Characterization of an alloherpesvirus from wild lake sturgeon Acipenser fulvescens in Wisconsin (USA)

Abstract

In the spring of 2017, 2 adult lake sturgeon (LS) Acipenser fulvescens captured from the Wolf River, Wisconsin (USA), presented with multiple cutaneous plaques that, upon microscopic examination, indicated proliferative epidermitis. Ultrastructural examination of affected keratinocytes revealed particles in the nucleus having a morphology typical of herpesviruses. A degenerate PCR assay targeting the DNA polymerase catalytic subunit (pol) gene of large double-stranded DNA viruses generated amplicons of the anticipated size from skin samples, and sequences of amplicons confirmed the presence of a novel alloherpesvirus (lake sturgeon herpesvirus, LSHV) related to acipenserid herpesvirus 1 (AciHV1). The complete genome (202660 bp) of this virus was sequenced using a MiSeq System, and phylogenetic analyses substantiated the close relationship to AciHV1. A PCR assay targeting the LSHV DNA packaging terminase subunit 1 (ter1) gene demonstrated the presence of the virus in 39/42 skin lesion samples collected from wild LS captured in 2017-2019 and 2021 in 4/4 rivers in Wisconsin. Future efforts to isolate LSHV in cell culture would facilitate challenge studies to determine the disease potential of the virus.

First Isolation of a Herpesvirus (Family Alloherpesviridae) from Great Lakes Lake Sturgeon (Acipenser fulvescens)

“…The draft genome generated for lake sturgeon herpesvirus isolate 200413-11TC consists of two unique, non-overlapping contigs (119,069 and 87,627 bp). Blastn searches produced no direct matches to any alloherpesvirus isolates in GenBank ( Tables S1 and S2 ) but did reveal a high degree of similarity (99.36%) across a 156-bp fragment of the DNA packaging terminase subunit I to lake sturgeon herpesvirus strains from the Chippewa (OL440177), Wolf (OL440173, OL440175) and Wisconsin (OL440170) Rivers in Wisconsin [ 22 ]. MAFFT alignments of the 4638 bp DNA polymerase catalytic subunit CDS from lake sturgeon herpesvirus isolate 200413-11TC with the Wolf River lake sturgeon herpesvirus (OK485036) and AciHV-1 from White Sturgeon (OK275729) revealed 92.6% nt (93.4% aa) and 79.8% nt (86.4% aa) similarity, respectively.…”

“…Similar levels of dissimilarity were observed for the remaining core alloherpesvirus ORFs ( Table 4 ). Moreover, phylogenies based on concatenation of translated ter1 and pol genes, as well as translations of the 12 core genes from 17 alloherpesviruses for which complete or near complete sequences were available ( Table S3 [ 22 , 38 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 ]), were consistent with Blastn results, indicating lake sturgeon herpesvirus isolate 200413-11TC is most similar, yet distinct from lake sturgeon herpesvirus Wolf River (OK485036) and AciHV-1 from White Sturgeon (OK275729; Figure 5 ).…”

“…No.) OK485036 (Lake sturgeon herpesvirus strain Wolf River) [ 22 ] and regions corresponding to the 12 core alloherpesvirus ORFs [ 38 ] (DNA packaging terminase subunit 1 (Acc. No.…”

“…Similarly, MAFFT alignments were performed on nucleotide and translated amino acid sequences using the complete CDS of the 12 core alloherpesvirus ORFs from 17 alloherpesviruses for which complete or nearly complete sequences are available ( Table S3 ) [ 22 ]. ML trees of the translated amino acid sequences for the complete DNA packaging terminase subunit 1 and DNA polymerase catalytic subunit CDS, as well as the 12 core alloherpesvirus genes were generated using the Le_Gascuel_2008 model with Gamma distribution and invariable rates (LG + G + I) with 100 replicates [ 41 ].…”

“…Despite this group of viruses having been detected in various North American sturgeon populations, an AciHV had never been detected in, or isolated from wild lake sturgeon. However, just prior to submission of the current manuscript, Walker et al (2022) reported the detection of a novel alloherpesvirus in lake sturgeon in Wisconsin, USA, via a degenerate PCR assay and electron microscopy [ 22 ]. Although this virus, termed lake sturgeon herpesvirus, was found in association with skin lesions, in vitro isolation was not reported and its pathogenic potential was not determined.…”