Defining the molecular determinants of filovirus… (F32AI202845) – Project Grant to The University Of Iowa

Abstract: Filoviruses are viral pathogens which cause sporadic outbreaks of severe hemorrhagic fever. The best characterized filovirus is ebola virus (ebov); but its genetic relative marburg virus (marv) is equally deadly and has caused two outbreaks in 2025 alone, with the ongoing outbreak being the first ever documented in ethiopia. While there is an efficacious, FDA-approved vaccine for ebov, this vaccine fails to provide cross-protection against other filoviruses such as marv. There are currently no FDA-approved vaccines or therapeutics to treat or prevent marv infections; this can in part be attributed to the wide and deep knowledge gaps that exist in how different filoviruses interact with the host to elicit innate immune responses. Macrophages (MΦ) are among the earliest and most consequential targets of filovirus infection. MΦ are major responders to type i and II interferons (ifns) and productive viral infection of MΦ is a central determinant of ebov pathogenicity and mortality. Type i ifns, such as IFN-β, induce broad and canonical innate anti-viral responses. Type II IFN (IFN-γ) activates a repertoire of isgs partially distinct from type i. IFN-γ signaling plays important roles in stimulating adaptive immune responses but is not commonly thought of as the front-line defense against virus infections, despite IFN-γ-elicited isgs restricting some viral infections. Ebov infection of MΦ is highly susceptible to IFN-γ pretreatment; however, detailed mechanistic studies into IFN-γ restriction of early events in ebov infection have not been reported. To date, no studies have evaluated the sensitivity of other filoviruses to IFN-γ pretreatment. Here, i demonstrate that, unlike the strong IFN-γ inhibition observed against entry events mediated by ebov glycoprotein (GP), marv GP entry is unaffected by IFN-γ pretreatment. As the increasing frequency of marv outbreaks make IT imperative to define filovirus responses to host innate immunity, we seek to define the mechanism of ebov restriction and evaluate the sensitivity of other filoviruses to IFN-γ. I hypothesize that IFN-γ restricts ebov GP-dependent entry into MΦ, but not marv GP-dependent, by induction of IFN-stimulated gene (ISG) expression. We will address this hypothesis through the proposed specific aims which define the (1) host determinants and (2) viral determinants of IFN-γ-stimulated ebov restriction. Experimental assessment of these aims includes evaluating IFN-γ elicited isgs for sufficiency and necessity in γ's restriction of ebov as well as structure-based recombination and adaptive evolution of filovirus GPS to identify GP sequences which modulate IFN sensitivity. Taken together, the proposed aims will elucidate the host and viral determinants of filovirus susceptibility and tolerance to IFN-γ-elicited innate immune responses. This will not only greatly expand our understanding of innate immunity as IT relates to filoviruses but will offer broader insights into how innate immune pressures shape disease and viral evolution. Finally, these aims are critical for establishing the conceptual footing needed for marv therapeutic development.

Defining the molecular determinants of filovirus interactions with IFN-y elicited host innate immune responses

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