The goal of the study was to test the effects of an antibiotic substitute, plectasin, on the growth performance, immune function, intestinal morphology and structure, intestinal microflora, ileal mucosal layer construction and tight junctions, ileal immune-related cytokines, and blood biochemical indices of yellow-feathered chickens. A total of 1,500 one-day-old yellow-feathered chicks were randomly divided into four dietary treatment groups with five replicates in each group and 75 yellow-feathered chicks in each replication, as follows: basal diet (group A); basal diet supplemented with 10 mg enramycin/kg of diet (group B), basal diet supplemented with 100 mg plectasin/kg of diet (group C), and basal diet supplemented with 200 mg plectasin/kg of diet (group D). It was found that the dietary antimicrobial peptide plectasin could improve the ADG and had better F/G for the overall period of 1–63 days. Dietary plectasin can enhance H9N2 avian influenza virus (AIV) and Newcastle disease virus (NDV) antibody levels of yellow-feathered chickens at 21, and 35 days of age. Dietary plectasin can enhance the intestine structure, inhibit Escherichia coli and proinflammatory cytokines in the ileum, and ameliorate the blood biochemical indices of yellow-feathered chickens at 21 days of age. This study indicates that the antimicrobial peptide plectasin has beneficial effects on the growth performance, intestinal health and immune function of yellow-feathered chickens.

Coronavirus (CoV) is an important pathogen of humans and animals, which can infect humans or animals through the respiratory mucosal route. Syndrome coronavirus 2 (SARS-CoV-2) is quite similar to syndrome coronavirus (SARS-CoV) with the same receptor, angiotensin-converting enzyme 2 (ACE2). The S and N proteins are the most important protective antigens of the SARS-CoV-2. The S protein on the viral membrane mediates the virus attachment with the host cells, and the N protein is the most abundant expression during infection. In this study, the recombinant viruses expressing the S and N proteins of SARS-CoV-2 were successfully constructed by Red/ET recombinant technology using Pseudorabies virus (PRV) strain Bartha-K61 as a vector. Genetic stability and growth kinetics analysis showed that the recombinant viruses rPRV-SARS-CoV-2-S and rPRV-SARS-CoV-2-N had similar genetic stability and proliferation characteristics to the parental PRV. The immunoassay results showed that mice immunized with recombinant viruses could produce total IgG antibodies. Therefore, PRV is feasible and promising as a viral vector to express SARS-CoV-2-S and SARS-CoV-2-N genes. This study can provide a reference for future research on live vector vaccines for domestic animals, pets, and wild animals.

An increasing number of new subtypes of avian influenza viruses (AIVs) are reported to be infecting humans, including H3N2, H5N1, H7N9, H10N8, and the recently emerged H3N8 virus in China in 2022. However, the genetic and biological properties of the currently prevalent H3N8 AIVs are not yet fully understood. This study reports the isolation of a novel triple reassortment H3N8 virus (GD-H3N8) from chicken flocks in Guangdong province, China, in 2022. The GD-H3N8 virus contains the Eurasian avian duck-origin H3 gene, the North American avian N8 gene, and dynamic internal genes of the H9N2 virus, and shows high homology with human H3N8 strains. The GD-H3N8 isolate has multiple mammalian adaptive mutations associated with receptor binding and virulence. Growth kinetics assays demonstrate that the GD-H3N8 isolate is capable of efficient replication in avian, mammalian, and human cells in vitro. In vivo, the GD-H3N8 isolate can replicate efficiently in mice without preadaptation, in addition to establishing systemic infection and transmission by direct contact in chickens. These findings underscore the need for continued surveillance of H3N8 viruses to identify circulating strains that may potentially threaten human health.