Transcriptome Analysis of Circulating Immune Cell Subsets Highlight the Role of Monocytes in Zaire Ebola Virus Makona Pathogenesis

Abstract

Existing models of Ebola virus disease (EVD) suggest antigen-presenting cells are initial targets of Zaire ebolavirus (ZEBOV). In vitro studies have shown that ZEBOV infection of monocytes and macrophages results in the production of inflammatory mediators, which may cause lymphocyte apoptosis. However, these findings have not been corroborated by in vivo studies. In this study, we report the first longitudinal analysis of transcriptional changes in purified monocytes, T-cells, and B-cells isolated from cynomolgus macaques following infection with ZEBOV-Makona. Our data reveal monocytes as one of the major immune cell subsets that supports ZEBOV replication in vivo. In addition, we report a marked increase in the transcription of genes involved in inflammation, coagulation, and vascular disease within monocytes, suggesting that monocytes contribute to EVD manifestations. Further, genes important for antigen presentation and regulation of immunity were downregulated, potentially subverting development of adaptive immunity. In contrast, lymphocytes, which do not support ZEBOV replication, showed transcriptional changes limited to a small number of interferon-stimulated genes (ISGs) and a failure to upregulate genes associated with an antiviral effector immune response. Collectively, these data suggest that ZEBOV-infected monocytes play a significant role in ZEBOV-Makona pathogenesis and strategies to suppress virus replication or modify innate responses to infection in these cells should be a priority for therapeutic intervention.

The role of mononuclear phagocytes in Ebola virus infection

“…These data suggest that these cells are either recruited to other locations or depleted due to virus‐induced cell killing. Additional studies that investigated the role of PBMCs in EBOV infection of NHPs demonstrated that monocytes purified from PBMCs contained the preponderance of EBOV transcripts that are found within blood leukocytes and this study suggests that infected blood monocytes may contribute significantly to overall virus load . Consistent with the presence of significant EBOV load in blood monocytes, host genes associated with type I IFN signaling and inflammation are up‐regulated in these cells.…”

“…Consistent with these observations, the ability of EBOV to infect and replicate in Mϕs and DCs has also been confirmed in numerous tissue culture models . Surprisingly, the role of circulating monocytes during filovirus infection is poorly studied and only recently examined . However, these studies suggest that this mononuclear phagocytic population may also play an important role during infection.…”

“…Other studies support a role for circulating PBMCs in active EBOV infection . A recent longitudinal study in a patient with severe EVD demonstrated that virus load in PBMCs correlates well with serum RNA levels, suggesting that virus replication in PBMCs contributes significantly to overall virus load.…”

“…[22][23][24][25] Surprisingly, the role of circulating monocytes during filovirus infection is poorly studied and only recently examined. [26][27][28] However, these studies suggest that this mononuclear phagocytic population may also play an important role during infection.…”

“…Although it is clear that tissue M s and DCs are permissive to EBOV in vivo and in vitro (reviewed in Martinez et al 29 ), many questions remain about interactions of filoviruses with these cells. Further, with the appreciation that bone marrow derived monocytes may also support EBOV infection, 26,27,30 traffic into tissues in response to pathogens, adapt to their new environment, and then disappear following resolution of infection, 31 the role of monocytes in filovirus infection and pathogenesis needs to be included in this discussion. It should be noted that in reviews, M s and DCs are frequently grouped together as early and critically important cells when discussed in the context of filovirus infection, yet the impact of virus infection on the functionality of these cell populations differs.…”