Parapoxvirus Interleukin-10 Homologues Vary in Their Receptor Binding, Anti-Inflammatory, and Stimulatory Activities.

Homologues of interleukin (IL)-10, a pleiotropic immunomodulatory cytokine, have been identified in the genus. The first identified, (ORFV) IL-10, greatly enhanced infection of its host, exhibiting immune modulatory effects equivalent to human IL-10. IL-10-like genes were then identified in (BPSV), (PCPV), (RDPV) and (GSPV). This study aimed to produce and characterise recombinant parapoxvirus IL-10s, then quantitatively compare their receptor binding and immunomodulatory activities. Recombinant IL-10s were expressed, purified, then characterised using bioinformatic, biochemical and enzymatic analyses. Anti-inflammatory effects were assessed in lipoteichoic acid-activated THP-1 monocytes, and stimulatory effects in MC/9 mast cells. IL-10 receptor (IL-10R)1 binding was detected in a competitive displacement assay. BPSV IL-10 inhibited production of monocyte chemoattractant protein (MCP)-1, IL-8 and IL-1β, induced mast cell proliferation, and bound IL-10R1 similarly to ORFV IL-10. PCPV IL-10 showed reduced MCP-1 inhibition, mast cell proliferation, and IL-10R1 binding. RDPV IL-10 displayed reduced inhibition of IL-8 and MCP-1 production. GSPV IL-10 showed limited inhibition of IL-1β production and stimulation of mast cell proliferation. These findings provide valuable insight into IL-10 receptor interactions, and suggest that the parapoxvirus IL-10s play similar pathogenic roles during infection of their hosts.