Tobias Hedberg - Academia.edu (original) (raw)

Papers by Tobias Hedberg

Research paper thumbnail of Construction and preclinical evaluation of mmCT, a novel mutant cholera toxin adjuvant that can be efficiently produced in genetically manipulated Vibrio cholerae

Vaccine, 2016

There is an urgent need for new adjuvants that are effective with mucosally administered vaccines... more There is an urgent need for new adjuvants that are effective with mucosally administered vaccines. Cholera toxin (CT) is the most powerful known mucosal adjuvant but is much too toxic for human use. In an effort to develop a useful mucosal adjuvant we have generated a novel non-toxic mutant CT molecule that retains much of the adjuvant activity of native CT. This was achieved by making the enzymatically active A subunit (CTA) recalcitrant to the site-specific proteolytic cleavage ("nicking") required for toxicity, which was found to require mutations not only in the two residues rendering the molecule resistant to trypsin but also in neighboring sites protecting against cleavage by Vibrio cholerae proteases. This multiple-mutated CT (mmCT) adjuvant protein could be efficiently produced in and purified from the extracellular medium of CT-deleted V. cholerae. The mmCT completely lacked detectable enterotoxicity in an infant mouse model and had >1000-fold reduced cAMP inducing activity compared to native CT in a sensitive mammalian target cell system. It nonetheless proved to have potent adjuvant activity on mucosal and systemic antibody as well as cellular immune responses to mucosally co-administered antigens including oral cholera and intranasal influenza vaccines. We conclude that mmCT is an attractive novel non-toxic mucosal adjuvant for enhancing immune responses to co-administered mucosal vaccines.

Research paper thumbnail of T Follicular Helper, but Not Th1, Cell Differentiation in the Absence of Conventional Dendritic Cells

The Journal of Immunology, 2015

Development of long-lived humoral immunity is dependent on CXCR5-expressing T follicular helper (... more Development of long-lived humoral immunity is dependent on CXCR5-expressing T follicular helper (Tfh) cells, which develop concomitantly to effector Th cells that support cellular immunity. Conventional dendritic cells (cDCs) are critical APCs for initial priming of naive CD4 + T cells but, importantly, also provide accessory signals that govern effector Th cell commitment. To define the accessory role of cDCs during the concurrent development of Tfh and effector Th1 cells, we performed high-dose Ag immunization in conjunction with the Th1-biased adjuvant polyinosinic:polycytidylic acid (pI:C). In the absence of cDCs, pI:C failed to induce Th1 cell commitment and IgG2c production. However, cDC depletion did not impair Tfh cell differentiation or germinal center formation, and long-lived IgG1 responses of unaltered affinity developed in mice lacking cDCs at the time point for immunization. Thus, cDCs are required for the pI:C-driven Th1 cell fate commitment but have no crucial accessory function in relation to Tfh cell differentiation.

Research paper thumbnail of Directed antigen targeting in vivo identifies a role for CD103+ dendritic cells in both tolerogenic and immunogenic T-cell responses

Research paper thumbnail of CD11chigh Dendritic Cells Are Essential for Activation of CD4+ T Cells and Generation of Specific Antibodies following Mucosal Immunization

The Journal of Immunology, 2009

To generate vaccines that protect mucosal surfaces, a better understanding of the cells required ... more To generate vaccines that protect mucosal surfaces, a better understanding of the cells required in vivo for activation of the adaptive immune response following mucosal immunization is required. CD11c high conventional dendritic cells (cDCs) have been shown to be necessary for activation of naive CD8 ؉ T cells in vivo, but the role of cDCs in CD4 ؉ T cell activation is still unclear, especially at mucosal surfaces. The activation of naive Ag-specific CD4 ؉ T cells and the generation of Abs following mucosal administration of Ag with or without the potent mucosal adjuvant cholera toxin were therefore analyzed in mice depleted of CD11c high cDCs. Our results show that cDCs are absolutely required for activation of CD4 ؉ T cells after oral and nasal immunization. Ag-specific IgG titers in serum, as well as Ag-specific intestinal IgA, were completely abrogated after feeding mice OVA and cholera toxin. However, giving a very high dose of Ag, 30-fold more than required to detect T cell proliferation, to cDC-ablated mice resulted in proliferation of Ag-specific CD4 ؉ T cells. This proliferation was not inhibited by additional depletion of plasmacytoid DCs or in cDC-depleted mice whose B cells were MHC-II deficient. This study therefore demonstrates that cDCs are required for successful mucosal immunization, unless a very high dose of Ag is administered.

Research paper thumbnail of Direct interaction between cholera toxin and dendritic cells is required for oral adjuvant activity

European Journal of Immunology, 2013

Cholera toxin (CT) binds to GM1-ganglioside receptors present on all nucleated cells. Despite thi... more Cholera toxin (CT) binds to GM1-ganglioside receptors present on all nucleated cells. Despite this, it is a very potent mucosal adjuvant that has a dramatic impact on immune cells, as well as nerve and epithelial cells, causing diarrhea. This fact has hampered our understanding of whether the adjuvanticity of CT is direct or indirect, as cells that bind CT may or may not be involved in its adjuvant function. The mucosal barrier is maintained by tight junctions between epithelial cells but dendritic cells (DCs) can protrude luminal dendrites. Here we investigated which cells are involved in the immune augmenting effect of CT. We explored oral immunizations with ovalbumin (OVA) and CT in bone marrow chimeric mice deficient in GM1-ganglioside in defined cellular subsets. We found that chimeric mice lacking GM1 in nonhematopoietic cells, including epithelial cells, mounted an unaltered intestinal IgA response. In contrast, chimeric mice lacking GM1-expressing hematopoietic cells in general, or specifically GM1-expressing conventional DCs (cDCs), largely failed to elicit anti-OVA adaptive immune responses. Therefore, the adjuvanticity of CT does not require epithelial activation, but is directly dependent on the binding of CT to gut cDCs via GM1-ganglioside. These results could have important implications for the generation of novel oral adjuvants.

Research paper thumbnail of The subcellular location of antigen expressed by adenoviral vectors modifies adaptive immunity but not dependency on cross-presenting dendritic cells

European Journal of Immunology, 2011

Adenoviral (Ad) vaccine vectors can generate protective immunity to various pathogens in animal s... more Adenoviral (Ad) vaccine vectors can generate protective immunity to various pathogens in animal studies. However, recent failures in clinical vaccine trials have underscored the need for a better understanding of how mucosal immune responses to Ad-encoded vaccine Ags are generated in vivo. In this study, we addressed whether directing Ad-encoded ovalbumin (OVA) to different subcellular compartments influences the generation of OVA-specific acquired immunity and the APCs required following i.n. immunization of mice. We show that both secreted and membrane-anchored OVA activate CD4 1 T cells, induce cytotoxic CD8 1 T lymphocytes (CTLs) and generate serum IgG. Additionally, vaginal IgG is induced when OVA is expressed at these subcellular locations, but only the secreted form generates a significant IgA response in the lungs. On the contrary, intracellular expression of OVA efficiently expands CD8 1 T cells but fails to activate CD4 1 T cells, results in poor CTL activity, and does not generate Abs. Finally, we show that regardless of the subcellular localization of OVA, conventional DCs (cDCs) are required for the activation of T cells. However, the direct transduction of conventional DCs is not essential. These findings have important implications for the improvement of Ad vector design and vaccine-induced mucosal immunity.

Research paper thumbnail of Individualized tissue‐engineered veins as vascular grafts: A proof of concept study in pig

Journal of Tissue Engineering and Regenerative Medicine

Research paper thumbnail of Construction and preclinical evaluation of mmCT, a novel mutant cholera toxin adjuvant that can be efficiently produced in genetically manipulated Vibrio cholerae

Vaccine, 2016

There is an urgent need for new adjuvants that are effective with mucosally administered vaccines... more There is an urgent need for new adjuvants that are effective with mucosally administered vaccines. Cholera toxin (CT) is the most powerful known mucosal adjuvant but is much too toxic for human use. In an effort to develop a useful mucosal adjuvant we have generated a novel non-toxic mutant CT molecule that retains much of the adjuvant activity of native CT. This was achieved by making the enzymatically active A subunit (CTA) recalcitrant to the site-specific proteolytic cleavage ("nicking") required for toxicity, which was found to require mutations not only in the two residues rendering the molecule resistant to trypsin but also in neighboring sites protecting against cleavage by Vibrio cholerae proteases. This multiple-mutated CT (mmCT) adjuvant protein could be efficiently produced in and purified from the extracellular medium of CT-deleted V. cholerae. The mmCT completely lacked detectable enterotoxicity in an infant mouse model and had >1000-fold reduced cAMP inducing activity compared to native CT in a sensitive mammalian target cell system. It nonetheless proved to have potent adjuvant activity on mucosal and systemic antibody as well as cellular immune responses to mucosally co-administered antigens including oral cholera and intranasal influenza vaccines. We conclude that mmCT is an attractive novel non-toxic mucosal adjuvant for enhancing immune responses to co-administered mucosal vaccines.

Research paper thumbnail of T Follicular Helper, but Not Th1, Cell Differentiation in the Absence of Conventional Dendritic Cells

The Journal of Immunology, 2015

Development of long-lived humoral immunity is dependent on CXCR5-expressing T follicular helper (... more Development of long-lived humoral immunity is dependent on CXCR5-expressing T follicular helper (Tfh) cells, which develop concomitantly to effector Th cells that support cellular immunity. Conventional dendritic cells (cDCs) are critical APCs for initial priming of naive CD4 + T cells but, importantly, also provide accessory signals that govern effector Th cell commitment. To define the accessory role of cDCs during the concurrent development of Tfh and effector Th1 cells, we performed high-dose Ag immunization in conjunction with the Th1-biased adjuvant polyinosinic:polycytidylic acid (pI:C). In the absence of cDCs, pI:C failed to induce Th1 cell commitment and IgG2c production. However, cDC depletion did not impair Tfh cell differentiation or germinal center formation, and long-lived IgG1 responses of unaltered affinity developed in mice lacking cDCs at the time point for immunization. Thus, cDCs are required for the pI:C-driven Th1 cell fate commitment but have no crucial accessory function in relation to Tfh cell differentiation.

Research paper thumbnail of Directed antigen targeting in vivo identifies a role for CD103+ dendritic cells in both tolerogenic and immunogenic T-cell responses

Research paper thumbnail of CD11chigh Dendritic Cells Are Essential for Activation of CD4+ T Cells and Generation of Specific Antibodies following Mucosal Immunization

The Journal of Immunology, 2009

To generate vaccines that protect mucosal surfaces, a better understanding of the cells required ... more To generate vaccines that protect mucosal surfaces, a better understanding of the cells required in vivo for activation of the adaptive immune response following mucosal immunization is required. CD11c high conventional dendritic cells (cDCs) have been shown to be necessary for activation of naive CD8 ؉ T cells in vivo, but the role of cDCs in CD4 ؉ T cell activation is still unclear, especially at mucosal surfaces. The activation of naive Ag-specific CD4 ؉ T cells and the generation of Abs following mucosal administration of Ag with or without the potent mucosal adjuvant cholera toxin were therefore analyzed in mice depleted of CD11c high cDCs. Our results show that cDCs are absolutely required for activation of CD4 ؉ T cells after oral and nasal immunization. Ag-specific IgG titers in serum, as well as Ag-specific intestinal IgA, were completely abrogated after feeding mice OVA and cholera toxin. However, giving a very high dose of Ag, 30-fold more than required to detect T cell proliferation, to cDC-ablated mice resulted in proliferation of Ag-specific CD4 ؉ T cells. This proliferation was not inhibited by additional depletion of plasmacytoid DCs or in cDC-depleted mice whose B cells were MHC-II deficient. This study therefore demonstrates that cDCs are required for successful mucosal immunization, unless a very high dose of Ag is administered.

Research paper thumbnail of Direct interaction between cholera toxin and dendritic cells is required for oral adjuvant activity

European Journal of Immunology, 2013

Cholera toxin (CT) binds to GM1-ganglioside receptors present on all nucleated cells. Despite thi... more Cholera toxin (CT) binds to GM1-ganglioside receptors present on all nucleated cells. Despite this, it is a very potent mucosal adjuvant that has a dramatic impact on immune cells, as well as nerve and epithelial cells, causing diarrhea. This fact has hampered our understanding of whether the adjuvanticity of CT is direct or indirect, as cells that bind CT may or may not be involved in its adjuvant function. The mucosal barrier is maintained by tight junctions between epithelial cells but dendritic cells (DCs) can protrude luminal dendrites. Here we investigated which cells are involved in the immune augmenting effect of CT. We explored oral immunizations with ovalbumin (OVA) and CT in bone marrow chimeric mice deficient in GM1-ganglioside in defined cellular subsets. We found that chimeric mice lacking GM1 in nonhematopoietic cells, including epithelial cells, mounted an unaltered intestinal IgA response. In contrast, chimeric mice lacking GM1-expressing hematopoietic cells in general, or specifically GM1-expressing conventional DCs (cDCs), largely failed to elicit anti-OVA adaptive immune responses. Therefore, the adjuvanticity of CT does not require epithelial activation, but is directly dependent on the binding of CT to gut cDCs via GM1-ganglioside. These results could have important implications for the generation of novel oral adjuvants.

Research paper thumbnail of The subcellular location of antigen expressed by adenoviral vectors modifies adaptive immunity but not dependency on cross-presenting dendritic cells

European Journal of Immunology, 2011

Adenoviral (Ad) vaccine vectors can generate protective immunity to various pathogens in animal s... more Adenoviral (Ad) vaccine vectors can generate protective immunity to various pathogens in animal studies. However, recent failures in clinical vaccine trials have underscored the need for a better understanding of how mucosal immune responses to Ad-encoded vaccine Ags are generated in vivo. In this study, we addressed whether directing Ad-encoded ovalbumin (OVA) to different subcellular compartments influences the generation of OVA-specific acquired immunity and the APCs required following i.n. immunization of mice. We show that both secreted and membrane-anchored OVA activate CD4 1 T cells, induce cytotoxic CD8 1 T lymphocytes (CTLs) and generate serum IgG. Additionally, vaginal IgG is induced when OVA is expressed at these subcellular locations, but only the secreted form generates a significant IgA response in the lungs. On the contrary, intracellular expression of OVA efficiently expands CD8 1 T cells but fails to activate CD4 1 T cells, results in poor CTL activity, and does not generate Abs. Finally, we show that regardless of the subcellular localization of OVA, conventional DCs (cDCs) are required for the activation of T cells. However, the direct transduction of conventional DCs is not essential. These findings have important implications for the improvement of Ad vector design and vaccine-induced mucosal immunity.

Research paper thumbnail of Individualized tissue‐engineered veins as vascular grafts: A proof of concept study in pig

Journal of Tissue Engineering and Regenerative Medicine