Duck cholera (duck hemorrhagic septicemia) is a highly contagious disease caused by Pasteurella multocida, and is one of the major bacterial diseases currently affecting the duck industry. Type A is the predominant pathogenic serotype. In this study, the genes encoding the lipoproteins VacJ, PlpE, and the outer membrane protein OmpH of P. multocida strain PMWSG-4 were cloned and expressed as proteins in E. coli. The recombinant VacJ (84.4 kDa), PlpE (94.8 kDa), and OmpH (96.7 kDa) proteins were purified, and subunit vaccines were formulated with a single water-in-oil adjuvant, while killed vaccines were prepared using a single oil-coated adjuvant. Antibody responses in ducks vaccinated with recombinant VacJ, PlpE, and OmpH proteins formulated with adjuvants were significantly antigenic (p<0.005). Protectivity of the vaccines was evaluated via the intraperitoneal challenge of ducks with 20 LD50 doses of P. multocida A: 1. The vaccine formulation consisting of rVacJ, rPlpE, rOmpH, and adjuvant provided 33.3%, 83.33%, and 83.33% protection, respectively, the vaccine formulation consisting of three recombinant proteins, rVacJ, rPlpE, rOmpH and adjuvant, was 100% protective, and the killed vaccine was 50% protective. In addition, it was shown through histopathological examination and tissue bacterial load detection that all vaccines could reduce tissue damage and bacterial colonization to varying (p<0.001). These findings indicated that recombinant PlpE or OmpH fusion proteins formulated with oil adjuvants have the potential to be used as vaccine candidates against duck cholera subunits.
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.
A Corrigendum onImmunogenicity and protective efficacy of the recombinant Pasteurella multocida lipoproteins VacJ and PlpE, and outer membrane protein H from P. multocida A:1 in ducks
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