Detection of a New Variant in Outbreak of Bovine Ephemeral Fever in Turkey, 2020

Background: In this study, partial nucleotide sequence analysis of the G gene was performed for the molecular characterization of the virus that caused the bovine ephemeral fever virus (BEFV) epidemic in Turkey in 2020. Phylogenetic analysis of these nucleotide sequences was performed with the virus nucleotide sequences of the epidemics seen in 2008 and 2012. These sequences were announced in GenBank. Phylogenetic analysis of these nucleotide sequences was performed with the virus nucleotide sequences of the epidemics seen in 2008 and 2012. Methods: The study was conducted in dairy cattle holdings located in Diyarbakır Sur, Çınar and Dicle regions in South-eastern Turkey in August-November 2020. The number of animals in the holdings consisted of 750 (n=750), 150 (n=150) and 200 (n=200) cattle, respectively. Result: Severe respiratory symptoms and high mortality in the affected animals were notable symptoms. As a result of the phylogenetic analysis, it was determined that the virus that caused the epidemic in Turkey in 2020 was formed by a new variant in the Turkey-2 group, which was similar to the Indian isolates, unlike the Turkey-1 group, which was close to the Middle East variants in 2008 and 2012 isolates.

A Senescence-Like Cellular Response Inhibits Bovine Ephemeral Fever Virus Proliferation

During industrial-scale production of viruses for vaccine manufacturing, anti-viral response of host cells can dampen maximal viral antigen yield. In addition to interferon responses, many other cellular responses, such as the AMPK signaling pathway or senescence-like response may inhibit or slow down virus amplification in the cell culture system. In this study, we first performed a Gene Set Enrichment Analysis of the whole-genome mRNA transcriptome and found a senescence-like cellular response in BHK-21 cells when infected with bovine ephemeral fever virus (BEFV). To demonstrate that this senescence-like state may reduce virus growth, BHK-21 subclones showing varying degrees of a senescence-like state were infected with BEFV. The results showed that the BHK-21 subclones showing high senescence staining could inhibit BEFV replication while low senescence-staining subclones are permissive to virus replication. Using a different approach, a senescence-like state was induced in BHK-21 using a small molecule, camptothecin (CPT), and BEFV susceptibility were examined. The results showed that CPT-treated BHK-21 is more resistant to virus infection. Overall, these results indicate that a senescence-like response may be at play in BHK-21 upon virus infection. Furthermore, cell clone selection and modulating treatments using small molecules may be tools in countering anti-viral responses.