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Björk, Rafael
Publications (4 of 4) Show all publications
Espaillat, A., Forsmo, O., El Biari, K., Björk, R., Lemaitre, B., Trygg, J., . . . Cava, F. (2016). Chemometric Analysis of Bacterial Peptidoglycan Reveals Atypical Modifications That Empower the Cell Wall against Predatory Enzymes and Fly Innate Immunity. Journal of the American Chemical Society, 138(29), 9193-9204
Open this publication in new window or tab >>Chemometric Analysis of Bacterial Peptidoglycan Reveals Atypical Modifications That Empower the Cell Wall against Predatory Enzymes and Fly Innate Immunity
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2016 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 138, no 29, p. 9193-9204Article in journal (Refereed) Published
Abstract [en]

Peptidoglycan is a fundamental structure for most bacteria. It contributes to the cell morphology and provides cell wall integrity against environmental insults. While several studies have reported a significant degree of variability in the chemical composition and organization of peptidoglycan in the domain Bacteria, the real diversity of this polymer is far from fully explored. This work exploits rapid ultraperformance liquid chromatography and multivariate data analysis to uncover peptidoglycan chemical diversity in the Class Alphaproteobacteria, a group of Gram negative bacteria that are highly heterogeneous in terms of metabolism, morphology and life-styles. Indeed, chemometric analyses revealed novel peptidoglycan structures conserved in Acetobacteria: amidation at the alpha-(L)-carboxyl of meso-diaminopimelic acid and the presence of muropeptides cross-linked by (1-3) L-Ala-D-(meso)diaminopimelate cross-links. Both structures are growth-controlled modifications that influence sensitivity to Type VI secretion system peptidoglycan endopeptidases and recognition by the Drosophila innate immune system, suggesting relevant roles in the environmental adaptability of these bacteria. Collectively our findings demonstrate the discriminative power of chemometric tools on large cell wall-chromatographic data sets to discover novel peptidoglycan structural properties in bacteria.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016
National Category
Chemical Sciences Microbiology in the medical area
urn:nbn:se:umu:diva-125551 (URN)10.1021/jacs.6b04430 (DOI)000380730000039 ()27337563 (PubMedID)
Available from: 2016-09-16 Created: 2016-09-13 Last updated: 2019-03-28Bibliographically approved
Normark, J., Nelson, M., Engström, P., Andersson, M., Björk, R., Moritz, T., . . . Bergström, S. (2014). Maladjusted Host Immune Responses Induce Experimental Cerebral Malaria-Like Pathology in a Murine Borrelia and Plasmodium Co-Infection Model. PLoS ONE, 9(7), Article ID e103295.
Open this publication in new window or tab >>Maladjusted Host Immune Responses Induce Experimental Cerebral Malaria-Like Pathology in a Murine Borrelia and Plasmodium Co-Infection Model
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2014 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 7, article id e103295Article in journal (Refereed) Published
Abstract [en]

In the Plasmodium infected host, a balance between pro- and anti-inflammatory responses is required to clear the parasites without inducing major host pathology. Clinical reports suggest that bacterial infection in conjunction with malaria aggravates disease and raises both mortality and morbidity in these patients. In this study, we investigated the immune responses in BALB/c mice, co-infected with Plasmodium berghei NK65 parasites and the relapsing fever bacterium Borrelia duttonii. In contrast to single infections, we identified in the co-infected mice a reduction of L-Arginine levels in the serum. It indicated diminished bioavailability of NO, which argued for a dysfunctional endothelium. Consistent with this, we observed increased sequestration of CD8+ cells in the brain as well over expression of ICAM-1 and VCAM by brain endothelial cells. Co-infected mice further showed an increased inflammatory response through IL-1 beta and TNF-alpha, as well as inability to down regulate the same through IL-10. In addition we found loss of synchronicity of pro- and anti-inflammatory signals seen in dendritic cells and macrophages, as well as increased numbers of regulatory T-cells. Our study shows that a situation mimicking experimental cerebral malaria (ECM) is induced in co-infected mice due to loss of timing and control over regulatory mechanisms in antigen presenting cells.

Place, publisher, year, edition, pages
PLOS ONE, 2014
National Category
Cell and Molecular Biology
urn:nbn:se:umu:diva-92942 (URN)10.1371/journal.pone.0103295 (DOI)000340028800036 ()
Available from: 2014-09-17 Created: 2014-09-09 Last updated: 2018-06-07Bibliographically approved
Rydén, P., Björk, R., Schäfer, M. L., Lundström, J. O., Petersén, B., Lindblom, A., . . . Johansson, A. (2012). Outbreaks of tularemia in a boreal forest region depends on mosquito prevalence. Journal of Infectious Diseases, 205(2), 297-304
Open this publication in new window or tab >>Outbreaks of tularemia in a boreal forest region depends on mosquito prevalence
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2012 (English)In: Journal of Infectious Diseases, ISSN 0022-1899, E-ISSN 1537-6613, Vol. 205, no 2, p. 297-304Article in journal (Refereed) Published
Abstract [en]

Background. We aimed to evaluate the potential association of mosquito prevalence in a boreal forest area with transmission of the bacterial disease tularemia to humans, and model the annual variation of disease using local weather data.

Methods. A prediction model for mosquito abundance was built using weather and mosquito catch data. Then a negative binomial regression model based on the predicted mosquito abundance and local weather data was built to predict annual numbers of humans contracting tularemia in Dalarna County, Sweden.

Results. Three hundred seventy humans were diagnosed with tularemia between 1981 and 2007, 94% of them during 7 summer outbreaks. Disease transmission was concentrated along rivers in the area. The predicted mosquito abundance was correlated (0.41, P < .05) with the annual number of human cases. The predicted mosquito peaks consistently preceded the median onset time of human tularemia (temporal correlation, 0.76; P < .05). Our final predictive model included 5 environmental variables and identified 6 of the 7 outbreaks.

Conclusions. This work suggests that a high prevalence of mosquitoes in late summer is a prerequisite for outbreaks of tularemia in a tularemia-endemic boreal forest area of Sweden and that environmental variables can be used as risk indicators.

francisella-tularensis; sweden; regression; culicidae; diptera
National Category
Immunology in the medical area Microbiology in the medical area Infectious Medicine
urn:nbn:se:umu:diva-50328 (URN)10.1093/infdis/jir732 (DOI)22124130 (PubMedID)
Available from: 2011-12-06 Created: 2011-12-06 Last updated: 2018-06-08Bibliographically approved
Eneslätt, K., Normark, M., Björk, R., Rietz, C., Zingmark, C., Wolfraim, L. A., . . . Sjöstedt, A. (2012). Signatures of T cells as correlates of immunity to Francisella tularensis. PLoS ONE, 7(3), e32367
Open this publication in new window or tab >>Signatures of T cells as correlates of immunity to Francisella tularensis
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2012 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 3, p. e32367-Article in journal (Refereed) Published
Abstract [en]

Tularemia or vaccination with the live vaccine strain (LVS) of Francisella tularensis confers long-lived cell-mediated immunity. We hypothesized that this immunity depends on polyfunctional memory T cells, i.e., CD4(+) and/or CD8(+) T cells with the capability to simultaneously express several functional markers. Multiparametric flow cytometry, measurement of secreted cytokines, and analysis of lymphocyte proliferation were used to characterize in vitro recall responses of peripheral blood mononuclear cells (PBMC) to killed F. tularensis antigens from the LVS or Schu S4 strains. PBMC responses were compared between individuals who had contracted tularemia, had been vaccinated, or had not been exposed to F. tularensis (naive). Significant differences were detected between either of the immune donor groups and naive individuals for secreted levels of IL-5, IL-6, IL-10, IL-12, IL-13, IFN-gamma, MCP-1, and MIP-1 beta. Expression of IFN-gamma, MIP-1 beta, and CD107a by CD4(+)CD45RO(+) or CD8(+) CD45RO(+) T cells correlated to antigen concentrations. In particular, IFN-gamma and MIP-1 beta strongly discriminated between immune and naive individuals. Only one cytokine, IL-6, discriminated between the two groups of immune individuals. Notably, IL-2- or TNF-alpha-secretion was low. Our results identify functional signatures of T cells that may serve as correlates of immunity and protection against F. tularensis.

National Category
Microbiology in the medical area
urn:nbn:se:umu:diva-55370 (URN)10.1371/journal.pone.0032367 (DOI)000303021100015 ()22412866 (PubMedID)
Available from: 2012-05-30 Created: 2012-05-14 Last updated: 2018-06-08Bibliographically approved

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