The LymphotoxinβReceptor Is Essential for Upregulation of IFN-Induced Guanylate-Binding Proteins and Survival afterToxoplasma gondiiInfection

Abstract

Lymphotoxinβreceptor (LTβR) signaling plays an important role in efficient initiation of host responses to a variety of pathogens, encompassing viruses, bacteria, and protozoans via induction of the type I interferon response. The present study reveals that afterToxoplasma gondiiinfection, LTβR−/−mice show a substantially reduced survival rate when compared to wild-type mice. LTβR−/−mice exhibit an increased parasite load and a more pronounced organ pathology. Also, a delayed increase of serum IL-12p40 and a failure of the protective IFNγresponse in LTβR−/−mice were observed. Serum NO levels in LTβR−/−animals rose later and were markedly decreased compared to wild-type animals. At the transcriptional level, LTβR−/−animals exhibited a deregulated expression profile of several cytokines known to play a role in activation of innate immunity inT. gondiiinfection. Importantly, expression of the IFNγ-regulated murine guanylate-binding protein (mGBP) genes was virtually absent in the lungs of LTβR−/−mice. This demonstrates clearly that the LTβR is essential for the induction of a type II IFN-mediated immune response againstT. gondii. The pronounced inability to effectively upregulate host defense effector molecules such as GBPs explains the high mortality rates of LTβR−/−animals afterT. gondiiinfection.