Search PubMed⌕ Search

Biomedical subjects

J Holmgren

Publications and source records attributed to J Holmgren.

At least 109 records · Page 6Linked to original sources
PubMed1994

Immunological memory after immunization with oral cholera B subunit--whole-cell vaccine in Swedish volunteers.

The capacity of peroral immunization with either two or three doses of B subunit-whole cell (B-WC) cholera vaccine to induce immunological memory was examined in Swedish volunteers by testing the immune responses to a single dose of B-WC vaccine given 10 months after the initial immunization. Antibody responses in serum and antibody-secreting cell (ASC) responses in peripheral blood were studied, since these responses seem to reflect the gut mucosal IgA immune responses after oral immunization with B-WC vaccine. Previously immunized volunteers responded to a single dose of B-WC vaccine more frequently and with higher levels of IgA and IgG antitoxin antibodies as well as vibriocidal antibodies in serum than did previously unvaccinated controls. The IgA-ASC responses to cholera toxin B subunit were also higher in primed volunteers than in controls. Two doses of B-WC vaccine were as effective as three doses in inducing immunological memory for cholera immunity. A new B-WC cholera vaccine based on recombinant B subunit had the same capacity as the first generation of B-WC vaccine to induce immunological memory for cholera antitoxin immunity.

Administration, Oral↗
PubMed1994

Enhanced urinary spontaneous luminescence in Duchenne muscular dystrophy.

Urinary spontaneous visible luminescence is enhanced in children with Duchenne Muscular Dystrophy (DMD). This result is indicative of systemic oxidative stress in DMD patients. It is proposed that measurement of the urinary luminescence could be employed to follow the progress of the disease, as well as the response of the patients to antioxidant therapy.

Biomarkers↗
PubMed1994

Intestinal and circulating antibody-forming cells in IgA-deficient individuals after oral cholera vaccination.

In search for a possible explanation for the different susceptibility to mucosal infections in IgA-deficient (IgAd) individuals, the frequency of total immunoglobulin-secreting cells (ISC) and vaccine-specific antibody-secreting cells (ASC) in intestinal mucosa and peripheral blood was determined by the enzyme-linked immunospot (ELISPOT) assay before and after peroral vaccination with a B subunit-whole cell cholera vaccine. Two groups of IgAd individuals, frequently infected and non-infected respectively, and normal controls were studied. Before cholera vaccination there were significantly higher frequencies of total IgM and IgG ISC in the gut, but not in the blood, in the IgAd individuals than in the controls. However, there were no significant differences between healthy and infection-prone IgAd individuals in this respect. In response to oral cholera vaccination, intestinal cholera toxin (CT)-specific IgG and IgM ASC were significantly more abundant among the IgAd individuals with a history of frequent infections than among the healthy IgAd individuals and controls. A similar difference in IgG and IgM ASC, although not significant, was also noted in blood. In IgAd individuals with frequent infections the vaccine induced variable anti-CT IgM ASC responses in the gut, ranging from no increase to a few strikingly high responses. In the controls, the CT-specific responses were dominated by IgA ASC. The data show that oral cholera vaccination evoked strong CT-specific IgG ASC responses, and in some cases also strong IgM ASC responses in the intestinal mucosa of IgAd patients with a history of frequent infections. The healthy IgAd individuals unexpectedly responded with lower numbers of CT-specific IgG ASC and did not show any increase of CT-specific IgM ASC in the intestinal mucosa. Thus, inability to mount a mucosal immune response to an oral antigen cannot in itself explain recurrent infections among many IgAd individuals.

Administration, Oral↗
PubMed1994

Cloning and sequencing of Vibrio cholerae mannose-sensitive haemagglutinin pilin gene: localization of mshA within a cluster of type 4 pilin genes.

The mannose-sensitive haemagglutinin (MSHA) pilus that is associated with Vibrio cholerae strains of El Tor biotype has been shown to be a potential colonization factor and protective antigen. The gene encoding the structural subunit of MSHA pili was cloned from size-fractionated SacI-cleaved chromosomal DNA in the expression phage vector lambda ZAPII. Positive clones carried a c. 5.3 kb SacI fragment and were identified on the basis of MSHA expression and hybridization with a synthetic oligonucleotide probe based upon the N-terminus of MshA, the structural subunit of MSHA. The mshA gene was localized to a 2.6 kb SalI-EcoRI fragment, which was subcloned and shown to express MshA from its own promoter in Escherichia coli. Nucleotide sequencing of the entire fragment revealed six open reading frames (ORFs) of which four were complete. The mshA gene encodes an 18,094 Da prepilin protein, which in its mature form has a size of 17,436 Da. MshA is a type 4 (N-MePhe) pilin protein that is more homologous to pilins produced by Pseudomonas aeruginosa and Neisseria gonorrhoeae than to TcpA, the structural subunit of the toxin-coregulated pilus of V. cholerae. The protein seems to be directly involved in receptor binding, as an in-frame mutation in the mshA gene was found to abolish both D-mannose-dependent haemagglutination and binding of V. cholerae bacteria to D-mannose-containing agarose beads. Three additional ORFs, all in the same transcriptional orientation as mshA, were found to encode type 4 pilin-like proteins. A potential promoter with a sequence homologous to that of cAMP-CRP-activated promoters in E. coli was identified upstream of ORF3, the gene preceding mshA.

Amino Acid Sequence↗
PubMed1994

The maltose regulon of Vibrio cholerae affects production and secretion of virulence factors.

The effects of maltose on production and secretion of virulence factors of Vibrio cholerae in strain X28214, classical biotype, and in maltose-defective transposon mutants constructed from this strain were characterized. Maltose was found to inhibit secretion of cholera toxin and to reduce production of the mannose-sensitive hemagglutinin and the soluble hemagglutinin-protease. In contrast, the amount of toxin-coregulated pilus was increased in the presence of maltose. The maltose effect was apparently mediated by genes of the maltose regulon, since inactivation of the malQ or malF gene of V. cholerae by transposon insertion was found to affect production and secretion of the same virulence factors that were responsive to maltose. The malQ and malF mutants showed, in addition, reduced virulence in an infant-mouse model. These results suggest that maltose may have a significant regulatory role in the production of virulence factors and that an intact maltose regulon is needed for full virulence of V. cholerae.

Animals↗
PubMed1994

Role of antibodies against biotype-specific Vibrio cholerae pili in protection against experimental classical and El Tor cholera.

Vibrio cholerae O1, which exists as two biotypes, classical and El Tor, expresses fimbrial antigens called toxin-coregulated pili (TCP) and mannose-sensitive hemagglutinin (MSHA) pili, respectively. We have raised rabbit antisera and monoclonal antibodies against these fimbrial antigens and prepared Fab fragments which possess specific antibodies directed against the respective fimbrial antigens from these antisera. The protective effect of these antibody preparations was studied in the infant mouse cholera model. Antibodies against TCP were able to protect baby mice against challenge with V. cholerae O1 of the classical but not of the El Tor biotype. Similar but reverse biotype differences in protection against challenge with classical and El Tor vibrios were observed when antibodies against MSHA pili were used. The protective effect of V. cholerae O1 antilipopolysaccharide (anti-LPS) antibodies, both alone and in combination with antifimbrial antibodies, was also evaluated. We showed that antibodies to the LPS component also prevented infections with V. cholerae O1. Moreover, our results indicate that antibodies against TCP or MSHA pili and against LPS cooperate at least additively, and possible even synergistically, in protecting baby mice against challenge with group O1 vibrios. These results indicate that TCP and MSHA pili as well as LPS play an important role in the pathogenesis of experimental cholera. We could also demonstrate that antibacterial immunity preventing colonization is biotype specific. Our results might be used for the generation of new oral cholera vaccines including both TCP and MSHA fimbrial antigens.

Animals↗
PubMed1994

Exploration of mucosal immunity in humans: relevance to vaccine development.

Although the immune system is remarkably diverse, there is evidence that certain types of immune responses take place and are restricted to certain anatomic locations within the body. The concept of a common mucosal immune system that provides immune reactivity not only at the site of antigen deposition but also at remote mucosal sites may be explained by the utilization of organ-specific recognition molecules by circulating precursors of mucosal immunoblasts and by the production of certain maturation factors (e.g. cytokines, hormones) produced preferentially in certain organs or parts of a given organ. This notion may explain the unification of immune responses in diverse mucosal sites and the physiologic segregation of mucosal from systemic immune mechanisms. Novel methods have been developed to enable studies of antigen specific B and T cell responses in various mucosal and extramucosal tissues in primates and rodents, using cholera toxin or its B subunit as prototype immunogens and mucosal carrier-delivery systems. The tissue localization and isotype commitment of antibody-secreting cells (ASC) and the homing potential of their circulating precursors have also been examined after oral, nasal, intra-tonsillar, rectal and/or genital immunization(s). The anatomical distribution of T- and accessory cell-derived cytokines has also been examined. These tools and approaches are being employed in studies attempting to induce optimal mucosal immune responses to several mucosal pathogens including HIV-1, in certain organs such as the lower gastrointestinal tract and the female urogenital tract.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Mucosal vaccines based on the use of cholera toxin B subunit as immunogen and antigen carrier.

Stimulation of strong mucosal IgA immune responses as a basis for vaccine-induced protection against various pathogens has proved difficult. Most soluble protein antigens administered either parenterally or oral-mucosally have given disappointing results. A notable exception in this regard are cholera toxin (CT) and, particularly in humans, its non-toxic B subunit pentamer moiety (CTB) both of which stimulate a strong intestinal IgA antibody response and long-lasting immunological memory. Based on this, CTB has become an important component in recently developed oral vaccines against cholera and diarrhea caused by enterotoxigenic E. coli. The strong immunogenicity of CT and CTB can to a large extent be explained by their ability to bind to receptors on the intestinal mucosal surface. This has promoted much recent interest in the use of CTB as an oral delivery carrier for other vaccine-relevant antigens. Oral administration of antigens coupled to CTB either chemically or genetically has in several systems been found to markedly potentiate both intestinal and extra-intestinal IgA immune responses against the CTB-coupled antigens and to elicit substantial circulating antibody responses. In contrast to CTB, CT also has strong adjuvant properties for stimulating mucosal IgA immune responses to unrelated, non-coupled antigens after oral co-immunization. This adjuvant activity appears to be closely linked to the A subunit-catalyzed ADP-ribosylating action of CT leading to enhanced cyclic AMP formation in the affected cells.

Adjuvants, Immunologic↗
PubMed1994

Strategies for the induction of immune responses at mucosal surfaces making use of cholera toxin B subunit as immunogen, carrier, and adjuvant.

The concept of a common mucosal immune system, through which specific antigen-activated lymphocytes from the gut can disseminate immunity both along the intestinal tract and to various other mucosal and glandular tissues, has generated much current interest in the possibility of developing oral vaccines, not only for enteric infections but also for infections in the respiratory and urogenital tracts. However, to date it has proven difficult in practice to stimulate strong mucosal IgA immune responses by either parenteral or oral-mucosal administration of most antigens, and experience with soluble protein antigens has, on the whole, been disappointing. A notable exception in this regard is cholera toxin (CT) and in humans more than in other species, its nontoxic B subunit pentamer moiety (CTB). Based on this, CTB has become an important component in recently developed oral vaccines against cholera as well as against diarrhea caused by enterotoxigenic Escherichia coli producing CT-like heat-labile enterotoxin(s). Since the strong immunogenicity of CT and CTB can, to a large extent, be explained by their ability to bind to receptors on the intestinal mucosal surface, there has recently been much interest in approaches using CTB as an oral delivery carrier system for other vaccine-relevant antigens, and much progress has been made in preparing immunogenic hybrid proteins by coupling various protein or peptide antigens chemically or genetically to CTB. Indeed, in several systems, oral administration of such hybrid antigens has been found to markedly potentiate both intestinal and extraintestinal IgA immune responses against the CTB-coupled antigens and also to elicit substantial circulating antibody responses. Besides the mucosal immunopotentiating effect of either CT or CTB owing to their similar capacity as oral antigen-delivery vehicles, CT, but in most systems tested not CTB, also has strong adjuvant properties for stimulating mucosal IgA immune responses to admixed (not coupled) unrelated antigens after oral immunization. This adjuvant activity appears to be closely linked to the ADP-ribosylating action of CT (and specifically of its A subunit) leading to enhanced cyclic AMP formation in the affected cell, and efforts to eliminate the enterotoxic activity without losing adjuvanticity have so far not met with success.

Adjuvants, Immunologic↗
PubMed1993

Immunological characterization of a rotavirus-neutralizing epitope fused to the cholera toxin B subunit.

A highly conserved neutralizing epitope from the surface protein VP4 (amino acids 296-313) of human rotaviruses was genetically fused to the B subunit of cholera toxin (CTB). Synthetic oligodeoxyribonucleotides encoding the VP4 peptide were inserted between the 3' end of the DNA that codes for the leader peptide, and the 5' end of the gene encoding mature CTB. The hybrid protein synthesized in Escherichia coli was found to maintain the ability of CTB to pentamerize, and to adhere to its cell receptor, the GM1 ganglioside. The chimera was efficiently recognized by a monoclonal antibody (mAb) directed at CTB and by a virus-neutralizing mAb against the VP4 peptide. The hybrid polypeptide was shown to induce high titers of serum antibodies (Ab) against CTB and the synthetic VP4 peptide following subcutaneous immunization; paradoxically, however, the Ab obtained did not recognize the virus by an enzyme-linked immunosorbent assay method, nor had detectable neutralizing activity. Potential implications of these results for future design and evaluation of fusion proteins as immunogens are discussed.

Amino Acid Sequence↗
PubMed1993

Extracellular secretion of STa heat-stable enterotoxin by Escherichia coli after fusion to a heterologous leader peptide.

The mature 19-amino acid STa heat-stable enterotoxin of E. coli has a preceding peptide of 53 amino acids which contains two domains called Pre (aa 1-19) and Pro (aa 20-53) sequences, proposed to be essential for extracellular toxin release by this host. The Pro sequence, however, has been proven not be indispensable for this process since Pro deletion mutants secrete STa. To find out if Pre and/or other unremoved natural STa flanking sequences are responsible for toxin secretion in those mutants we genetically fused mature STa directly to the leader peptide of the periplasmic E. coli heat-labile enterotoxin B-subunit (LTB). Expression of this gene fusion resulted in extracellular secretion of biologically active STa by E. coli independently of natural STa neighboring genetic sequences. Moreover, these results suggest that STa might be able to gain access to the extracellular milieu simply upon its entry into the E. coli periplasm once guided into this compartment by the LTB leader peptide. To test if extracellular secretion in this fashion might be extended to other disulfide bond-rich small peptides, the 13 amino acid conotoxin GI and a non-enterotoxic STa-related decapeptide were cloned. None of the two peptides was found in culture supernatants, in spite of high structural homology to the toxin. Failure to be secreted most likely leads to degradation as peptides were also not detected in bacterial sonicates. We hypothesize that cysteine-rich peptides must have an amino acid length and/or number of disulfide bridges closer to those in STa for them to follow this toxin secretory pathway in E. coli.

Amino Acid Sequence↗
PubMed1993

Biodegradable microparticles for oral immunization.

Ovalbumin (OVA) was entrapped in poly(lactide-co-glycolide) microparticles and administered to mice. Following intraperitoneal immunization, the microparticles induced both proliferative T-cell responses and cytotoxic T-cell responses in spleen cells. Following oral immunization, the mean salivary IgA antibody response to microparticles was significantly greater than the response to soluble OVA (p < 0.0001). Serum IgG antibody levels were also significantly greater in the group administered microparticles (p < 0.001). Cholera toxin B subunit was also entrapped in microparticles. Following oral immunization in mice, specific antibody-secreting cells were detected both in the spleens and in the mesenteric lymph nodes.

Administration, Oral↗
PubMed1993

Cholera toxin and cholera B subunit as oral-mucosal adjuvant and antigen vector systems.

Cholera toxin (CT) and the analogous heat-labile enterotoxin (LT) from Escherichia coli have several immunomodulating effects which alone or in combination might explain their strong adjuvant action in stimulating mucosal IgA and other immune responses to admixed unrelated antigens after oral immunization. These effects include, depending on animal species and experimental systems, enhanced antigen presentation by a variety of cell types; promotion of isotype differentiation in B cells leading to increased IgA formation; and complex stimulatory as well as inhibitory effects on T-cell proliferation and lymphokine production. This adjuvant activity appears to be closely linked to the ADP-ribosylating action of CT and LT associated with enhanced cyclic AMP formation in the affected cells, and thus it may prove difficult to eliminate the enterotoxic activity without loss of adjuvanticity. However, through a separate mechanism, as an antigen-carrier system providing specific binding to epithelium including the M cells of intestinal Peyer's patches, both CT and its non-toxic binding subunit moiety (CTB) have been shown to markedly enhance the mucosal immune response to various foreign antigens or epitopes covalently linked to these molecules. This gives promise for the future use of CTB or related non-toxic binding derivatives as vehicles to facilitate induction of mucosal immune responses to a broad range of antigens for human vaccination purposes.

Adjuvants, Immunologic↗
PubMed1993

Evaluation of different immunization schedules for oral cholera B subunit-whole cell vaccine in Swedish volunteers.

Different immunization schedules for oral B subunit-whole cell (B-WC) cholera vaccine were evaluated in Swedish volunteers to obtain information for recommendations of vaccine use in non-endemic areas. Two peroral doses of B-WC vaccine were as effective as three doses in inducing IgA and IgG antitoxin as well as vibriocidal antibody responses in serum. Administration of two vaccine doses either at 7, 14 or 28-42 day intervals resulted in comparable antitoxin responses in serum, whereas a 3-day immunization interval resulted in significantly lower titre increases. Vibriocidal antibody responses were comparable after the different time intervals tested (3-42 days). The B-WC vaccine can be effectively administered together with a cheap, commercially available sodium bicarbonate powder dissolved in water to protect the vaccine from gastric acid.

Administration, Oral↗
PubMed1993

Intestinal antibody response after oral immunization with a prototype cholera B subunit-colonization factor antigen enterotoxigenic Escherichia coli vaccine.

A prototype oral enterotoxigenic Escherichia coli (ETEC) vaccine containing formalin-inactivated whole bacteria expressing colonization factor antigens CFA/I and CFA/II and cholera B subunit (CTB) has been tested for safety and immunogenicity in 20 adult Swedish volunteers. When given in three doses with 2-week intervals the vaccine was found to be safe and to give rise to specific IgA antibody responses in intestinal lavage fluid in most of the volunteers (CFA/I 82%, CFA/II 82% and CTB 91%). The frequencies and magnitudes of these responses, which were already maximal after two doses, were comparable with those previously found in patients convalescing from severe ETEC diarrhoea. All the vaccinated volunteers also responded with antitoxin IgA as well as IgG antibodies in serum, whereas the serum antibody responses against the CFAs were weaker and mainly of the IgA isotype.

Administration, Oral↗
PubMed1993

Large-scale production of Vibrio cholerae toxin B subunit for use in oral vaccines.

By systematically manipulating promoter and ribosome binding structures, plasmid copy number and the structure of the cholera toxin B (CTB) subunit gene, we were able to develop a plasmid expression system that, when used in conjunction with an optimized growth medium, provided yields of CTB approaching one gram per liter. The CTB protein which was secreted to > 95%, could readily be purified from the growth medium of a V. cholerae production strain and was shown to be immunologically indistinguishable from previously used vaccine preparations of native or recombinant CTB.

Amino Acid Sequence↗
PubMed1993

Induction and assessment of immunity at enteromucosal surfaces in humans: implications for vaccine development.

It is now almost axiomatic that vaccines against enteric infections must be able to stimulate the gut lymphoid tissue to be efficacious and that this goal is usually better achieved by administering immunogens orally rather than parenterally. On the basis of the notion of a common mucosal immunologic system that provides immune reactivity not only at the site of antigen deposition but also at remote mucosal sites, there is much interest in developing oral vaccines against infections in the respiratory and urogenital tracts. Recent studies indicate that oral administration of small amounts of protein antigens that are chemically or genetically linked to intestinal binding carrier molecules (such as the B subunit of cholera toxin) can evoke vigorous mucosal and extramucosal immune responses. The apparent compartmentalization of systemic and mucosal immune responses may explain not only why parenteral vaccines are just partly effective in protecting against mucosal pathogens but also why currently employed immunoanalytical methods do not provide accurate information regarding mucosal immune status. Following the developments of oral vaccines against infections due to Vibrio cholerae and enterotoxigenic Escherichia coli, two archetypes of enteropathogens, we have devoted extensive efforts to gaining insight into the humoral and cellular events involved in the development of protective immunity in the human intestinal tract. We have developed preparative and analytical methods for studying vaccine-induced intestinal and extraintestinal immune responses in humans. These include techniques for collecting intestinal fluid and lymphoid cells as well as procedures to quantitate secretory antibodies and lymphokines secreted by activated intestinal immunocytes. These developments should serve the dual purpose of facilitating analyses of human mucosal immune responses in general and assessing the immunogenicity of enteric vaccines in particular.

Administration, Oral↗