Rewiring PBMC responses to prevent CHIKV infection-specific monocyte subset redistribution and cytokine responses

Infection with the mosquito-borne Chikungunya virus (CHIKV) causes acute or chronic arthritis in humans. Inflammatory responses mediated by monocytes, the primary target cells of CHIKV infection in the blood, are considered to play an important role in CHIKV pathogenesis. A recent study revealed that the acute phase of CHIKV infection is characterized by a monocyte-driven response, with an expansion of the intermediate monocyte (IM) subset. In this study, we adopted a previously established in vitro model of CHIKV infection in peripheral blood mononuclear cells, to elucidate the mechanism and relevance of IM expansion in CHIKV replication and associated inflammatory responses. Our data show that infectious but not replication-incompetent CHIKV increases the frequency of IM and to a lesser extent, non-classical (NM) monocytes while reducing the number of classical monocytes (CM). The increase of IM or NM frequency coincided with the activation of inflammatory response and occurred in the absence of lymphocytes implying that monocyte-derived cues are sufficient to drive this effect. Importantly, priming of monocytes with LPS prevented expansion of IM and NM but had no effect on viral replication. It did however alter CHIKV-induced cytokine signature. Taken together, our data delineate the role of IM in CHIKV infection-specific innate immune responses and provide insight for the development of therapeutic strategies that may focus on rewiring monocyte immune responses to prevent CHIKV-mediated arthralgia and arthritis.