Infection with measles virus induces leukopenia and rash in a humanized immune system mouse model

Humans are the natural hosts of the measles virus (MV). With the exception of non-human primates, no other animal species are naturally susceptible to MV infection. Thus, no small animal models exist to study the mechanisms of MV pathogenicity. The aim of the present study was to establish a small animal model of MV infection using NOD/LtSz-scid/IL2Rγ null (NSG) immunodeficient mice implanted with human-cord-blood-derived CD34 + cells and to evaluate its suitability as a measles model. Upon infecting the humanized mice with a recombinant wild-type strain MV expressing enhanced green fluorescent protein (EGFP), a strong EGFP signal was detected in the spleen, lymph nodes, and bone marrow. This fluorescence was confirmed to be associated with MV infection in human T and B cells. Furthermore, the mice exhibited leukopenia and rash-like green fluorescent foci reminiscent of a measles rash. These foci originated from the accumulation of human leukocytes adjacent to hair follicles, consistent with the pathology observed in non-human primate models. These results suggest that this small animal model could be a valuable tool for elucidating the mechanisms of MV infection and its pathogenicity.