We cloned five new subtypes of cDNA encoding canine interferon-alpha (CaIFN-alpha) from a canine epithelial cell line. CaIFN-alphas were divided into two groups by amino acid sequences and a molecular phylogenic tree. Two subtypes of them were expressed in Escherichia coli, and IFN proteins were purified. Recombinant CaIFN-alphas were highly species-specific and showed antiviral activity against Vesicular stomatitis New Jersey virus and canine adenovirus-1 , but not against canine herpesvirus-1.

Porcine reproductive and respiratory syndrome virus (PRRSV) is an important pathogen in the swine industry. We report for the first time the detection of NADC34-like PRRSV strains in Japan. Serum samples from 18 piglets in Okinawa Prefecture were analyzed for the open reading frame 5 (ORF5) gene encoding glycoprotein 5, which revealed that all samples belonged to sublineage 1.5 (L1A) of Lineage 1. Phylogenetic analysis, restriction fragment length polymorphism patterns, and glycosylation site characteristics confirmed the presence of NADC34-like strains that caused severe outbreaks in the U.S. and Asia. Despite its known pathogenicity, the farm showed only a transient increase in mortality. These findings highlight the need for further investigation into the pathogenicity of PRRSV strains and their potential for the emergence of new variants in Japan.

Porcine reproductive and respiratory syndrome virus (PRRSV) poses a significant economic challenge to Japan’s swine industry. This review synthesizes the epidemiological evolution of PRRSV in Japan by examining the available scientific literature from its initial Type 2 isolation in 1993 to recent events. Endemic Type 2 strains, initially dominated by Cluster III (Lineage 4), have diversified significantly. This diversification was marked by key events including the emergence of vaccine-associated Cluster II (Lineage 5) and incursions of virulent Cluster IV/Lineage 1F (MN184A-like) strains and Type 1 virus around 2008. By 2018–2020, Clusters II and IV predominated nationwide, a trend strongly linked to widespread modified live virus (MLV) vaccination. The recent detection of the globally significant NADC34-like (Lineage 1A) strain underscores ongoing foreign incursion risks. Current MLV vaccines face challenges, including safety concerns and limited cross-protection against diverse field strains. Consequently, effective control requires integrated strategies, comprising optimized vaccination, stringent biosecurity, advanced molecular surveillance, improved diagnostics, and coordinated regional control programs guided by systematic herd classification and stakeholder partnerships. The development of next-generation vaccines and sustained multi-stakeholder collaboration are critical for mitigating the impact of PRRSV in Japan.

Two kinds of FeIFN-alpha consisting of 166 amino acids (aa) and 171 aa were expressed in Escherichia coli, and the purified proteins were tested for antiviral activity on homologous and heterologous animal cells. Crude FeIFN induced in feline cells revealed antiviral activity on both homologous and heterologous animal cells. In contrast, both types of recombinant FeIFN-alpha revealed antiviral activity only on the feline cells. All of the FeIFN-alpha subtypes showed high activity to vesicular stomatitis virus, and the three species of feline viruses belonging to different families.