Protection of laying chickens against the Canadian DMV/1639 infectious bronchitis virus infection through priming with heterologous live vaccine and boosting with heterologous or homologous inactivated vaccine

Structural characterization and immune activity evaluation of polysaccharide purified from Viola phillipica

This study investigated the structure of Viola phillipica polysaccharide (VPP) and its effect as an immune adjuvant for the Newcastle disease vaccine (ND Vaccine). The results showed that VPP comprised of the galacturonic acid, galactose, rhamnose, arabinose with the molar ratio of 36.20: 23.41: 19.72: 11.54 and a molecular weight (Mw) of 1080 kDa. Additionally, the composition of VPP was assessed via FT-IR, methylation, AFM and SEM analyses, indicating that the backbone of the VPP was consisted of T-Ara (f), T-Gal (p), 4-Gal (p)-UA, and T-Rha (p) linkages. Furthermore, VPP was used as an immune adjuvant in combination with ND vaccine in chickens. Remarkable enhancements were observed in the thymus, spleen, and bursa indices of the chickens, the serum levels of ND antibodies and the expression of IL-4 and IFN-γ cytokines, thereby fostering the proliferation of T and B lymphocytes within the spleen. Notably, histopathological analysis indicated that the VPP groups showed increased lymphoid follicles and splenic nodules, as well as greater splenic red pulp density and bursa of Fabricius area. In summary, these findings suggest that VPP could serve as an adjuvant to enhance the immunogenicity of NDV.

Two opposite abilities of the infectious bronchitis virus helicase Nsp13: separating the duplex and promoting the annealing of single-stranded nucleic acid

Genome replication is a key step in the coronavirus life cycle and requires the involvement of a range of virally encoded non-structural proteins. The non-structural protein 13 (Nsp13) of coronaviruses is a highly conserved helicase and is considered an ideal drug target. However, the activity characteristics of the helicase Nsp13 of the infectious bronchitis virus (IBV) remain unclear. In this study, we expressed and biochemically characterized the purified recombinant IBV Nsp13 and found that IBV Nsp13 was able to unwind duplex substrates in a 5'-to-3' direction by using the energy from the hydrolysis of all nucleotide triphosphate (NTP) and deoxyribonucleoside triphosphate (dNTP). We also explored the substrate selectivity and influencing factors of the unwinding activity of IBV Nsp13. The nucleic acid continuity of the loading strand was essential for Nsp13 to unwind duplex substrates. In addition, we first demonstrated that IBV helicase Nsp13 also had an annealing activity to promote two single-stranded nucleic acids to form a double-stranded nucleic acid. Biochemical analysis of the unwinding and annealing activities of IBV Nsp13 was helpful for deeply revealing the replication mechanism of coronavirus and the development of antiviral drugs.

Heterologous maternal antibodies derived from infectious bronchitis vaccines prevent the development of lesions associated with false layer syndrome

Infectious bronchitis virus (IBV) strains of the Delmarva (DMV)/1639 genotype have been causing false layer syndrome (FLS) in the Eastern Canadian layer operations since the end of 2015. FLS is characterized by the development of cystic oviducts in layer pullets infected at an early age. Currently, there are no homologous vaccines for the control of this IBV genotype. Our previous research showed that a heterologous vaccination regimen incorporating Massachusetts (Mass) and Connecticut (Conn) IBV types protects layers against DMV/1639 genotype IBV. The aim of this study was to investigate the role of maternal antibodies conferred by breeders received the same vaccination regimen in the protection against the development of DMV/1639-induced FLS in pullets. Maternal antibody-positive (MA+) and maternal antibody-negative (MA-) female progeny chicks were challenged at 1 day of age and kept under observation for 16 weeks. Oviductal cystic formations were observed in 3 of 14 birds (21.4 %) in the MA- pullets, while the lesions were notably absent in the MA+ pullets. Milder histopathological lesions were observed in the examined tissues of the MA+ pullets. However, the maternal derived immunity failed to demonstrate protection against the damage to the tracheal ciliary activity, viral shedding, and viral tissue distribution. Overall, this study underscores the limitations of maternal derived immunity in preventing certain aspects of viral pathogenesis, emphasizing the need for comprehensive strategies to address different aspects of IBV infection.

Salmonella typhimurium Vaccine Candidate Delivering Infectious Bronchitis Virus S1 Protein to Induce Protection

Infectious bronchitis (IB) is a highly infectious viral disease of chickens which causes significant economic losses in the poultry industry worldwide. An effective vaccine against IB is urgently needed to provide both biosafety and high-efficiency immune protection. In this study, the S1 protein of the infectious bronchitis virus was delivered by a recombinant attenuated Salmonella typhimurium vector to form the vaccine candidate χ11246(pYA4545-S1). S. typhimurium χ11246 carried a sifA- mutation with regulated delayed systems, striking a balance between host safety and immunogenicity. Here, we demonstrated that S1 protein is highly expressed in HD11 cells. Immunization with χ11246(pYA4545-S1) induced the production of antibody and cytokine, leading to an effective immune response against IB. Oral immunization with χ11246(pYA4545-S1) provided 72%, 56%, and 56% protection in the lacrimal gland, trachea, and cloaca against infectious bronchitis virus infection, respectively. Furthermore, it significantly reduced histopathological lesions in chickens. Together, this study provides a new idea for the prevention of IB.