The Role of Apoptosis in the Biology of New World Arenaviruses

• Applicant: Privatdozentin Allison Groseth, Ph.D.
• Subject Area: Virology
• Term: since 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 324484564

Arenaviruses frequently cause severe disease with hemorrhagic and/or neurological manifestations. During infection they use a number of mechanisms to regulate host cell responses such as innate immune induction and apoptosis (i.e. caspase-mediated programmed cell death). However, they do so differently, and while some arenaviruses evade apoptosis entirely, the highly virulent New World arenavirus Junín virus (JUNV) actively suppresses caspase activity, and thus apoptosis, by sacrificing a portion of its nucleoprotein (NP) pool as a substrate for caspase cleavage. In contrast, the closely related but apathogenic Tacaribe virus (TCRV) does not do this, and strongly induces apoptosis, suggesting that apoptosis evasion may act as a virulence determinant. However, while the regulation of apoptosis is increasingly being appreciated as important in the cellular response to infection, little is known about how infection is being sensed and how these signals are propagated to induce caspase activation and ultimately cell death.The first funding phase of this project sought to clarify the host factors responsible for regulating apoptosis induction in response to TCRV infection. As a result we identified activation of the transcription factor p53 and the associated upregulation of the pro-apoptotic proteins Puma and Noxa as critical pro-apoptotic stimuli. At the same time, inactivation of the pro-apoptotic factor BAD appears to play a role in delaying cell death. Intriguingly, both the activation of p53 and the inactivation of BAD are controlled by their phosphorylation status. A number of host cell kinases, and particularly mitogen activated protein kinases (MAPKs), have been associated with phosphorylation of p53 and BAD in other contexts. Thus, the second phase of this project will focus on clarifying the role of various MAPKs in activation of these factors during TCRV infection. Further, it will examine a possible connection between activation of MAPK pathways for apoptosis and cytokine induction in response to arenavirus infection – a trait that we have also shown differs between pathogenic and apathogenic arenaviruses. Finally, we will examine the role that caspase cleavage of JUNV NP plays in regulation of these processes using NP cleavage-deficient recombinant JUNVs in order to obtain a definitive understanding of the relevance of apoptosis evasion observed during JUNV infection.This work will provide a better understanding of arenavirus interactions with host cell pathways, and help us to understand the relationship between apoptosis regulation and pathogenesis at a mechanistic level. As such, it has the potential to inform the development of new treatment strategies by identifying crucial pathways and interaction partners involved in host cell responses to arenavirus infection, and aid in performing risk assessments for newly identified/emerging arenavirus species based on their ability to modulate various aspects of the host cell response.

• DFG Programme: Research Grants