Coinfection with Streptococcus pneumoniae Negatively Modulates the Size and Composition of the Ongoing Influenza-Specific CD8+ T Cell Response.

J Immunol. 2014 Oct 13. pii: 1400529. [Epub ahead of print]

Coinfection with Streptococcus pneumoniae Negatively Modulates the Size and Composition of the Ongoing Influenza-Specific CD8+ T Cell Response.

Blevins LK1, Wren JT1, Holbrook BC1, Hayward SL1, Swords WE1, Parks GD1, Alexander-Miller MA2.

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Abstract

Infection with influenza A virus can lead to increased susceptibility to subsequent bacterial infection, often with Streptococcus pneumoniae. Given the substantial modification of the lung environment that occurs following pathogen infection, there is significant potential for modulation of immune responses. In this study, we show that infection of mice with influenza virus, followed by the noninvasive EF3030 strain of Streptococcus pneumoniae, leads to a significant decrease in the virus-specific CD8+ T cell response in the lung. Adoptive-transfer studies suggest that this reduction contributes to disease in coinfected animals. The reduced number of lung effector cells in coinfected animals was associated with increased death, as well as a reduction in cytokine production in surviving cells. Further, cells that retained the ability to produce IFN-γ exhibited a decreased potential for coproduction of TNF-α. Reduced cytokine production was directly correlated with a decrease in the level of mRNA. Negative regulation of cells in the mediastinal lymph node was minimal compared with that present in the lung, supporting a model of selective regulation in the tissue harboring high pathogen burden. These results show that entry of a coinfecting pathogen can have profound immunoregulatory effects on an ongoing immune response. Together, these findings reveal a novel dynamic interplay between concurrently infecting pathogens and the adaptive immune system.

Copyright © 2014 by The American Association of Immunologists, Inc.

PMID: 25311807 [PubMed - as supplied by publisher]

Ethanol-induced alcohol dehydrogenase E (AdhE) potentiates pneumolysin in Streptococcus pneumoniae.

Infect Immun. 2014 Oct 13. pii: IAI.02434-14. [Epub ahead of print]

Ethanol-induced alcohol dehydrogenase E (AdhE) potentiates pneumolysin in Streptococcus pneumoniae.

Luong TT1, Kim EH1, Bak JP1, Nguyen CT1, Choi S2, Briles DE3, Pyo S1, Rhee DK4.

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Abstract

Alcohol impairs the host immune system, rendering hosts more vulnerable to infection. Therefore, alcoholics are at increased risk of acquiring serious bacterial infections caused by Streptococcus pneumoniae, including pneumonia. Nevertheless, how alcohol affects pneumococcal virulence remains unclear. Here we showed that S. pneumoniae type 2 D39 is ethanol tolerant, and that alcohol up-regulates alcohol dehydrogenase E (AdhE) and potentiates pneumolysin (Ply). Hemolytic activity, colonization, and virulence of S. pneumoniae, as well as host cell myeloperoxidase activity, pro-inflammatory cytokine secretion, and inflammation, were significantly attenuated in adhE mutant bacteria (ΔadhE) compared to D39 wild-type bacteria. Therefore, AdhE might act as a pneumococcal virulence factor. Moreover, in the presence of ethanol, S. pneumoniae AdhE produced acetaldehyde and NADH, which subsequently led Rex (redox-sensing transcriptional repressor) to dissociate from the adhE promoter. An increase in AdhE in the ethanol condition conferred an increase of Ply and H2O2 levels. Consistently, S. pneumoniae D39 caused higher cytotoxicity to RAW 264.7 cells than ΔadhE during the ethanol stress condition, and alcoholic mice were more susceptible to infection with the D39 wild-type bacteria than the ΔadhE. Taken together, these data indicate that AdhE increases Ply in the ethanol stress condition, thus potentiating pneumococcal virulence.

Copyright © 2014, American Society for Microbiology. All Rights Reserved.

PMID: 25312953 [PubMed - as supplied by publisher]

Topology of Streptococcus pneumoniae CpsC, a Polysaccharide co-polymerase and BY-kinase adaptor protein.

J Bacteriol. 2014 Oct 13. pii: JB.02106-14. [Epub ahead of print]

Topology of Streptococcus pneumoniae CpsC, a Polysaccharide co-polymerase and BY-kinase adaptor protein.

Whittall JJ1, Morona R1, Standish AJ2.

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Abstract

In Gram-positive bacteria, tyrosine kinases are split into two proteins, the cytoplasmic tyrosine kinase and a transmembrane adaptor protein. In Streptococcus pneumoniae this transmembrane adaptor is CpsC, with the C-terminus of CpsC critical for interaction and subsequent tyrosine kinase activity of CpsD. Topology predictions suggest CpsC has two transmembrane domains, with the N and C-termini present in the cytoplasm. In order to investigate CpsC topology, we used a chromosomal HA-tagged Cps2C protein in D39. Incubation of both protoplasts and membranes with the CP-B resulted in complete degradation of HA-Cps2C in all cases, indicating that the C-terminus of Cps2C was likely extra-cytoplasmic, and hence the protein's topology was not as predicted. Similar results were seen with membranes from TIGR4, indicating Cps4C also showed similar topology. A chromosomally encoded fusion of HA-Cps2C and Cps2D was not degraded by CP-B, suggesting that the fusion fixed the C-terminus within the cytoplasm. However, capsule synthesis was unaltered by this fusion. Detection of the CpsC C-terminus by flow cytometry indicated that it was extra-cytoplasmic in approximately 30% of cells. Interestingly, a mutant in the protein tyrosine phosphatase CpsB had a significantly greater proportion of positive cells, although this affect was independent of its phosphatase activity. Our data indicate that CpsC possesses a varied topology, with the C-terminus flipping across the cytoplasmic membrane where it interacts with CpsD in order to regulate tyrosine kinase activity.

Copyright © 2014, American Society for Microbiology. All Rights Reserved.

PMID: 25313397 [PubMed - as supplied by publisher]

Mutant prevention concentration of tigecycline for clinical isolates of Streptococcus pneumoniae and Staphylococcus aureus.

J Antimicrob Chemother. 2014 Oct 16. pii: dku389. [Epub ahead of print]

Mutant prevention concentration of tigecycline for clinical isolates of Streptococcus pneumoniae and Staphylococcus aureus.

Hesje CK1, Drlica K2, Blondeau JM3.

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Abstract

BACKGROUND:

The mutant prevention concentration (MPC) reflects the antimicrobial susceptibility of the resistant mutant subpopulations present in large bacterial populations. In principle, combining the MPC with pharmacokinetic measurements can guide treatment to restrict the enrichment of resistant subpopulations, just as the MIC is used with pharmacokinetics to restrict the growth of bulk, susceptible populations. Little is known about the MPC of tigecycline, one of the more recently approved antimicrobials. Tigecycline is particularly interesting because it shows good activity against Gram-positive pathogens.

METHODS:

MPCs were determined using tigecycline-containing agar plates for clinical isolates of Streptococcus pneumoniae (n = 47), MRSA (n = 50) and MSSA (n = 50).

RESULTS:

Trypticase soy agar containing sheep red blood cells, commonly used for the growth of S. pneumoniae, gave tigecycline MPC90 values that were two orders of magnitude higher than expected. The addition of agar to Todd-Hewitt broth (solidified Todd-Hewitt broth) allowed the high-density growth of S. pneumoniae in the absence of red blood cells and lowered the MPC90 of tigecycline by 100-fold to 0.5 mg/L. The addition of red blood cells to solidified Todd-Hewitt broth raised the MPC90 by 100-fold. Thus, red blood cells reduce the efficacy of tigecycline against S. pneumoniae. The growth of Staphylococcus aureus was not sensitive to red blood cells; values of MPC90 were 2 and 4 mg/L for MSSA and MRSA, respectively.

CONCLUSIONS:

Values of MPC constitute a concentration threshold for restricting the emergence of tigecycline resistance that can now be used in animal studies to determine pharmacodynamic thresholds. The off-label treatment of S. pneumoniae blood infections with tigecycline may require caution due to blood-cell-mediated interference with the antimicrobial.

© The Author 2014. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

KEYWORDS:

blood agar; mutant selection window; resistance

PMID: 25324419 [PubMed - as supplied by publisher]

Structural Determinants of Host Specificity of Complement Factor H Recruitment by Streptococcus pneumoniae.

Biochem J. 2014 Oct 21. [Epub ahead of print]

Structural Determinants of Host Specificity of Complement Factor H Recruitment by Streptococcus pneumoniae.

Achila D, Liu A, Banerjee R, Li Y, Martinez-Hackert E, Zhang JR, Yan H.

Abstract

Many human pathogens have strict host specificity, which affects not only their epidemiology but also development of animal models and vaccines. Complement factor H (FH) is recruited to pneumococcal cell surface in a human-specific manner via the N-terminal domain of the pneumococcal protein virulence factor CbpA (CbpAN). FH recruitment enables Streptococcus pneumoniae to evade surveillance by human complement system and contributes to pneumococcal host specificity. The molecular determinants of host specificity of complement evasion are unknown. Here we show that a single human FH domain is sufficient for tight binding of CbpAN, present the crystal structure of the complex, and identify the critical structural determinants for host-specific FH recruitment. The results offer new approaches to development of better animal models for pneumococcal infection and redesign of the virulence factor for pneumococcal vaccine development, and reveal how FH recruitment can serve as a mechanism for both pneumococcal complement evasion and adherence.

PMID: 25330773 [PubMed - as supplied by publisher] 

Pronounced metabolic changes in adaptation to biofilm growth by Streptococcus pneumoniae.

PLoS One. 2014 Sep 4;9(9):e107015. doi: 10.1371/journal.pone.0107015. eCollection 2014.

Pronounced metabolic changes in adaptation to biofilm growth by Streptococcus pneumoniae.

Allan RN1, Skipp P2, Jefferies J3, Clarke SC4, Faust SN5, Hall-Stoodley L6, Webb J7.

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Abstract

Streptococcus pneumoniae accounts for a significant global burden of morbidity and mortality and biofilm development is increasingly recognised as important for colonization and infection. Analysis of protein expression patterns during biofilm development may therefore provide valuable insights to the understanding of pneumococcal persistence strategies and to improve vaccines. iTRAQ (isobaric tagging for relative and absolute quantification), a high-throughput gel-free proteomic approach which allows high resolution quantitative comparisons of protein profiles between multiple phenotypes, was used to interrogate planktonic and biofilm growth in a clinical serotype 14 strain. Comparative analyses of protein expression between log-phase planktonic and 1-day and 7-day biofilm cultures representing nascent and late phase biofilm growth were carried out. Overall, 244 proteins were identified, of which >80% were differentially expressed during biofilm development. Quantitatively and qualitatively, metabolic regulation appeared to play a central role in the adaptation from the planktonic to biofilm phenotype. Pneumococci adapted to biofilm growth by decreasing enzymes involved in the glycolytic pathway, as well as proteins involved in translation, transcription, and virulence. In contrast, proteins with a role in pyruvate, carbohydrate, and arginine metabolism were significantly increased during biofilm development. Downregulation of glycolytic and translational proteins suggests that pneumococcus adopts a covert phenotype whilst adapting to an adherent lifestyle, while utilization of alternative metabolic pathways highlights the resourcefulness of pneumococcus to facilitate survival in diverse environmental conditions. These metabolic proteins, conserved across both the planktonic and biofilm phenotypes, may also represent target candidates for future vaccine development and treatment strategies. Data are available via ProteomeXchange with identifier PXD001182.

PMID: 25188255 [PubMed - in process] PMCID: PMC4154835