Human hepatocytes depletion in the presence of HIV-1 infection in dual reconstituted humanized mice

HIV-1 infection impairs liver function, and liver diseases have become a leading cause of morbidity in infected patients. The immunopathology of liver damage caused by HIV-1 remains unclear. We used chimeric mice dually reconstituted with a human immune system and hepatocytes to address the relevance of the model to pathobiology questions related to human hepatocytes survival in the presence of systemic infection. TK-NOG males were transplanted with mismatched human hematopoietic stem/progenitor cells and hepatocytes; human albumin concentration and the presence of human immune cells in blood were monitored for hepatocytes and immune reconstitution; and mice were infected with HIV-1. HIV-1-infected animals showed a decline in human albumin concentration with a significant reduction in percentage of human hepatocytes compared to uninfected mice. The decrease in human albumin levels correlated with a decline in CD4 cells in the liver and with an increase in HIV-1 viral load. HIV-1 infection elicited proinflammatory response in the immunological milieu of the liver in HIV-infected mice compared to uninfected animals determined by upregulation of IL23, CXCL10 and multiple toll-like receptors expression. The inflammatory reaction associated with HIV-1 infection in vivo could contribute to the depletion and dysfunction of hepatocytes. Conclusion. The dual reconstituted TK-NOG mouse model is a feasible platform to investigate hepatocyte-related HIV-1 immunopathogenesis. B io lo gy O pe n • A cc ep te d m an us cr ip t by guest on January 27, 2018 http://bio.biologists.org/ Downloaded from Introduction Liver injury remains an important contributor to morbidity and mortality among approximately 1.2 million persons in the United States and nearly 37 million human immunodeficiency virus (HIV)-infected patients worldwide (Smith et al., 2010). HIV-1 causes damage of liver cells, i.e. hepatocytes (Hep), stellate cells, and Kupffer cells; and direct and indirect inflammation-associated mechanisms were suggested and investigated in vitro (Crane et al., 2012; Kong et al., 2012). However, in vitro cell culture experiments are limited in various ways, and the results of human studies vary based on time of infection, co-infections with hepatitis viruses, opportunistic infections, antiretroviral drug treatment, and damage of gut immune barriers and associated immune activation (Sherman et al., 2015). More coherent information can be obtained in vivo using HIV-1-infected chimeric mice carrying human hematolymphoid tissue and human Hep to recapitulate HIV-1 immunopathogenesis. However, syngeneic Hep and human CD34 hematopoietic stem/progenitor cells (HSPC) co-transplantation has limitations due to availability of matched cells and uncertainties. We sought to investigate how mismatched model, and possible alloreactivity would affect outcomes. To explore such mismatched experimental conditions, we created dual liverand immune system-transplanted humanized mice and addressed the effects of HIV-1 on hepatocyte survival and function. In this experimental system, we used Hep derived from a single donor for transplantation into NOD/scid-IL2Rγc (NOG) mice expressing herpes simplex virus type 1 thymidine kinase (TK) transgene within the liver (TK-NOG) (Hasegawa et al., 2011). A human immune system was established by co-transplantation of human CD34HSPC derived from 8 single donors. Experimental animals were infected with macrophage-tropic CCR5 co-receptor using the HIV-1ADA strain. Five weeks postinfection, we found a decreased concentration of human albumin (ALB) in the blood, which coincided with a reduced number of engrafted human Hep in the liver of dualreconstituted mice. It is noteworthy that we observed no changes in human ALB levels and preserved Hep in the uninfected mice transplanted with mismatched cells, which suggests that HIV-infection contributes to hepatocyte injury. To explore the processes that could be involved in Hep damage in dual reconstituted humanized mice, we evaluated the presence of infected cells in liver tissue as well as the pathomorphology associated with this observation. We also compared profiles of inflammation-associated gene transcripts in the livers of infected and uninfected dual B io lo gy O pe n • A cc ep te d m an us cr ip t by guest on January 27, 2018 http://bio.biologists.org/ Downloaded from humanized mice at the end-point of observation to explore liver-immune cells milieu environment. HIV-1-infection elicited significant upregulation of pattern-recognition receptors and inflammatory cytokines/chemokines in vivo. The depletion of human hepatocytes and the decline of human ALB levels in vivo could be results of HIV-1 infection of the liver-immune cell milieu and not related to mismatched transplantation of human HSPC and hepatocytes.