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Biomedical subjects

B Wahren

Publications and source records attributed to B Wahren.

At least 19 recordsLinked to original sources
PubMed2000

Effective construction of DNA vaccines against variable influenza genes by homologous recombination.

We demonstrate the potential of cloning by homologous recombination as a rapid method to construct DNA molecules encoding newly developing hemagglutinins (HA) of influenza A virus. The variable parts of the HA genes were cloned into a basic construct containing the HA gene from an H3N2 strain. The recombinant DNAs thus created encode different variable domains with neutralising epitopes from four recently circulating influenza A H3 strains. The technology allows rapid production of DNA constructs for vaccines that can induce antibody and, particularly, cellular immune responses. These new constructs were also capable of conferring protection to challenge in mice. The technology may hence be a valuable tool for rapid adaptation of influenza vaccines to changes in the circulating influenza strains.

Amino Acid Substitution↗
PubMed2000

Limitation of nitric oxide production: cells from lymph node and spleen exhibit distinct difference in nitric oxide production.

Many types of cells in the immune system have been found to produce nitric oxide (NO), which performs multiplex functions. However, in myelin basic protein peptide 68-86 (MBP 68-86)-induced experimental autoimmune encephalomyelitis (EAE) in Lewis rats, we found that elevated NO production was generated from spleen cells (SC), not from lymph node cells (LNC). LNC expressed lower NO synthase 2 (NOS2) and produced lower levels of NO than SC upon MBP 68-86 stimulation. Expression of B7-1(CD80) and B7-2(CD86) molecules was much lower on LNC than on SC. Blocking of B7-1 or B7-2 ligation resulted in reduced NO production by SC. Unlike SC, LNC were resistant to interferon-gamma- or lipopolysaccharide-induced NO production. NO derived from SC suppressed cell proliferation and induced apoptosis in vitro. Addition of N(omega)-nitrol-L-arginine methylester (L-NAME) into cell cultures promoted cell expansion and reduced apoptosis. These results indicate that NO production originates from SC, but not from LNC. Low expression of co-stimulatory molecules and NOS2 of LNC limits NO induction. The high levels of NO derived from SC are involved in the self-limiting mechanisms of autoimmune responses by inhibiting cell expansion and promoting cell apoptosis.

Amino Acid Sequence↗
PubMed2000

Rolipram suppresses experimental autoimmune neuritis and prevents relapses in Lewis rats.

Rolipram, a phosphodiesterase type 4 inhibitor, can markedly down-regulate antigen-driven T cell proliferation and suppress TNF-alpha production in vitro and in vivo. Here we report the effects of Rolipram on experimental autoimmune neuritis (EAN), which can be induced by immunization with myelin components of the peripheral nervous system (PNS) combined with Freund's complete adjuvant (FCA), and which represents a CD4+ T cell-mediated animal model for human Guillain-Barré syndrome. EAN induced in Lewis rats by inoculation with the PNS P2 protein peptide 57-81 and FCA was strongly suppressed by Rolipram administered twice daily intraperitoneally from day 9 post immunization (p.i.), i.e. after onset of clinical EAN. Suppression of EAN was associated with down-regulated myelin antigen-induced T cell responses as well as down-regulated IFN-gamma and TNF-alpha production. A relapse of clinical EAN occurred upon treatment of a short duration (7 days), while prolongation of treatment resulted in the prevention of clinical EAN relapse. There was no relationship between clinical EAN relapse and high levels of TNF-alpha. The immunomodulatory effects of Rolipram call for further research into the potential role of drugs acting on the immune system in the treatment of autoimmune diseases.

Animals↗
PubMed2000

A retro-inverso miniantibody with anti-HIV activity.

An HIV-1-specific miniantibody, a peptide representing the third heavy chain complementarity-determining region (CDR) of an HIV-specific mouse antibody, was characterized and modified with unnatural D-isomeric amino acids. The CDR peptide and its parent antibody bound to a similar epitope, located in the V3 region of HIV-1 gp120. A shortened CDR sequence was modified with D-amino acids to create an all-D-amino acid retro-inverso (RI) peptide with a reversed sequence order. The RI CDR was less susceptible to proteolytic degradation than its L-counterpart and had a higher affinity for HIV-1 peptides. The miniantibody and its parent antibody showed neutralization of both primary and laboratory strains of HIV-1. In accordance with the binding studies, the RI CDR showed a stronger HIV-inhibiting capacity than its L-counterpart. We conclude that the anti-HIV retro-inverso CDR identified in this study has the potential to become a future anti-HIV drug. It has a virus-neutralizing capacity in vitro and appears to be stable. Future research should focus on characterizing its antiviral activity in vivo.

Amino Acid Sequence↗
PubMed2000

Seroprevalence of viral childhood infections in Eritrea.

BACKGROUND: The seroprevalence of viral childhood infections in Africa has not been thoroughly investigated. The relatively recently discovered human parvovirus B19 (B19) and human herpesvirus 6 (HHV-6) have received particularly little attention. OBJECTIVE: To investigate the seroprevalence of viral childhood infections in different Eritrean populations and to define groups at high risk for infection. STUDY DESIGN: Five population groups in Eritrea have been examined to define the prevalence of specific antibodies to several childhood viruses. The study population of more than 400 persons consisted of children, pregnant women, female sex workers and members of a secluded tribe called Rashaida. RESULTS: All groups showed a high prevalence of antibodies to measles and HHV-6 (> 85%). For rubella, the seroprevalence was very high in all adult groups (93-99%) except the Rashaida group (71%). The mumps prevalence was surprisingly low in the Rashaida group (29%) compared to 46-85% in the other adults. Late encounter of mumps and rubella was also observed among the Rashaidas. The pattern of antibodies to B19 showed a higher seroprevalence in all groups (56-91%) compared to what has been reported from the western world. CONCLUSION: The findings represent what might be expected in an unvaccinated population. The exception was the Rashaidas, which had low seroprevalences and late encounter of mumps and rubella. This is of importance because it makes this tribe vulnerable to these infections, which are associated with complications when acquired in adult age. Also noteworthy is the high frequency of antibodies to HHV-6 and particularly B19 in all groups, indicative of an early encounter of both these viruses.

Adolescent↗
PubMed2000

Th1-biased immune responses induced by DNA-based immunizations are mediated via action on professional antigen-presenting cells to up-regulate IL-12 production.

The efficacy of DNA-based immunization in conferring protective immunity against certain microbial pathogens including human immunodeficiency virus type 1 (HIV-1) has been described. The potential advantage of DNA-based immunization over the traditional vaccines largely results from its capacity to efficiently induce Th1-biased immune responses against an encoded antigen. We describe how Th1-biased immune responses are induced by DNA-based immunization, using a DNA vaccine construct encoding HIV-1 gp160 cDNA and an eukaryotic expression plasmid carrying murine IFN-gamma cDNA. Transfection of an eukaryotic expression plasmid carrying immunostimulatory sequences (ISS) as well as a gene of interest (DNA vaccine) into professional antigen presenting cells (APC) induced transactivation of IL-12 mRNA, which resulted in antigen-specific Th1-biased immune responses against the encoded antigen. Th1-biased immune responses induced by DNA-based immunization were substantially upregulated by a codelivery of an ectopic IFN-gamma expression system, and this augmentation was mediated via action on professional antigen presenting cells to upregulate IL-12 production. Taken together, it appears likely that Th1-biased immune responses induced by DNA-based immunization are mediated via action on professional antigen-presenting cells to produce IL-12. Interestingly, the model provided strikingly resembles that previously described in infection with Listeria monocytogenes, an intracellular Gram-positive bacterium that induces strong Th1-biased immune responses. The result suggests that DNA-based immunization mimics certain aspects of natural infection with microbial organisms like attenuated vaccines, which in turn provides a rationale to the question of why DNA-based immunization so efficiently induces protective immunity against these microbial pathogens.

AIDS Vaccines↗
PubMed2000

Parvovirus B19 infection: association with third-trimester intrauterine fetal death.

OBJECTIVE: To identify the presence of parvovirus B19 infection as a possible cause of fetal loss in the third trimester. DESIGN: Prospective study of women experiencing third-trimester intrauterine fetal death (IUFD). SETTING: All cases of IUFD at Danderyd Hospital from 1992 to 1998. POPULATION: Ninety-three women with IUFD in 33,759 deliveries (0.3%). METHODS: Detection of B19 DNA by polymerase chain reaction (PCR) in placental and fetal tissue. Placental pathology and B19-specific immunohistochemistry. Maternal serology in consecutive samples. RESULTS: Among 93 cases of IUFD, seven (7.5%) had detectable B19 DNA in freshly-frozen placental tissue. The detection of B19 DNA in these tissues was confirmed by detection of B19 DNA in six separately stored paraffin-embedded placental tissues. No other explanations for the fetal deaths were found. None of the women had experienced any clinical signs of infection prior to fetal demise. None of the seven fetuses were hydropic. Histopathologic examination of the placentas revealed only minor abnormalities. Serology on maternal samples at birth revealed delayed or absent B19 IgG responses in five of seven cases. Two women were B19 IgG seropositive at the time of delivery but had unusual infection patterns; persistent viraemia for at least five months before birth in one case and likely persistence or re-infection by B19 in the other. CONCLUSION: In our study, 7.5% of IUFDs in the third trimester may have been caused by parvovirus B19 infection, without signs of fetal hydrops. This finding indicates that B19 PCR should be included in the routine investigation of IUFD.

Adult↗
PubMed2000

Cross-reactive T-helper responses in patients infected with different subtypes of human immunodeficiency virus type 1.

Immunization with a recombinant glycoprotein 160 envelope immunogen derived from a virus of genetic subtype B induced strong specific T-helper cell responses in asymptomatic human immunodeficiency virus (HIV) carriers infected with subtypes B to G. This indicates that the HIV-specific T-helper immunity, which is the basis for development of antibodies and cytotoxic T lymphocytes, can be improved by both homologous and heterologous antigens. It also suggests that a particular immunogen can be effective against many different HIV strains.

AIDS Vaccines↗
PubMed1999

Dose-response resistance to HIV-1/MuLV pseudotype virus ex vivo in a hairpin ribozyme transgenic mouse model.

We have investigated the efficacy of a hairpin ribozyme targeting the 5' leader sequence of HIV-1 RNA in a transgenic model system. Primary spleen cells derived from transgenic or control mice were infected with HIV-1/MuLV pseudotype virus. A significantly reduced susceptibility to infection in ribozyme-expressing transgenic spleen cells (P = 0.01) was shown. Variation of transgene-expression levels between littermates revealed a dose response between ribozyme expression and viral resistance, with an estimated cut off value below 0.2 copies of hairpin ribozyme per cell. These findings open up possibilities for studies on ribozyme efficacy and anti-HIV-1 gene therapy.

Animals↗
PubMed1999

Immune responses in asymptomatic HIV-1-infected patients after HIV-DNA immunization followed by highly active antiretroviral treatment.

Intensive chemotherapy is capable of reducing the viral load in HIV-1-infected individuals while infected cells are still present. A special property of DNA immunization is to induce both new CTL and Ab responses. We evaluated the possibility of inducing new immune responses in already infected individuals by means of DNA constructs encoding the nef, rev, or tat regulatory HIV-1 genes. Significant changes in viral loads and CD4+ counts were observed in four patients who started highly active antiretroviral treatment (HAART) during the immunization study. The DNA immunization induced Ag-specific T cell proliferation, which persisted up to 9 mo after the last DNA injection, and cytolytic activities but did not, by itself, reduce viral load. Increased levels of CTL precursor cells were induced in all nine DNA-immunized patients. The profile of IFN-gamma secretion observed when human PBMC were transfected with the nef, rev, and tat DNA resembled that found in the CTL activity (nef > tat > rev). Ab responses that occurred after immunizations were of a low magnitude. In accordance with the high IL-6 production induced by the nef DNA plasmid, IgG titers were highest in patients immunized with nef DNA. The initiation of HAART appears to contribute to the induction of new HIV-specific CTL responses, but by itself did not cause obvious re-induction of these activities.

AIDS Vaccines↗
PubMed1999

Immunological responses to envelope glycoprotein 120 from subtypes of human immunodeficiency virus type 1.

The outer envelope glycoprotein (gp120) from subtypes A-E of HIV-1 was purified using a specific high mannose-binding lectin, Galanthus nivalis agglutinin. All isolates were grown in peripheral blood lymphocyte cells in order to avoid selection in cell lines. A comparison of the reactivities of the envelope proteins was made using sera from patients infected with the different subtypes. In this study, the B and C subtype envelope glycoproteins showed the strongest immunological reactivity, when reacted with sera from patients infected with the same subtype of virus. On the other hand, sera of patients infected with subtype A or C virus had the strongest and broadest reactivities, to envelope glycoproteins of many subtypes. The purified gp120 proteins from all five subtypes stimulated mononuclear cells from HIV-1 (subtype B)-infected patients, indicating conserved T cell-activating epitopes. The immunological reactivities indicate that strong antigenicity does not always predict the broadest immunogenicity of an envelope glycoprotein. Glycoprotein 120 from foreign subtypes may serve to induce strong cross-reactive immune responses.

Amino Acid Sequence↗
PubMed1999

Therapeutic immunisation with recombinant gp160 in HIV-1 infection: a randomised double-blind placebo-controlled trial. Nordic VAC-04 Study Group.

BACKGROUND: The immune system's ability to scavenge and destroy detrimental HIV-1 products has an important effect on virion production and the course of infection. In earlier trials of therapeutic immunisation with envelope protein recombinant gp160 (rgp160) we observed a transient positive effect on CD4-lymphocyte counts. This randomised placebo-controlled study investigated whether our preliminary findings represented a potential for a more benign clinical course. METHODS: 835 HIV-seropositive patients from 20 centres in Sweden, Norway, and Finland with CD4-cell counts above 200/microL were randomly assigned to receive 160 microg rgp160 or placebo (alum adjuvant alone) every 3 months for 3 years after an induction period, as well as optimum available treatment. Analyses were by intention to treat. FINDINGS: 63 of 416 vaccine-group patients and 61 of 419 placebo-group patients reached a primary clinical endpoint (AIDS-defining event or death); the time to first clinical endpoint did not differ between the groups (p=0.864). Significantly fewer vaccine-group patients than placebo-group patients reached the primary immunological endpoint of a decrease of more than 30% from baseline CD4-cell count (157 vs 189, p=0.03). A higher proportion of the vaccine group had CD4-cell counts higher than baseline at 6 months (167 vs 133, p=0.014). HIV-1-specific T-cell immune reactivity was induced in all vaccine recipients studied. No severe adverse events associated with the vaccine were noted during the study. There were significantly fewer deaths among the vaccine recipients than among the placebo-group patients at 2 years, but not at the end of the study. INTERPRETATION: Therapeutic immunisations with rgp160 have a modest effect on CD4-cell counts, but this treatment alone did not lead to clinical benefit when given in addition to best clinical practice at the time of the trial. Immunisation in conjunction with antiretroviral therapy was also effective, which strongly suggests that a combination with highly active therapy would improve the total effect.

AIDS Vaccines↗
PubMed1999

Induction of mucosal IgA by a novel jet delivery technique for HIV-1 DNA.

Novel ways of delivering plasmid DNA to elicit humoral IgA, IgG and cell-mediated immune responses in mice were investigated. Intraoral administration of DNA in the cheek, using a jet immunization technique, elicited the highest IgA mucosal responses. Intranasal immunization gave strong mucosal IgA responses and persistent systemic IgG. Immunoglobulin isotype analysis revealed an IgG1 profile for intramuscular tongue and gene gun immunizations and an IgG2a profile following oral jet injection and intranasal application. The route of delivery was of importance for the characteristics and quality of the mucosal immune response following DNA immunization. For DNA vaccine delivery, the intraoral jet injection technique has the advantages of being a simple and rapid way of administering the DNA in solution and of provoking specific mucosal IgA when administered in the mucosal associated lymphoid tissue.

Administration, Intranasal↗
PubMed1999

Eukaryotic expression of enzymatically active human immunodeficiency virus type 1 reverse transcriptase.

Reverse transcriptase of human immunodeficiency virus type I is a vitalenzyme in the HIV-1 replication cycle and an attractive target of attempts to arrest a primary viral infection. We designed a vector for eukaryotic expression of the 66 kDa subunit of reverse transcriptase under the control of the immediate early cytomegalovirus promoter. Efficient transient expression of the 66 kDa subunit of reverse transcriptase was achieved in a variety of cells. Immunostaining of the transfected cells revealed the cytoplasmatic localization of reverse transcriptase. Reverse transcriptase activity was detected in all transfected cell lines. Injection of this plasmid encoding the 66 kDa subunit of reverse transcriptase into mice resulted in strong reverse transcriptase-specific immune responses indicating that the 66 kDa subunit of reverse transcriptase is expressed in vivo. Sera from DNA-immunized mice inhibited reverse transcription in vitro.

3T3 Cells↗
PubMed1999

[Promising experiments with DNA vaccine against HIV. A complete eradication of the virus is a formidable task].

The past few years have witnessed encouraging progress in experimental HIV vaccination. Several new vaccine candidates have been shown to elicit immune response and provide protection in animals, and the first immunotherapy trials in humans have been reported. Difficulties remain to be overcome, however. No consensus exists regarding trials in humans. Some researchers and clinicians believe that we must await a vaccine demonstrably and reproducibly effective in animals. Immunogenicity alone is considered insufficient to ensure clinical protection. Others consider animal experiments valuable, but believe that actual trials should be made in humans in the target population. Trials are urgently needed in countries with high transmission rates, even if optimal efficacy cannot be guaranteed.

Animals↗
PubMed1999

Antigen-specific immunosuppression: nasal tolerance to P0 protein peptides for the prevention and treatment of experimental autoimmune neuritis in Lewis rats.

Experimental autoimmune neuritis (EAN) is an autoimmune inflammatory demyelinating disease of the peripheral nervous system (PNS), and represents an animal model of the human Guillain-Barré syndrome (GBS). In this study, we report that nasal administration of the neuritogenic peptide 180-199 and of the cryptic peptide 56-71 of the rat neuritogenic P0 protein of peripheral nerve myelin prevents EAN and attenuates ongoing EAN. Both peptides effectively decreased the severity and shortened clinical EAN. Both a prophylactic and a therapeutic approach proved to be beneficial. These effects were associated with T and B cells hyporesponsiveness to the peptide antigens, reflected by downregulated Th1 cell responses (interferon-gamma secretion) and macrophage function, whereas Th2 cell responses (IL-4 secretion) and transforming growth factor-beta mRNA expression were upregulated.

Administration, Intranasal↗
PubMed1999

Induction of experimental autoimmune neuritis in CD4-8-C57BL/6J mice.

The C57BL/6J mice strain is known to be reputedly resistant to induction of experimental autoimmune neuritis (EAN), an animal model of Guillain-Barré syndrome in humans. Here we describe the induction of EAN in mice of the C57BL/6J background by transfer into naive syngeneic recipients bovine peripheral nerve myelin (BPM)-primed donor lymph node cells that had been stimulated in vitro with the bovine peripheral nervous system (PNS) myelin P2 protein peptide 57-81 followed by challenge with BPM, Freund's complete adjuvant and pertussis toxin. EAN was more severe, both clinically and histologically, and accompanied by extensive infiltration of inflammatory cells and demyelination in peripheral nerves when examined on day 30 after transfer of primed T cells from CD4- 8- mice into identical naive hosts than after transfer of cells from primed wild type, CD4-/- or CD8-/- mice to corresponding recipient animals. EAN in CD4-8- mice was also associated with elevated numbers of P2 peptide-reactive interferon-y (TFN-gamma) secreting cells and alphabeta T cells were present in lymph nodes and spleens. The data suggest that PNS myelin activated T cells from an EAN-resistant mice strain are capable of homing to the PNS. The expanded CD4-8- alphabeta T cells may have helper and effector functions, related to initiation of EAN in the CD4-8- mice. Lack of CD4+ and CD8+ expressing cells does not prevent the initiation of an autoimmune disease.

Animals↗