Nonhuman Primate Models of Huntington's Disease and Their Application in Translational Research.

Huntington's disease (HD) is a monogenic, autosomal dominant inherited fatal disease that affects 1 in 10,000 people worldwide. Given its unique genetic characteristics, HD would appear as one of the most straightforward neurodegenerative diseases to replicate in animal models. Indeed, mutations in the HTT gene have been used to generate a variety of animal models that display differential pathologies and have significantly increased our understanding of the pathological mechanisms of HD. However, decades of efforts have also shown the complexity of recapitulating the human condition in other species. Here we describe the three different types of models that have been generated in nonhuman primate species, stating their advantages and limitations and attempt to give a critical perspective of their translational value to test the efficacy of novel therapeutic strategies. Obtaining construct, phenotypic, and predictive validity has proven to be challenging in most animal models of human diseases. In HD in particular, it is hard to assess the predictive validity of a new therapeutic strategy when no effective "benchmark" treatment is available in the clinic. In this light, only phenotypic/face validity and construct validity are discussed.