Erik Nygren - Academia.edu (original) (raw)

Papers by Erik Nygren

Research paper thumbnail of Plasmacytoid Dendritic Cells Compared to That of Myeloid and Peptide Receptor Family Agonists Radicals in Response to Formyl Dendritic Cells To Secrete Oxygen Ability of Monocyte-Derived

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 Development of Stable Vibrio cholerae O1 Hikojima Type Vaccine Strains Co–Expressing the Inaba and Ogawa Lipopolysaccharide Antigens

PLoS ONE, 2014

We describe here the development of stable classical and El Tor V. cholerae O1 strains of the Hik... more We describe here the development of stable classical and El Tor V. cholerae O1 strains of the Hikojima serotype that coexpress the Inaba and Ogawa antigens of O1 lipopolysaccharide (LPS). Mutation of the wbeT gene reduced LPS perosamine methylation and thereby gave only partial transformation into Ogawa LPS on the cell surface. The strains express approximately equal amounts of Inaba-and Ogawa-LPS antigens which are preserved after formalin-inactivation of the bacteria. Oral immunizations of both inbred and outbred mice with formalin-inactivated whole-cell vaccine preparations of these strains elicited strong intestinal IgA anti-LPS as well as serum vibriocidal antibody responses against both Inaba and Ogawa that were fully comparable to the responses induced by the licensed Dukoral vaccine. Passive protection studies in infant mice showed that immune sera raised against either of the novel Hikojima vaccine strains protected baby mice against infection with virulent strains of both serotypes. This study illustrates the power of using genetic manipulation to improve the properties of bacteria strains for use in killed whole-cell vaccines.

Research paper thumbnail of Murine antibody responses following systemic or mucosal immunization with viable or inactivated Vibrio cholerae

Vaccine, 2008

Protocols are described for the induction of strong, consistent serum and mucosal antibody respon... more Protocols are described for the induction of strong, consistent serum and mucosal antibody responses to Vibrio cholerae O1 or O139 lipopolysaccharide (LPS) following intranasal or oral immunization of adult mice with viable or formalin-killed bacteria. A simplified two-dose schedule for intranasal immunization has been identified, whereby viable bacteria elicit strong serum responses and, most importantly, also induce significant, sustained intestinal IgA responses. Using higher doses of bacteria it was also possible to generate consistently high intestinal and serum anti-LPS responses by the oral route. The efficacy of these immunization schedules was not dependent on co-administration of adjuvant. Gut responses were estimated using two sampling techniques involving the collection of fresh faecal pellets or the preparation of intestinal tissue extracts. The significant correlation between these estimates validates the more convenient approach of measuring intestinal responses using faecal pellet extracts, which allows repeated sampling from the same animals. V. cholerae O1 and O139 were similarly immunogenic by either mucosal route. More intensive immunization schedules for administration of formalin-killed bacteria have also been defined. Using these regimes it was possible to generate serum and gut antibody responses comparable to those elicited by viable V. cholerae. The established immunization protocols will allow evaluation of the systemic and mucosal immunogenicity of new vaccine formulations.

Research paper thumbnail of Construction of novel vaccine strains of Vibrio cholerae co-expressing the Inaba and Ogawa serotype antigens

Vaccine, 2011

The approach of inducing protective immunity against cholera by oral vaccination with killed whol... more The approach of inducing protective immunity against cholera by oral vaccination with killed whole Vibrio cholerae cells is effective, but the complexity of current cholera vaccines makes them difficult and relatively expensive to manufacture, especially if recombinant cholera toxin B subunit is included in the formulation. In an effort to simplify the composition of a new generation of oral cholera vaccines we have generated a novel non-toxigenic candidate vaccine strain of V. cholerae O1 that stably expresses both the Ogawa and Inaba serotype antigens on its surface. This was done by introducing a functional wbeT gene without a functional promoter into the chromosome of an O1 Inaba strain. The resulting low levels of expression of the wbeT gene product allowed for the desired partial serotype switching. This strain (MS1342) can potentially replace the three virulent strains used in currently manufactured cholera vaccines. Oral immunization of mice with formalin-killed MS1342 bacteria gave rise to Ogawa-specific, Inaba-specific and cross-reactive serum antibodies that were detectable both by lipopolysaccharide (LPS)specific ELISAs and as vibriocidal antibodies that are considered to predict protective efficacy. These responses as well as intestinal mucosal IgA anti-LPS antibody responses were fully comparable with those obtained by immunization with the internationally licensed oral cholera vaccine Dukoral ®. We propose that such a strain may form the basis of a single strain killed whole cell cholera vaccine protecting against cholera caused by either the Inaba or Ogawa serotype of V. cholerae O1.

Research paper thumbnail of Development and preclinical evaluation of safety and immunogenicity of an oral ETEC vaccine containing inactivated E. coli bacteria overexpressing colonization factors CFA/I, CS3, CS5 and CS6 combined with a hybrid LT/CT B subunit antigen, administered alone and together with dmLT adjuvant

Vaccine, 2013

A first-generation oral inactivated whole-cell enterotoxigenic Escherichia coli (ETEC) vaccine, c... more A first-generation oral inactivated whole-cell enterotoxigenic Escherichia coli (ETEC) vaccine, comprising formalin-killed ETEC bacteria expressing different colonization factor (CF) antigens combined with cholera toxin B subunit (CTB), when tested in phase III studies did not significantly reduce overall (generally mild) ETEC diarrhea in travelers or children although it reduced more severe ETEC diarrhea in travelers by almost 80%. We have now developed a novel more immunogenic ETEC vaccine based on recombinant non-toxigenic E. coli strains engineered to express increased amounts of CF antigens, including CS6 as well as an ETEC-based B subunit protein (LCTBA), and the optional combination with a nontoxic double-mutant heat-labile toxin (LT) molecule (dmLT) as an adjuvant. Two test vaccines were prepared under GMP: (1) A prototype E. coli CFA/I-only formalin-killed whole-cell+LCTBA vaccine, and (2) A "complete" inactivated multivalent ETEC-CF (CFA/I, CS3, CS5 and CS6 antigens) whole-cell+LCTBA vaccine. These vaccines, when given intragastrically alone or together with dmLT in mice, were well tolerated and induced strong intestinal-mucosal IgA antibody responses as well as serum IgG and IgA responses to each of the vaccine CF antigens as well as to LT B subunit (LTB). Both mucosal and serum responses were further enhanced (adjuvanted) when the vaccines were co-administered with dmLT. We conclude that the new multivalent oral ETEC vaccine, both alone and especially in combination with the dmLT adjuvant, shows great promise for further testing in humans.

Research paper thumbnail of Over-expression of major colonization factors of enterotoxigenic Escherichia coli, alone or together, on non-toxigenic E. coli bacteria

Vaccine, 2010

Enterotoxigenic Escherichia coli (ETEC) is an important cause of diarrheal disease and deaths amo... more Enterotoxigenic Escherichia coli (ETEC) is an important cause of diarrheal disease and deaths among children in developing countries and the major cause of traveller's diarrhea. Since surface protein colonization factors (CFs) of ETEC are important for pathogenicity and immune protection is mainly mediated by locally produced IgA antibodies in the gut, much effort has focused on the development of an oral CFbased vaccine. We have recently described the development of recombinant strains over-expressing CFA/I; the most prevalent CF among human clinical ETEC isolates. Here, non-toxigenic recombinant E. coli strains over-expressing Coli surface antigen 2 (CS2), CS4, CS5, and CS6, either alone, or each in combination with CFA/I were constructed by cloning the genes required for expression and assembly of each CF into expression vectors harboring a strong promoter. Immunological assays showed that recombinant strains expressing single CFs produced those in significantly larger amounts than did corresponding naturally high producing reference strains. Recombinant strains co-expressing CFA/I together with another CF also expressed significantly larger amounts of both CFs compared with the corresponding references strains. Further, when tested in mice, oral immunization with formalin-killed recombinant bacteria coexpressing one such double-expression CF pair, CFA/I + CS2, induced specific serum IgG + IgM and fecal IgA antibody responses against both CFs exceeding the responses induced by immunizations with natural reference strains expressing CFA/I and CS2, respectively. We conclude that the described type of recombinant bacteria over-expressing major CFs of ETEC, alone or in combination, may be useful as candidate strains for use in an oral whole-cell CF-ETEC vaccine.

Research paper thumbnail of Alkaline pH Is a Signal for Optimal Production and Secretion of the Heat Labile Toxin, LT in Enterotoxigenic Escherichia Coli (ETEC)

PLoS ONE, 2013

Enterotoxigenic Escherichia coli (ETEC) cause secretory diarrhea in children and travelers to end... more Enterotoxigenic Escherichia coli (ETEC) cause secretory diarrhea in children and travelers to endemic areas. ETEC spreads through the fecal-oral route. After ingestion, ETEC passes through the stomach and duodenum before it colonizes the lower part of the small intestine, exposing bacteria to a wide range of pH and environmental conditions. This study aimed to determine the impact of external pH and activity of the Cyclic AMP receptor protein (CRP) on the regulation of production and secretion of heat labile (LT) enterotoxin. ETEC strain E2863wt and its isogenic mutant E2863DCRP were grown in LBK media buffered to pH 5, 7 and 9. GM1 ELISA, cDNA and cAMP analyses were carried out on bacterial pellet and supernatant samples derived from 3 and 5 hours growth and from overnight cultures. We confirm that CRP is a repressor of LT transcription and production as has been shown before but we show for the first time that CRP is a positive regulator of LT secretion both in vitro and in vivo. LT secretion increased at neutral to alkaline pH compared to acidic pH 5 where secretion was completely inhibited. At pH 9 secretion of LT was optimal resulting in 600 percent increase of secreted LT compared to unbuffered LBK media. This effect was not due to membrane leakage since the bacteria were viable at pH 9. The results indicate that the transition to the alkaline duodenum and/or exposure to high pH close to the epithelium as well as activation of the global transcription factor CRP are signals that induce secretion of the LT toxin in ETEC.

Research paper thumbnail of A Proinflammatory Peptide from Herpes Simplex Virus Type 2 Glycoprotein G Affects Neutrophil, Monocyte, and NK Cell Functions

The Journal of Immunology, 2005

We have identified a synthetic peptide derived from the secreted portion of HSV type 2 glycoprote... more We have identified a synthetic peptide derived from the secreted portion of HSV type 2 glycoprotein G, denoted gG-2p20, which has proinflammatory properties in vitro. The gG-2p20 peptide, corresponding to aa 190-205 of glycoprotein G-2, was a chemoattractant for both monocytes and neutrophils in a dose-dependent fashion, and also induced the release of reactive oxygen from these cells. The receptor mediating the responses was identified as the formyl peptide receptor. The gG-2p20-induced activation of phagocytes had a profound impact on NK cell functions. The reactive oxygen species produced by gG-2p20-activated phagocytes both inhibited NK cell cytotoxicity and accelerated the apoptotic cell death in NK cell-enriched lymphocyte populations. Hence, we have for the first time been able to identify a potential function of the secreted portion of HSV-2 glycoprotein G. We propose that the proinflammatory gG-2p20 peptide identified could contribute to a reduced function and viability of NK cells during HSV-2 infection due to its ability to recruit and activate phagocytic cells.

Research paper thumbnail of Establishment of an Adult Mouse Model for Direct Evaluation of the Efficacy of Vaccines against Vibrio cholerae

Infection and Immunity, 2009

We describe here a new animal model that offers the prospect of using conventional adult mice for... more We describe here a new animal model that offers the prospect of using conventional adult mice for direct evaluation of the protective potential of new cholera vaccines. Pretreatment of adult mice with oral streptomycin allowed intestinal colonization by streptomycin-resistant Vibrio cholerae strains of either the O1 or the O139 serogroup. Bacteria were recovered in greatest numbers from the cecum and large intestine, but recoveries from all regions of the gut correlated significantly with bacterial excretion in fresh fecal pellets, which thus provides a convenient indicator of the extent and duration of gut colonization. Mice immunized mucosally or systemically with viable or inactivated V. cholerae were shown to be comparatively refractory to colonization after challenge with the immunizing strain. Several variables were examined to optimize the model, the most significant being the size of the challenge inoculum; surprisingly, a smaller challenge dose resulted in more consistent and sustained colonization. Studies with mutant strains unable to produce cholera toxin or toxin-coregulated pili revealed that neither factor contributed significantly to colonization potential. Protection against V. cholerae challenge was shown to be serogroup restricted, and significant inverse correlations were detected between serum and intestinal anti-lipopolysaccharide antibody responses and the levels of excretion of challenge organisms.

Research paper thumbnail of Mucosal adjuvants and anti-infection and anti-immunopathology vaccines based on cholera toxin, cholera toxin B subunit and CpG DNA

Expert Review of Vaccines, 2003

The mucosal immune system consists of an integrated network of lymphoid cells that work in concer... more The mucosal immune system consists of an integrated network of lymphoid cells that work in concert with innate host factors to promote host defence. Mucosal immunization can be used both to protect the mucosal surfaces against colonization and invasion by microbial pathogens and to provide a means for immunological treatment of selected autoimmune, allergic or infectious-immunopathological disorders through the induction of antigen-specific tolerance. The development of mucosal vaccines, whether for prevention of infectious diseases or for oral tolerance immunotherapy, requires efficient antigen delivery and adjuvant systems. Significant progress has recently been made to generate partly or wholly detoxified derivatives of cholera toxin (including the completely nontoxic cholera toxin B subunit) and the closely related Escherichia coli heat-labile enterotoxin, with retained adjuvant activity. Cholera toxin B subunit is a protective component of a widely registered oral vaccine against cholera, and has proven to be a promising vector for either giving rise to anti-infective immunity or for inducing peripheral anti-inflammatory tolerance to chemically or genetically linked foreign antigens administered mucosally. Promising advances have also recently been made in the design of efficient mucosal adjuvants based on bacterial DNA that contains CpG-motifs and various imidazoquinoline compounds binding to different Toll-like receptors on mucosal antigen-presenting cells.

Research paper thumbnail of Preparation and evaluation of a freeze-dried oral killed cholera vaccine formulation

European Journal of Pharmaceutics and Biopharmaceutics, 2011

Different oral liquid cholera vaccines have proved to be safe and effective, but their formulatio... more Different oral liquid cholera vaccines have proved to be safe and effective, but their formulations present problems for use in low-income countries, since large package volumes have to be transported and cold chain maintenance is required. A solid state formulation would here be more advantageous, and consequently, the possibility to develop a dry cholera vaccine formulation by freeze-drying was investigated. The ability of sucrose, trehalose and mannitol to provide process stabilization during freeze-drying was tested on a formalin-killed whole-cell Vibrio cholerae model vaccine. A matrix of sucrose or trehalose prevented bacterial aggregation, preserved cell morphology and maintained practically completely the protective lipopolysaccharide (LPS) antigen on the cell surface and its reactivity with specific antibody in vitro. After reconstitution, this formulation also retained the capacity to elicit a strong serum and gut mucosal anti-LPS antibody response in orally immunized mice, as compared to the corresponding liquid vaccine formulation. The full preservation of the in vivo immunogenicity was also maintained when the internationally widely licensed oral cholera vaccine Dukoral™, which comprises a cocktail of inactivated V. cholerae together with cholera toxin B-subunit (CTB), was freeze-dried using sucrose for stabilization. Thus, we present a process generating a dry oral inactivated whole-cell cholera vaccine formulation with attractive features for public health use in cholera-afflicted settings.

Research paper thumbnail of Th17 development and autoimmune arthritis in the absence of reactive oxygen species

European Journal of Immunology, 2008

Dendritic cells (DC) express a functional NADPH oxidase and produce reactive oxygen species (ROS)... more Dendritic cells (DC) express a functional NADPH oxidase and produce reactive oxygen species (ROS) upon interaction with microbes and T cells. Exposure to ROS leads to DC activation and maturation, as evidenced by phenotypic and functional changes. We have evaluated how endogenous ROS production affects the cytokine secretion pattern and T cell-activating capacity of bone marrow-derived murine DC. DC treated with ROS scavengers, as well as DC from mice that lack a functional NADPH oxidase (and thereby inherently deficient in ROS production) produced significantly increased levels of IL-1b, IL-6, TNF-a and TGF-b in response to microbial activation. DC deficient in ROS production induced high levels of IFN-c and IL-17 in responding T cells after Ag-specific or superantigen-induced activation. Finally, we show that ROS deficiency affected the induction of a T cell-dependent inflammatory condition, collagen-induced arthritis (CIA). C57BL/6 mice that lack a functional NADPH oxidase developed a severe and erosive CD4dependent CIA, whereas the majority of the congenic wild-type animals remained healthy. These data suggest that ROS act as immunomodulators in DC-driven T cell activation and perhaps also in T cell-dependent immunopathology.

Research paper thumbnail of Ability of Monocyte-Derived Dendritic Cells To Secrete Oxygen Radicals in Response to Formyl Peptide Receptor Family Agonists Compared to That of Myeloid and Plasmacytoid Dendritic Cells

Clinical and Vaccine Immunology, 2007

We show that human monocyte-derived dendritic cells (DC) differ considerably from freshly isolate... more We show that human monocyte-derived dendritic cells (DC) differ considerably from freshly isolated blood-derived myeloid and plasmacytoid DC in their abilities to produce reactive oxygen species in response to different agonists to the formyl peptide receptor family and are thus poor representatives of blood DC in this field of research.

Research paper thumbnail of A mouse model for direct evaluation of cholera vaccines

Page 1. A mouse model for direct evaluation of cholera vaccines Erik Nygren Department of Microbi... more Page 1. A mouse model for direct evaluation of cholera vaccines Erik Nygren Department of Microbiology and Immunology Institute of Biomedicine The Sahlgrenska Academy at University of Gothenburg Sweden 2009 Page 2. “When things go wrong, don't go with them” ...

Research paper thumbnail of Plasmacytoid Dendritic Cells Compared to That of Myeloid and Peptide Receptor Family Agonists Radicals in Response to Formyl Dendritic Cells To Secrete Oxygen Ability of Monocyte-Derived

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 Development of Stable Vibrio cholerae O1 Hikojima Type Vaccine Strains Co–Expressing the Inaba and Ogawa Lipopolysaccharide Antigens

PLoS ONE, 2014

We describe here the development of stable classical and El Tor V. cholerae O1 strains of the Hik... more We describe here the development of stable classical and El Tor V. cholerae O1 strains of the Hikojima serotype that coexpress the Inaba and Ogawa antigens of O1 lipopolysaccharide (LPS). Mutation of the wbeT gene reduced LPS perosamine methylation and thereby gave only partial transformation into Ogawa LPS on the cell surface. The strains express approximately equal amounts of Inaba-and Ogawa-LPS antigens which are preserved after formalin-inactivation of the bacteria. Oral immunizations of both inbred and outbred mice with formalin-inactivated whole-cell vaccine preparations of these strains elicited strong intestinal IgA anti-LPS as well as serum vibriocidal antibody responses against both Inaba and Ogawa that were fully comparable to the responses induced by the licensed Dukoral vaccine. Passive protection studies in infant mice showed that immune sera raised against either of the novel Hikojima vaccine strains protected baby mice against infection with virulent strains of both serotypes. This study illustrates the power of using genetic manipulation to improve the properties of bacteria strains for use in killed whole-cell vaccines.

Research paper thumbnail of Murine antibody responses following systemic or mucosal immunization with viable or inactivated Vibrio cholerae

Vaccine, 2008

Protocols are described for the induction of strong, consistent serum and mucosal antibody respon... more Protocols are described for the induction of strong, consistent serum and mucosal antibody responses to Vibrio cholerae O1 or O139 lipopolysaccharide (LPS) following intranasal or oral immunization of adult mice with viable or formalin-killed bacteria. A simplified two-dose schedule for intranasal immunization has been identified, whereby viable bacteria elicit strong serum responses and, most importantly, also induce significant, sustained intestinal IgA responses. Using higher doses of bacteria it was also possible to generate consistently high intestinal and serum anti-LPS responses by the oral route. The efficacy of these immunization schedules was not dependent on co-administration of adjuvant. Gut responses were estimated using two sampling techniques involving the collection of fresh faecal pellets or the preparation of intestinal tissue extracts. The significant correlation between these estimates validates the more convenient approach of measuring intestinal responses using faecal pellet extracts, which allows repeated sampling from the same animals. V. cholerae O1 and O139 were similarly immunogenic by either mucosal route. More intensive immunization schedules for administration of formalin-killed bacteria have also been defined. Using these regimes it was possible to generate serum and gut antibody responses comparable to those elicited by viable V. cholerae. The established immunization protocols will allow evaluation of the systemic and mucosal immunogenicity of new vaccine formulations.

Research paper thumbnail of Construction of novel vaccine strains of Vibrio cholerae co-expressing the Inaba and Ogawa serotype antigens

Vaccine, 2011

The approach of inducing protective immunity against cholera by oral vaccination with killed whol... more The approach of inducing protective immunity against cholera by oral vaccination with killed whole Vibrio cholerae cells is effective, but the complexity of current cholera vaccines makes them difficult and relatively expensive to manufacture, especially if recombinant cholera toxin B subunit is included in the formulation. In an effort to simplify the composition of a new generation of oral cholera vaccines we have generated a novel non-toxigenic candidate vaccine strain of V. cholerae O1 that stably expresses both the Ogawa and Inaba serotype antigens on its surface. This was done by introducing a functional wbeT gene without a functional promoter into the chromosome of an O1 Inaba strain. The resulting low levels of expression of the wbeT gene product allowed for the desired partial serotype switching. This strain (MS1342) can potentially replace the three virulent strains used in currently manufactured cholera vaccines. Oral immunization of mice with formalin-killed MS1342 bacteria gave rise to Ogawa-specific, Inaba-specific and cross-reactive serum antibodies that were detectable both by lipopolysaccharide (LPS)specific ELISAs and as vibriocidal antibodies that are considered to predict protective efficacy. These responses as well as intestinal mucosal IgA anti-LPS antibody responses were fully comparable with those obtained by immunization with the internationally licensed oral cholera vaccine Dukoral ®. We propose that such a strain may form the basis of a single strain killed whole cell cholera vaccine protecting against cholera caused by either the Inaba or Ogawa serotype of V. cholerae O1.

Research paper thumbnail of Development and preclinical evaluation of safety and immunogenicity of an oral ETEC vaccine containing inactivated E. coli bacteria overexpressing colonization factors CFA/I, CS3, CS5 and CS6 combined with a hybrid LT/CT B subunit antigen, administered alone and together with dmLT adjuvant

Vaccine, 2013

A first-generation oral inactivated whole-cell enterotoxigenic Escherichia coli (ETEC) vaccine, c... more A first-generation oral inactivated whole-cell enterotoxigenic Escherichia coli (ETEC) vaccine, comprising formalin-killed ETEC bacteria expressing different colonization factor (CF) antigens combined with cholera toxin B subunit (CTB), when tested in phase III studies did not significantly reduce overall (generally mild) ETEC diarrhea in travelers or children although it reduced more severe ETEC diarrhea in travelers by almost 80%. We have now developed a novel more immunogenic ETEC vaccine based on recombinant non-toxigenic E. coli strains engineered to express increased amounts of CF antigens, including CS6 as well as an ETEC-based B subunit protein (LCTBA), and the optional combination with a nontoxic double-mutant heat-labile toxin (LT) molecule (dmLT) as an adjuvant. Two test vaccines were prepared under GMP: (1) A prototype E. coli CFA/I-only formalin-killed whole-cell+LCTBA vaccine, and (2) A "complete" inactivated multivalent ETEC-CF (CFA/I, CS3, CS5 and CS6 antigens) whole-cell+LCTBA vaccine. These vaccines, when given intragastrically alone or together with dmLT in mice, were well tolerated and induced strong intestinal-mucosal IgA antibody responses as well as serum IgG and IgA responses to each of the vaccine CF antigens as well as to LT B subunit (LTB). Both mucosal and serum responses were further enhanced (adjuvanted) when the vaccines were co-administered with dmLT. We conclude that the new multivalent oral ETEC vaccine, both alone and especially in combination with the dmLT adjuvant, shows great promise for further testing in humans.

Research paper thumbnail of Over-expression of major colonization factors of enterotoxigenic Escherichia coli, alone or together, on non-toxigenic E. coli bacteria

Vaccine, 2010

Enterotoxigenic Escherichia coli (ETEC) is an important cause of diarrheal disease and deaths amo... more Enterotoxigenic Escherichia coli (ETEC) is an important cause of diarrheal disease and deaths among children in developing countries and the major cause of traveller's diarrhea. Since surface protein colonization factors (CFs) of ETEC are important for pathogenicity and immune protection is mainly mediated by locally produced IgA antibodies in the gut, much effort has focused on the development of an oral CFbased vaccine. We have recently described the development of recombinant strains over-expressing CFA/I; the most prevalent CF among human clinical ETEC isolates. Here, non-toxigenic recombinant E. coli strains over-expressing Coli surface antigen 2 (CS2), CS4, CS5, and CS6, either alone, or each in combination with CFA/I were constructed by cloning the genes required for expression and assembly of each CF into expression vectors harboring a strong promoter. Immunological assays showed that recombinant strains expressing single CFs produced those in significantly larger amounts than did corresponding naturally high producing reference strains. Recombinant strains co-expressing CFA/I together with another CF also expressed significantly larger amounts of both CFs compared with the corresponding references strains. Further, when tested in mice, oral immunization with formalin-killed recombinant bacteria coexpressing one such double-expression CF pair, CFA/I + CS2, induced specific serum IgG + IgM and fecal IgA antibody responses against both CFs exceeding the responses induced by immunizations with natural reference strains expressing CFA/I and CS2, respectively. We conclude that the described type of recombinant bacteria over-expressing major CFs of ETEC, alone or in combination, may be useful as candidate strains for use in an oral whole-cell CF-ETEC vaccine.

Research paper thumbnail of Alkaline pH Is a Signal for Optimal Production and Secretion of the Heat Labile Toxin, LT in Enterotoxigenic Escherichia Coli (ETEC)

PLoS ONE, 2013

Enterotoxigenic Escherichia coli (ETEC) cause secretory diarrhea in children and travelers to end... more Enterotoxigenic Escherichia coli (ETEC) cause secretory diarrhea in children and travelers to endemic areas. ETEC spreads through the fecal-oral route. After ingestion, ETEC passes through the stomach and duodenum before it colonizes the lower part of the small intestine, exposing bacteria to a wide range of pH and environmental conditions. This study aimed to determine the impact of external pH and activity of the Cyclic AMP receptor protein (CRP) on the regulation of production and secretion of heat labile (LT) enterotoxin. ETEC strain E2863wt and its isogenic mutant E2863DCRP were grown in LBK media buffered to pH 5, 7 and 9. GM1 ELISA, cDNA and cAMP analyses were carried out on bacterial pellet and supernatant samples derived from 3 and 5 hours growth and from overnight cultures. We confirm that CRP is a repressor of LT transcription and production as has been shown before but we show for the first time that CRP is a positive regulator of LT secretion both in vitro and in vivo. LT secretion increased at neutral to alkaline pH compared to acidic pH 5 where secretion was completely inhibited. At pH 9 secretion of LT was optimal resulting in 600 percent increase of secreted LT compared to unbuffered LBK media. This effect was not due to membrane leakage since the bacteria were viable at pH 9. The results indicate that the transition to the alkaline duodenum and/or exposure to high pH close to the epithelium as well as activation of the global transcription factor CRP are signals that induce secretion of the LT toxin in ETEC.

Research paper thumbnail of A Proinflammatory Peptide from Herpes Simplex Virus Type 2 Glycoprotein G Affects Neutrophil, Monocyte, and NK Cell Functions

The Journal of Immunology, 2005

We have identified a synthetic peptide derived from the secreted portion of HSV type 2 glycoprote... more We have identified a synthetic peptide derived from the secreted portion of HSV type 2 glycoprotein G, denoted gG-2p20, which has proinflammatory properties in vitro. The gG-2p20 peptide, corresponding to aa 190-205 of glycoprotein G-2, was a chemoattractant for both monocytes and neutrophils in a dose-dependent fashion, and also induced the release of reactive oxygen from these cells. The receptor mediating the responses was identified as the formyl peptide receptor. The gG-2p20-induced activation of phagocytes had a profound impact on NK cell functions. The reactive oxygen species produced by gG-2p20-activated phagocytes both inhibited NK cell cytotoxicity and accelerated the apoptotic cell death in NK cell-enriched lymphocyte populations. Hence, we have for the first time been able to identify a potential function of the secreted portion of HSV-2 glycoprotein G. We propose that the proinflammatory gG-2p20 peptide identified could contribute to a reduced function and viability of NK cells during HSV-2 infection due to its ability to recruit and activate phagocytic cells.

Research paper thumbnail of Establishment of an Adult Mouse Model for Direct Evaluation of the Efficacy of Vaccines against Vibrio cholerae

Infection and Immunity, 2009

We describe here a new animal model that offers the prospect of using conventional adult mice for... more We describe here a new animal model that offers the prospect of using conventional adult mice for direct evaluation of the protective potential of new cholera vaccines. Pretreatment of adult mice with oral streptomycin allowed intestinal colonization by streptomycin-resistant Vibrio cholerae strains of either the O1 or the O139 serogroup. Bacteria were recovered in greatest numbers from the cecum and large intestine, but recoveries from all regions of the gut correlated significantly with bacterial excretion in fresh fecal pellets, which thus provides a convenient indicator of the extent and duration of gut colonization. Mice immunized mucosally or systemically with viable or inactivated V. cholerae were shown to be comparatively refractory to colonization after challenge with the immunizing strain. Several variables were examined to optimize the model, the most significant being the size of the challenge inoculum; surprisingly, a smaller challenge dose resulted in more consistent and sustained colonization. Studies with mutant strains unable to produce cholera toxin or toxin-coregulated pili revealed that neither factor contributed significantly to colonization potential. Protection against V. cholerae challenge was shown to be serogroup restricted, and significant inverse correlations were detected between serum and intestinal anti-lipopolysaccharide antibody responses and the levels of excretion of challenge organisms.

Research paper thumbnail of Mucosal adjuvants and anti-infection and anti-immunopathology vaccines based on cholera toxin, cholera toxin B subunit and CpG DNA

Expert Review of Vaccines, 2003

The mucosal immune system consists of an integrated network of lymphoid cells that work in concer... more The mucosal immune system consists of an integrated network of lymphoid cells that work in concert with innate host factors to promote host defence. Mucosal immunization can be used both to protect the mucosal surfaces against colonization and invasion by microbial pathogens and to provide a means for immunological treatment of selected autoimmune, allergic or infectious-immunopathological disorders through the induction of antigen-specific tolerance. The development of mucosal vaccines, whether for prevention of infectious diseases or for oral tolerance immunotherapy, requires efficient antigen delivery and adjuvant systems. Significant progress has recently been made to generate partly or wholly detoxified derivatives of cholera toxin (including the completely nontoxic cholera toxin B subunit) and the closely related Escherichia coli heat-labile enterotoxin, with retained adjuvant activity. Cholera toxin B subunit is a protective component of a widely registered oral vaccine against cholera, and has proven to be a promising vector for either giving rise to anti-infective immunity or for inducing peripheral anti-inflammatory tolerance to chemically or genetically linked foreign antigens administered mucosally. Promising advances have also recently been made in the design of efficient mucosal adjuvants based on bacterial DNA that contains CpG-motifs and various imidazoquinoline compounds binding to different Toll-like receptors on mucosal antigen-presenting cells.

Research paper thumbnail of Preparation and evaluation of a freeze-dried oral killed cholera vaccine formulation

European Journal of Pharmaceutics and Biopharmaceutics, 2011

Different oral liquid cholera vaccines have proved to be safe and effective, but their formulatio... more Different oral liquid cholera vaccines have proved to be safe and effective, but their formulations present problems for use in low-income countries, since large package volumes have to be transported and cold chain maintenance is required. A solid state formulation would here be more advantageous, and consequently, the possibility to develop a dry cholera vaccine formulation by freeze-drying was investigated. The ability of sucrose, trehalose and mannitol to provide process stabilization during freeze-drying was tested on a formalin-killed whole-cell Vibrio cholerae model vaccine. A matrix of sucrose or trehalose prevented bacterial aggregation, preserved cell morphology and maintained practically completely the protective lipopolysaccharide (LPS) antigen on the cell surface and its reactivity with specific antibody in vitro. After reconstitution, this formulation also retained the capacity to elicit a strong serum and gut mucosal anti-LPS antibody response in orally immunized mice, as compared to the corresponding liquid vaccine formulation. The full preservation of the in vivo immunogenicity was also maintained when the internationally widely licensed oral cholera vaccine Dukoral™, which comprises a cocktail of inactivated V. cholerae together with cholera toxin B-subunit (CTB), was freeze-dried using sucrose for stabilization. Thus, we present a process generating a dry oral inactivated whole-cell cholera vaccine formulation with attractive features for public health use in cholera-afflicted settings.

Research paper thumbnail of Th17 development and autoimmune arthritis in the absence of reactive oxygen species

European Journal of Immunology, 2008

Dendritic cells (DC) express a functional NADPH oxidase and produce reactive oxygen species (ROS)... more Dendritic cells (DC) express a functional NADPH oxidase and produce reactive oxygen species (ROS) upon interaction with microbes and T cells. Exposure to ROS leads to DC activation and maturation, as evidenced by phenotypic and functional changes. We have evaluated how endogenous ROS production affects the cytokine secretion pattern and T cell-activating capacity of bone marrow-derived murine DC. DC treated with ROS scavengers, as well as DC from mice that lack a functional NADPH oxidase (and thereby inherently deficient in ROS production) produced significantly increased levels of IL-1b, IL-6, TNF-a and TGF-b in response to microbial activation. DC deficient in ROS production induced high levels of IFN-c and IL-17 in responding T cells after Ag-specific or superantigen-induced activation. Finally, we show that ROS deficiency affected the induction of a T cell-dependent inflammatory condition, collagen-induced arthritis (CIA). C57BL/6 mice that lack a functional NADPH oxidase developed a severe and erosive CD4dependent CIA, whereas the majority of the congenic wild-type animals remained healthy. These data suggest that ROS act as immunomodulators in DC-driven T cell activation and perhaps also in T cell-dependent immunopathology.

Research paper thumbnail of Ability of Monocyte-Derived Dendritic Cells To Secrete Oxygen Radicals in Response to Formyl Peptide Receptor Family Agonists Compared to That of Myeloid and Plasmacytoid Dendritic Cells

Clinical and Vaccine Immunology, 2007

We show that human monocyte-derived dendritic cells (DC) differ considerably from freshly isolate... more We show that human monocyte-derived dendritic cells (DC) differ considerably from freshly isolated blood-derived myeloid and plasmacytoid DC in their abilities to produce reactive oxygen species in response to different agonists to the formyl peptide receptor family and are thus poor representatives of blood DC in this field of research.

Research paper thumbnail of A mouse model for direct evaluation of cholera vaccines

Page 1. A mouse model for direct evaluation of cholera vaccines Erik Nygren Department of Microbi... more Page 1. A mouse model for direct evaluation of cholera vaccines Erik Nygren Department of Microbiology and Immunology Institute of Biomedicine The Sahlgrenska Academy at University of Gothenburg Sweden 2009 Page 2. “When things go wrong, don't go with them” ...