Association between IL-10a single nucleotide polymorphisms and resistance to cyprinid herpesvirus-3 infection in common carp (Cyprinus carpio)

Analysis of gene polymorphisms and disease association is essential for assessing putative candidate genes affecting susceptibility or resistance to disease. In this paper, we report the results of an association analysis between single nucleotide polymorphisms (SNPs) in common carp (Cyprinus carpio) innate immune response genes and resistance to cyprinid herpesvirus-3 (CyHV-3) infection. Twenty-three SNPs from 14 genes were genotyped in the progeny of a full-sib family, which was subjected to a CyHV-3 challenge. The challenge was carried out by cohabitation of naïve fish with CyHV-3-infected fish and the experimental fish subsequently were scored as susceptible or resistant. Fisher exact probability and chi-square tests were used to assess the association of SNP genotypes or alleles with CyHV-3 resistance. No association between SNPs in common carp immune response genes and resistance to CyHV-3 was found, except for SNPs in IL-10a. For IL-10a, both heterozygous and homozygous fish carrying the GCG haplotype were more susceptible to CyHV-3 infection (P < 0.001). To identify the source of susceptible and resistant alleles, we genotyped fish from the parental common carp strains. We found that the susceptible allele was more common among fish from the wild CyHV-3-resistant strain (Sassan) whereas the resistant allele was found in all the fish sampled from the susceptible domesticated strain (Našice). The implications of our findings to the development of a domesticated CyHV-3-resistant stock through marker-assisted selection or gene-introgression, and the possible impact of the IL-10a polymorphisms we identified on susceptibility to CyHV-3 infection in common carp are discussed.