Distribution of zoonotic variegated squirrel bornavirus 1 in naturally infected variegated and Prevost’s squirrels

Abstract

Recently, the zoonotic capacity of the newly discovered variegated squirrel bornavirus 1 (VSBV-1) was confirmed in humans with a lethal encephalitis. Transmission to humans occurred by variegated and Prevost’s squirrels as presumed reservoir hosts but possible ways of virus shedding and the route of infection still need to be elucidated. Thus, the tissue distribution of VSBV-1 antigen and RNA was investigated in detail via immunohistochemistry (IHC) in six variegated and eight Prevost’s squirrels and by in situ hybridisation (ISH) in one Prevost’s squirrel, respectively. VSBV-1 antigen and RNA positive cells were most numerous in the nervous system and were also found in nearly all tissues and different cell types indicating a broad organ and cell tropism of VSBV-1. Presence of VSBV-1 in several organs might indicate potential virus shedding via various routes and implies the risk of intra- and interspecies transmission, respectively.

Tissue Distribution of Parrot Bornavirus 4 (PaBV-4) in Experimentally Infected Young and Adult Cockatiels (Nymphicus hollandicus)

“…Tissue of the adrenal glands was only available in 1/6 animals for ISH, so no valid statement about the tissue RNA distribution is possible and more animals must be investigated. These discrepancies have also been reported in VSBV-1-infected squirrels and might be due an uneven viral tissue distribution or low amounts of viral antigen not detectable by IHC [ 27 ].…”

“…IHC- and ISH-analysis were performed by applying a semiquantitative scoring system, as used elsewhere [ 27 ]. The scoring system is shown in Table 1 and reaches from “–“ meaning no detectable signal to “++++” meaning plenty of detectable signals in IHC or ISH.…”

“…In both, BoDV-1 [ 15 , 16 , 18 , 19 ] and VSBV-1 [ 14 , 25 ] infections, dead-end hosts, or possible spill-over hosts show a severe and lethal disease with a restriction mainly to the central nervous system (CNS) with single exceptions. In contrast, BoDV-1 or VSBV-1 infected reservoir hosts are clinically inconspicuous, showing a broad viral tissue distribution [ 14 , 26 , 27 , 28 ].…”

First isolation, in-vivo and genomic characterization of zoonotic variegated squirrel Bornavirus 1 (VSBV-1) isolates

“…As secondary antibody, goat-IgG against rabbit (Agilent, Santa Clara, CA, USA) was used and detected with avidin–biotin-complex with DAB as substrate. Antigen distribution and quantity was scored according to Petzold et al [ 27 ].…”

“…Viral RNA distribution was further evaluated by in-situ hybridization with RNA-Scope probes according to manufacturer’s instructions, using RNAscope 2.5 HD Assay-BROWN (ACD, Advanced Cell Diagnostics, Newark, CA) and RNAscope probe V-VSBV1-N. The same score was applied for viral RNA distribution as for viral antigen [ 27 ].…”