PNEUMONIA

Neuraminidase A-Exposed Galactose Promotes Streptococcus pneumoniae Biofilm Formation during Colonization.(link is external) 
Blanchette KA, Shenoy AT, Milner J 2nd, Gilley RP, McClure E, Hinojosa CA, Kumar N, Daugherty SC, Tallon LJ, Ott S, King SJ, Ferreira DM, Gordon SB, Tettelin H, Orihuela CJ. Infect Immun. 2016 Sep 19;84(10):2922-32. doi: 10.1128/IAI.00277-16. Print 2016 Oct. 
 

Streptococcus pneumoniae is an opportunistic pathogen that colonizes the nasopharynx. Herein we show that carbon availability is distinct between the nasopharynx and bloodstream of adult humans: glucose is absent from the nasopharynx, whereas galactose is abundant. We demonstrate that pneumococcal neuraminidase A (NanA), which cleaves terminal sialic acid residues from host glycoproteins, exposed galactose on the surface of septal epithelial cells, thereby increasing its availability during colonization. We observed that S. pneumoniaemutants deficient in NanA and β-galactosidase A (BgaA) failed to form biofilms in vivo despite normal biofilm-forming abilities in vitro. Subsequently, we observed that glucose, sucrose, and fructose were inhibitory for biofilm formation, whereas galactose, lactose, and low concentrations of sialic acid were permissive. Together these findings suggested that the genes involved in biofilm formation were under some form of carbon catabolite repression (CCR), a regulatory network in which genes involved in the uptake and metabolism of less-preferred sugars are silenced during growth with preferred sugars. Supporting this notion, we observed that a mutant deficient in pyruvate oxidase, which converts pyruvate to acetyl-phosphate under non-CCR-inducing growth conditions, was unable to form biofilms. Subsequent comparative transcriptome sequencing (RNA-seq) analyses of planktonic and biofilm-grown pneumococci showed that metabolic pathways involving the conversion of pyruvate to acetyl-phosphate and subsequently leading to fatty acid biosynthesis were consistently upregulated during diverse biofilm growth conditions. We conclude that carbon availability in the nasopharynx impacts pneumococcal biofilm formation in vivo. Additionally, biofilm formation involves metabolic pathways not previously appreciated to play an important role.

 

Pulmonary dry powder vaccine of pneumococcal antigen loaded nanoparticles. (link is external)Kunda NK, Alfagih IM, Miyaji EN, Figueiredo DB, Gonçalves VM, Ferreira DM, Dennison SR, Somavarapu S, Hutcheon GA, Saleem IY. Int J Pharm. 2015 Nov 30;495(2):903-12. doi: 10.1016/j.ijpharm.2015.09.034
 

Pneumonia, caused by Streptococcus pneumoniae, mainly affects the immunocompromised, the very young and the old, and remains one of the leading causes of death. A steady rise in disease numbers from non-vaccine serotypes necessitates a new vaccine formulation that ideally has better antigen stability and integrity, does not require cold-chain and can be delivered non-invasively. In this study, a dry powder vaccine containing an important antigen of S. pneumoniae, pneumococcal surface protein A (PspA) that has shown cross-reactivity amongst serotypes to be delivered via the pulmonary route has been formulated. The formulation contains the antigen PspA adsorbed onto the surface of polymeric nanoparticles encapsulated in l-leucine microparticles that can be loaded into capsules and delivered via an inhaler. We have successfully synthesized particles of ∼150 nm and achieved ∼20 μg of PspA adsorption per mg of NPs. In addition, the spray-dried powders displayed a FPF of 74.31 ± 1.32% and MMAD of 1.70 ± 0.03 μm suggesting a broncho-alveolar lung deposition facilitating the uptake of the nanoparticles by dendritic cells. Also, the PspA released from the dry powders maintained antigen stability (SDS-PAGE), integrity (Circular dichroism) and activity (lactoferrin binding assay). Moreover, the released antigen also maintained its antigenicity as determined by ELISA.

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First human challenge testing of a pneumococcal vaccine. Double-blind randomized controlled trial. 
Collins AM, Wright AD, Mitsi E, Gritzfeld JF, Hancock CA, Pennington SH, Wang D, Morton B, Ferreira DM, Gordon SB. Am J Respir Crit Care Med. 2015 Oct 1;192(7):853-8. doi: 10.1164/rccm.201503-0542OC.

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Rationale: New vaccines are urgently needed to protect the vulnerable from bacterial pneumonia. Clinical trials of pneumonia vaccines are slow and costly, requiring tens of thousands of patients. Studies of pneumococcal vaccine efficacy against colonization have been proposed as a novel method to down-select between vaccine candidates.

Objectives: Using our safe and reproducible experimental human pneumococcal colonization model, we aimed to determine the effect of 13-valent pneumococcal conjugate vaccine (PCV) on colonization.
Methods: A total of 100 healthy participants aged 18-50 years were recruited into this double-blind randomized placebo-controlled trial. They were randomly assigned to PCV (n = 49) or hepatitis A (control, n = 50) vaccination and inoculated with 80,000 CFU/100 μl of Streptococcus pneumoniae (6B) per naris.

Measurements and Main Results: Participants were followed up for 21 days to determine pneumococcal colonization by culture of nasal wash. The PCV group had a significantly reduced rate of 6B colonization (10% [5 of 48]) compared with control subjects (48% [23 of 48]) (risk ratio, 0.22; confidence interval, 0.09-0.52; P < 0.001). Density of colonization was reduced in the PCV group compared with the control group following inoculation. The area under the curve (density vs. day) was significantly reduced in the PCV compared with control group (geometric mean, 259 vs. 11,183; P = 0.017).

Conclusions: PCV reduced pneumococcal colonization rate, density, and duration in healthy adults. The experimental human pneumococcal colonization model is a safe, cost-effective, and efficient method to determine the protective efficacy of new vaccines on pneumococcal colonization; PCV provides agold standard against which to test these novel vaccines. Clinical trial registered with
Isrctn: 45340436.

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Modulation of nasopharyngeal innate defenses by viral coinfection predisposes individuals to experimental pneumococcal carriage. 
Glennie S, Gritzfeld JF, Pennington SH, Garner-Jones M, Coombes N, Hopkins MJ, Vadesilho CF, Miyaji EN, Wang D, Wright AD, Collins AM, Gordon SB, Ferreira DM. Mucosal Immunol. 2016 Jan;9(1):56-67. doi: 10.1038/mi.2015.35.

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Increased nasopharyngeal colonization density has been associated with pneumonia. We used experimental human pneumococcal carriage to investigate whether upper respiratory tract viral infection predisposes individuals to carriage. A total of 101 healthy subjects were screened for respiratory virus before pneumococcal intranasal challenge. Virus was associated with increased odds of colonization (75% virus positive became colonized vs. 46% virus-negative subjects; P=0.02). Nasal Factor H (FH) levels were increased in virus-positive subjects and were associated with increased colonization density. Using an in vitro epithelial model we explored the impact of increased mucosal FH in the context of coinfection. Epithelial inflammation and FH binding resulted in increased pneumococcal adherence to the epithelium. Binding was partially blocked by antibodies targeting the FH-binding protein Pneumococcal surface protein C (PspC). PspC epitope mapping revealed individuals lacked antibodies against the FH binding region. We propose that FH binding to PspC in vivo masks this binding site, enabling FH to facilitate pneumococcal/epithelial attachment during viral infection despite the presence of anti-PspC antibodies. We propose that a PspC-based vaccine lacking binding to FH could reduce pneumococcal colonization, and may have enhanced protection in those with underlying viral infection.

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The adult nasopharyngeal microbiome as a determinant of pneumococcal acquisition.(link is external)
Cremers AJ, Zomer AL, Gritzfeld JF, Ferwerda G, van Hijum SA, Ferreira DM, Shak JR, Klugman KP, Boekhorst J, Timmerman HM, de Jonge MI, Gordon SB, Hermans PW. Microbiome. 2014 Dec 15;2:44. doi: 10.1186/2049-2618-2-44.
 

Background: Several cohort studies have indicated associations between S. pneumoniae and other microbes in the nasopharynx. To study causal relationships between the nasopharyngeal microbiome and pneumococcal carriage, we employed an experimental human pneumococcal carriage model. Healthy adult volunteers were assessed for pneumococcal carriage by culture of nasal wash samples (NWS). Those without natural pneumococcal carriage received an intranasal pneumococcal inoculation with serotype 6B or 23F. The composition of the nasopharyngeal microbiome was longitudinally studied by 16S rDNA pyrosequencing on NWS collected before and after challenge.

Results: Among 40 selected volunteers, 10 were natural carriers and 30 were experimentally challenged. At baseline, five distinct nasopharyngeal microbiome profiles were identified. The phylogenetic distance between microbiomes of natural pneumococcal carriers was particularly large compared to non-carriers. A more diverse microbiome prior to inoculation was associated with the establishment of pneumococcal carriage. Perturbation of microbiome diversity upon pneumococcal challenge was strain specific. Shifts in microbiome profile occurred after pneumococcal exposure, and those volunteers who acquired carriage more often diverted from their original profile. S. pneumoniae was little prominent in the microbiome of pneumococcal carriers.
Conclusion: Pneumococcal acquisition in healthy adults is more likely to occur in a diverse microbiome and appears to promote microbial heterogeneity.

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Density and duration of experimental human pneumococcal carriage. (link is external)

Gritzfeld JF, Cremers AJ, Ferwerda G, Ferreira DM, Kadioglu A, Hermans PW, Gordon SB. Clin Microbiol Infect. 2014 Dec;20(12):O1145-51. doi: 10.1111/1469-0691.12752. (link is external)Epub 2014 Aug 11.

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The density and duration of pneumococcal carriage are considered to affect the likelihood of transmission and invasive disease. Because of its importance in both spreading and causing disease, carriage has been suggested as an endpoint in future vaccine studies. Culture is the current gold standard for detection, but may not be sensitive enough to detect changes at low density. Healthy adult volunteers received an intranasal inoculation of Streptococcus pneumoniae serotype6B. Pneumococcal density in nasal washes collected at six time-points post-inoculation was determined by culture and quantitative PCR (qPCR). Natural pneumococcal carriers detected at initial screening were followed in parallel. In 331 nasal washes from 79 volunteers, the sensitivity and specificity of pneumococcal detection by qPCR, as compared with culture, were 92.3% and 75.9%. The estimation of pneumococcal density by culture and qPCR was highly correlated (r(s)=0.73, p<0.0001), although qPCR had a lower detection limit. Pneumococcaldensity fluctuated within a carriage episode, and occasionally fell below the detection limit of both methods. The duration of carriage episodes was underestimated when only one method was used. Similar fluctuations in density were observed in natural carriers. Pneumococcal carriage is a dynamic event. Culture and qPCR are complementary for surveying the density and duration of pneumococcal carriage episodes.

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Mapping of epitopes recognized by antibodies induced by immunization of mice with PspA and PspC. 
Vadesilho CF, Ferreira DM, Gordon SB, Briles DE, Moreno AT, Oliveira ML, Ho PL, Miyaji EN. Clin Vaccine Immunol. 2014 Jul;21(7):940-8. doi: 10.1128/CVI.00239-14. Epub 2014 May 7.
 

Pneumococcal surface protein A (PspA) and pneumococcal surface protein C (PspC) are important candidates for an alternative vaccine against pneumococcal infections. Since these antigens show variability, the use of variants that do not afford broad protection may lead to the selection of vaccine escape bacteria. Epitopes capable of inducing antibodies with broad cross-reactivities should thus be the preferred antigens. In this work, experiments using peptide arrays show that most linear epitopes recognized by antibodies induced in mice against different PspAs were located at the initial 44 amino acids of the mature protein and that antibodies against these linear epitopes did not confer protection against a lethal challenge. Conversely, linear epitopes recognized by antibodies to PspC included the consensus sequences involved in the interaction with human factor H and secretory immunoglobulin A (sIgA). Since linear epitopes of PspA were not protective, larger overlapping fragments containing 100 amino acids of PspA of strain Rx1 were constructed (fragments 1 to 7, numbered from the N terminus) to permit the mapping of antibodies with conformational epitopes not represented in the peptide arrays. Antibodies from mice immunized with fragments 1, 2, 4, and 5 were capable of binding onto the surface of pneumococci and mediating protection against a lethal challenge. The fact that immunization of mice with 100-amino-acid fragments located at the more conserved N-terminal region of PspA (fragments 1 and 2) induced protection against a pneumococcal challenge indicates that the induction of antibodies against conformational epitopes present at this region may be important in strategies for inducing broad protection against pneumococci. 

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Increased IgG but normal IgA anti-pneumococcal protein antibodies in lung of HIV-infected adults.(link is external) 

Collins AM, Batrawy SE, Gordon SB, Ferreira DM. Vaccine. 2013 Aug 2;31(35):3469-72. doi: 10.1016/j.vaccine.2013.04.062. Epub 2013 May 10. 

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PspA and pneumolysin (Ply) are important protein vaccine candidates. HIV infection is associated with increased susceptibility to pneumococcal pneumonia and concomitantly high pneumococcal carriage rates. Pneumococcal exposure is immunizing at the mucosa in healthy adults and so we wished to determine if the increased pneumococcal exposure in HIV-infected adults would be associated with altered pneumococcal specific antibody responses. We measured serum and bronchoalveolar lavage (BAL) fluid immunoglobulin (Ig)G and IgA to PspA and Ply in HIV-infected and healthy age-matched adults. Naturally generated anti-Ply and anti-PspA IgG levels but not IgA were significantly increased in HIV-infected subjects in BAL independent of the hyperglobulinaemia commonly associated with HIV. There was therefore no evidence of a defect in mucosal responses to pneumococcal protein antigens among HIV-infected adults. With regard to future vaccination strategies, simply increasing mucosal anti-pneumococcal protein Ig levels, without addressing functional protective response, is not likely to be effective in preventing pneumococcal pneumonia in HIV-infected individuals. 

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Experimental human pneumococcal carriage augments IL-17A-dependent T-cell defence of the lung. 

Wright AK, Bangert M, Gritzfeld JF, Ferreira DM, Jambo KC, Wright AD, Collins AM, Gordon SB. PLoS Pathog. 2013 Mar;9(3):e1003274. doi: 10.1371/journal.ppat.1003274. 

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Pneumococcal carriage is both immunising and a pre-requisite for mucosal and systemic disease. Murine models of pneumococcal colonisation show that IL-17A-secreting CD4+ T-cells (Th-17 cells) are essential for clearance of pneumococci from the nasopharynx. Pneumococcal-responding IL-17A-secreting CD4+ T-cells have not been described in the adult human lung and it is unknown whether they can be elicited by carriage and protect the lungfrom pneumococcal infection. We investigated the direct effect of experimental human pneumococcal nasal carriage (EHPC) on the frequency and phenotype of cognate CD4+ T-cells in broncho-alveolar lavage and blood using multi-parameter flow cytometry. We then examined whether they could augment ex vivo alveolar macrophage killing of pneumococci using an in vitro assay. We showed that human pneumococcal carriage leads to a 17.4-fold (p = 0.007) and 8-fold (p = 0.003) increase in the frequency of cognate IL-17A+ CD4+ T-cells in BAL and blood, respectively. The phenotype with the largest proportion were TNF+/IL-17A+ co-producing CD4+ memory T-cells (p<0.01); IFNγ+ CD4+ memory T-cells were not significantly increased following carriage. Pneumococci could stimulate large amounts of IL-17A protein from BAL cells in the absence of carriage but in the presence of cognate CD4+ memory T-cells, IL-17A protein levels were increased by a further 50%. Further to this we then show that alveolar macrophages, which express IL-17A receptors A and C, showed enhanced killing of opsonised pneumococci when stimulated with rhIL-17A (p = 0.013). Killing negatively correlated with RC (r = −0.9, p = 0.017) but not RA expression. We conclude that human pneumococcal carriage can increase the proportion of lung IL-17A-secreting CD4+ memory T-cells that may enhance innate cellular immunity against pathogenic challenge. These pathways may be utilised to enhance vaccine efficacy to protect the lung against pneumonia.

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Controlled Human Infection and Re-Challenge with Streptococcus Pneumoniae Reveals the Protective Efficacy of Carriage in Healthy Adults.(link is external) 
Ferreira DM, Neill DR, Bangert M, Gritzfeld JF, Green N, Wright AK, Pennington SH, Moreno LB, Moreno AT, Miyaji EN, Wright AD, Collins AM, Goldblatt D, Kadioglu A, Gordon SB. Am J Respir Crit Care Med. 2013 Jan 31 

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RATIONALE: The immunological and protective role of pneumococcal carriage in healthy adults is not known but high rates of disease and death in elderly are associated with low carriage prevalence. OBJECTIVES: We employed an experimental human pneumococcal carriage model to investigate the immunizing effect of a single carriage episode. METHODS: Seventy healthy adults were challenged and of those with carriage 10 were re-challenged intranasally with live 6B Streptococcus pneumoniae up to 11 months after clearance of first carriage episode. Serum and nasal wash antibody response were measured before and after each challenge.
MEASUREMENTS AND MAIN RESULTS: 29 subjects were experimentally colonized. No subjects were colonized by experimental re-challenge demonstrating the protective effect of initial carriage against subsequent infection. Carriage increased both mucosal and serum IgG levels to pneumococcal proteins and polysaccharide, resulting in a fourfold increase in opsonophagocytic activity. Importantly, passive transfer of post-carriage sera from colonized subjects conferred 70% protection against lethal challenge by a heterologous strain in a murine model of invasive pneumococcal pneumonia. These levels were significantly higher than the protection conferred by either pre-carriage sera (30%) or saline (10%).
CONCLUSIONS: Experimental human carriage resulted in mucosal and systemic immunological responses that conferred protection against re-colonization and invasive pneumococcal disease. These data suggest that mucosal pneumococcal vaccination strategies maybe important for vulnerable patient groups, particularly the elderly, who do not sustain carriage.

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Experimental human pneumococcal carriage.(link is external) 
Gritzfeld JF, Wright AD, Collins AM, Pennington SH, Wright AK, Kadioglu A, Ferreira DM, Gordon SB. J Vis Exp. Feb 15;(72). 2013 

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Human nasal challenge with Streptococcus pneumoniae is immunising in the absence of carriage.(link is external) 

Ferreira DM*, Wright AK*, Gritzfeld JF, Wright AD, Armitage K, Jambo KC, Bate E, El Batrawy S, Collins A, Gordon SB.. PLoS Pathog. Apr;8(4):e1002622. 2012 (*contributed equally to the work) 

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Infectious challenge of the human nasal mucosa elicits immune responses that determine the fate of the host-bacterial interaction; leading either to clearance, colonisation and/or disease. Persistent antigenic exposure from pneumococcal colonisation can induce both humoral and cellular defences that are protective against carriage and disease. We challenged healthy adults intra-nasally with live 23F or 6B Streptococcus pneumoniae in two sequential cohorts and collected nasal wash, bronchoalveolar lavage (BAL) and blood before and 6 weeks after challenge. We hypothesised that both cohorts would successfully become colonised but this did not occur except for one volunteer. The effect of bacterial challenge without colonisation in healthy adults has not been previously assessed. We measured the antigen-specific humoral and cellular immune responses in challenged but not colonised volunteers by ELISA and Flow Cytometry. Antigen-specific responses were seen in each compartment both before and after bacterial challenge for both cohorts. Antigen-specific IgG and IgA levels were significantly elevated in nasal wash 6 weeks after challenge compared to baseline. Immunoglobulin responses to pneumococci were directed towards various protein targets but not capsular polysaccharide. 23F but not 6B challenge elevated IgG anti-PspA in BAL. Serum immunoglobulins did not increase in response to challenge. In neither challenge cohort was there any alteration in the frequencies of TNF, IL-17 or IFNγ producing CD4 T cells before or after challenge in BAL or blood. We show that simple, low dose mucosal exposure with pneumococci may immunise mucosal surfaces by augmenting anti-protein immunoglobulin responses; but not capsular or cellular responses. We hypothesise that mucosal exposure alone may not replicate the systemic immunising effect of experimental or natural carriage in humans. 

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Experimental human pneumococcal carriage models for vaccine research.(link is external) 
Ferreira DM, Jambo KC, Gordon SB. Experimental human pneumococcal carriage models for vaccine research.Trends in Microbiology. 2011 Sep;19(9):464-70. Epub 2011 Jul 23. Review

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Pneumococcal conjugate vaccines have had unprecedented success in controlling vaccine-type invasive pneumococcal disease. As serotype replacement and the complexity of designing vaccines to multiple capsular polysaccharides ultimately pose a threat to these vaccines, the development of alternative protein vaccines is important. Protein vaccines offer the promise of extended serotype coverage, reduced cost, and improved protection against otitis media and pneumococcal pneumonia. As placebo-controlled trials are not currently ethically justifiable, human pneumococcal challenge modelsusing prevention of carriage as a test endpoint offer an attractive link between preclinical studies and clinical efficacy trials. Experimental humanpneumococcal carriage studies offer a means of describing mechanisms of protection against carriage and a clinical tool to choose between vaccine candidates