Yeast cell surface displaying VP28 antigen and its potential application for shrimp farming.

VP28 is an envelope protein of White Spot Syndrome Virus (WSSV), which has been shown in previous studies to induce a high immune response in shrimp. VP28 has been produced in some host systems such as Escherichia coli, Bacillus subtilis, and Pichia pastoris as free protein. Here we showed a new strategy of anchoring VP28 on the Saccharomyces cerevisiae yeast surface and using the yeast cell extract combined with probiotic as an oral vaccine for shrimp farming. We have successfully constructed a recombinant yeast cell capable of expressing VP28 on the cell surface. The feeding diet combined with VP28 anchored yeast cell extract provided significant assurance to Litopenaeus vannamei, challenged by WSSV, resulting in a relative percent survival (RPS) of 87.10 ± 2.15%. Interestingly, the utilization of VP28 anchored yeast cell extract could enhance the efficiency of probiotic strains like Lactobacillus and Bacillus on shrimp farming. The results in both laboratory scales and field trials using extract of VP28 displaying Saccharomyces showed a growth-promoting effect in shrimp, assessed through average shrimp weight. Taken together, our results in this study demonstrated a new successful strategy of using yeast cell surface as a tool to produce VP28-based oral vaccine for shrimp aquaculture. KEY POINTS: • A new strategy of using VP28 antigen as anchored protein on S. cerevisiae yeast cell surface (S. cerevisiae::VP28) • The utilization of VP28 antigen and yeast as S. cerevisiae::VP28 extract enhanced potential protection of Litopenaeus vannamei against White Spot Syndrome Virus (RPS 87.10%) • The use of S. cerevisiae::VP28 extract increased efficiency of probiotic on shrimp growth-promoting effect either lab-scale or field trial.

An assessment of genetic diversity and population structures of fifteen Vietnamese indigenous pig breeds for supporting the decision making on conservation strategies.

The study aimed to characterize genetic diversity, genetic clusters, and phylogenetic relationships of 15 Vietnamese indigenous pig breeds across the country for supporting the decision making of the conservation strategies. For this purpose, 638 samples from the breeds together with two wild pig breeds and an exotic breed were genotyped with 19 microsatellite markers recommended from FAO/ISAG for diversity studies. The higher genetic diversity was observed for indigenous breeds (mean He = 0.67) and wild breeds (mean He = 0.74); the indigenous CoAluoi breed compared the out-breed Landrace (He = 0.59). Fifteen percent of the genetic variation came from differences among breeds. The unrooted neighbor-joining dendrogram obtained from Nei's genetic distances showed three nodes with 100% supported bootstrap values. The first node included the three indigenous breeds (Hung, LungPu, and MuongKhuong), the second node included the indigenous BaXuyen and the exotic Landrace, and the third node included the two wild Thailand and Vietnam pig breeds. The discriminant analysis of principal component (DAPC) of 18 studied breeds resulted in 12 genetic clusters. Unlike the other indigenous breeds, the BaXuyen was in the same genetic cluster with the exotic Landrace-which agreed with the 100% bootstrap value of their node-so the BaXuyen should not be conserved. The five indigenous pig breeds-Huong, VanPa, Soc, ChuProng, and CoAluoi-were assigned to their own clusters, which agreed with the low supported bootstrap values of their nodes. These five breeds should be in the high conservation priority. Finally, the 9 indigenous pig breeds (MuongKhuong, LungPu, Hung, TapNa, MongCai, HaLang, Lung, Meo, and Ban breeds) formed four genetic admixture structures. These results suggest the conservation strategies should be built based on from five to nine pig groups thus reducing the cost of conservation whereas still remaining the genetic diversity of the studied breeds.