# Exogenous amdoparvoviruses (Parvoviridae) in arvicoline voles: the molecular evolution and ecology of a novel host-viral association

## TL;DR

This study identifies a new amdoparvovirus in field voles, revealing its evolutionary history, host specialization, and potential to cause disease.

## Contribution

The first detailed molecular and ecological analysis of an amdoparvovirus in wild rodents, highlighting a novel host-virus association.

## Key findings

- FVAV is an exogenous, high-prevalence virus in field voles with evidence of recombination and horizontal transmission.
- FVAV shares conserved molecular structures with other amdoparvoviruses but shows host-specific adaptations in its capsid protein.
- RNA-sequencing of lung tissue proved effective for detecting and characterizing FVAV and similar viruses in individual hosts.

## Abstract

Amdoparvoviruses are best known as agents of disease in carnivorans, but here we provide the first in-depth molecular evolutionary and ecological information for an amdoparvovirus in wild rodents (field voles, Microtus agrestis). We applied an RNA-sequencing approach in lung tissue that yielded high diagnostic sensitivity and multiple full or near-full coding sequences for the new virus (field vole amdoparvovirus, FVAV) in individual voles. FVAV is most similar to amdoparvoviruses in European foxes and wildcats. We present evidence that FVAV is an exogenous, endemic, high-prevalence infection with a short-term history of horizontal transmission and recombination within voles and arising from an ancestral background of dynamic host usage and inter-lineage recombination. FVAV molecular structures involved in host exploitation share a highly conserved functional and evolutionary pattern with those in other amdoparvoviruses. The more variable regions within these structures evolve principally by apparently neutral processes and FVAV within-population mutation distribution mirrors that across the Amdoparvovirus phylogeny. Nonetheless, we did find some evidence of adaptive selection in the most variable regions and we also found convergent host-specific features in the modelled capsid protein of divergent arvicoline-associated lineages that might tend to restrict host range and support that FVAV is a vole-specialist. Increasing FVAV expression was associated with pulmonary inflammation and suppressed splenic T-cell activation, consistent with a potential to drive disease processes as in other amdoparvoviruses. Importantly, our approach highlights the de novo sequence assembly of viral RNA products from shotgun sequencing of rRNA-depleted RNA from tropic tissues in individual hosts as a sensitive and robust means of detecting and characterising not only RNA viruses but also DNA viruses.

Amdoparvoviruses are small DNA viruses usually associated with significant disease in carnivorans. Here we confirm the endemicity of a novel, exogenous amdoparvovirus in a rodent. We provide detailed evolutionary and ecological information for this new virus (field vole amdoparvovirus, FVAV), which occurs at high prevalence in the lungs of arvicoline rodents (field voles) in Northern England. We quantified infection and characterised the nucleic acid sequences coding for viral proteins via RNA-sequencing of lung tissue from individual hosts. Our work highlights this approach, targeting viral RNA products, as a good prospect for the discovery and characterisation of novel respiratory viruses of similar type, which hitherto may have been under-sampled. From our sequencing data we were able to reconstruct multiple full viral coding sequences, allowing molecular evolutionary analyses in relation to other members of the Amdoparvovirus genus. This revealed that FVAV is most closely related to amdoparvoviruses infecting wildcats and foxes in Northern Spain. Evidence of frequent recombination (which requires within-host contacts) amongst amdoparvoviral lineages, and their varied host usage, may reflect evolutionary host-switching. On the other hand, FVAV displays convergences of capsid structure with distantly related endogenized amdoparvoviruses that also occur in arvicoline (vole-like) hosts, suggesting it is an arvicoline specialist.