Plasma-derived extracellular vesicles from Plasmodium vivax patients signal spleen fibroblasts via NF-kB facilitating parasite cytoadherence

Abstract

Plasmodium vivax is the most widely distributed human malaria parasite. Previous studies have shown that circulating microparticles during P. vivax acute attacks are indirectly associated with severity. Extracellular vesicles (EVs) are therefore major components of circulating plasma holding insights into pathological processes. Here, we demonstrate that plasma-derived EVs from Plasmodium vivax patients (PvEVs) are preferentially uptaken by human spleen fibroblasts (hSFs) as compared to the uptake of EVs from healthy individuals. Moreover, this uptake induces specific upregulation of ICAM-1 associated with the translocation of NF-kB to the nucleus. After this uptake, P. vivax-infected reticulocytes obtained from patients show specific adhesion properties to hSFs, reversed by inhibiting NF-kB translocation to the nucleus. Together, these data provide physiological EV-based insights into the mechanisms of human malaria pathology and support the existence of P. vivax-adherent parasite subpopulations in the microvasculature of the human spleen.

Multiparameter Flow Cytometry Analysis of the Human Spleen Applied to Studies of Plasma-Derived EVs From Plasmodium vivax Patients

“…CD71 is the major component of reticulocyte-derived exosomes ( Harding Stahl, 1983 ; Pan et al, 1985 ; Díaz-Varela et al, 2018 ) and it is a reticulocyte-specific receptor for P. vivax ( Gruszczyk et al, 2018 ). Importantly we have recently shown by mass spectrometry-based proteomics and molecular profiling that CD71 is a component of circulating EVs from P. vivax patients ( Toda et al, 2020 ). Therefore, we used it as a surrogate molecular marker of EVs derived from P. vivax -infected reticulocytes for selection of SEC fractions from individual patients ( Supplementary Data Sheet 4A ) and healthy donors ( Supplementary Data Sheet 4B ) to compose a pool of vesicles for spleen cells interaction experiments.…”

“…However, the increased interaction observed in DCs when whole splenocytes were in contact with PKH-labeled Pv EVs can reflect its specific phagocytosis. Indeed, we have previously demonstrated that human reticulocyte-derived exosomes are specifically taken up by DCs in a Siglec-1-dependent manner ( Díaz-Varela et al, 2018 ) and circulating EVs in patients with acute P. vivax infection contain parasite proteins ( Toda et al, 2020 ). In the absence of supportive evidence, this remains to be determined.…”

“…One potential mechanism for the Pv EVs increased interaction with splenic phagocytic cells (monocytes and B cells) could be the recognition by Fc receptors of immune complexes formed by host antibodies and parasite antigens in EVs. Indeed, VIR proteins are associated to Pv EVs ( Toda et al, 2020 ) and anti-VIR IgGs have been detected in the serum of P. vivax patients ( Oliveira et al, 2006 ). Although there are no published reports that have demonstrated the formation of immune complexes with EVs from malaria patients, EV-derived circulating immune complexes have been described in chronic Chagas disease ( Díaz Lozano et al, 2017 ), reinforcing this hypothetical interaction mechanism.…”

“…The local ethical committee of FMT-HVD approved these studies. Clinical data of patients participating of this study has been recently published ( Toda et al, 2020 ). Plasma from healthy donors (HD) was obtained at the Hospital Germans Trias i Pujol (Badalona, Barcelona, Spain) after expressed consent from the donors.…”

“…Thus, the physiological role of EVs in human malaria infections remains to be determined. Remarkably, using EVs obtained from circulating blood of P. vivax patients, we recently showed that they contain parasite proteins and are taken up by human spleen fibroblasts inducing expression of ICAM-1 via NF-kB and facilitating cytoadherence of P. vivax -infected reticulocytes obtained from patients ( Toda et al, 2020 ).…”