Scientific Publications by FDA Staff

J Virol 2015 Aug 1;89(15):7567-83

Different temporal effects of Ebola virus VP35 and VP24 proteins on the global gene expression in human dendritic cells.

Ilinykh PA, Lubaki NM, Widen SG, Renn LA, Theisen TC, Rabin RL, Wood TG, Bukreyev A

Ebola virus (EBOV) causes a severe hemorrhagic fever with a deficient immune response, lymphopenia and lymphocyte apoptosis. Dendritic cells (DC), which trigger the adaptive response, do not mature despite EBOV infection. We recently demonstrated that DC maturation is unblocked by disabling the innate response antagonizing domains (IRADs) in EBOV VP35 and VP24 by mutations R312A and K142A, respectively. Here we analyzed the effects of VP35 and VP24 with the IRADs disabled on global gene expression in human DC. Human monocyte-derived DC were infected by wild-type EBOV (wt EBOV), or EBOVs carrying the mutation in VP35 (EBOV/VP35m), VP24 (EBOV/VP24m), or both (EBOV/VP35m/VP24m). Global gene expression at 8 and 24 hrs was analyzed by deep sequencing, and the expression of interferon (IFN) subtypes up to 5 days post-infection was analyzed by quantitative RT-PCR (qRT-PCR). Wt EBOV induced a weak global gene expression response, including markers of DC maturation, cytokines, chemokines, chemokine receptors, and multiple IFN. The VP35 mutation unblocked the expression resulting in a dramatic increase in expression of these transcripts at 8 and 24 hrs. Surprisingly, DC infected with EBOV/VP24m expressed lower levels of many of these transcripts at 8 hrs after infection, compared to wt EBOV. In contrast, at 24 hrs, expression of the transcripts increased in DC infected with any of the three mutants, as compared to wt EBOV. Moreover, sets of genes affected by the two mutations only partially overlapped. Pathway analysis demonstrated that the VP35 mutation unblocked pathways involved in antigen processing and presentation, and IFN signaling. These data suggest EBOV IRADs have profound effects on the host adaptive immune response through massive transcriptional downregulation of DC. IMPORTANCE: The study shows that infection of DC with EBOV, but not its mutant forms with VP35 and/or VP24 IRADs disabled, causes the global block in expression of host genes. The temporal effects of mutations disrupting the two IRADs differ, and the lists of affected genes only partially overlap such that VP35 and VP24 IRADs each have profound effects on antigen presentation by exposed DC. The global modulation of DC gene expression and the resulting lack of their maturation represent a major mechanism by which EBOV disables the T cell response, and suggests that these suppressive pathways are a therapeutic target that may unleash the T cell responses during EBOV infection.