GENETICS OF ANIMAL SPONGIFORM ENCEPHALOPA THIES

Genetic control of sheep resistance to Scrapie (Tremblante) is well es tablished. The incubation period of the natural or experimental diseas e is strongly associated with polymorphisms of codons 136 (Ala/Val) an d 171 (Arg/Glu) from the Prion protein PrP. However, all of the observ ed genetic variability can't be related to these polymorphisms and oth er mutations of the PrP gene, or/and other genes, are probably concern ed with the host susceptibility to spongiform encephalopathies. The re sistance of immunodeficient mice (SCID mice) to the dissemination of p athogens in their bodies suggests a role of immune cells. A local infl ammatory reaction (astrocytosis, microgliosis, secretion of interleuki n-1 and TNF-alpha) has been demonstrated in the central nervous system . A possible role in the regulation of the incubation period or expres sion of the disease by genes of the immune system (genes of the major histocompatibility complex, of cytokines and membrane receptors, etc) remains to be studied, in particular during the early phases of infect ion during which we have at present no means of detecting affected ani mals.