• A new reporter mouse cytomegalovirus reveals maintained immediate-early gene expression but poor virus replication in cycling liver sinusoidal endothelial cells.

      Dag, Franziska; Weingärtner, Adrien; Butueva, Milada; Conte, Ianina; Holzki, Julia; May, Tobias; Adler, Barbara; Wirth, Dagmar; Cicin-Sain, Luka; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2013-06-17)
      The MCMV major immediate early promoter/enhancer (MIEP) is a bidirectional promoter that drives the expression of the three immediate early viral genes, namely ie1, ie2 and ie3. The regulation of their expression is intensively studied, but still incompletely understood.
    • Activation of Innate and Adaptive Immunity by a Recombinant Human Cytomegalovirus Strain Expressing an NKG2D Ligand.

      Tomić, Adriana; Varanasi, Pavankumar R; Golemac, Mijo; Malić, Suzana; Riese, Peggy; Borst, Eva M; Mischak-Weissinger, Eva; Guzmán, Carlos A; Krmpotić, Astrid; Jonjić, Stipan; et al. (2016-12)
      Development of an effective vaccine against human cytomegalovirus (HCMV) is a need of utmost medical importance. Generally, it is believed that a live attenuated vaccine would best provide protective immunity against this tenacious pathogen. Here, we propose a strategy for an HCMV vaccine that aims at the simultaneous activation of innate and adaptive immune responses. An HCMV strain expressing the host ligand ULBP2 for the NKG2D receptor was found to be susceptible to control by natural killer (NK) cells, and preserved the ability to stimulate HCMV-specific T cells. Infection with the ULBP2-expressing HCMV strain caused diminished cell surface levels of MHC class I molecules. While expression of the NKG2D ligand increased the cytolytic activity of NK cells, NKG2D engagement in CD8+ T cells provided co-stimulation and compensated for lower MHC class I expression. Altogether, our data indicate that triggering of both arms of the immune system is a promising approach applicable to the generation of a live attenuated HCMV vaccine.
    • Activity and composition of methanotrophic bacterial communities in planted rice soil studied by flux measurements, analyses of pmoA gene and stable isotope probing of phospholipid fatty acids.

      Shrestha, Minita; Abraham, Wolf-Rainer; Shrestha, Pravin Malla; Noll, Matthias; Conrad, Ralf; Max-Planck-Institut für terrestrische Mikrobiologie, Karl-von-Frisch-Strasse, D-35043, Marburg, Germany. (2008-02)
      Methanotrophs in the rhizosphere of rice field ecosystems attenuate the emissions of CH(4) into the atmosphere and thus play an important role for the global cycle of this greenhouse gas. Therefore, we measured the activity and composition of the methanotrophic community in the rhizosphere of rice microcosms. Methane oxidation was determined by measuring the CH(4) flux in the presence and absence of difluoromethane as a specific inhibitor for methane oxidation. Methane oxidation started on day 24 and reached the maximum on day 32 after transplantation. The total methanotrophic community was analysed by terminal restriction fragment length polymorphism (T-RFLP) and cloning/sequencing of the pmoA gene, which encodes a subunit of particulate methane monooxygenase. The metabolically active methanotrophic community was analysed by stable isotope probing of microbial phospholipid fatty acids (PLFA-SIP) using (13)C-labelled CH(4) directly added to the rhizospheric region. Rhizospheric soil and root samples were collected after exposure to (13)CH(4) for 8 and 18 days. Both T-RFLP/cloning and PLFA-SIP approaches showed that type I and type II methanotrophic populations changed over time with respect to activity and population size in the rhizospheric soil and on the rice roots. However, type I methanotrophs were more active than type II methanotrophs at both time points indicating they were of particular importance in the rhizosphere. PLFA-SIP showed that the active methanotrophic populations exhibit a pronounced spatial and temporal variation in rice microcosms.
    • ADAP Promotes Degranulation and Migration of NK Cells Primed During vivo Listeria monocytogenes Infection in Mice.

      Böning, Martha A L; Trittel, Stephanie; Riese, Peggy; van Ham, Marco; Heyner, Maxi; Voss, Martin; Parzmair, Gerald P; Klawonn, Frank; Jeron, Andreas; Guzman, Carlos A; et al. (Frontiers, 2019-01-01)
      The adhesion and degranulation-promoting adaptor protein (ADAP) serves as a multifunctional scaffold and is involved in the formation of immune signaling complexes. To date only limited and moreover conflicting data exist regarding the role of ADAP in NK cells. To extend existing knowledge we investigated ADAP-dependency of NK cells in the context of in vivo infection with the intracellular pathogen Listeria monocytogenes (Lm). Ex vivo analysis of infection-primed NK cells revealed impaired cytotoxic capacity in NK cells lacking ADAP as indicated by reduced CD107a surface expression and inefficient perforin production. However, ADAP-deficiency had no global effect on NK cell morphology or intracellular distribution of CD107a-containing vesicles. Proteomic definition of ADAPko and wild type NK cells did not uncover obvious differences in protein composition during the steady state and moreover, similar early response patterns were induced in NK cells upon infection independent of the genotype. In line with protein network analyses that suggested an altered migration phenotype in naïve ADAPko NK cells, in vitro migration assays uncovered significantly reduced migration of both naïve as well as infection-primed ADAPko NK cells compared to wild type NK cells. Notably, this migration defect was associated with a significantly reduced expression of the integrin CD11a on the surface of splenic ADAP-deficient NK cells 1 day post-Lm infection. We propose that ADAP-dependent alterations in integrin expression might account at least in part for the fact that during in vivo infection significantly lower numbers of ADAPko NK cells accumulate in the spleen i.e., the site of infection. In conclusion, we show here that during systemic Lm infection in mice ADAP is essential for efficient cytotoxic capacity and migration of NK cells.
    • Adaptation of microbial communities in soil contaminated with polychlorinated biphenyls, leading to the transformation of more highly chlorinated congeners in biofilm communities

      Macedo, A.J.; Neu, T. R.; Kuhlicke, U.; Abraham, Wolf-Rainer; 'Helmholtz Zentrum für Infektionsforschung (Cambridge University Press, 2006)
    • Adenosine in the inflamed gut: a Janus faced compound.

      Estrela, A B; Abraham, Wolf-Rainer; Helmholtz Center for Infection Research, Chemical Microbiology, Inhoffenstrasse 7, 38124 Braunschweig, Germany. (2011)
      The purine ribonucleoside adenosine (Ado) has been recognized for its regulatory functions in situations of cellular stress like ischemia, hypoxia and inflammation. The importance of extracellular Ado as a modulator in the immune system is a theme of great appreciation and the focus of recent increasing interest in the field of gastrointestinal inflammation. In this review, the different aspects of Ado signaling during inflammatory responses in the gut are discussed, considering the contribution of the four known Ado receptors (ARs; A(1), A(2A), A(2B), and A(3)), their mechanisms and expression patterns. Activation of these receptors in epithelial cells as well as in immune cells recruited to the inflamed intestinal mucosa determines the overall effect, ranging from a protective, anti-inflammatory modulation to a strong pro-inflammatory induction. Here we present the current advances in agonists and antagonists development and their potential therapeutic application studied in animal models of intestinal inflammation. In addition, alternative complementary approaches to manipulate such a complex signaling system are discussed, for example, the use of AR allosteric modulators or interference with Ado metabolism. Special features of the gut environment are taken into account: the contribution of diet components; the involvement of Ado in intestinal infections; the interactions with the gut microbiome, particularly, the recent exciting finding that an intestinal bacterium can directly produce extracellular Ado in response to host defense mechanisms in an inflammation scenario. Understanding each component of this dynamic system will broaden the possibilities for applying Ado signaling as a therapeutic target in gut inflammation.
    • Advances and Challenges of Biodegradable Implant Materials with a Focus on Magnesium-Alloys and Bacterial Infections

      Rahim, Muhammad; Ullah, Sami; Mueller, Peter; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (MPDI, 2018-07-10)
      Medical implants made of biodegradable materials could be advantageous for temporary applications, such as mechanical support during bone-healing or as vascular stents to keep blood vessels open. After completion of the healing process, the implant would disappear, avoiding long-term side effects or the need for surgical removal. Various corrodible metal alloys based on magnesium, iron or zinc have been proposed as sturdier and potentially less inflammatory alternatives to degradable organic polymers, in particular for load-bearing applications. Despite the recent introduction of magnesium-based screws, the remaining hurdles to routine clinical applications are still challenging. These include limitations such as mechanical material characteristics or unsuitable corrosion characteristics. In this article, the salient features and clinical prospects of currently-investigated biodegradable implant materials are summarized, with a main focus on magnesium alloys. A mechanism of action for the stimulation of bone growth due to the exertion of mechanical force by magnesium corrosion products is discussed. To explain divergent in vitro and in vivo effects of magnesium, a novel model for bacterial biofilm infections is proposed which predicts crucial consequences for antibacterial implant strategies.
    • Advances in cytomegalovirus (CMV) biology and its relationship to health, diseases, and aging.

      Nikolich-Žugich, Janko; Čicin-Šain, Luka; Collins-McMillen, Donna; Jackson, Sarah; Oxenius, Annette; Sinclair, John; Snyder, Christopher; Wills, Mark; Lemmermann, Niels (Springer, 2020-03-11)
      The complexity of host-associated microbial ecosystems requires host-specific reference catalogs to survey the functions and diversity of these communities. We generate a comprehensive resource, the integrated mouse gut metagenome catalog (iMGMC), comprising 4.6 million unique genes and 660 metagenome-assembled genomes (MAGs), many (485 MAGs, 73%) of which are linked to reconstructed full-length 16S rRNA gene sequences. iMGMC enables unprecedented coverage and taxonomic resolution of the mouse gut microbiota; i.e., more than 92% of MAGs lack species-level representatives in public repositories (<95% ANI match). The integration of MAGs and 16S rRNA gene data allows more accurate prediction of functional profiles of communities than predictions based on 16S rRNA amplicons alone. Accompanying iMGMC, we provide a set of MAGs representing 1,296 gut bacteria obtained through complementary assembly strategies. We envision that integrated resources such as iMGMC, together with MAG collections, will enhance the resolution of numerous existing and future sequencing-based studies.
    • Analysis of bacterial core communities in the central Baltic by comparative RNA-DNA-based fingerprinting provides links to structure-function relationships.

      Brettar, Ingrid; Christen, Richard; Höfle, Manfred G; Department of Vaccinology and Applied Microbiology, Helmholtz Centre of Infection Research (HZI), Braunschweig, Germany. (2012-01)
      Understanding structure-function links of microbial communities is a central theme of microbial ecology since its beginning. To this end, we studied the spatial variability of the bacterioplankton community structure and composition across the central Baltic Sea at four stations, which were up to 450 km apart and at a depth profile representative for the central part (Gotland Deep, 235 m). Bacterial community structure was followed by 16S ribosomal RNA (rRNA)- and 16S rRNA gene-based fingerprints using single-strand conformation polymorphism (SSCP) electrophoresis. Species composition was determined by sequence analysis of SSCP bands. High similarities of the bacterioplankton communities across several hundred kilometers were observed in the surface water using RNA- and DNA-based fingerprints. In these surface communities, the RNA- and DNA-based fingerprints resulted in very different pattern, presumably indicating large difference between the active members of the community as represented by RNA-based fingerprints and the present members represented by the DNA-based fingerprints. This large discrepancy changed gradually over depth, resulting in highly similar RNA- and DNA-based fingerprints in the anoxic part of the water column below 130 m depth. A conceivable mechanism explaining this high similarity could be the reduced oxidative stress in the anoxic zone. The stable communities on the surface and in the anoxic zone indicate the strong influence of the hydrography on the bacterioplankton community structure. Comparative analysis of RNA- and DNA-based community structure provided criteria for the identification of the core community, its key members and their links to biogeochemical functions.
    • Analysis of structure and composition of bacterial core communities in mature drinking water biofilms and bulk water of a citywide network in Germany.

      Henne, Karsten; Kahlisch, Leila; Brettar, Ingrid; Höfle, Manfred G (2012-05)
      The bacterial core communities of bulk water and corresponding biofilms of a more than 20-year-old drinking water network were compared using 16S rRNA single-strand confirmation polymorphism (SSCP) fingerprints based on extracted DNA and RNA. The structure and composition of the bacterial core community in the bulk water was highly similar (>70%) across the city of Braunschweig, Germany, whereas all biofilm samples contained a unique community with no overlapping phylotypes from bulk water. Biofilm samples consisted mainly of Alphaproteobacteria (26% of all phylotypes), Gammaproteobacteria (11%), candidate division TM6 (11%), Chlamydiales (9%), and Betaproteobacteria (9%). The bulk water community consisted primarily of Bacteroidetes (25%), Betaproteobacteria (20%), Actinobacteria (16%), and Alphaproteobacteria (11%). All biofilm communities showed higher relative abundances of single phylotypes and a reduced richness compared to bulk water. Only biofilm communities sampled at nearby sampling points showed similar communities irrespective of support materials. In all of our bulk water studies, the community composition determined from 16S rRNA was completely different from the 16S rRNA gene-based community composition, whereas in biofilms both molecular fractions resulted in community compositions that were similar to each other. We hypothesize that a higher fraction of active bacterial phylotypes and a better protection from oxidative stress in drinking water biofilms are responsible for this higher similarity.
    • Anti-nuclear autoantibodies in the general German population: prevalence and lack of association with selected cardiovascular and metabolic disorders-findings of a multicenter population-based study.

      Akmatov, Manas K; Röber, Nadja; Ahrens, Wolfgang; Flesch-Janys, Dieter; Fricke, Julia; Greiser, Halina; Günther, Kathrin; Kaaks, Rudolf; Kemmling, Yvonne; Krone, Bastian; et al. (2017-06-06)
      We determined the prevalence of anti-nuclear autoantibodies (ANAs) in the German adult population and examined the association between ANAs and cardiovascular and metabolic disorders.
    • Antimicrobial agent susceptibilities of Legionella pneumophila MLVA-8 genotypes.

      Sharaby, Yehonatan; Nitzan, Orna; Brettar, Ingrid; Höfle, Manfred G; Peretz, Avi; Halpern, Malka; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Nature publishing group, 2019-04-16)
      Legionella pneumophila causes human lung infections resulting in severe pneumonia. High-resolution genotyping of L. pneumophila isolates can be achieved by multiple-locus variable-number tandem-repeat analysis (MLVA-8). Legionella infections in humans occur as a result of inhalation of bacteria-containing aerosols, thus, our aim was to study the antimicrobial susceptibilities of different MLVA-8 genotypes to ten commonly used antimicrobial agents in legionellosis therapy. Epidemiological cut-off values were determined for all antibiotics. Significant differences were found between the antimicrobial agents’ susceptibilities of the three studied environmental genotypes (Gt4, Gt6, and Gt15). Each genotype exhibited a significantly different susceptibility profile, with Gt4 strains (Sequence Type 1) significantly more resistant towards most studied antimicrobial agents. In contrast, Gt6 strains (also Sequence Type 1) were more susceptible to six of the ten studied antimicrobial agents compared to the other genotypes. Our findings show that environmental strains isolated from adjacent points of the same water system, exhibit distinct antimicrobial resistance profiles. These differences highlight the importance of susceptibility testing of Legionella strains. In Israel, the most extensively used macrolide for pneumonia is azithromycin. Our results point at the fact that clarithromycin (another macrolide) and trimethoprim with sulfamethoxazole (SXT) were the most effective antimicrobial agents towards L. pneumophila strains. Moreover, legionellosis can be caused by multiple L. pneumophila genotypes, thus, the treatment approach should be the use of combined antibiotic therapy. Further studies are needed to evaluate specific antimicrobial combinations for legionellosis therapy.
    • Antimicrobial and biofilm inhibiting diketopiperazines.

      de Carvalho, M P; Abraham, Wolf-Rainer; Helmholtz Center for Infection Research, Chemical Microbiology, Inhoffenstrasse 7, 38124 Braunschweig, Germany. wolf-rainer.abraham@helmholtz-hzi.de. (2012-07-01)
      Diketopiperazines are the smallest cyclic peptides known. 90% of Gram-negative bacteria produce diketopiperazines and they have also been isolated from Gram-positive bacteria, fungi and higher organisms. Biosynthesis of cyclodipeptides can be achieved by dedicated nonribosomal peptide synthetases or by a novel type of synthetases named cyclopeptide synthases. Since the first report in 1924 a large number of bioactive diketopiperazines was discovered spanning activities as antitumor, antiviral, antifungal, antibacterial, antiprion, antihyperglycemic or glycosidase inhibitor agents. As infections are of increasing concern for human health and resistances against existing antibiotics are growing this review focuses on the antimicrobial activities of diketopiperazines. The antibiotic bicyclomycin is a diketopiperazine and structure activity studies revealed the unique nature of this compound which was finally developed for clinical applications. The antimicrobial activities of a number of other diketopiperazines along with structure activity relationships are discussed. Here a special focus is on the activity-toxicity problem of many compounds setting tight limitations to their application as drugs. Not only these classical antimicrobial activities but also proposed action in modulating bacterial communication as a new target to control biofilms will be evaluated. Pathogens organized in biofilms are difficult to eradicate because of the increase of their tolerance for antibiotics for several orders. Diketopiperazines were reported to modulate LuxR-mediated quorum-sensing systems of bacteria, and they are considered to influence cell-cell signaling offering alternative ways of biofilm control by interfering with microbial communication. Concluding the review we will finally discuss the potential of diketopiperazines in the clinic to erase biofilm infections.
    • Applications and impacts of stable isotope probing for analysis of microbial interactions.

      Abraham, Wolf-Rainer; group of Chemical microbiology, Helmholtz Centre for infection research, Inhoffenstr. 7, D-38124 Braunschweig, Germany. (2014-06)
      Probing the interactions between microbes and their environment with stable isotopes became a powerful technique over the last years. While quadruple mass spectrometry or isotope ratio mass spectrometry (IRMS) require at least 300,000 bacterial cells, analysis at the single-cell level is possible with secondary ion mass spectrometry (SIMS) or Raman microspectrometry. While SIMS needs enrichments of more than 0.1 and Raman microscopy of more than 25 at.-%, IRMS can deal with 0.0001 at.-%. To find out who eats what, one has to discern between the different species in a community. Several methods have been introduced to discern between the different taxa in microbial communities, e.g., by using fatty acids as biomarkers, density centrifugation of DNA/RNA, or fluorescent in situ hybridization (FISH) with phylogenetic probes. While the biomarker approach can be coupled with the high sensitivity of the IRMS, the DNA approach gives in general a better phylogenetic resolution of the metabolic active microbes. A combination of both is the separation via coupling of FISH-probes to magnetic beads or fluorescent assisted cell sorting (FACS) of stained cells leading to fractions which can be analyzed by IRMS. Applying these techniques over a time course can reveal the metabolic kinetics and food webs. In this review, the different methods are presented with examples and their advantages and disadvantages are discussed. An outlook on the combination of the various techniques and their applications in microbial ecology is given.
    • Arvoredol: An unusual chlorinated and biofilm inhibiting polyketide from a marine Penicillium sp. of the Brazilian coast

      Scopel, Marina; Mothes, Beatriz; Lerner, Clea B.; Henriques, Am?lia T.; Macedo, Alexandre J.; Abraham, Wolf-Rainer; Helmholtz Centre for infection research, Inhoffenstr. 7., 38124 Braunschweig, Germany. (2017-06)
      Penicillium sp. F37 has been isolated from the marine sponge Axinella corrugata and shown to be closely related to Penicillium maximae. From the culture of Penicillium sp. F37 arvoredol, a novel chlorinated polyketide with 6,7-dihydro-4(5H)-benzofuranone moiety has been isolated and characterized by spectroscopic methods Arvoredol prevented biofilm formation of the human pathogen Staphylococcus epidermidis at a concentration of 125 μg mL−1 by 40%. It was also active against colorectal carcinoma HCT116 cells with a MIC of 7.9 μg mL−1. © 2017 Phytochemical Society of Europe
    • Assessing the viability of bacterial species in drinking water by combined cellular and molecular analyses.

      Kahlisch, Leila; Henne, Karsten; Gröbe, Lothar; Brettar, Ingrid; Höfle, Manfred G; Department of Vaccinology and Applied Microbiology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany. (2012-02)
      The question which bacterial species are present in water and if they are viable is essential for drinking water safety but also of general relevance in aquatic ecology. To approach this question we combined propidium iodide/SYTO9 staining ("live/dead staining" indicating membrane integrity), fluorescence-activated cell sorting (FACS) and community fingerprinting for the analysis of a set of tap water samples. Live/dead staining revealed that about half of the bacteria in the tap water had intact membranes. Molecular analysis using 16S rRNA and 16S rRNA gene-based single-strand conformation polymorphism (SSCP) fingerprints and sequencing of drinking water bacteria before and after FACS sorting revealed: (1) the DNA- and RNA-based overall community structure differed substantially, (2) the community retrieved from RNA and DNA reflected different bacterial species, classified as 53 phylotypes (with only two common phylotypes), (3) the percentage of phylotypes with intact membranes or damaged cells were comparable for RNA- and DNA-based analyses, and (4) the retrieved species were primarily of aquatic origin. The pronounced difference between phylotypes obtained from DNA extracts (dominated by Betaproteobacteria, Bacteroidetes, and Actinobacteria) and from RNA extracts (dominated by Alpha-, Beta-, Gammaproteobacteria, Bacteroidetes, and Cyanobacteria) demonstrate the relevance of concomitant RNA and DNA analyses for drinking water studies. Unexpected was that a comparable fraction (about 21%) of phylotypes with membrane-injured cells was observed for DNA- and RNA-based analyses, contradicting the current understanding that RNA-based analyses represent the actively growing fraction of the bacterial community. Overall, we think that this combined approach provides an interesting tool for a concomitant phylogenetic and viability analysis of bacterial species of drinking water.
    • Asticcacaulis benevestitus sp. nov., a psychrotolerant, dimorphic, prosthecate bacterium from tundra wetland soil.

      Vasilyeva, Lina V; Omelchenko, Marina V; Berestovskaya, Yulia Y; Lysenko, Anatolii M; Abraham, Wolf-Rainer; Dedysh, Svetlana N; Zavarzin, George A; S. N. Winogradsky Institute of Microbiology, Russian Academy of Sciences, Prospect 60-let Octyabrya 7/2, Moscow 117312, Russia. (2006-09)
      A Gram-negative, aerobic, heterotrophic, non-pigmented, dimorphic prosthecate bacterium was isolated from tundra wetland soil and designated strain Z-0023(T). Cells of this strain had a dimorphic life cycle and developed a non-adhesive stalk at a site not coincident with the centre of the cell pole, a characteristic typical of representatives of the genus Asticcacaulis. A highly distinctive feature of cells of strain Z-0023(T) was the presence of a conical, bell-shaped sheath when grown at low temperature. This prosthecate bacterium was a psychrotolerant, moderately acidophilic organism capable of growth between 4 and 28 degrees Celsius (optimum 15-20 degrees Celsius) and between pH 4.5 and 8.0 (optimum 5.6-6.0). The major phospholipid fatty acid was 18 : 1omega7c and the major phospholipids were phosphatidylglycerols. The G+C content of the DNA was 60.4 mol%. On the basis of 16S rRNA gene sequence similarity, strain Z-0023(T) was most closely related to Asticcacaulis biprosthecium (98 % similarity), Asticcacaulis taihuensis (98 %) and Asticcacaulis excentricus (95 %). However, low levels of DNA-DNA relatedness to these organisms and a number of distinctive features of the tundra wetland isolate indicated that it represented a novel species of the genus Asticcacaulis, for which the name Asticcacaulis benevestitus sp. nov. is proposed. The type strain is Z-0023(T) (=DSM 16100(T)=ATCC BAA-896(T)).
    • The avid competitors of memory inflation.

      Abassi, Leila; Cicin-Sain, Luka; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Elsevier, 2020-10-08)
      Cytomegaloviruses (CMV) coevolve with their hosts and latently persist in the vast majority of adult mammals. Therefore, persistent T-cell responses to CMV antigens during virus latency offer a fascinating perspective on the evolution of the T-cell repertoire in natural settings. We addressed here the life-long interactions between CMV antigens presented on MHC-I molecules and the CD8 T-cell response. We present the mechanistic evidence from the murine model of CMV infection and put it in context of clinical laboratory results. We will highlight the remarkable parallels in T-cell responses between the two biological systems, and focus in particular on memory inflation as a result of competitive processes, both between viral antigenic peptides and between T-cell receptors on the host’s cytotoxic lymphocytes
    • The bacterial second messenger cdiGMP exhibits promising activity as a mucosal adjuvant.

      Ebensen, Thomas; Schulze, Kai; Riese, Peggy; Morr, Michael; Guzmán, Carlos A; Department of Vaccinology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, D-38124 Braunschweig, Germany. (2007-08)
      The development of mucosal adjuvants is still a critical need in vaccinology. In the present work, we show that bis(3',5')-cyclic dimeric GMP (cdiGMP), a second messenger that modulates cell surface properties of several microorganisms, exerts potent activity as a mucosal adjuvant. BALB/c mice were immunized intranasally with the model antigen beta-galactosidase (beta-Gal) coadministered with cdiGMP. Animals receiving cdiGMP as an adjuvant showed significantly higher anti-beta-Gal immunoglobulin G (IgG) titers in sera than controls (i.e., 512-fold [P < 0.05]). Coadministration of cdiGMP also stimulated efficient beta-Gal-specific secretory IgA production in the lung (P < 0.016) and vagina (P < 0.036). Cellular immune responses were observed in response to both the beta-Gal protein and a peptide encompassing its major histocompatibility complex class I-restricted epitope. The IgG1-to-IgG2a ratio of anti-beta-Gal antibodies and the observed profiles of secreted cytokines suggest that a dominant Th1 response pattern is promoted by mucosal coadministration of cdiGMP. Finally, the use of cdiGMP as a mucosal adjuvant also led to the stimulation of in vivo cytotoxic T-lymphocyte responses in C57BL/6 mice intranasally immunized with ovalbumin and cdiGMP (up to 30% of specific lysis). The results obtained indicate that cdiGMP is a promising tool for the development of mucosal vaccines.