The role of pneumolysin in mediating lung damage in a lethal pneumococcal pneumonia murine model

BACKGROUND: Intranasal inoculation of Streptococcus pneumoniae D39 serotype 2 causes fatal pneumonia in mice. The cytotoxic and inflammatory properties of pneumolysin (PLY) have been implicated in the pathogenesis of pneumococcal pneumonia. METHODS: To examine the role of PLY in this experimental model we performed ELISA assays for PLY quantification. The distribution patterns of PLY and apoptosis were established by immunohistochemical detection of PLY, caspase-9 activity and TUNEL assay on tissue sections from mice lungs at various times, and the results were quantified with image analysis. Inflammatory and apoptotic cells were also quantified on lung tissue sections from antibody treated mice. RESULTS: In bronchoalveolar lavages (BAL), total PLY was found at sublytic concentrations which were located in alveolar macrophages and leukocytes. The bronchoalveolar epithelium was PLY-positive, while the vascular endothelium was not PLY reactive. The pattern and extension of cellular apoptosis was similar. Anti-PLY antibody treatment decreased the lung damage and the number of apoptotic and inflammatory cells in lung tissues. CONCLUSION: The data strongly suggest that in vivo lung injury could be due to the pro-apoptotic and pro-inflammatory activity of PLY, rather than its cytotoxic activity. PLY at sublytic concentrations induces lethal inflammation in lung tissues and is involved in host cell apoptosis, whose effects are important to pathogen survival

Identifying Host Genetic Risk Factors in the Context of Public Health Surveillance for Invasive Pneumococcal Disease

Host genetic factors that modify risk of pneumococcal disease may help target future public health interventions to individuals at highest risk of disease. We linked data from population-based surveillance for invasive pneumococcal disease (IPD) with state-based newborn dried bloodspot repositories to identify biological samples from individuals who developed invasive pneumococcal disease. Genomic DNA was extracted from 366 case and 732 anonymous control samples. TagSNPs were selected in 34 candidate genes thought to be associated with host response to invasive pneumococcal disease, and a total of 326 variants were successfully genotyped. Among 543 European Americans (EA) (182 cases and 361 controls), and 166 African Americans (AA) (53 cases and 113 controls), common variants in surfactant protein D (SFTPD) are consistently underrepresented in IPD. SFTPD variants with the strongest association for IPD are intronic rs17886286 (allelic OR 0.45, 95% confidence interval (CI) [0.25, 0.82], with p = 0.007) in EA and 5′ flanking rs12219080 (allelic OR 0.32, 95%CI [0.13, 0.78], with p = 0.009) in AA. Variants in CD46 and IL1R1 are also associated with IPD in both EA and AA, but with effects in different directions; FAS, IL1B, IL4, IL10, IL12B, SFTPA1, SFTPB, and PTAFR variants are associated (p≤0.05) with IPD in EA or AA. We conclude that variants in SFTPD may protect against IPD in EA and AA and genetic variation in other host response pathways may also contribute to risk of IPD. While our associations are not corrected for multiple comparisons and therefore must be replicated in additional cohorts, this pilot study underscores the feasibility of integrating public health surveillance with existing, prospectively collected, newborn dried blood spot repositories to identify host genetic factors associated with infectious diseases

Complement and surfactant protein D in the innate immunity to streptoccus pneumoniae

The aim of this project was to investigate the role of complement and lung surfactant protein D in innate immunity to S. pneumoniae. Pneumolysin, a cytolytic toxin produced by S. pneumoniae, is able to activate the classical complement pathway. The deletion of the ability of pneumolysin to activate complement affected the early growth of pneumococcus in the lungs, the onset of bacteraemia, the histological changes and the recruitment of T lymphocytes into lung tissue during bronchopneimionia.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Complement and surfactant Protein D in the innate immunity to streptococcus pneumoniae

The aim of this project was to investigate the role of complement and lung surfactant protein D in innate immunity to S. pneumoniae.;Pneumolysin, a cytolytic toxin produced by S. pneumoniae, is able to activate the classical complement pathway. The deletion of the ability of pneumolysin to activate complement affected the early growth of pneumococcus in the lungs, the onset of bacteraemia, the histological changes and the recruitment of T lymphocytes into lung tissue during bronchopneumonia.;Lung complement C3 was substantially activated after intranasal infection with wild-type S. pneumoniae in comparison with the isogenic mutant strain unable to produce pneumolysin (PLN-A).;Data presented in this thesis showed that the classical complement pathway plays a critical role in the innate immunity to S. pneumoniae infection. Deficiency in C1q increased the susceptibility to pneumococcal infection and was associated with defects in pneumococcal clearance from lungs and blood, less severe histological changes, recruitment of T cells and a substantial decrease in the activation of complement C3 in the lung.;In vitro studies showed that lung surfactant protein D or its receptor gp-340 is able to bind and agglutinate several strains of S. pneumoniae. Sp-D did not enhance the uptake of pneumococcus by neutrophils. The capsule-type is not a determinant for S. pneumoniae aggregation by Sp-D or gp-340.;Sp-D-deficient mice showed increased susceptibility to pneumococcal infection. Deficiency in Sp-D was associated with decreased pneumococcal clearance in lungs and trachea, early onset and increased levels of bacteraemia. In the infected lung, accumulation of T lymphocytes and more severe inflammation were observed in the absence of Sp-D

Pneumococcal Behavior and Host Responses during Bronchopneumonia Are Affected Differently by the Cytolytic and Complement-Activating Activities of Pneumolysin

Pneumolysin, a multifunctional toxin produced by all clinical isolates of Streptococcus pneumoniae, is strongly implicated in the pathogenesis of pneumococcal bronchopneumonia and septicemia. Using isogenic mutant strains, we examined the effect of deletion of the cytotoxic activity or complement-activating activity of pneumolysin on bacterial growth in lungs and blood, histological changes in infected lung tissue, and the pattern of inflammatory cell recruitment. Both of the activities of pneumolysin contributed to the pathology in the lungs, as well as the timing of the onset of bacteremia. Histological changes in the lungs were delayed after infection with either mutant compared to the changes seen after infection with the wild-type pneumococcus. The complement-activating activity of pneumolysin affected the accumulation of T cells, whereas the toxin's cytolytic activity influenced neutrophil recruitment into lung tissue

rs6837671A>G in <i>FAM13A</i> Is a Trans-Ethnic Genetic Variant Interacting with Vitamin D Levels to Affect Chronic Obstructive Pulmonary Disease

(1) Background and objectives: Chronic obstructive pulmonary disease (COPD) is a leading cause of mortality throughout the world. In addition to genetics, increasing evidence suggests that Vitamin D (VitD) might be involved in different pathogenic mechanisms in COPD. Furthermore, the prevalence of VitD insufficiency is exceptionally high in COPD patients and increases with the severity. Based on the above, we first tested the relation between the top 10 single nucleotide polymorphisms from genome-wide association studies and the risk of COPD. Then, we investigated whether VitD levels might also have a role in COPD. A meta-analysis followed, combining our participants with previously published European and non-European populations (15,716 cases and 48,107 controls). (2) Methods: 631 Lebanese participants were recruited, of which ~28% were affected with COPD. Demographic and clinical data were collected, and DNA was genotyped using Kompetitive allele-specific PCR (KASPTM). Adjusted multiple logistic regression models were used. Bonferroni corrections were also applied. The statistical power was also assessed. (3) Results: Both rs6837671A>G in FAM13A and VitD levels were significantly associated with increased risk of COPD (OR = 1.75, p = 0.01, and OR = 3.10, p G in FAM13A and VitD levels, which increased COPD risk, was found (OR = 3.35 and p G in FAM13A is a trans-ethnic genetic variant that interact with VitD to affect COPD

rs6837671A&gt;G in FAM13A Is a Trans-Ethnic Genetic Variant Interacting with Vitamin D Levels to Affect Chronic Obstructive Pulmonary Disease

(1) Background and objectives: Chronic obstructive pulmonary disease (COPD) is a leading cause of mortality throughout the world. In addition to genetics, increasing evidence suggests that Vitamin D (VitD) might be involved in different pathogenic mechanisms in COPD. Furthermore, the prevalence of VitD insufficiency is exceptionally high in COPD patients and increases with the severity. Based on the above, we first tested the relation between the top 10 single nucleotide polymorphisms from genome-wide association studies and the risk of COPD. Then, we investigated whether VitD levels might also have a role in COPD. A meta-analysis followed, combining our participants with previously published European and non-European populations (15,716 cases and 48,107 controls). (2) Methods: 631 Lebanese participants were recruited, of which ~28% were affected with COPD. Demographic and clinical data were collected, and DNA was genotyped using Kompetitive allele-specific PCR (KASPTM). Adjusted multiple logistic regression models were used. Bonferroni corrections were also applied. The statistical power was also assessed. (3) Results: Both rs6837671A&gt;G in FAM13A and VitD levels were significantly associated with increased risk of COPD (OR = 1.75, p = 0.01, and OR = 3.10, p &lt; 0.001 respectively). An interaction between rs6837671A&gt;G in FAM13A and VitD levels, which increased COPD risk, was found (OR = 3.35 and p &lt; 0.001). The meta-analysis showed that rs6837671G increases COPD risk in populations from different origins; Europeans, Asians, and now in Middle-Eastern. (4) Conclusions: Our results suggest that rs6837671A&gt;G in FAM13A is a trans-ethnic genetic variant that interact with VitD to affect COPD

Binding and Agglutination of Streptococcus pneumoniae by Human Surfactant Protein D (SP-D) Vary between Strains, but SP-D Fails To Enhance Killing by Neutrophils

Recombinant human surfactant protein D (SP-D) expressed in Escherichia coli, consisting of the head and neck regions of the native molecule, bound to all strains of Streptococcus pneumoniae that were tested, but the extent of binding varied between strains of differing capsular serotypes. The recombinant protein expressed in the yeast Pichia pastoris did not bind. Full-length native SP-D aggregated pneumococci in a calcium-dependent manner that was inhibited by maltose acting as a competitive sugar. The ability of SP-D to modulate the uptake and killing of pneumococci by human neutrophils was also addressed. Neither recombinant truncated SP-D nor native full-length SP-D enhanced the killing of pneumococci by human neutrophils. Aggregation of pneumococci varied not only between strains of the same multilocus sequence type and different serotypes but also between strains of the same serotype. However, use of recombinant strains in which the serotype had been changed showed that the degree of aggregation was influenced by the capsular type. Indeed, a 19F serotype strain which was not aggregated by SP-D did exhibit aggregation when the original isogenic strain was capsule switched to capsular serotype 3. However, although our results show that SP-D is capable of aggregating most pneumococci, no correlation between the degree of aggregation and the capsule or multilocus sequence type of the pneumococcus was clearly apparent. Therefore, although the capsule serotype is not the only determinant of aggregation by SP-D, the data presented here indicate that it does have a role to play