Protective effect of the AT137RQ and ARQK176 PrP allele against classical scrapie in Sarda breed sheepGabriele Vaccari1, Gaia Scavia1, Marcello Sala2, Gianmario Cosseddu1, Barbara Chiappini1, Michela Conte1, Elena Esposito1, Raniero Lorenzetti2, Gabriella Perfetti2, Paola Marconi2, Francesco Scholl2, Katia Barbaro2, Antonino Bella1, Romolo Nonno1 and Umberto Agrimi1
1 Istituto Superiore di Sanita, Viale Regina Elena 299, 00161 Rome, Italy
2 Istituto Zooprofilattico Sperimentale delle Regioni Lazio e Toscana, Via Appia Nuova 1411, 00178 Rome, Italy
Received 11 July 2008; accepted 22 January 2009; published online 27 January 2009
Abstract - The susceptibility of sheep to scrapie is under the control of the host's prion protein (PrP gene and is also influenced by the strain of the agent. PrP polymorphisms at codons 136 (A/V), 15 (R/H) and 171 (Q/R/H) are the main determinants of susceptibility/resistance of sheep to classica scrapie. They are combined in four main variants of the wild-type ARQ allele: VRQ, AHQ, ARH and ARR. Breeding programmes have been undertaken on this basis in the European Union and th USA to increase the frequency of the resistant ARR allele in sheep populations. Herein, we report th results of a multi-flock study showing the protective effect of polymorphisms other than those a codons 136, 154 and 171 in Sarda breed sheep. All ARQ/ARQ affected sheep (n = 154) and 37 negative ARQ/ARQ controls from four scrapie outbreaks were submitted to sequencing of the Pr gene. The distribution of variations other than those at the standard three codons, between scrapi cases and negative controls, was statistically different in all flocks. In particular, the AT137RQ an ARQK176 alleles showed a clear protective effect. This is the first study demonstrating a protectiv influence of alleles other than ARR under field conditions. If further investigations in other shee breeds and with other scrapie sources confirm these findings, the availability of various protectiv alleles in breeding programmes of sheep for scrapie resistance could be useful in breeds with a low frequency of the ARR allele and would allow maintaining a wider variability of the PrP gene.
Key words: transmissible spongiform encephalopathy / PrP / genetics / scrapie / sheep
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© INRA, EDP Sciences 2009