Molecular evolutionary insights into the host-virus relationship between Marburg Virus and its bat reservoir.

Bats, often silent carriers of lethal pathogens, serve as natural reservoirs for numerous viruses capable of crossing species barriers with devastating effects. Among them, Rousettus aegyptiacus (R. aegyptiacus) has emerged as a pivotal species in understanding viral spillovers. This fruit bat hosts the Marburg virus (MARV), supporting its replication and occasional transmission to humans, where it causes fatal hemorrhagic fever. However, a striking paradox remains while MARV infection is deadly in humans, R. aegyptiacus remains asymptomatic. Driven by this contrast, our study explores the codon usage patterns to reveal evolutionary mechanisms underlying viral adaptation and host tolerance. Far from being a passive carrier, R. aegyptiacus represents an insightful model for antiviral research. Our analysis revealed distinct codon usage patterns in MARV, indicating fine-tuned evolutionary alignment with the host's codon preferences. MARV exhibited low codon bias, suggesting broad compatibility with the host's translational machinery. Further, COA and PR2 analyses suggested that ecological factors shape codon selection in both virus and host. RNA modification analysis revealed frequent cytosine-to-thymine transitions, implying conserved mutational pressures or host-driven editing. Variations in RCDI values indicated deoptimized codon usage.