Estudo do envolvimento de polimorfismos do NRAMP1 na resistência a Brucelose bovina

Abstract

Brucellosis is an economically important reproductive disease of cattle caracterized by abortion during the last trimester of gestation. The natural resistance against intracellular pathogens, like Brucella abortus, has been associated to the Nramp1 gene in mice, humam, and cattle. The Nramp1 gene encodes a divalent cation tranporter that is located in tha phagolysosome membrane in macrophages. The Nramp1 in mice plays an important role in innate immunity, favouring the control of bacterial growth by macrophages during the early phase of infection. In addition, Nramp1 influences the adaptive immunity. In cattle, natural resistance against brucellosis is associated with polymorphisms at the 3untranslated region (3UTR) Nramp1 gene, which are detectable by single strand conformational analysis (SSCA). This study compared the frequency of the Nramp1 3UTR polymorphisms between Brazilian Zebu breeds (Gir, Guzerá, and Nelore) and Holsteins. It was also studied the association between Nramp1 3UTR polymorphisms and natural resistance against brucellosis in experimental and natural infections by Brucella abortus. A marked difference in the frequency of alleles was detected between the zebu and Holstein cattle (p<0.001). No association was found between the Nramp1 resistant allele and the resistant fenotype neither in experimental nor in naturally-occuring brucellosis. These results imply that Nramp1 3UTR polymorphisms cannot be used as maker of natural resistence against bovine brucelosis.