Praveen Akmeemana, University of Guelph

Praveen Akmeemana (1), Igor Santos (1), Alexander Leacy (1), Antonius El-khoury (1), Phuc H. Pham (1), Leonardo Susta (1). (1) Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada

Discovering & Evolving

Orthobornaviruses are negative-sense, single-stranded RNA viruses that establish chronic, non-cytolytic, intranuclear infections in nervous tissue. Whether this persistence affects susceptibility to other viruses remains unclear. Here, we investigated whether cells persistently infected with parrot bornavirus-4 (PaBV-4) or aquatic bird bornavirus-1 (ABBV-1) could support the replication of ABBV-1 or PaBV-4, respectively, or Newcastle disease virus (NDV). Quail fibrosarcoma cells (QT35) persistently infected with PaBV-4 or ABBV-1 were infected with ABBV-1 or PaBV-4, respectively, at 0.01 MOI (multiplicity of infection). Naïve QT-35 were also simultaneously infected with PaBV-4 and ABBV-1 at the same MOI. Cells were serially passaged for 45 days, and virus RNA copies quantified at selected days post-infection (dpi). Additionally, PaBV-4-persistently infected QT35 were infected with a lentogenic NDV at 0.01 MOI, and infectious NDV titered in the supernatant up until 48 hours post-infection (hpi). Naive (control) cells supported robust replication, exhibiting a 1200- and 300-fold RNA increase for PaBV-4 and ABBV-1, respectively, by 45 dpi. In persistently infected cells, the superinfecting PaBV-4 or ABBV-1 showed no RNA increase. During simultaneous infection, PaBV-4 reached RNA levels similar to single infection, whereas ABBV-1 established persistence but at a lower level (~50 vs.~300-fold). QT-35 persistently infected with PaBV-4 supported NDV propagation, with only a transient ~10-fold titer reduction at 34 hpi. These findings indicate strong mutual interference between orthobornaviruses once persistence is established, but limited interference with distantly related mononegaviruses, such as NDV. Simultaneous exposure with two orthobornaviruses can yield co-persistent infection, suggesting reinfection or multi-strain persistence is biologically plausible.