Platelet-stored antibodies potently diminish viral infection in vitro and in vivo

• Main Authors: Schrottmaier, Waltraud C., Salzmann, M., Badrnya, S., Morava, S., Luik, A-L, Kral-Pointner, J. B., Mussbacher, M., Karlsson, M., Forsell, Mattias, Assinger, A.
• Format: Conference Proceeding
• Language: English
• Subjects: Medicin och hälsovetenskap
• ISSN: 1748-1716; 1748-1708
• DOI: 10.1111/apha.13366

Besides their primary role in haemostasis, platelets are actively involved in immune responses as they respond to various inflammatory stimuli, including microbial infection. Further, platelets contain intracellular IgG, but their physiologic function remains unknown. Thus, we aimed to elucidate the function of platelet-derived IgGs and their effect on viral infections. Human and murine platelets contained IgG which were released upon shear stress. However, IgG loss did not correlate with P-Selectin exposure or CXCL4 release and α-granule deficient (Nbeal2-/-) platelets failed to show reduced IgG content and release, indicating an extragranular IgG storage site within platelets. While platelet IgG could derive from megakaryocytes that have taken up IgG from the bone marrow microenvironment, naïve platelets also took up IgG directly from plasma in vitro and in vivo. Murine platelets from anti-IAV IgG seropositive mice reduced IAV infection in vitro and in vivo more efficiently than plasma containing comparable IgG levels. Further, human platelets from anti-CMV IgG seropositive but not seronegative donors also potently neutralized in vitro CMV-infection of HUVEC under microvascular shear stress. Our data indicate that IgG storage in platelets may not be restricted to α-granules. Further, our results show that platelets have the potential to mediate potent IgG-mediated antiviral effects both in vitro and in vivo directly at foci of infection. This indicates that platelet-derived IgG may represent a yet unexplored mechanism for focused serological immunity.