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.

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.

A halotolerant, exopolysaccharide-producing bacterium isolated from the Salar de Uyuni salt flat in Bolivia was identified as Bacillus atrophaeus using next-generation sequencing. Comparisons indicate that the genome most likely (p-value: 0.0024) belongs to a subspecies previously not represented in the database. The growth of the bacterial strain and its ability to produce exopolysaccharides (EPS) in synthetic media with glucose or xylose as carbon sources, and in hydrolysates of quinoa stalks, was investigated. The strain grew well in all synthetic media, but the growth in glucose was better than that in xylose. Sugar consumption was better when initial concentrations were low. The growth was good in enzymatically produced cellulosic hydrolysates but was inhibited in hemicellulosic hydrolysates produced using hydrothermal pretreatment. The EPS yields were up to 0.064 g/g on initial glucose and 0.047 g/g on initial xylose, and was higher in media with relatively low sugar concentrations. The EPS was isolated and purified by a sequential procedure including centrifugation, cold ethanol precipitation, trichloroacetic acid treatment, dialysis, and freeze-drying. Glucose and mannose were the main sugars identified in hydrolyzed EPS. The EPS was characterized by size-exclusion chromatography, Fourier-transform infrared (FTIR) spectroscopy, heteronuclear single-quantum coherence nuclear magnetic resonance (HSQC NMR) spectroscopy, scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis. No major differences were elucidated between EPS resulting from cultivations in glucose- or-xylose-based synthetic media, while some divergences with regard to molecular-weight averages and FTIR and HSQC NMR spectra were detected for EPS from hydrolysate-based media.

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-1β, IL-6, TNF-α and TGF-β in response to microbial activation. DC deficient in ROS production induced high levels of IFN-γ 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 CD4-dependent 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. 

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 E2863ΔCRP 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.

Mucosal immunisation may be used both to protect the mucosal surfaces against infections and as a means for immunological treatment of peripheral immunopathological disorders through the induction of systemic antigen-specific tolerance ('oral tolerance'). The development of mucosal vaccines, whether for prevention of infectious diseases or for oral tolerance immunotherapy, requires efficient antigen delivery and adjuvant systems that can help to present the appropriate vaccine or immunotherapy antigens to the mucosal immune system. The most potent (but also toxic) mucosal adjuvants are cholera toxin (CT) and the closely related Escherichia coli heat-labile enterotoxin (LT), and much effort and significant progress have been made recently to generate toxicologically acceptable derivatives of these toxins with retained adjuvant activity. Among these are the non-toxic, recombinantly produced cholera toxin B-subunit (CTB). CTB is a specific protective antigen component of a widely registered oral cholera vaccine as well as a promising vector for either giving rise to mucosal anti-infective immunity or for inducing peripheral anti-inflammatory tolerance to chemically or genetically linked foreign antigens administered mucosally. CT and CTB have also recently been used as combined vectors and adjuvants for markedly promoting ex vivo dendritic cell (DC) vaccination with different antigens and also steering the immune response to the in vivo-reinfused DCs towards either broad Th1 + Th2 + CTL immunity (CT) or Th2 or tolerance (CTB). Another type of mucosal adjuvants is represented by bacterial DNA or synthetic oligodeoxynucleotides containing CpG-motifs, which especially when linked to CTB have been found to effectively stimulate both innate and adaptive mucosal immune responses. The properties and clinical potential of these different classes of adjuvants are being discussed. © 2004 Elsevier B.V. All rights reserved.

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 (LCTB. A), 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. +. LCTB. A vaccine, and (2) A "complete" inactivated multivalent ETEC-CF (CFA/I, CS3, CS5 and CS6 antigens) whole-cell. +. LCTB. A 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. 

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. 

We describe here the development of stable classical and El Tor V. cholerae O1 strains of the Hikojima serotype that co-express the Inaba and Ogawa antigens of O1 lipopolysaccharide (LPS). Mutation of the wbeTgene 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.

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. 

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

Cholera continues to be an important cause of morbidity and mortality in large parts of the developing world and is a significant negative factor for economic development. Vibrio cholerae bacteria of the O1 or O139 serogroup can cause disease due to their ability to colonize the intestine and produce an enterotoxin, cholera toxin (CT). An effective oral vaccine against V. cholerae O1 is available, whereas vaccine against O139 is lacking. Development and pre-clinical evaluation of cholera vaccines have been hampered by the fact that man is the only natural host for V. cholerae. Although various animal models have been described, there exists no convenient and inexpensive model that allows evaluation of vaccine-induced protection against a challenge infection. The main objective of this thesis was to develop a model that allows direct evaluation of the immunogenicity and protective efficacy of cholera vaccine candidates in conventional adult mice. Paper I demonstrates that strong serum and mucosal antibody responses to V. cholerae O1 or O139 lipopolysaccharide (LPS) can be induced in adult mice vaccinated intranasally or orally with either live or formalin-killed bacteria. Standardized intestinal IgA antibody responses estimated using extracts prepared from faecal pellets or from intestinal mucosa were found to correlate significantly, hence validating the use of the more convenient fecal pellets extracts for measuring gut mucosal antibody responses in vaccinated hosts. Paper II describes an adult mouse model for studying intestinal colonization by V. cholerae and associated immune responses. It was shown that oral pre-treatment of mice with streptomycin (Sm) allows intestinal colonization by Sm-resistant V. cholerae O1 or O139 bacteria, and that mice immunized with viable or inactivated V. cholerae as described in Paper I were comparatively refractory to colonization following infection/challenge with the immunizing strain, with protection resulting in accelerated clearance of the challenge organisms correlating inversely with the intestinal IgA anti-LPS response. In paper III this model was further used to evaluate immune responses and protection by orally administered live and killed O1 and O139 whole cell vaccines and the impact of co-administration of CT on the immunogenicity and protective effect. CT proved to be an effective adjuvant, markedly potentiating antibody responses and also increasing the protective effect against both serogroup homologous and heterologous challenge. The results presented in this thesis suggest that the new adult mouse model may be used to broaden our understanding of immune protection against V. cholerae infection, and thus be a useful tool in the pre-clinical evaluation of oral cholera vaccines.

The hospital environment represents an important mediator for the transmission of healthcare-associated infections through direct and indirect hand contact with hard surfaces and textiles. In this study, bacteria on high-touch sites, including textiles and hard surfaces in two care wards in Sweden, were identified using microbiological culture methods and 16S rDNA sequencing. During a cross-sectional study, 176 high-touch hard surfaces and textiles were identified and further analysed using microbiological culture for quantification of total aerobic bacteria, Staphylococcus aureus, Clostridium difficile and Enterobacteriacae. The bacterial population structures were further analysed in 26 samples using 16S rDNA sequencing. The study showed a higher frequency of unique direct hand-textile contacts (36 per hour), compared to hard surfaces (2.2 per hour). Hard surfaces met the recommended standard of ≤ 5 CFU/cm2 for aerobic bacteria and ≤ 1 CFU/cm2 for S. aureus (53% and 35%, respectively) to a higher extent compared to textiles (19% and 30%, respectively) (P = 0.0488). The number of bacterial genera was higher on textiles than on the hard surfaces. Staphylococcus (30.4%) and Corynebacterium (10.9%) were the most representative genera for textiles and Streptococcus (13.3%) for hard surfaces. The fact that a big percentage of the textiles did not fulfil the criteria for cleanliness, combined with the higher bacterial diversity, compared to hard surfaces, are indicators that textiles were bacterial reservoirs and potential risk vectors for bacterial transmission. However, since most of the bacteria found in the study belonged to the normal flora, it was not possible to draw conclusions of textiles and hard surfaces as sources of healthcare associated infections. 2023 Nygren et al.

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.

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. 

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 CF-based 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 co-expressing 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. 

More knowledge regarding persistence of antibody response to SARS-CoV-2 infections in the general population with mild symptoms is needed. We measured and compared levels of SARS CoV-2 spike- and nucleocapsid-specific IgG-antibodies in serum samples from 145 laboratory confirmed COVID-19 cases and 324 non-cases. The IgG-antibody levels against the spike protein in cases were stable over the time-period studied (14 to 256 days), while antibody levels against the nucleocapsid protein decreased over time