Impacts of oral Vibrio mimicus double-targeted DNA vaccine on the gut microbiota in grass carps (Ctenopharyngodon idella) and correlations with intestinal mucosa innate immunity

• Published in: Aquaculture 2021-02, Vol.533, p.736201, Article 736201
• Main Authors: Cao, Shou-Lin, Guo, Jia-Jing, Zhao, Wen-ping, Yang, Wen-Fei, Zhang, Shu-Liu, Tao, Hui-Zhu, Li, Jin-Nian
• Format: Article
• Language: English
• Subjects: Ctenopharyngodon idella; Gut microbiota; Immune-related gene; Intestinal macrophage activity; Vibrio mimicus double-targeted DNA vaccine
• ISSN: 0044-8486; 1873-5622
• DOI: 10.1016/j.aquaculture.2020.736201

Intestinal microbiota plays an important role in host metabolism, immunity and health maintenance. In previous studies, we developed an oral double-targeted DNA vaccine of Vibrio mimicus and demonstrated that the vaccine could elicit significantly higher immunoprotection than did naked DNA vaccine. However, the effects of the vaccine on gut microbiota of grass carp (Ctenopharyngodon idella) and intestinal mucosa innate immunity, as well as their correlations, remain largely undefined. The present study used 16S rRNA amplicon-sequencing to investigate the distribution of microbiota in different gut segments, changes of microbiota community after vaccination, and further explored the transcriptional expression of immune-related genes in hindgut and the activity of macrophages isolated from hindgut. The results showed that the distribution of microbiota varied in different gut segments of healthy grass carps at genus level. The vaccine obviously changed the microbiota community, especially in the hindgut, at 21 days post vaccination (dpv). At genus level, the relative abundance of Bacteroides and Cetobacterium in both midgut and hindgut as well as Aeromonas in both foregut and midgut significantly increased, while the relative abundance of some genera, such as Ruminococcaceae_unclassified (in all gut segments), Sphingomonas and Methylobacterium (in both midgut and hindgut), Porphyromonadaceae_unclassified (in both foregut and hindgut), Lactobacillus (in hindgut) and Vibrio (in foregut), significantly decreased. The expression levels of investigated immune-related genes (IL-6, TNF-α, MHC-Iα and MHC-IIβ) were markedly up-regulated at each test time point post vaccination compared with those in the control group. Likewise, the phagocytic ability and respiratory burst activity of the intestinal macrophages at each examined time post vaccination were also significantly higher than those in the control group. Furthermore, statistical analyses indicated that both immune-related genes expression and intestinal macrophages activity in hindgut were positively correlated with the relative abundance of Bacteroides in hindgut at 21 dpv (Pearson's r = 0.950–0.968, P