A COVID-19 Vaccine for Dogs Prevents Reverse Zoonosis.

COVID-19 is caused by severe acute respiratory syndrome virus type 2 (SARS-CoV-2), which can infect both humans and animals. SARS-CoV-2 originated from bats and can affect various species capable of crossing the species barrier due to active mutation. Although reports on reverse zoonosis (human-to-animal transmission) of SARS-CoV-2 remain limited, reverse zoonosis has been reported in many species such as cats, tigers, minks, etc. Therefore, transmission to more animals cannot be ruled out. Moreover, the wide distribution of SARS-CoV-2 in the human population could result in an increased risk of reverse zoonosis. To counteract reverse zoonosis, we developed the first COVID-19 subunit vaccines for dogs, which are representative companion animals, and the vaccine includes the SARS-CoV-2 recombinant protein of whole S1 protein and the receptor-binding domain (RBD). A subunit vaccine is a vaccine developed by purifying only the protein region that induces an immune response instead of the whole pathogen. This type of vaccine is safer than the whole virus vaccine because there is no risk of infection and proliferation through back-mutation of the virus. Vaccines were administered to beagles twice at an interval of 3 weeks subcutaneously and antibody formation rates were assessed in serum. We identified a titer, comparable to that of vaccinated people, shown to be sufficient to protect against SARS-CoV-2. Therefore, the vaccination of companion animals, such as dogs, may prevent reverse zoonosis by protecting animals from SARS-CoV-2; thus, reverse zoonosis of COVID-19 is preventable.

The protective effect of dietary supplementation of Salmonella-specific bacteriophages in post-weaning piglets challenged with Salmonella typhimurium.

OBJECTIVE: The efficacy of Salmonella typhimurium-specific bacteriophage STP-1 on S. typhimurium infection in weaning piglets was evaluated in this study. MATERIAL AND METHODS: Twenty-eight weaning piglets were randomly allocated to four groups (Group A: non-challenged/basal; Group B: non-challenged/+phage; Group C: challenged/basal; Group D: challenged/+phage) according to S. typhimurium infection or bacteriophage administration. The total experimental period (14 days) was subdivided in to non-challenged periods (phase I; day 1-7) and challenged periods (phase II; day 7-14) based on the challenging date (day 7). Each group was fed with basal feed or feed supplemented with bacteriophage STP-1 [1.0 × 109 plaque-forming unit (PFU)/kg] during the whole period (day 1-14). Body weights (BW) were measured to evaluate growth performance. Clinical symptoms (rectal temperatures and fecal consistency) induced by S. typhimurium were regularly checked. Bacteria colonization levels in feces and intestinal tissue samples were measured using real-time polymerase chain reaction (PCR). After necropsy, small intestine samples (jejunum) were collected. Villus height and crypt depth (CD) were measured through histological examination with H&E staining. RESULTS: The supplementation of bacteriophage significantly reduced bacterial colonization and intestine damage in the piglets infected with S. typhimurium. In the antigen concentrations of the feces and jejunum, Group C showed 5.8 ± 0.6, 5.7 ± 0.6, and 1.2 ± 2.0 log colony-forming unit (CFU)/ml on 1, 3, and 7 days post-inoculation (DPI) and 2.8 ± 1.3 log CFU/ml, whereas Group D showed 3.5 ± 1.7, 2.2 ± 2.1, and 0.3 ± 0.9 log CFU/ml on 1, 3, and 7 DPI and 5.1 ± 0.9 log CFU/ml. In the villous height, Groups C and D showed 266.3 ± 24.1 and 324.6 ± 18.0 µm, respectively. In the goblet cell density of villi and crypts, Group C showed 10.0 ± 1.8 and 16.0 ± 3.7, while Group D showed 15.0 ± 4.8 and 21.1 ± 5.4. Also, the supplementation of bacteriophage significantly improved the growth performance in the infected piglets. The average daily gains of Groups C and D were 91 ± 24 and 143 ± 23, respectively, during the period after inoculation with S. typhimurium. CONCLUSION: The dietary supplementation of the phage was effective for alleviating S. typhimurium infection in post-weaning piglets.

Radiation-Inactivated S. gallinarum Vaccine Provides a High Protective Immune Response by Activating Both Humoral and Cellular Immunity.

Salmonella enterica subsp. enterica serovar Gallinarum (SG) is a common pathogen in chickens, and causes an acute systemic disease that leads to high mortality. The live attenuated vaccine 9R is able to successfully protect chickens older than six weeks by activating a robust cell-mediated immune response, but its safety and efficacy in young chickens remains controversial. An inactivated SG vaccine is being used as an alternative, but because of its low cellular immune response, it cannot be used as a replacement for live attenuated 9R vaccine. In this study, we employed gamma irradiation instead of formalin as an inactivation method to increase the efficacy of the inactivated SG vaccine. Humoral, cellular, and protective immune responses were compared in both mouse and chicken models. The radiation-inactivated SG vaccine (r-SG) induced production of significantly higher levels of IgG2b and IgG3 antibodies than the formalin-inactivated vaccine (f-SG), and provided a homogeneous functional antibody response against group D, but not group B Salmonella. Moreover, we found that r-SG vaccination could provide a higher protective immune response than f-SG by inducing higher Th17 activation. These results indicate that r-SG can provide a protective immune response similar to the live attenuated 9R vaccine by activating a higher humoral immunity and a lower, but still protective, cellular immune response. Therefore, we expect that the radiation inactivation method might substitute for the 9R vaccine with little or no side effects in chickens younger than six weeks.

GFP-expressing influenza A virus for evaluation of the efficacy of antiviral agents.

To address its value as a screening tool in the development of antiviral drugs, a recombinant influenza virus expressing green fluorescent protein (rPR8-GFP virus) was investigated in vitro and in vivo. The inhibition of viral growth by a neuraminidase inhibitor in the cells or lower respiratory tracts of mice could be visualized by the level of fluorescence. In addition, the rPR8-GFP virus exhibited high pathogenicity in mice. Taken together, these results suggest that the rPR8-GFP virus can be a useful tool for the rapid identification of antiviral drugs active against influenza viruses.