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. 2023 Dec 6;85(12):1291-1295.
doi: 10.1292/jvms.23-0354. Epub 2023 Oct 31.

Enzootic bovine leukosis caused by bovine leukemia virus classified as Group C based on viral whole genome sequencing in a 23-month-old Holstein-Friesian heifer

Yusuke Daiji  1 , Masaki Maezawa  2 , Kento Ishikawa  3 , James K Chambers  3 , Kazuyuki Uchida  3 , Hisashi Inokuma  2   4
Affiliations

Enzootic bovine leukosis caused by bovine leukemia virus classified as Group C based on viral whole genome sequencing in a 23-month-old Holstein-Friesian heifer

Yusuke Daiji et al. J Vet Med Sci. .

Abstract

A 23-month-old Holstein-Friesian heifer presented with inactivity and diarrhea. On physical examination, no enlargement of superficial lymph nodes was observed. Hematological examination revealed lymphocytosis. The bovine leukemia virus (BLV) proviral load was 2,122 copies/10 ng DNA, and BLV was classified as Group C based on whole genome phylogenetic analysis. Monoclonal proliferation of B-cells and monoclonal integration of the BLV provirus in the bovine genome were detected by a clonality test of B-cells and inverse PCR, respectively. Although lymph nodes were not swollen at necropsy, histopathological examination revealed neoplastic lymphocyte proliferation in lymph nodes, which were immune positive for CD5 and CD20, and negative for CD3. The heifer was diagnosed with EBL caused by BLV classified as Group C.

Keywords: bovine leukemia virus; bovine leukemia virus Group C strain; early onset; enzootic bovine leukosis; heifer.

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Conflict of interest statement

The Laboratory of OSG Veterinary Science for Global Disease Management is an endowment laboratory, supported by a grant from OSG Corporation.

Figures

Fig. 1.
Fig. 1.
Emaciation, diarrhea, and no swelling of superficial lymph nodes were noted on Day 5.
Fig. 2.
Fig. 2.
Phylogenetic analysis of the whole bovine leukemia virus (BLV) genome sequence. A maximum-likelihood phylogenetic tree was constructed from the whole BLV genome sequence of the present case and 15 reference sequences. BLV strains were divided into 5 groups (A, B-1, B-2, C, and other) based on a previous study. Numbers on the figure denote branch lengths.
Fig. 3.
Fig. 3.
Results of inverse PCR. Lane 1: DNA from peripheral blood; Lane 2: typical enzootic bovine leukosis (EBL); Lane 3: mastitis; Lane 4: persistent lymphocytosis; Lane 5: clinically healthy with bovine leukemia virus (BLV) infection; Lane 6: clinically healthy without BLV infection; Lane 7: distilled water; M: molecular weight marker.
Fig. 4.
Fig. 4.
Histopathology and immunohistochemistry of the mesenteric lymph node. Neoplastic cells had round nuclei with nuclear atypia and granular patterned chromatin (inset). These cells stained positive for CD5 and CD20 and were negative for CD3. (A) Hematoxylin and eosin stain. (B) CD3, (C) CD5, and (D) CD20 with Mayer’s hematoxylin counterstain. Bar=25 μm.
See this image and copyright information in PMC

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