Isolation and complete genome characterization of Bovine gammaherpesvirus-4 (BoHV-4) as the primary viral agent for respiratory infection in cattle

Abstract

The Bovine gammaherpesvirus type 4 (BoHV-4) has been detected worldwide in healthy and disease-exhibiting cattle. Notably, BoHV-4 has recently been identified in bovine respiratory system infections. This study focuses on the isolation and complete genome characterization of Bovine gammaherpesvirus-4 (BoHV-4) as a primary viral agent responsible for respiratory infections in cattle. Cytopathogenic effects were observed in MDBK cells, confirming the presence of an enveloped DNA virus in identification tests. The viral titer of isolate BoHV-4/9746 at the 7th passage level was 6.75 log₁₀ TCID₅₀/0.1 mL. PCR tests (TK gene) identified BoHV-4 as the only viral agent present, ruling out other common respiratory (BCoV, BoHV-1, BVDV, BRSV, BPIV-3, IDV, and BEV) applied to the 5th passage supernatant. WGS analysis revealed a partial LUR sequence (86870 bp) of the BoHV-4 /9746 Bursa-TR isolate, which showed high similarity (99.8%) to the reference V.test strain. The results of phylogenetic analyses applied according to partial LUR and TK gene regions also support each other, and BoHV-4 BoHV-4/9746 isolate branches among Genotype-1 sequences, similar to other European BoHV-4 strains. Cross-neutralization antibody reactions put forth a four-fold decrease in the neutralizing capacity of the BoHV-1 hyperimmune sera against the isolate BoHV-4 /9746. In conclusion, negative results of lung sample for other viral agents affecting the respiratory tract suggest that BoHV-4 may act as a primary viral agent. This study is the first report of a partial LUR genome of a Turkish BoHV-4 isolated from the respiratory tract.

Keywords: Bovine gammaherpesvirus-4; Bovine respiratory disease; PCR; Phylogeny analysis; Whole genome sequencing.