NOD/LtSz-Rag1null mice:: An immunodeficient and radioresistant model for engraftment of human hematolymphoid cells, HIV infection, and adoptive transfer of NOD mouse diabetogenic T cells

Development of a small animal model for the in vivo study of human immunity and infectious disease remains an important goal, particularly for investigations of HIV vaccine development. NOD/Lt mice homozygous for the severe combined immunodeficiency (Prkdc(scid)) mutation readily support engraftment with high levels of human hematolymphoid cells. However, NOD/LtSz-scid mice are highly radiosensitive, have short life spans, and a small number develop functional lymphocytes with age. To overcome these limitations, we have backcrossed the null allele of the recombination-activating gene (Rag1) for 10 generations onto the NOD/LtSz strain background, Mice deficient in RAG1 activity are unable to initiate V(D)J recombination in Ig and TCR genes and lack functional T and B lymphocytes, NOD/LtSz-Rag1(null) mice have an increased mean life span compared with NODntSz-scid mice due to a later onset of lymphoma development, are radioresistant, and lack serum Ig throughout life. NOD/LtSz-Rag1(null) mice were devoid of mature T or B cells. Cytotoxic assays demonstrated low NK cell activity. NOD/LtSz-Rag1(null) mice supported high levels of engraftment with human lymphoid cells and human hemopoietic stem cells. The engrafted human T cells were readily infected with HIV, Finally, NOD/LtSz-Rag1(null) recipients of adoptively transferred spleen cells from diabetic NOD/Lt+/+ mice rapidly developed diabetes. These data demonstrate the advantages of NOD/LtSz-Rag1(null) mice as a radiation and lymphoma-resistant model for long-term analyses of engrafted human hematolymphoid cells or diabetogenic NOD lymphoid cells.