Investigating the role of interleukin 1 alpha during Listeria monocytogenes infection




Kim, Andrew J.


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Listeria monocytogenes (LM) causes listeriosis, one of the leading causes of death by foodborne illness in the United States. Although generally self-limiting in immunocompetent people, listeriosis can cause meningitis or sepsis in immunocompromised people and spontaneous abortion in pregnant women. Our interest in interleukin 1 alpha (IL-1α), a cytokine historically associated with inflammation and alarmin activity, stemmed from a previous study in our lab where we observed that immune cells isolated from LM infected mice produced IL-1α. Currently, the role of IL-1α during infection is largely unexplored. Elucidating the role of IL-1α during LM infection will determine if IL-1α can potentially be used as a therapeutic agent and will expand our understanding of this cytokine. Enzyme-linked immunosorbent assay (ELISA) was used to measure IL-1α concentration produced by LM infected RAW 264.7 macrophages and LM infected Hepa 1-6 hepatocytes. Dose response and kinetic experiments were performed to optimize culture conditions. Cell viability of macrophage cultures, hepatocyte cultures, and cocultures of macrophages and hepatocytes was measured using trypan blue to determine if the culture conditions severely impacted cell viability. LM burden of infected macrophage cultures, infected hepatocyte cultures, and infected cocultures of macrophages and hepatocytes were quantified using colony forming unit counting method and compared with control. Infected cultures were treated with recombinant (r-) IL-1α, r-interferon gamma (r-IFN-ℽ), r-interleukin 1 beta (r-IL-1β), or anti-IL-1α. IL-1α production was significantly increased in LM infected RAW 264.7 macrophage cultures compared to uninfected control. The concentration of IL-1α produced by infected macrophage cultures and infected cocultures increased, plateaued, and then decreased at 6, 12, 18, and 24 hours post LM infection. IL-1α was not detected in infected hepatocyte cultures. LM burden of infected macrophage cultures, infected hepatocyte cultures and infected cocultures treated with r-IL-1α was reduced compared to control. Our data suggest that macrophages contribute significantly to IL-1α production during LM infection and r-IL-1α may contribute to LM resistance.