Little is known about the temporal patterns of infection and transmission of Lassa virus (LASV) within its natural reservoir (Mastomys natalensis). Here we characterize infection dynamics and transmissibility of a LASV isolate (Soromba-R) in adult lab-reared M. natalensis originating from Mali. The lab-reared M. natalenesis proved to be highly susceptible to LASV isolates from geographically distinct regions of West Africa via multiple routes of exposure, with 50% infectious doses of < 1 TCID50. Post-inoculation, LASV Soromba-R established a systemic infection with no signs of clinical disease. Viral RNA was detected in all nine tissues examined with peak concentrations detected between days 7 and 14 post-infection within most organs. There was an overall trend towards clearance of virus within 40 days of infection in most organs. The exception is lung specimens, which retained positivity throughout the course of the 85-day study. Direct (contact) and indirect (fomite) transmission experiments demonstrated 40% of experimentally infected M. natalensis were capable of transmitting LASV to naïve animals, with peak transmissibility occurring between 28 and 42 days post-inoculation. No differences in patterns of infection or transmission were noted between male and female experimentally infected rodents. Adult lab-reared M. natalensis are highly susceptible to genetically distinct LASV strains developing a temporary asymptomatic infection associated with virus shedding resulting in contact and fomite transmission within a cohort.

The RIG-I like receptor pathway, which signals through the mitochondrial anti-viral signaling (MAVS) protein, initiates the type I interferon (IFN) response to RNA viruses such as vesicular stomatitis virus (VSV) and Ebola Virus (EBOV). To investigate the mechanism of MAVS-mediated control of VSV and EBOV infections in vivo, we utilized single cell RNA sequencing and multiplex immunohistochemistry (mIHC) in C57Bl/6J and MAVS−/− animals to understand the cellular response spatially and transcriptomically in the draining lymph nodes (dLN). Identification of virally infected cells through scRNA-Seq allowed contrast of infected cells and bystander cells. Viral quantification of EBOV and VSV samples showed an increased viral load in MAVS−/− conditions and distinct patterns of dissemination through the LN. The relationship between viral load and IFN signaling revealed a negative correlation in EBOV infected cells with no relationship in VSV infected cells highlighting the importance of viral inhibition of the IFN response in EBOV infections. To assess these patterns spatially, mIHC antibody panels have been implemented on control and experimental tissue. An in-house algorithm for cell segmentation called RAPID was applied to a controlled experiment and revealed extensive batch effects from the staining process. Current work to perform batch normalization is being carried out to better assess changes in protein marker expression. Combining information gained from the sequencing analysis with the observed spatial organization through mIHC, we aim to develop a model illustrating the role of the MAVS-dependent pathway in controlling early virus replication. Supported by Intramural research program of the NIH