  Prion diseases are invariably fatal and highly infectious neurodegenerative
diseases affecting humans and animals. By now there have not been some
effective therapeutic approaches to treat all these prion diseases. In 2008,
canine mammals including dogs (canis familials) were the first time
academically reported to be resistant to prion diseases (Vaccine 26: 2601--2614
(2008)). Rabbits are the mammalian species known to be resistant to infection
from prion diseases from other species (Journal of Virology 77: 2003--2009
(2003)). Horses were reported to be resistant to prion diseases too
(Proceedings of the National Academy of Sciences USA 107: 19808--19813 (2010)).
By now all the NMR structures of dog, rabbit and horse prion proteins had been
released into protein data bank respectively in 2005, 2007 and 2010
(Proceedings of the National Academy of Sciences USA 102: 640--645 (2005),
Journal of Biomolecular NMR 38:181 (2007), Journal of Molecular Biology 400:
121--128 (2010)). Thus, at this moment it is very worth studying the NMR
molecular structures of horse, dog and rabbit prion proteins to obtain insights
into their immunity prion diseases.
  This article reports the findings of the molecular structural dynamics of
wild-type horse, dog, and rabbit prion proteins. The dog and horse prion
proteins have stable molecular structures whether under neutral or low pH
environments. Rabbit prion protein has been found having stable molecular
structures under neutral pH environment, but without structural stability under
low pH environment. Under low pH environment, the salt bridges such as
D177--R163 were broken and caused the collapse of the stable $\alpha$-helical
molecular structures.
