Transcriptome comparative analysis of immune tissues from asymptomatic and diseased Epinephelus moara naturally infected with nervous necrosis virus

Epinephelus moara is an economically important fish in Southeast Asian countries but is suffering from nervous necrosis virus (NNV) infection. A deeper understanding of the host-NNV interaction mechanisms makes sense for disease control, however, at present, the pathogenesis of natural NNV infection and the resistance mechanism in host remains poorly understood. In this study, asymptomatic and diseased E. moara with clinical symptoms of viral nervous necrosis (VNN) from a grouper farm were both detected with a positive RT-PCR signal of NNV, then transcriptome sequencing of their immune tissues (liver, spleen and kidney) were performed for comparation analysis. The de novo assemblies yielded 53,789 unigenes which had a length varied from 201 to 19,675 bp and a N50 length of 2115 bp, and 29,451 unigenes were functionally annotated, with 83, 250 and 5632 unigenes being differentially expressed in liver, spleen and kidney respectively. KEGG pathway enrichment analysis of the DEGs showed many DEGs were enriched in immune related pathways. Although the expression of class I major histocompatibility complex (MHC) was significantly higher in three immune tissues of the diseased grouper, many immune related genes, including humoral immune molecules (such as antibodies), the cellular mediated cytotoxic molecules (such as perforin) and some adhesion related genes were down regulated in the diseased grouper. Our results provided many unigenes that might play important roles in NNV resistance for further research. Furthermore, a total of 8666 unigenes containing 11,623 simple sequence repeats (SSRs) were identified, which provided useful information for screening molecular markers associated with NNV resistance in E. moara.

BoLA-6*01301 and BoLA-6*01302, two allelic variants of the A18 haplotype, present the same epitope from the Tp1 antigen of Theileria parva

We have recently shown that the BoLA-A18 variant haplotype (BoLA-6*01302) is more prevalent than the BoLA-A18 haplotype (BoLA-6*01301) in a sample of Holstein/Friesian cattle in Kenya. These MHC class I allelic variants differ by a single amino acid polymorphism (Glu97 to Leu97) in the peptide-binding groove. We have previously mapped an 11-mer peptide epitope from the Theileria parva antigen Tp1 (Tp1214-224) that is presented by BoLA-6*01301. Crystal structure data indicates that Glu97 in the MHC molecule plays a role in epitope binding through electro-static interaction with a lysine residue in position 5 of the epitope, which also functions as an additional anchor residue. In contrast to expectations, we demonstrate that the amino acid substitution in BoLA-6*01302 does not divert the CTL response away from Tp1214-224. The two MHC molecules exhibit similar affinity for the Tp1 epitope and can present the epitope to parasite-specific CTLs derived from either BoLA allelic variants. These data confirm that this BoLA polymorphism does not alter Tp1 epitope specificity and that both allelic variants can be used for Tp1 vaccine studies.