Dengue viral pathogenesis and immune response in humanized Rag2-/-gamma c-/- (RAG-hu) mice
Date
2009
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Abstract
Dengue viral pathogenesis and vaccine studies are hampered by the lack of an ideal animal model mimicking human disease and eliciting an adaptive immune response. We utilized a novel mouse model that permits multi-lineage human hematopoiesis and immune response following transplantation with human hematopoietic stem cells. To generate immuno-competent humanized mice, we xenografted neonatal Rag2-/-γc-/- mice with human CD34+ hematopoietic stem cells, resulting in the de novo development of functional human adaptive immune system. To evaluate susceptibility to dengue viral infection, humanized mice were challenged with dengue virus (DENV). We observed viremia that lasted three weeks post infection with all four serotypes of dengue virus. We also demonstrated the presence of human anti-dengue antibodies. Anti-dengue IgM was first detected at 2 weeks post infection followed by IgG at 6 weeks. Our results demonstrated for the first time that humanized mice were capable of dengue viral primary immune responses, thus paving the way for further dengue immunopathogenesis studies. We challenged the mice that survived a primary infection with a secondary infection of dengue virus. We report increased viremia, severe dehydration, hemorrhage and morbidity in several mice during a secondary infection. We demonstrate the first instance of dengue hemorrhagic fever or dengue shock syndrome (DHF/DSS) like phenomenon reported in any humanized mouse model for dengue infections. We also report the identification of cells that are actively infected with DENV in the spleen and lymph nodes of these mice using in situ hybridization and immunofluoresence staining methods. We used a SCID-hu model with an engrafted human thymus to study the direct infection of T-cells by dengue virus. We demonstrate that T-cells and CD34+ hematopoietic stem cells do not support a dengue viral infection. We were also able to infect monocytes and dendritic cells that were isolated and developed from human peripheral blood in vitro. In order to develop a consistent assay for antibody dependent enhancement (ADE) of dengue infection we were able to infect macrophages that were differentiated in vitro from CD34+ hematopoietic stem cells. In summary, this model provides a new tool to further our understanding of a complex disease like dengue hemorrhagic fever and dengue shock syndrome as well as provide a new system to test new vaccines as well as therapeutics against dengue viruses in the human context.
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Subject
dengue
hemorrhagic shock
immune response
viral pathogenesis
virology
immunology