Akira Onishi

Transgenic Pig Research Unit

［Abstract］

The nuclear transfer has made it possible to produce immunodeficient pigs for the first time using fibroblasts targeted disruption of the X-linked interleukin-2 receptor gamma chain (Il2rg) gene.

［Keywords］

immunodeficiency, somatic cell cloning, regenerative medicine, antibody drug, pigs as experiment animal

［Background］

In recent years, humanized mice transplanted human tissue or cells to the immune-deficient mice have been widely used in various fields such as human disease models and as substitute to human type organs. Pigs are markedly similar to human in terms of anatomy, physiology and genetics. Therefore, a porcine model of severe combined immunodeficiency (SCID) promises to facilitate human cancer studies, the humanization of tissue for xenotransplantation, and the evaluation of stem cells for clinical therapy.

［Results and Discussion］

1. Fibroblasts containing a targeted disruption of the X-linked interleukin-2 receptor gamma chain gene, Il2rg, were used as donors to generate cloned pigs by serial nuclear transfer.
2. Germline transmission of the Il2rg deletion produced healthy Il2rg(+/-) females, while Il2rg(-/Y) males were athymic (Fig.1) and exhibited markedly impaired immunoglobulin (Fig.2) and T and NK cell production, robustly recapitulating human SCID.
3. Two of the ASRs also showed anti-silencing activity in other plant species such as Ipomoea batatas and Arabidopsis thaliana.
4. The immunodeficient pigs usually live shorter even under controlled laboratory conditions. However, following allogeneic bone marrow transplantation, donor cells were stably integrated in Il2rg (-/Y) heterozygotes and reconstituted the Il2rg (-/Y) lymphoid lineage. This resulted in long-term survival of immunodeficient pigs (Fig. 3).

1. This study will pave for the development of human disease models ranging from small animals to large animals with high similarity to human.
2. Pig models will have wide applications in medical research including long term evaluation of stem cells for more efficient and safer utilization of iPS cells for clinical therapy.
3. The immunodeficient pigs have less immune functions and therefore demonstrate less rejection to foreign tissues. This could lead to the development of technologies to facilitate the utilization of pig models in studies involving the reproduction of human tissues and organs for regenerative medicine.
4. This study will also pave the way for more efficient production of human antibodies and antibody drugs.
5. Utilization of pigs as model experiment animals may also lead to new hog raising business.

Fig.1. Lack of thymus in the immunodeficient (Il2rg-/Y) pig

Fig.2. Impaired antibody (IgG, IgA, IgM) production in immunodeficient pig

Fig.3. An immunodeficient pig survived longer after bone marrow transplantation

 

[Reference]

1. Suzuki S, Iwamoto M, Saito Y, Fuchimoto D, Sembon S, Suzuki M, Mikawa S, Hashimoto M, Aoki Y, Najima Y, Takagi S, Suzuki N, Suzuki E, Kubo M, Mimuro J, Kashiwakura Y, Madoiwa S, Sakata Y, Perry A, Ishikawa F, Onishi A (2012) Il2rg gene-targeted severe combined immunodeficiency pigs Cell Stem Cell 10(6):753-758