HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 INFECTION OF NEONATAL SEVERE COMBINED IMMUNODEFICIENT MICE XENOGRAFTED WITH HUMAN CORD-BLOOD CELLS

In these studies, neonatal C.B-17 severe combined immunodeficient (nSC ID) mice were reconstituted with human cord blood leukocytes (hu-CBLs) . The resulting hu-CBL-nSCLD mice contained readily detectable human C D3(+) T lymphocytes and CD20(+) human B cells, and produced substantia l levels of human IgM and IgG (including all subclasses). Human cells persisted in lymphoid organs and peripheral blood for at least 8 weeks , and CD4(+) T cells outnumbered CD8(+) T cells. Engraftment of human cells in peripheral lymphoid organs and blood was much greater than th at seen in adult SCID mice grafted with adult peripheral blood leukocy tes (PBLs). Hu-CBL-nSCID mice were susceptible to infection with labor atory-adapted and fresh clinical human immunodeficiency virus type 1 ( HIV-1) isolates. Following infection with HIV-1, virus could be recove red by the coculture of spleen, lymph node, peritoneal cavity, liver, and plasma samples from hu-CBL-nSCID mice with fresh human peripheral blood mononuclear cells, and proviral copies were detectable following amplification using the polymerase chain reaction (PCR). HIV p24 core antigen levels in hu-CBL-nSCID mouse plasma were consistent with ongo ing viral replication and high viral burdens. Rapid CD4(+) T cell depl etion occurred following infection with laboratory isolates of HIV-1 o r a syncytium-inducing clinical isolate, but a non-syncytium-inducing clinical isolate caused expansion of CD8(+) T cells, leading to an inv ersion of the CD4:CD8. ratio with only a transient decrease in CD4(+) T cells. These results suggest that the hu-CBL-nSCID mouse system has unique features that mimic certain aspects of pediatric HIV infection, and distinguish it from other animal models of HIV infection, includi ng the related hu-PBL-SCID model.