Pathogenicity and transmissibility of current H3N2 swine influenza virus in Southern China: A zoonotic potential

CD46 inhibits the replication of swine influenza viruses by promoting the production of type I IFNs in PK-15 cells

Swine flu caused by swine influenza A virus (swIAV) is an acute respiratory viral disease that is spreading in swine herds worldwide. Although the effect of some host factors on replication of swIAV has been identified, the role of CD46 in this process is unclear. Here, we report that CD46 inhibits the replication of swIAV by promoting the production of type I interferons (IFNs) in porcine kidney (PK-15) cells. CD46 knockout (CD46-KO) and stably expressing (CD46-overexpression) PK-15 cells were prepared using lentivirus-mediated CRISPR/Cas9 gene editing and seamless cloning technology. The results of virus infection in CD46-overexpression PK-15 cells showed that the replication of H1N1 and H3N2 swIAVs were inhibited, and the production of type I IFNs (IFN-α, IFN-β), interferon regulatory factor (IRF) 3, and mitochondrial antiviral-signaling protein (MAVS) was enhanced. Virus infection in CD46-KO PK-15 cells showed the opposite results. Further results showed that CD46-KO PK-15 cells have a favorable ability to proliferate influenza viruses compared to Madin-Darby canine kidney (MDCK) and PK-15 cells. These findings indicate that CD46 acts as promising target regulating the replication of swIAV, and help to develop new agents against infection and replication of the virus.

An Update in Knowledge of Pigs as the Source of Zoonotic Pathogens

The available data indicate that the human world population will constantly grow in the subsequent decades. This constant increase in the number of people on the Earth will lead to growth in food demand, especially in food of high nutritional value. Therefore, it is expected that the world livestock population will also increase. Such a phenomenon enhances the risk of transmitting pathogens to humans. As pig production is one of the most significant branches of the world's livestock production, zoonoses of porcine origins seem to be of particular importance. Therefore, in this review, we aim to introduce the latest data concerning, among other things, epidemiology and available preventive measures to control the most significant porcine zoonoses of viral, bacterial, and parasitic origin.

Molecular characterization, complete genome sequencing, and pathogenicity of Novel Duck Reovirus from South Coastal Area in China

Novel Duck Reovirus (NDRV) that has been found throughout the world in waterfowl, and it has been extensively described. Here, we report the complete genome sequence of a NDRV strain isolated in China called NDRV YF10. This strain was collected from 87 samples with infected ducks in South Coastal Area. The NDRV genome consists of 23,419 bp. With the assistance of computer analysis, the promoter and terminator of each gene segment and 10 viral genes segments were identified, which encode polypeptides ranging from 98 to 1,294 amino acids. All gene fragments of this virus strain were determined and compared to previously reported strains, revealing genetic variation with similarity rates ranging from 96 to 99% for each gene segment. Each gene segment formed 2 host-associated groups, the waterfowl-derived reovirus and the avian-derived reovirus, except for the S1 gene segment, which was closely related to ARV evolution and formed a host-independent subcluster. This difference may be due to Avian Reovirus (ARV) evolving in a host-dependent manner. In order to evaluate the pathogenicity of YF10, a novel isolated strain of NDRV was tested in 2 types of ducks. It was observed that the YF10 isolated strain exhibits varying degrees of virulence, highlighting the potential risk posed to different types of ducks. In conclusion, our findings emphasize the importance of epidemiology studies, molecular characterization, and prevention of NDRV in waterfowl.

Protection efficacy of the H1 and H3 bivalent virus-like particle vaccine against swine influenza virus infection

Swine influenza (SI) is widely prevalent in pig herds worldwide, causing huge economic losses to the pig industry and public health risks. The traditional inactivated swine influenza virus (SIV) vaccines are produced in chicken embryos, and egg-adaptive substitutions that occur during production process can impact vaccine effectiveness. Thus, developing an SI vaccine that can decrease the dependence on chicken embryos with a high immunogenicity is urgently needed. In this study, the utility of insect cell-derived SIV H1 and H3 bivalent virus-like particle (VLP) vaccines containing HA and M1 proteins of Eurasian avian-like (EA) H1N1 SIV and recent human-like H3N2 SIV were assessed in piglets. Antibody levels were monitored, and the protection efficacy of the vaccine after viral challenge was evaluated and compared with the inactivated vaccine. Results show that piglets produced high hemagglutination inhibition (HI) titers of antibodies against H1 and H3 SIV after immunization with SIV VLP vaccine. The neutralizing antibody level was significantly higher in SIV VLP vaccine than in the inactivated vaccine at 6 weeks post vaccination (p < 0.05). Furthermore, piglets immunized with the SIV VLP vaccine were protected against the challenge of H1 and H3 SIV, displaying inhibition of viral replication in piglets, and reduced lung damage. These results show that SIV VLP vaccine has good application prospects, thus laying the foundation for further research and commercialization of SIV VLP vaccine.

Pathogenicity and transmissibility studies on live attenuated duck enteritis virus vaccine in non-target species

In the second half of 2021, a highly pathogenic case occurred in a mixed chicken and duck family farm in Guangdong, China. After the duck flocks were immunized with live attenuated duck enteritis virus vaccine (live attenuated DEV vaccine), the chickens of the same farm showed clinical symptoms similar to duck enteritis, such as pericardial effusion, hepatic hemorrhagic spots, kidney enlargement, and intestinal bleeding, with mass mortality. The infection model of target animal tested, as well as the non-target species, was established according to the risk of live attenuated DEV vaccine and transmission in chickens. Live attenuated DEV vaccine was initially replicated in host animals, released the virus, and effectively colonized in the common environment, according to birds challenged experiments. There was evidence to suggest the mode of transmission of duck enteritis virus, and horizontal transmission is the main route of DEV transmission. In addition, high levels of virus titer were detected in chicken embryos and different tissues of SPF chickens. Different degrees of pathological damage occurred in the tissue of chickens. After the SPF chickens were inoculated with live attenuated DEV vaccine, different degrees of virulence were exhibited, pointing to a potential risk to other domestic bird species.

Potential Threats to Human Health from Eurasian Avian-Like Swine Influenza A(H1N1) Virus and Its Reassortants

During 2018-2020, we isolated 32 Eurasian avian-like swine influenza A(H1N1) viruses and their reassortant viruses from pigs in China. Genomic testing identified a novel reassortant H3N1 virus, which emerged in late 2020. Derived from G4 Eurasian H1N1 and H3N2 swine influenza viruses. This virus poses a risk for zoonotic infection.

Protective effect of bivalent H1N1 and H3N2 VLP vaccines against Eurasian avian-like H1N1 and recent human-like H3N2 influenza viruses in a mouse model

Eurasian avian-like (EA) H1N1 swine influenza viruses (SIVs) are currently the most prevalent SIVs in Chinese swine populations, but recent human-like H3N2 SIV subtypes have also been frequently isolated. Hence, there is an urgent need to develop an effective vaccine against both EA H1N1 and recent human-like H3N2 infections. In this study, we utilized the baculovirus expression system to produce virus-like particles (VLPs) containing hemagglutinin protein (HA) and matrix protein (M1) based on A/Swine/Guangdong/YJ4/2014 (H1N1) and A/swine/Guangdong/L22/2010 (H3N2). An immunological experiment showed that in a mouse model, bivalent VLP vaccines against H1N1 and H3N2 can induce stronger humoral and cellular immune responses than whole influenza virus vaccines. Compared with monovalent inactivated vaccines that cannot offer protection against different SIV subtypes, monovalent H1N1 or H3N2 VLP vaccines can provide partial protection against lethal challenge by viruses of different subtypes. Meanwhile, bivalent VLP vaccines against H1N1 and H3N2 can provide full protection against lethal doses of homologous and heterologous viruses belonging to the EA H1N1 or recent human-like H3N2 lineage. These results suggest a promising approach to the development of vaccines against SIVs.