Identification of Cytotoxic T lymphocyte (CTL) Epitope and design of an immunogenic multi-epitope of Bovine Ephemeral Fever Virus (BEFV) Glycoprotein G for Vaccine Development

In silico analysis of virulence factors of Streptococcus uberis for a chimeric vaccine design

Streptococcus uberis is one of the causative agents of bovine mastitis, which has detrimental effects on animal health and the dairy industry. Despite decades of research, the requirement for effective vaccines against the disease remains unmet. The goal of this study was to create a multi-epitope vaccine using five virulence factors of S. uberis through the reverse vaccinology approach, which has been employed due to its high efficiency and applicability. Plasminogen activator A (PauA), glyceraldehyde-3-phosphate dehydrogenase C (GapC), C5a peptidase, S. uberis adhesion molecule (SUAM), and sortase A (SrtA) were selected for the T cytotoxic (CTL) and B cell epitope analyses as they were extensively studied in S. uberis or other pathogens. Eighteen CTL and ten B cell epitopes that were antigenic, non-toxic, and non-allergenic were selected in order to design a chimeric vaccine candidate that in silico analysis revealed to be potentially immunogenic, non-allergenic, and stable. Molecular docking analysis of the vaccine candidate with Toll-like receptor (TLR) 2 and TLR 4 revealed stable interactions between the candidate and the immune receptors. Meanwhile, the stability of the docked complexes was confirmed using normal mode analysis. Additionally, in silico immune simulation of the vaccine candidate demonstrated the stimulation of primary immune responses, indicating that the chimeric protein can hold promise as a viable vaccine candidate for preventing S. uberis mastitis. Moreover, the current study can provide a background for designing epitope-based vaccines based on the explored epitopes.

Genetic Analysis of Orf Virus (ORFV) Strains Isolated from Goats in China: Insights into Epidemiological Characteristics and Evolutionary Patterns

Contagious ecthyma (CE) is an acute infectious zoonosis caused by orf virus (ORFV) that mainly infects sheep and goats and causes obvious lesions and low market value of livestock, resulting in huge economic losses for farmers. In this study, two strains of ORFV were isolated from Shaanxi Province and Yunnan Province in China, named FX and LX. The two ORFVs were located in the major clades of domestic strains respectively, and exhibited distinct sequence homology. We analyzed the genetic data of core genes (B2L, F1L, VIR, ORF109) and variable genes (GIF, ORF125 and vIL-10) of ORFV to investigate its epidemiological and evolutionary characteristics. The sequences from 2007 to 2018 constituted the majority of the viral population, predominantly concentrated in India and China. Most genes were clustered into SA00-like type and IA82-like type, and the hotspots in East and South Asia were identified in the ORFV transmission trajectories. For these genes, VIR had the highest substitution rate of 4.85 × 10-4, both VIR and vIL-10 suffered the positive selection pressure during ORFV evolution. Many motifs associated with viral survival were distributed among ORFVs. In addition, some possible viral epitopes have been predicted, which still require validation in vivo and in vitro. This work gives more insight into the prevalence and phylogenetic relationships of existing orf viruses and facilitate better vaccine design.

Development and validation of a DIVA ELISA for differentiating BEFV infected from vaccinated animals

Inactivated vaccine is considered safe and used for prevention of bovine ephemeral fever in several endemic countries. To differentiate between BEFV-infected and vaccinated animals, we developed an ELISA capable of detecting infection-related antibodies against BEFV. Recombinant proteins, including N, P, M, L, G_NS, α2, β and γ, were expressed in E. coli and screened by Western blotting and ELISA. The results showed G_NS, α2 and β specifically reacted with sera from BEFV infected cattle but not sera from vaccinated cattle. A DIVA ELISA based on a C-terminal truncated form of G_NS was developed, with 100% sensitivity and 98.0% specificity at a sample to positive-control optical density ratio (S/P) threshold of 0.18. Specificity analysis showed that the assay has no cross-reactivity with antisera of other common bovine viruses. Anti-G_NS antibody appears at 3-4 days post infection (dpi) and persists up to 240-300 dpi in the experimentally infected cattle. Sero-epidemiological survey using sera collected from vaccinated cattle in an endemic area in Jiangsu Province revealed sero-positive rate of 2.36% (6/254), indicating that the DIVA ELISA could be used as a reliable diagnostic tool for differentiating BEFV infected from vaccinated animals.