With the study of Lacroux et al., 2013, there are now two experimental studies that show the high level of scrapie resistance contributed by the 222K allele in goats. These experimental challenge studies in goats confirm the findings in the field that the 222K allele confers a high level of unsusceptibility to scrapie in goats, supporting its usefulness for breeding programs.
The Lacroux represents a broad and independent study and appeared on November 27, 2013 with the title: "Genetic resistance to scrapie infection in experimentally challenged goats" in the Journal of Virology ahead of print. Intracerebral challenge with natural goat scrapie lead to confirmed disease in two heterozygous 222Q/K animals only after very long incubation times of 1900-2200 days, and 2100 days in a single 222K/K homozygous animal. The previously published Italian study of Acutis et al., 2012 found absence of disease signs until the end of the experiment, which was stopped at 1650 days being earlier than the Lacroux study.
Lacroux and colleagues also performed oral challenges in very young goats (two administrations, 2 and 30 days after birth) of five different genotypes, including a group carriers of the 222K/Q allele. All 222K allele carriers remained TSE negative of which four even for over 2500 days.
Other allele polymorphisms (wild type, 142M, 154H, 211Q) were also investigated in this broad study, where intracerebral infection was 100% transmitted through the intracerebral route and in wild type and 142M carriers through the oral route. Interestingly, the 154H and 211Q (heterozygous) animals in the oral challenge also remained negative for the duration of the experiment.