Preliminary Analysis of MicroRNA Transcriptome Altered by Vaccine and Marek’s Disease Virus in Chickens

MicroRNAs are a class of small, non-coding RNAs that regulate gene expression at the post-transcriptional level and play important roles in many biological processes such as development, cell signaling and immune response. Mature miRNAs are about 22 nucleotides in length. Reportedly, the growth of various tumors, including cancers, is mediated by dysfunctional regulation by miRNAs, and differential expression of miRNA is associated with virus infection and tumorigenesis. This study was aimed to explore the microRNA transcriptome and to profile microRNA expression in response to vaccination or Marek’s disease virus infection in two highly inbred lines of chickens by next-generation sequencing.

Deep sequencing yielded 498 and 502 microRNA sequences expressed in spleen tissues of the highly inbred line 6₃ and line 7₂ chickens at 10 days of age, respectively. The line 6₃ is known resistant to tumor formation. In contrast, the line 7₂ is highly susceptible to Marek’s disease. Preliminary analysis of the sequence data identified 15 (6 known and 9 novel) microRNAs that were highly differentially expressed between the two lines of chickens. Marek’s disease vaccine, HVT or CVI988/Rispens, was given on the day of hatch. At 10 days of age, HVT and CVI988/Rispens upregulated the expression of 12 and 11, downregulated 42 and 4 microRNAs in line 6₃, respectively; HVT and CVI988/Rispens upregulated the expression of 2 and 12,  downregulated 30 and 57 microRNAs in line 7₂. Marek’s disease virus altered 44 and 71 microRNAs in expression in the line 6₃ and 7₂ chickens, respectively. Validation studies will follow.