Functional Characterization of Egyptian rousette Bat Innate immune synapses

The long-term goal is to characterize the cellular and molecular constituents of the bat immune system. Our group had been working on Marburg virus (MARV) spillover and transmission from Egyptian rousette (ERB, Rousettus aegyptiacus) bats. The ultimate goal of One Health pathogen surveillance programs is the identification of the most likely source of pathogen spillovers, and the practices more likely to facilitate the barrier jump. After this, the fate of emergence depends on the pathogen ability to transmit within humans. Our central hypothesis is that the immunological differences between the zoonotic host and humans are a significant determinant of the frequency of spillovers. After a detailed genome comparison, we reported multiple immune-related gene families that have undergone expansion in ERB compared to humans: the expansion of natural Killer Lectin-like Receptor-C (KLRC or NKG2) and KLR-D (or CD94) gene families, MHC Class I genes and type I interferon -ω and -α. Later, we revealed an increase in copy number of IGHV genes known to act in viral protection in humans; a duplication of functional IgE genes with different tissue expression patterns and theoretical functions; distinctive putative functions and structural characteristics of the four IgGs; lack of expansion of FcR for IgG (FcγR) compared to primates and potential different functionality; and the complete absence of functional short pentraxins. All these observations indicate that ERB establishes a tolerogenic state to deal with pathogen infection. Here, we propose to functionally characterize ERBs unique NK and IFN immunological synapses. The objective of this proposal is to confirm experimentally the predicted genomic functionality. The rationale is that Tolerance could be the basis for the unusual resilience of bats to withstand viral infections that are highly virulent and/or lethal in humans. The central hypothesis will be tested by pursuing 2 specific aims: 1) To determine the NKG2-CD94 association potential to form a functional receptor and the signaling downstream of the heterodimers to evaluate ERB NK activation mechanisms.; 2) To determine functionality and signaling cascade downstream ERBs Type I IFNs to test whether the expansion of IFN -ω and -α correlates with biological differences. We will pursue them using an innovative combination of immunological techniques that take advantage from NIAID investments in the Atlas of Immune Cells, and single- cell genomics as well as previous investments to generate ERB specific reagents. This research is significant, because it will advance knowledge at the crucial interphase that determine transmission and pathogenesis if the differences between the immunological status of different mammals are a driver for zoonotic spillovers. The proximate expected outcome of this work is an understanding of the particularities of the bat innate immunological system and an assessment of its baseline status. The results will have an immediate positive impact on the studies on MARV spillover. Moreover, as other bat immunological systems are similarly characterized, this work will lay the groundwork to assess bats immunological features.