Mammarenaviruses establish chronic infections in their natural rodent reservoirs across the world, and
mammarenavirus zoonoses can pose important public health problems in their endemic regions.
Mammarenaviruses can subvert the innate immune responses in infected individuals, thus compromising the
development of an effective antiviral adaptive immune response, which facilitates unrestricted virus
multiplication and associated pathological manifestations and disease. The mammarenavirus lymphocytic
choriomeningitis virus (LCMV) provides us with a highly tractable experimental system to elucidate virus-host
immune system interactions contributing to these events. We have documented that LCMV nucleoprotein (NP),
as well as NPs from other mammarenaviruses, inhibits production of interferon ß (IFNß), a key player in the
host innate immune defense against viral infections. The type I IFN (IFN-I) counteracting activity of
mammarenavirus NP correlated with the NP's ability to inhibit activation of IRF3 and NF-kB. Arenavirus NP's
anti-IFN-I activity was mapped to the C-terminal region of NP that contains a functional 3'-5' exonuclease
(ExoN) domain and an overlapping IKKe-interacting domain. The experiments in this application are designed
to elucidate the following issues: 1) whether arenavirus NP's ability to inhibit induction of IFNß production
requires its binding to IKKe or its ExoN activity, or both; and, 2) the mechanisms by which mutations affecting
NP-IKKe interaction or NP's ExoN activity affect virus fitness and whether this result in the loss of LCMV's
ability to persist in its natural host, the mouse. To this end, we propose to complete the following specific aims:
1. Determine whether NP-IKKe interaction is required for NP-mediated inhibition of IFNß induction in LCMV-
infected cells: We will identify residues within arenavirus NP that are required for NP-IKKe interaction, and
functionally characterize NP mutants impaired in their ability to associate with NP-IKKe, including their ExoN
activity and ability to counteract induction of IFNß.
2. Evaluate the contribution of the ExoN activity of arenavirus NP to inhibition of IFNß induction and virus
fitness in the absence of a functional IFN-I system: We will conduct mutation-function studies to determine
whether the ExoN activity of NP is strictly required for its anti-IFNß activity, and to promote normal LCMV
multiplication in the absence of a host cell functional IFN-I system. These studies will examine the role of the
ExoN activity of NP viral transcription and LCMV replication fidelity.
3. Roles of NP's anti-IFN-I and ExoN activities in virulence and the establishment of the natural carrier state of
LCMV in mice: We will use reverse genetics to generate rLCMVs carrying the different types of NP mutations.
These rLCMVs will be first confirmed to exhibit their predicted phenotypes in cultured cells, and then will be
examined for their in vivo phenotypic features in the context of LCMV infection of its natural host, the mouse.