Canine parvovirus-2 (CPV-2) has been reported worldwide as a major pathogen associated with acute hemorrhagic enteritis. The disease is a major infectious cause of death, particularly in young dogs. The earliest type of CPV-2 was replaced with three main subspecies, CPV-2a, CPV-2b, and CPV-2c, within a few years. Vaccination is carried out regularly, but the emergence of antigenic variants and the influence of maternal antibodies have limited the efficacy of commercial vaccines. New vaccines, such as the subunit vaccine, have been developed for alternative, safe, and effective vaccination. The baculovirus expression vector system (BEVS) is an excellent eukaryotic expression system with a high-level expression of foreign proteins and the ability of post-translational modification. Therefore, it is used widely to produce recombinant protein and subunit vaccines. In this study, the VP2 protein of CPV-2b cloned in the gateway vector system was generated using a baculovirus expression system in Spodoptera frugiperda (SF9) insect cells. Hemagglutination assay (HA) titers (24) were obtained, and the expression was detected in 6-His tagged VP2 and monoclonal antibody (mAb) against CPV-2 by western blotting. The VP2 protein of CPV-2b expressed in this study may provide a basis for a clinical diagnosis and vaccination applications for CPV-2.

Influenza A viruses (IAVs) are members of the family Orthomyxoviridae and genus Orthomyxovirus. Avian and mammalian species are the host of IAVs, which includes humans and dogs. Canine influenza virus (CIV) is an emerging pathogen that causes severe and acute respiratory diseases in dogs. This study monitored the antigen and antibody against CIV in dogs in the Republic of Korea (ROK) from 2016 to 2021. One thousand and seventy-two nasal swabs and 1,545 blood samples were collected from animal hospitals and animal shelters. Five nasal swabs in 2017 and seven in 2018 from stray dogs were positive for CIV according to RT-PCR. The prevalence of H3N2 CIV ranged from 9.5% to 24.8%, according to the hemagglutination inhibition (HI) assay. On the other hand, none of the serum samples from 2018 to 2021 showed seropositivity against the avian H5, H7, and H9 viruses. The HI titers for H3N2 ranged from 16 to 512. The distribution of HI titer 16–32 was 57.6% in seropositive samples. The pet dogs were vaccinated against CIV, but the stray and military dogs were unvaccinated. In 2017 and 2018, the seroprevalence of CIV in stray dogs was higher than in the other years, and viral RNA was detected in nasal swabs. It may mean previous exposure of stray dogs to CIV. With the increasing number of pet dogs and the close contact between humans and dogs, canines could serve as an intermediate host for transmitting IAVs to humans. Therefore, continuous surveillance of CIV is needed for public health and the potential emergence of novel zoonotic viruses.