Characterizing the Duck NLRP3 Inflammasome

Abstract

Ducks, as the natural reservoir host of influenza A virus (IAV), do not exhibit the same detrimental symptoms when infected by IAV as other susceptible host species, such as chickens and humans. A dysregulated NLRP3 inflammasome response activated by IAV has been linked to severe host outcomes, potentially leading to death. It is not known whether dampening of the NLRP3 inflammasome is a mechanism by which ducks avoid damage due to IAV. Here, I have cloned the duck NLRP3 inflammasome components, assessed their function, and examined their expression in duck tissues following an IAV infection. I cloned and expressed recombinant proteins of the duck NLRP3 inflammasome to examine their interactions in vitro using confocal microscopy and immunoprecipitation. I created expression constructs for NLRP3, Caspase-1, and Interleukin-1beta. I was unable to identify ASC, the adaptor molecule apoptosis-associated speck-like protein containing a CARD, one component of the inflammasome, suggesting that the NLRP3 inflammasome may be incomplete in ducks. To activate the duck NLRP3 inflammasome and examine whether the proteins interacted, I used polyinosinic: polycytidylic acid (poly I:C) and nigericin, a known NLRP3 inflammasome agonist. qPCR and RNA-seq were used to investigate the priming step of the duck NLRP3 inflammasome and how it differed from the priming responses of other species. I found little evidence that the TLR3 transcriptional priming pathway that is activated by poly I:C triggered the downstream NLRP3 inflammasome. This suggests that a lower level of activity is exhibited by the NLRP3 inflammasome during an IAV infection in ducks. This may be a mechanism by which the natural reservoir host of IAV could avoid detrimental damage induced by hyper-inflammation and cytokine storms.