Background: Tibetan antelope (Rhinopithecus), blue sheep (Pseudois nayauris) and plateau pika (Ochotona curzoniae) are wild animals living in Qinghai-Tibet Plateau. Up to now, there is no report of naturally occurred TSE upon these animals. Their PRNP genes are not described in literature.
Methods: We obtained and sequenced the PRNP genes from 21 Tibetan antelopes, 4 blue sheep and 3 plateau pikas. Then we prepared their recombinant proteins. Using scrapie strains 263K, 139A, ME7 and S15 as the seeds, we tested the reactivities of the PrP proteins from sheep (rSheepPrP25-234) and pika (rPikaPrP23-230) in RT-QuIC. We also did the PMCA tests of the brain homogenates of domestic sheep and rabbit with the seeds of strains 263K and ME7.
Results: The PRNP genes of bovids were 771 bp long and encoded 256 amino acids (aa.), showing 100% homology with wild-type sheep PrP aa. sequence. The PRNP gene of pika was 759 bp long and encoded 252 amino acids, showing 92.1% homology with aa. sequence of domestic rabbit. Both the proteins of sheep and pika revealed positive reactions in 10-5 diluted seeds. Only rPikaPrP23-230 produced positive curves in 10-7 diluted seeds. PMCA tests ailed to produce PK-resistant PrP (PrPres).
Conclusion: It is the first description of PRNP genes and PrP aa. sequences of those three animals in Qinghai-Tibet Plateau. In the presences of rodent prions, the PrPs of sheep and pika efficiently form fibrillation in RT-QuIC, but do not generate PrPres in PMCA. Our results indicate that pika, as one of the important links in the biological chain in Qinghai-Tibet Plateau, may play an important role in prion circulation. And pika PrP deserves further analysis for its potential application value in the assays for human prion disease.