Structure of the bovine natural resistance associated macrophage protein (NRAMP 1) gene and identification of a novel polymorphism

Effect of polymorphisms in the Slc11a1 coding region on resistance to brucellosis by macrophages in vitro and after challenge in two Bos breeds (Blanco Orejinegro and Zebu)

The resistance/susceptibility of selected cattle breeds to brucellosis was evaluated in an F1 population generated by crossing animals classified as resistant (R) and susceptible (S) (R x R, R x S, S x R, S x S) based on challenges in vitro and in vivo. The association between single nucleotide polymorphisms identified in the coding region of the Slc11a1 gene and resistance/susceptibility was estimated. The trait resistance or susceptibility to brucellosis, evaluated by a challenge in vitro, showed a high heritable component in terms of additive genetic variance (h(2) = 0.54 ± 0.11). In addition, there was a significant association (p < 0.05) between the control of bacterial survival and two polymorphisms (a 3'UTR and SNP4 located in exon 10). The antibody response of animals classified as resistant to infection by Brucella abortus differed significantly (p < 0.05) from that of susceptible animals. However, there was no significant association between single nucleotide polymorphisms located in the Slc11a1 gene and the antibody response stimulated by a challenge in vivo.

SLC11A1 gene polymorphisms are not associated to somatic cell score and milk yield in Chinese Holstein

It has been well established that mutations of the solute carrier family 11 A1 (SLC11A1) gene are responsible for susceptibility to a number of intracellular pathogens. Mastitis is the most common and most costly disease of dairy cattle, commonly caused by bacteria. As SLC11A1 protein is involved in bacterial killing, we assumed SLC11A1 gene as a candidate gene for bovine mastitis resistance. In this study, polymorphisms in the SLC11A1 gene were identified in the Chinese Holstein population. Genotypes were constructed, and their associations with somatic cell score and milk yield were determined. Single-strand conformation polymorphisms and DNA sequencing were used to reveal polymorphisms in SLC11A1 gene. A SNP in coding region and a variation of GT repeats in 3'-untranslated region were detected. The SNP resulted in an amino acid variation of p.P356A in transmembrane 8 of SLC11A1 peptide, which is the most conserved consecutive region. However, no associations were observed between the detected polymorphisms and somatic cell scores and milk yield in the Chinese Holstein population.

NRAMP1 3' untranslated region polymorphisms are not associated with natural resistance to Brucella abortus in cattle

The NRAMP1 gene encodes a divalent cation transporter, located in the phagolysosomal membrane of macrophages, that has been associated with resistance to intracellular pathogens. In cattle, natural resistance against brucellosis has been associated with polymorphisms at the 3' untranslated region (3'UTR) of the NRAMP1 gene, which are detectable by single-strand conformational analysis (SSCA). This study aimed to evaluate the association between NRAMP1 3'UTR polymorphisms and resistance against bovine brucellosis in experimental and natural infections. In experimentally infected pregnant cows, abortion occurred in 42.1% of cows with a resistant genotype (SSCA(r); n = 19) and in 43.1% of those with a susceptible genotype (SSCA(s); n = 23). Furthermore, no association between intensity of pathological changes and genotype was detected. In a farm with a very high prevalence of bovine brucellosis, the percentages of strains of the SSCA(r) genotype were 86 and 84% in serologically positive (n = 64) and negative (n = 36) cows, respectively. Therefore, no association was found between the NRAMP1-resistant allele and the resistant phenotype in either experimental or naturally occurring brucellosis. To further support these results, bacterial intracellular survival was assessed in bovine monocyte-derived macrophages from cattle with either the resistant or susceptible genotype. In agreement with our previous results, no difference was observed in the rates of intracellular survival of B. abortus within macrophages from cattle with susceptible or resistant genotypes. Taken together, these results indicate that these polymorphisms at the NRAMP1 3'UTR do not affect resistance against B. abortus in cattle and that they are therefore not suitable markers of natural resistance against bovine brucellosis.