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Role of complement in host defense against pneumococcal otitis media.

ABSTRACT: Strategies to limit complement deposition on Streptococcus pneumoniae are established as virulence features for invasive disease, but their role in respiratory tract infection requires further analysis. We evaluated complement C3 protein deposition on discordant S. pneumoniae isolates of the same serotype (6A) and their capacity to cause nasopharyngeal (NP) colonization and experimental otitis media (EOM) in an animal model. We compared C3 binding to five 6A isolates from asymptomatic NP carriers with five 6A strains that caused invasive disease, and we observed less C3 ( approximately 10-fold less fluorescence) binding to invasive isolates. We selected two high-level C3-binding carriage and two low-level C3-binding invasive 6A isolates for further study. In the EOM model, 11/12 (92%) ears challenged with a low-level C3-binding 6A strain became infected. Only 2/8 (25%) ears challenged with the discordant high-level C3-binding 6A isolate developed disease (P = 0.005). Results with the second discordant 6A isolate pair were comparable. Cobra venom factor (CoVF) treatment, which depletes C3 and consumes complement, restored virulence of the high-level C3-binding strain; 8/8 (100%) ears in CoVF-treated animals developed EOM compared to only 25% of ears in naïve animals (P = 0.007). These studies demonstrate the critical role for complement evasion in pneumococcal EOM. Colonization with carriage isolates that bound high levels of C3 caused EOM in fewer animals compared to low-level C3-binding invasive strains. Thus, limiting C3 deposition on the surface of S. pneumoniae correlates with increased incidence of EOM following NP colonization and barotrauma in the animal model.

SUBMITTER: Sabharwal V

PROVIDER: S-EPMC2643640 | biostudies-literature | 2009 Mar

REPOSITORIES: biostudies-literature

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Role of complement in host defense against pneumococcal otitis media.

Sabharwal Vishakha V Ram Sanjay S Figueira Marisol M Park In Ho IH Pelton Stephen I SI

Infection and immunity 20090112 3

Strategies to limit complement deposition on Streptococcus pneumoniae are established as virulence features for invasive disease, but their role in respiratory tract infection requires further analysis. We evaluated complement C3 protein deposition on discordant S. pneumoniae isolates of the same serotype (6A) and their capacity to cause nasopharyngeal (NP) colonization and experimental otitis media (EOM) in an animal model. We compared C3 binding to five 6A isolates from asymptomatic NP carrier ...[more]

PMID: 19139190

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Project description:Influenza A virus (IAV) predisposes individuals to secondary infections with the bacterium Streptococcus pneumoniae (the pneumococcus). Infections may manifest as pneumonia, sepsis, meningitis or otitis media (OM). It remains controversial as to whether secondary pneumococcal disease is due to the induction of an aberrant immune response or IAV induced immunosuppression. Moreover, as the majority of studies have been performed in the context of pneumococcal pneumonia, it remains unclear how far these findings can be extrapolated to other pneumococcal disease phenotypes. Here, we demonstrate that the viral hemagglutinin (HA) mediates bacterial OM by inducing a pro-inflammatory response in the middle ear cavity in a replication-dependent manner. Importantly, our findings show that it is the inflammatory response that mediates pneumococcal replication; not viral suppression of the immune system or epithelial damage. This study provide the first evidence that HA induced inflammation drives pneumococcal replication in the middle ear cavity, which has important consequences to the treatment of pneumococcal OM. Five-day old C57BL/6 mice were colonised intranasally (i.n.) with 2M-CM-^W103 colony forming units (CFU) of S. pneumoniae EF3030Lux in 3 M-BM-5Ls of PBS. Alternatively, mice were mock-infected with an equivalent volume of phosphate buffered saline (PBS). At 14-days of age, infant mice were infected i.n. with 20 plaque forming units (PFU) (PR8/34, Cambridge/34 and WSN/33) or 102.5 PFU (all other virus strains) of egg-grown IAV in 3 M-BM-5Ls of PBS. Viral doses were selected to ensure a reproducible infection with minimum morbidity and no mortality. Six days post-IAV infection, mice were euthanised and organs were collected for analysis. Six independent biological replicates (where both ears from one mouse were pooled to create one sample) were used for each condition and analyzed using the NimbleGen platform (12M-CM-^W135K Mouse Gene Expression Arrays, Roche Nimblegen, USA). Indirect labeling, hybridization and washing was performed according to the manufacturerM-bM-^@M-^Ys instructions. Array images were acquired with a NimbleGen MS200 scanner, and images were processed with NimbleScan software using the RMA algorithm. Data was processed using Arraystar (DNASTAR, USA) with default settings as described in the manual. Differential expression tests were performed with a moderated T-test implemented in Arraystar, followed by FDR correction of the P values (Q-values) according to the method of Storey and Tibshirani

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Role of complement in host defense against pneumococcal otitis media.

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Role of complement in host defense against pneumococcal otitis media.

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