Abstract Number: PB1637
Meeting: ISTH 2020 Congress
Background: Community-acquired pneumonia is one of the most common acute infections and a leading cause of morbidity and mortality worldwide and mostly caused by Streptococcus pneumoniae. Its toxin pneumolysin renders platelets non-functional, preventing them from covering endothelial cell lesions leading to extravasation of fluid and respiratory impairment.
Aims: To investigate whether antibodies protect platelets from damage by pneumococcal pneumolysin.
Methods: Platelets were isolated from healthy donors (n≥3) and incubated with 300ng/mL pneumolysin in the absence or presence of a polyclonal rabbit-anti-pneumolysin-antibody, a monoclonal mouse-anti-pneumolysin-antibody (abcam) and human derived pharmaceutical i.v.IgG. We assessed the impact of pneumolysin in the presence or absence of antibodies on platelet viability using RealTime-Glo cell viability kit and on platelet activation by measuring cytosolic Ca2+ and CD62P expression. Subsequent TRAP6-stimulation was performed to assess remaining platelet functionality. Adhesion and pore-sealing capacity was tested in a Boyden-chamber-assay and thrombus formation on collagen-surfaces was measured in a flow chamber.
Results: Both antibodies and i.v.IgG protect platelets from pneumolysin-induced cell death (Fig.1A). They also prevented increase of free cytosolic Ca2+ and CD62P-expression induced by pneumolysin (Fig.1B). In presence of pneumolysin and antibodies, platelets remained sensitive to subsequent TRAP-6 stimulation (Fig.1B). Platelets can adhere to Boyden-chamber membranes and seal pores, which is severely impaired in the presence of pneumolysin. Addition of i.v.IgG preserved the pore-sealing capacity of platelets (Fig.2A) and thrombus formation in whole blood (Fig.2B).
Conclusions: Specific antibodies as well as i.v.IgG can protect platelets against pneumolysin-induced perforation and preserve platelet functionality. This indicates that antibody treatment might be able to prevent acute respiratory distress syndrome in pneumococcal infections by preserving platelet function and prevention of capillary leakage.
This work was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Project number 374031971 – TRR 240.
To cite this abstract in AMA style:Handtke S, Jahn K, Palankar R, Kohler TP, Hammerschmidt S, Greinacher A. Antibodies Protect Platelets against Streptococcus Pneumoniae Toxin Pneumolysin [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/antibodies-protect-platelets-against-streptococcus-pneumoniae-toxin-pneumolysin/. Accessed January 23, 2022.
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