Bacterial and Pneumocystis Infections in the Lungs of Gene-Knockout Rabbits with Severe Combined Immunodeficiency.

Jun Song,Kong Chen,Michael Bradley,Jibing Yang,Jay K Kolls,Kelsey Cornelius,Samantha Eckley,Jifeng Zhang,Dongshan Yang,Li Peng,Mark J Hoenerhoff,Yuqing Eugene Chen,Robert Sigler,Patrick A Lester,Jinxue Ruan,Guoshun Wang,Liang Ma,Jie Xu,Fei Sun

doi:10.3389/fimmu.2018.00429

Abstract

Using the CRISPR/Cas9 gene-editing technology, we recently produced a number of rabbits with mutations in immune function genes, including FOXN1, PRKDC, RAG1, RAG2, and IL2RG. Seven founder knockout rabbits (F0) and three male IL2RG null (−/y) F1 animals demonstrated severe combined immunodeficiency (SCID), characterized by absence or pronounced hypoplasia of the thymus and splenic white pulp, and absence of immature and mature T and B-lymphocytes in peripheral blood. Complete blood count analysis showed severe leukopenia and lymphocytopenia accompanied by severe neutrophilia. Without prophylactic antibiotics, the SCID rabbits universally succumbed to lung infections following weaning. Pathology examination revealed severe heterophilic bronchopneumonia caused by Bordetella bronchiseptica in several animals, but a consistent feature of lung lesions in all animals was a severe interstitial pneumonia caused by Pneumocystis oryctolagi, as confirmed by histological examination and PCR analysis of Pneumocystis genes. The results of this study suggest that these SCID rabbits could serve as a useful model for human SCID to investigate the disease pathogenesis and the development of gene and drug therapies.

Highlights

Severe combined immunodeficiency (SCID), caused by mutations in genes affecting lymphocyte development or function, such as IL-2RG, RAG1 and/or RAG2, and PRKDC, accounts for the most severe phenotypes among primary immunodeficient patients [1, 2]
Since Pneumocystis is a major cause of pneumonia in both primary and acquired immunodeficient patients, we investigated if Pneumocystis oryctolagi (P. oryctolagi), the rabbit-specific Pneumocystis species [15], was present in post-weaning severe combined immunodeficiency (SCID) rabbits
Respiratory complications are a major cause of morbidity and mortality in human SCID patients

Summary

Introduction

Severe combined immunodeficiency (SCID), caused by mutations in genes affecting lymphocyte development or function, such as IL-2RG, RAG1 and/or RAG2, and PRKDC, accounts for the most severe phenotypes among primary immunodeficient patients [1, 2]. SCID patients are highly susceptible to bacterial, viral, and fungal infections in early infancy, with the lungs being the most commonly affected site [1, 2]. Mice have been the dominant animal species to model SCID. Cas nuclease tool [5, 6]. Their small body size and short lifespan sometimes limit their application in translational studies [7]. Development of a model utilizing an animal species with a larger body size and a longer lifespan is desirable to enhance the ability to predict clinical outcomes of the human SCID disease, especially given the fact that the SCID patients’ lifespan is expected to continue increasing

Methods

Results

Conclusion