Pro-inflammatory cytokine production by activated monocytes and macrophages in response to cowpox virus infection in cynomologus macaques (VIR9P.1144)

Monocytes and macrophages play pivotal roles in host defense against microbial and viral pathogens through production of inflammatory and cytotoxic mediators, phagocytic activity, and activation of T cells. In previous studies, we reported significant expansion of CD14+ cells following intravenous cowpox virus Brighton Red (CPXV) infection of cynomologus macaques accompanied by increased levels of pro-inflammatory cytokines in plasma. Here, monocytes were assayed for production of pro-inflammatory cytokines and chemotactic factors during CPXV disease progression at days 3, 4, 6, and 7 post-infection in a serial sacrifice study of cynomologus macaques intravenously inoculated with 5 x 10 6 PFU CPXV. We measured monocyte absolute cell numbers in blood, frequencies of monocytes and macrophages in blood, and compared normal and infected monocytes through production of pro-inflammatory cytokines IL-6, IL-8, MCP-1, and IFNγ. Our results demonstrated an early increase in frequency and absolute numbers of total monocytes in blood with a rapid decline in moribund animals. Cytokine and chemokine analysis demonstrated an increase in IL-8 and MCP-1 expression over the course of disease but little IFNγ or IL-6. Pox antigen positive monocytes also expressed IL-8, but were not observed to express MCP-1. This suggests pox infection may alter cytokine production profiles of monocytes and may play a role in disease progression.