Transcriptome Analysis of Human Peripheral Blood Mononuclear Cells Exposed to Lassa Virus and to the Attenuated Mopeia/Lassa Reassortant 29 (ML29), a Vaccine Candidate

Zapata, Juan Carlos; Carrion, Ricardo; Patterson, Jean L.; Crasta, Oswald; Zhang, Yan; Mani, Sachin; Jett, Marti; Poonia, Bhawna; Djavani, Mahmoud; White, David M.; Lukashevich, Igor S.; Salvato, Maria S.

Coagulation defects associated with LF disease could potentially be affected by LASV-upregulation of six coagulation-related genes, the most notable being thrombomodulin (THBD). THBD is predominantly synthesized by vascular endothelial cells as a 60 kDa type I trans-membrane protein that inhibits thrombotic, inflammatory and redox related responses [90] . THBD forms a 1:1 molar complex with thrombin and significantly enhances the rate of thrombin inactivation by ATIII while accelerating activation of protein C (aPC). We observed levels of secreted THBD in dendritic cell (DC) culture medium that correlated with our transcriptome data. DC exposure to LASV up-regulated secretion of THBD, whereas exposure to ML29 had the opposite effect. Notably, LPS treatment of LASV-exposed cells resulted in lowering THBD as well. In the presence of thrombin, THBD generates aPC, which inhibits pro-coagulant and pro-inflammatory responses including: fibrinogen cleavage, factor V activation, platelet activation or local cytokine-induced chemotaxis for monocytes, neutrophils and up-regulation of leukocyte adhesion molecules [91] , [92] , [93] . It has been shown that THBD mRNA half-life is shortened by treatment of cells with IFN-c [94] . This observation in addition to the LASV-increased THBD expression seen here, and the absence of IFN responses seen in vitro, are in agreement with LF findings where there is no clear inflammatory response and no cellular infiltrates, in conjunction with the high viral loads seen in the presence of hemorrhagic symptoms. The absence of THBD up-regulation in the LCMV-WE infected model for LF may be a key failing of the model (see details in Table S2 ).