Immunoprotective Effects of Two Histone H2A Variants in the Grass Carp Against Infection.

In teleost fish, the nucleotide polymorphisms of histone H2A significantly affect the resistance or susceptibility of zebrafish to infection. Whether histone H2A variants can enhance the resistance of grass carp to infection remains unclear. Here, the effects of 7 previously obtained variants (gcH2A-1gcH2A-7) and 5 novel histone H2A variants (gcH2A-11, gcH2A-13gcH2A-16) in response to infection were investigated. It was found that these histone H2A variants could be divided into type I and II. Among them, 5 histone H2A variants had no any effects on the infection, however 7 histone H2A variants had antibacterial activity against infection. The gcH2A-4 and gcH2A-11, whose antibacterial activity was the strongest in type I and II histone H2A variants respectively, were picked out for yeast expression. Transcriptome data for the samples from the intestines of grass carp immunized with the engineered expressing PYD1, gcH2A-4 or gcH2A-11 revealed that 5 and 12 immune-related signaling pathways were significantly enriched by gcH2A-4 or gcH2A-11, respectively. For the engineered expressing gcH2A-4, NOD-like receptor and Toll-like receptor signaling pathways were enriched for up-regulated DEGs. Besides NOD-like receptor and Toll-like receptor signaling pathways, the engineered expressing gcH2A-11 also activated Cytosolic DNA-sensing pathway, RIG-I-like receptor signaling pathway and C-type lectin receptor signaling pathway. Furthermore, grass carp were immunized with the engineered expressing PYD1, gcH2A-4 or gcH2A-11 for 1 month and challenged with These grass carp immunized with gcH2A-4 or gcH2A-11 showed lower mortality and fewer numbers of than did the control group. All these results suggest that gcH2A-4 and gcH2A-11 play important roles in evoking the innate immune responses and enhancing disease resistance of grass carp against infection.