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Association of MHC IIA polymorphisms with disease resistance in Aeromonas hydrophila-challenged Nile tilapia

El-Magd, Mohammed A., El-Said, Karim S., El-Semlawy, Aml A., Tanekhy, Mahmoud, Afifi, Mohamed, Mohamed, Tarek M.
Developmental and comparative immunology 2019 v.96 pp. 126-134
Aeromonas hydrophila, Oreochromis niloticus, Toll-like receptor 7, alleles, disease resistance, fish, gene expression, genotype, immune response, immunoglobulin M, interleukin-1beta, kidneys, lysosomes, major histocompatibility complex, messenger RNA, mutants, nucleotides, phagocytosis, polymerase chain reaction, protein content, risk factors, single nucleotide polymorphism, spleen, stop codon, tumor necrosis factor-alpha
The major histocompatibility complex (MHC) genes show high polymorphisms in vertebrates depending on animal immunity status. Herein, MHC class IIA gene in Aeromonas hydrophila-challenged Nile tilapia was screened for presence of polymorphisms using sequencing. Twelve nucleotides deletion polymorphism was determined with a PCR product size of 267 bp in the resistant fish and 255 bp in the control and susceptible/diseased fish. Additionally, a non-synonymous right frameshift c.712 T > G (P. 238 * > G) SNP was detected at the stop codon (*). SNP-susceptibility association analysis revealed that fish carrying GG genotype and allele G were high susceptible (risk) for A. hydrophila, and had lower immune response as indicated by significant reduction in non-specific immune parameters (total protein, globulin, IgM, phagocytic activity, phagocytic index, and lysosome activity) and mRNA level of MHC IIA, interleukin 1 beta (IL1β), tumor necrosis factor alfa (TNFα), and toll-like receptor 7 (TLR7) in the spleen and head kidney. Thus, G allele could be considered as a risk (recessive or mutant) allele for c. 712 T > G (P. 238 * > G) SNP and so selection of Nile tilapia with protective allele (T) for this SNP could improve the disease resistant of the fish.