructural (NS) 3 protein has been shown to possess at least two enzymatic domains. The amino terminal third contains a serine-protease domain, whereas the carboxy terminal two thirds is comprised of an adenosine triphosphatase (ATPase)/helicase domain. These domains are essential for the maturation of the carboxy-terminal portion of the HCV polyprotein and catalyze the cap synthesis of the RNA genome. In this report, human and murine antibody responses induced by NS3 were characterized using a recombinant full-length NS3 (NS3-FL) protein, or the isolated protease or ATPase/ helicase domains, expressed and purified from Escherichia coli. Sera from 40 patients with chronic HCV infection were assayed in enzyme-linked immunoassays (EIAs) for antibody binding to the panel of NS3 proteins. Virtually all patient sera contained antibodies specific for NS3-FL and the ATPase/helicase domain, whereas only 10% of sera reacted with the protease domain of NS3. Human antibodies reactive with NS3-FL were highly restricted to the immunoglobulin G1 (IgG1) isotype and were inhibited by soluble ATPase/helicase, but not by the protease domain. The anti-NS3 (ATPase/helicase) reactivity decreased on denaturation by sodium dodecyl sulfate (SDS) and beta-mercaptoethanol (2ME), suggesting the recognition of nonlinear or conformational B-cell determinants. Similar to infected humans, mice immunized with NS3-FL developed high-titered primary antibody responses to the NS3 ATPase/ helicase domain, whereas an anti-NS3 protease response was not observed after primary or secondary immunizations. Thus, the human and murine humoral immune responses to the HCV NS3 protein are focused on the ATPase/helicase domain, are restricted to the IgG1 isotype in humans, and are conformationally dependent. Unexpectedly, in both species, the NS3 protease domain, present in the context of the full-length NS3, appears to possess low intrinsic immunogenicity in terms of antibody production.

Adenosine Triphosphatases↗
PubMed1998

Are HLA class II and immunoglobulin constant region genes involved in the pathogenesis of mixed cryoglobulinemia type II after hepatitis C virus infection?

BACKGROUND/AIMS: Hepatitis C virus infection is known to play an important role in the pathogenesis of essential mixed cryoglobulinemia type II. Progression of hepatitis C virus infection to mixed cryoglobulinemia may be influenced by host immune response. To analyze the immunogenetic background of mixed cryoglobulinemia, we studied HLA-DR, DQ loci and the switch regions of immunoglobulin heavy chain gamma1 and gamma4 constant genes. METHODS: HLA typing was performed in 84 hepatitis C virus-infected patients (46 with cryoglobulins and 38 without), and 109 healthy controls, through analysis of restriction fragment length polymorphisms, supplemented with other techniques. Immunoglobulin heavy chain gamma1 and gamma4 polymorphisms, detected by restriction fragment length polymorphisms, were studied in 41 patients with mixed cryoglobulinemia and 51 controls. RESULTS: The gene frequency of DRB1*11 was significantly higher in patients with mixed cryoglobulinemia than in controls (0.36 and 0.20, respectively; p= 0.0035). However, DRB1*11 was also increased in the subgroup of patients without mixed cryoglobulinemia who did not develop severe liver disease, while it was decreased in those with severe liver damage (0.50 and 0.13; p=0.0035). The frequency of 5.4 kb allele of the immunoglobulin heavy chain gamma1 switch region was higher in patients with mixed cryoglobulinemia than in controls (0.47 and 0.22; pc=0.002), while the frequency of 5.5 kb allele was lower (0.51 and 0.78; pc= 0.001). CONCLUSIONS: Susceptibility to develop cryoglobulins after hepatitis C virus infection was not associated with HLA-DR or DQ. HLA-DRB1*11-positive individuals were protected from serious chronic liver disease after hepatitis C virus infection. Immunoglobulin heavy chain constant gamma1 switch region restriction fragment length polymorphisms were associated with mixed cryoglobulinemia.

Adult↗
PubMed1998

The antiviral compound ribavirin modulates the T helper (Th) 1/Th2 subset balance in hepatitis B and C virus-specific immune responses.

Ribavirin is effective in combination therapies against chronic hepatitis C virus (HCV) infection, although its direct antiviral properties are unclear. We therefore studied the immune-modulatory effects of ribavirin on hepatitis B virus (HBV)- and HCV-specific immune responses. During a 24 week placebo-controlled ribavirin trial in ten patients with chronic HCV infection, HCV antibodies and alanine aminotransferase (ALT) levels decreased transiently whereas the serum levels of HCV RNA remained stable. Effects of ribavirin on human and murine phytohaemagglutinin (PHA)-activated T cells included inhibition of in vitro proliferation and modulation of IL-2, IL-4, IFN-gamma and TNF-alpha levels. HBcAg- and HBeAg-specific IL-2 and IFN-gamma levels were > or = 25-fold higher in mice immunized with HBV core- or e-antigens (HBcAg, HBeAg) while receiving ribavirin compared to untreated mice, but IL-4 and IL-6 remained constant. Concordantly, a slight shift was observed in the IgG subclass distribution of the humoral responses of ribavirin-treated mice to HBeAg and HCV NS3 protein. Ribavirin treatment of HBeAg-transgenic (HBeAg-Tg) mice induced a dose-dependent down-regulation of T helper (Th)2-mediated antibody production to HBeAg. In ribavirin-treated HBeAg-Tg mice anti-HBe IgG1 (positively regulated by Th2 cytokines) decreased simultaneously as both anti-HBe IgG2a (positively regulated by Th1 cytokines) levels and in vitro T-cell IFN-gamma production increased, indicating a change in the Th1/Th2 balance. Thus, the present data suggest that ribavirin is not strictly an antiviral compound, but rather it alters the T-cell balance in the immune system.

Animals↗
PubMed1998

Human immunodeficiency virus type 1 disease progression, CCR5 genotype, and specific immune responses.

The correlation among the presence of a 32-bp deletion in the CC-chemokine receptor 5 (CCR5) gene, disease progression, and human immunodeficiency virus type 1 (HIV-1)-specific immune responses was analyzed for a cohort of 79 Caucasian HIV-1-infected patients. The CCR5 genotype (CCR5/CCR5 = wild type/wild type or delta32CCR5/CCR5 = 32-bp deletion/wild type) in peripheral blood mononuclear cells was determined by PCR, followed by sequencing of both wild-type and delta32CCR5 gene fragments. HIV-1-specific humoral responses to gp41 and V3MN peptides were determined by enzyme immunoassays. The prevalence of the delta32CCR5 allele was lower among 37 patients with rapid progression (progression to AIDS or to a CD4 cell count of <200 x 10(6)/liter in less than 9 years; P < 0.01) compared to that for 42 patients with slow progression (no AIDS and CD4 cell count of >200 x 10(6)/liter after at least 9 years from infection) or to that for 25 non-HIV-1-infected Swedish blood donors (P < 0.05). No differences were observed in the wild-type CCR5 sequences between the different groups of patients. For three analyzed patients, the 32-bp delta32CCR5 gene deletions were identical. The antibody titers against gp41 and a V3MN peptide in patients with the delta32CCR5/CCR5 genotype were not significantly different from those in pair-matched CCR5/CCR5 controls. However, in 13 analyzed patients, a stronger serum neutralizing activity was associated with the delta32CCR5/CCR5 genotype. Thus, a CCR5/CCR5 genotype correlates with a shortened AIDS-free HIV-1 infection period and possibly with a worse neutralizing activity, without an evident influence on the antibody response to two major antigenic regions of HIV-1 envelope.

Amino Acid Sequence↗
PubMed1998

Detection of hepatitis G virus RNA in persons with and without known risk factors for blood-borne viral infections in Sweden and Honduras.

We analyzed 224 and 163 serum samples from individuals in Sweden and Honduras, respectively, for the presence of the hepatitis G virus (HGV or GB virus-C) RNA. HGV infection in both Sweden and Honduras was related to common risk factors for blood-borne infections, despite a surprisingly high frequency in groups without known risk factors.

Base Sequence↗