Exogenous hFH fails to attenuate disease scores, inflammatory cytokine production, and vascular leakage in the liver.

<p>Mice infected with 1x10⁷ CFU of <i>S</i>. <i>pneumoniae</i> (TIGR4) and sham infected control mice were all treated with antibiotics at t = 17 h and indicated groups received an injection with hFH or PBS as control (n = 10). The disease score was monitored at t = 17, t = 21 and t = 26 hours after inoculation (A). The black bar represents uninfected mice, gray bar infected control mice and white bar hFH treated mice. Data points represent the median value with interquartile range. At t = 26 h, serum pro-inflammatory cytokines IL-6 and MIP-2 were measured by ELISA (B, C). Liver vascular leakage was measured by Evans Blue-albumin extravasation to quantify vascular permeability (D). Raw fluorescence intensities (RFI) were recorded and multiplied by the wet organ weight to estimate the concentration of Evans Blue in the organ. Each point depicted in graphs B,C and D indicates one mouse. One infected mice of the PBS treated group reached the humane endpoint at t = 22 h and was excluded from the graphs. Furthermore one (IL-6 Fig 1B) respectively two data points (MIP-2 Fig 1C) are missing, as insufficient serum was available. In addition, one data point is missing in the vascular leakage graph, because of a technical failure during injection of EB in one mouse. Cytokine values were analyzed after logarithmic transformation; the horizontal line represents the median. Dash line indicates lower limit of detection. Comparison between groups were performed by using the non-parametric Mann-Whitney test with Bonferroni correction * p < 0.05 was considered significant. ** p< 0.01, *** p<0.001, ns = not significant.</p

Streptococcus pneumoniae PspC-subgroup prevalence in invasive disease and difference in contribution to complement evasion

Pneumococcal capsular serotype is an important determinant of complement resistance and invasive disease potential, but other virulence factors have also been found to contribute. Pneumococcal surface protein C (PspC), a highly variable virulence protein that binds complement factor H to evade C3 opsonization, is divided into two subgroups: choline-bound subgroup I and LPxTG-anchored subgroup II. The prevalence of different PspC subgroups in invasive pneumococcal disease (IPD) and functional differences in complement evasion are unknown. Prevalence of PspC subgroups in IPD isolates was determined in a collection of 349 sequenced strains of S. pneumoniae isolated from adult patients. PspC deletion and isogenic pspC-switch mutants were constructed to study differences in factor H binding and complement evasion in relation to capsule thickness. Subgroup I pspC was far more prevalent in IPD isolates than subgroup II pspC. The presence of capsule was associated with a greater ability of bound factor H to reduce complement opsonization. Pneumococcal subgroup I PspC bound significantly more factor H and showed more effective complement evasion compared to subgroup II PspC in isogenic encapsulated pneumococci. We conclude that variation in PspC subgroup, independent of capsule serotypes, affects pneumococcal factor H binding and its ability to evade complement deposition