While much has been learned about the interactions between Human Immunodeficiency Virus type 1(HIV-1)and the human immune system, many questions remain unanswered, most importantly how best to stimulateand sustain effective anti-HIV-1 immunity with a preventive or therapeutic vaccine. We believe that thecareful and detailed interrogation of the interaction of HIV-1 with immune cells in the lymph node will becritical for improving our ability to stimulate anti-HIV-1 immunity. The powerful new technology of multiphotonintravital microscopy (MV-IVM) has allowed for the visualization of immune cell migration and cell-cellinteraction in lymph nodes, but current MP-IVM technology can only be applied to small animals, such asrodents. There has been long-standing interest in developing a small animal model of HIV-1 infection, andthe advent of MP-IVM gives additional impetus to achieve this goal. Recently, we and others havedeveloped a markedly improved humanized mouse model of HIV-1 by transplanting human CD34+ stemcells and autologous human thymic grafts into immunodeficient mice. These mice generate robust anti-HIV-1 cellular and humoral immune responses, and achieve repopulation of their lymph nodes with humanimmune cells adequate to support MP-IVM studies. Using MP-IVM, we have demonstrated, for the first time,that adoptively transferred human T cells can home to humanized mouse lymph nodes from the blood andmigrate normally once in the lymph node.
In Aim 1 of this project, we will perform, for the first time, athorough analysis of the migratory behavior of human T cells and dendritic cells in a humanized mouse. Thisunique study will allow a more complete understanding of this potentially important model of the humanimmune system in action, in real time. Then in Aim 2, we will take advantage of this improved humanizedmouse model to study questions regarding the biology of HIV-1 not readily approachable through humanstudies. Using fluorescently labeled virus, we will determine how HIV-1 is delivered to the lymph node eitheras a free virus or a virus associated with dendritic cells or T cells. We will then determine the anatomy ofHIV-1 spread within the LN over time using an HIV-1 mutant inducing the expression of GFP in infectedcells. In addition to addressing these questions of viral transport and cell-cell interactions, we will be able touse our improved model of HIV-1 infection to address important questions of immune cell function in thecontext of HIV-1 infection. As a dramatic example of the usefulness of our mouse model of HIV-1 infection,we have found that similar to humans infected with HIV-1, CD4+ and CD8+ T cells in our humanized micedramatically increase their cell surface expression of PD-1 following HIV-1 infection. PD-1 negativelyregulates T cell activity, is highly expressed on HIV-1-specific T cells and is associated with T cell exhaustionand predictors of HIV-1 progression.
In Aim 3, we will use our humanized mouse model of HIV-1 todetermine if blockade of the PD-1 pathway will reinvigorate the cellular and humoral immune response toHIV-1 and lead to better control of HIV-1 replication. The project will benefit from and synergize with theexpertise of the other investigators in this PPG focused on viral transport in lymph nodes, the biology of thePD-1 family, and the humoral immune response to pathogens, as well as the BL2+-contained MP-IVM core.
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