Biomedical subjects

K L Bengtsson

Publications and source records attributed to K L Bengtsson.

9 recordsLinked to original sources

PubMed1999

Iscom and iscom-matrix enhance by intranasal route the IgA responses to OVA and rCTB in local and remote mucosal secretions.

Iscoms, with rCTB incorporated via the GM1 receptor, enhanced in mice the mucosal immunogenicity of rCTB as antigen after intranasal (i.n.) administration both by inducing IgA response in the remote intestinal tract mucosa and by a 100-fold increase of the specific IgA locally in the lungs. Iscom-matrix as a separate entity mixed with rCTB enhanced the rCTB-IgA response similarly. While OVA in iscoms induced high mucosal IgA responses, iscom-matrix co-administered with OVA induced low or no mucosal IgA response to OVA. A synergism between iscoms and rCTB could only be seen as an adjuvant targeting effect enhancing the IgA response to OVA in the remote genital tract mucosa. In serum, the immunomodulatory effect of iscoms after i.n. administration was seen as an enhanced serum IgG2a response.

Adjuvants, Immunologic↗

PubMed1999

Immunomodulation by iscoms, immune stimulating complexes.

The iscom is a uniform stable complex consisting of cholesterol, phospholipid, adjuvant-active saponin, and antigen. The iscom matrix is a particulate complex with identical composition, shape, and morphology, but lacking the incorporated antigen. The assembly of the complex is based on hydrophobic interactions, but antigens that are not hydrophobic can be conjugated with a hydrophobic tail or hidden hydrophobic regions can be exposed, e.g., by acid treatment, to facilitate the incorporation into iscoms. The functional aspects of iscoms are described emphasizing immunomodulation in mouse models. Iscoms prominently enhance the antigen targeting, uptake, and activity of antigen presenting cells including dendritic and B cells and macrophages resulting in the production of proinflammatory cytokines, above all interleukin (IL)-1, IL-6, and IL-12. The expression of costimulatory molecules major histocompatibility complex (MHC) class II, B7.1 and B7.2, is also enhanced. The latter partly explains why the iscom is an efficient adjuvant for elderly mice. Iscoms enhance the Th1 type of response with increased production of IL-2 and interferon gamma. However, with some antigens and particularly in monkeys immunized with HIV iscoms, the production of IL-4 was enhanced. IL-4, IL-2, and interferon gamma (IFNgamma) together with the beta chemokines MIP-1alpha and MIP-1beta correlated with protection against challenge infection with a chimeric virus (simian immunodeficiency virus-human immunodeficiency virus). Iscoms were also shown to induce a potent immune response in the newborn and to be an efficient delivery system for mucosal administration. Technical information is given about formulation of iscoms and about handling of antigens to optimize their incorporation into iscoms.

Adjuvants, Immunologic↗

PubMed1998

Vaccination with recombinant Parasite Surface Antigen 2 from Leishmania major induces a Th1 type of immune response but does not protect against infection.

Vaccination with the native Parasite Surface Antigen 2 of Leishmania major with Corynebacterium parvum as adjuvant protects mice from leishmaniasis through a Th1 mediated response. Here we show that vaccination with a recombinant form of this protein, purified from Escherichia coli and administered in iscoms or with C. parvum as adjuvant, does not induce protective immunity despite the induction of Th1 responses. The results suggest that protective immunity depends on the ability of the vaccinating antigen to induce Th1-like T cells with ability to be recalled by infection. Therefore, the conformation of antigens may play a more major role for the induction of T cell mediated immunity than originally considered.

Animals↗

PubMed1998

Functional aspects of iscoms.

The iscom is a delivery system, designed for both parenteral and mucosal modes of administration, for both antigens and adjuvants, components which are interchangeable. By the parenteral route a prominent systemic Th1 type of response is evoked, but the mucosal immunoglobulin A (IgA) response was insignificant. Intranasal (i.n.) immunization with iscoms evoked potent mucosal IgA response and serum IgG which was much higher than that induced by i.n. administration of the B subunit of cholera toxin (rCTB), both to rCTB itself as well as to co-administered antigen. The immunomodulatory effect on rCTB or co-administered antigens imposed by the iscom was demonstrated by a potent mucosal IgA switch and an enhanced IgG2a serum response. The incorporation of a targeting molecule in the iscom enhanced the remote IgA response in the genital tract mucosa. The capacity to induce CD8-restricted cytotoxic T lymphocytes (CTL) is unique for the iscom as a nonreplicating system, which is facilitated by the delivery of antigens to the cytosol. The immunomodulatory capacity of iscoms also paved the way to override the inhibitory effect of maternally derived antibodies and the relative unresponsiveness of an immature neonatal immune system.

Animals↗

PubMed1997

Use of a recombinant antigen, SAG2, expressed as a glutathione-S-transferase fusion protein to immunize mice against Toxoplasma gondii.

The capacity of Toxoplasma gondii surface protein SAG2 to induce protective immunity against the parasite in mice was studied using recombinant SAG2 expressed as a glutathione-S-transferase (GST) fusion protein incorporated into immune stimulating complexes (iscoms). Immunization with the iscoms resulted in the production of antibodies recognizing SAG2 as well as GST. After oral challenge infection with T. gondii oocysts or tissue cysts, no protective effect was observed. On the contrary, mice immunized with fusion SAG2 or with GST iscoms died earlier than non-immunized control mice.

Animals↗

PubMed1997

Influenza (H1N1)-ISCOMs enhance immune responses and protection in aged mice.

Aging is associated with a decline in immune function and the elderly are therefore more susceptible to infectious disease and less responsive to vaccination. Influenza antigens complexed as immunostimulatory complexes (ISCOMs) generate more potent protective immune responses compared with non-adjuvanted flu antigens in young adult mice. We report on the protective efficacy of flu-ISCOMs compared with the current split flu vaccine in an aged mouse model. DBA/2 mice aged 2 or 18 months were immunized with flu vaccine, ISCOMs or live virus, prior to challenge with the homologous virus. In aged mice, flu-ISCOMs induced significantly higher serum hemagglutination inhibition (HAI) titers compared to vaccine, similar to the levels obtained in young adult mice that received the split vaccine. Flu-ISCOMs but not vaccine induced cytotoxic T lymphocyte (CTL) responses in young and to a lesser degree in aged mice. In aged mice flu-ISCOMs significantly reduced illness and enhanced recovery from viral infection compared with vaccine. Our data suggests that flu-ISCOMs may offer an improved vaccine strategy for protection of elderly humans against the complications of influenza infection.

Aging↗

PubMed1997

Kinetics, localization and cytokine profile of T cell responses to immune stimulating complexes (iscoms) containing human influenza virus envelope glycoproteins.

Immune stimulating complexes (iscoms) are 40 nm particles combining adjuvant-active Quillaja saponins and multimeric presentation of antigens. The distribution in mice of influenza virus iscoms and the resulting T cell responses in the lymph nodes (LN) and spleen were characterized. After a single subcutaneous injection, iscoms were delivered to the draining LN where they induced a transient population of LN cells which responded with proliferation and secretion of interleukin-2 (IL-2), gamma-interferon (IFN-gamma) and interleukin-4 (IL-4) after restimulation. The response in the spleen developed more slowly, sustained for 12 weeks and was characterized by cells producing in particular IL-2 and IFN-gamma but also IL-4. A booster resulted in a dramatic enhancement of the production of IFN-gamma, indicating that iscoms efficiently recruit cells with Th1 properties. Comparisons of T cell responses to iscoms and to influenza virus antigen in Freund's complete adjuvant demonstrate that these adjuvants affect both the localization and cytokine profile of T cell responses.

Animals↗

PubMed1996

Adjuvant activity of iscoms; effect of ratio and co-incorporation of antigen and adjuvant.

We have studied the importance of co-incorporation of antigen and adjuvant in iscoms and the effects of different ratios of adjuvant and antigen in the iscom particles. Immune responses to influenza virus antigens (flu-Ag) in iscoms were compared to those induced by flu-Ag mixed with iscom-matrix, i.e. antigen and adjuvant delivered in separate packages. Higher doses of Quil A were required with iscom-matrix to induce strong immune responses compared to iscoms containing the same amount of antigen. The immunogenic properties of iscoms were affected by the ratio between antigen and adjuvant in the particles. Both iscoms and flu-Ag mixed with iscom-matrix induced antigen-specific antibodies with similar IgG subclass distribution and activated spleen cells producing high levels of IL-2 and IFN-gamma in vitro.

Adjuvants, Immunologic↗

PubMed1996

Novel adjuvants and vaccine delivery systems.

Conventionally the efficiency of an adjuvant is measured by the capacity to induce enhanced antibody serum titres and cell mediated immunity (CMI) to a given antigen. Nowadays the capacity of an adjuvant is also measured by the quality as well as the magnitude of the induced immune response, guided by the protective immune response required. Quality includes isotype and IgG subclass responses, T-helper cell responses characterized by the cytokine profile and cytotoxic T cells (CTL). In the early phase of immunization some adjuvants influence the antigen administration and uptake by a so-called depot effect exemplified by aluminium hydroxide gel and oil adjuvants, which possibly is not as desired as alledged. A modern depot is exerted by slow release formulations continuously releasing the antigen over a period of time or by pulses at intervals aiming at 'single injection' vaccine. Great efforts are made to formulate efficient delivery formulations targeting the antigens from the site of administration, to draining lymph nodes or distant lymphatic tissue or to mucosal surfaces by parenteral or mucosal administrations. Nowadays, non-replicating carriers besides replicating vaccines are formulated to induce mucosal immune responses encompassing secretory IgA and CMI. Efforts to evoke immune responses on mucosal membranes distant from the site of administration have resulted mostly in little success. For a long time it was considered that CTL under the restriction of MHC Class I only could be evoked by replicating viruses or intracellular parasites. However, novel adjuvant delivery systems readily induce CTL by delivering the antigen to the APC resulting in intracellular transport to the cytosol for the MHC Class I presentation system, as well as to the endosomal pathway for the MHC Class II presentation.

Adjuvants, Immunologic↗