Boosting human dendritic cell development, homeostasis and function in xenografted immunodeficient mice

Abstract

The present invention relates to a transgenic animal mode system based on the development of transgenic mice bearing components of the human immune system. Specifically, the Invention relates to a Flk2 deficient Rag “γc” transgenic mouse and the engraftment of said mouse with human hematopoietic stem cells. The present invention further presides methods for increasing the numbers of functionally competent human dendritic cells is and the hematopoietic targets cells that they interact with in said transgenic mouse through the administration of Flk2L. The transgenic animal model system of the invention may be used for testing human vaccine candidates, for screening potential Immune adjuvants and for developing novel therapeutics.

1 . A mouse deficient for Rag2 and or Rag1, interleukin-2 receptor gamma chain, and Flk2. 
     
     
         2 . The mouse of  claim 1 , having the genotype Rag2 −/− , γc −/− , Flk2 −/− . 
     
     
         3 . The mouse of  claim 1 , further having a Balb/c background. 
     
     
         4 . The mouse of  claim 1 , further comprising engrafted human hematopoietic cells. 
     
     
         5 . A process for preparing a mouse having increased numbers of human dendritic cells comprising exposing the mouse of  claim 4  to Flk2L. 
     
     
         6 . A method for producing a chimeric mouse having a functional xenogenic immune system, comprising the step of: transplanting xenogenic hematopoietic progenitor cells into a mouse according to  claim 1 . 
     
     
         7 . A method for analysing the development of the immune system of a xenogenic species in vivo, comprising:
 (i) transplanting xenogenic hematopoietic progenitor cells into a Rag −/− , γ c   −/− , Flk2 −/−  transgenic mouse; and   (ii) assaying for the presence of functional T, B or dendritic cells of the xenogenic species, for example human, in the transplanted mouse.   
     
     
         8 . The method of  claim 7  further comprising the administration of Flk2L to the transgenic mouse. 
     
     
         9 . A method for analysing the immune response of a xenogenic species to an antigen in vivo comprising:
 (i) contacting a Rag −/− , γc −/− , Flk2 −/−  transgenic mouse transplanted with xenogenic hematopoietic progenitor cells with an antigen of interest; and   (ii) assaying for the presence of an immune response.   
     
     
         10 . The method of  claim 9  wherein the presence of an immune response is detected by assaying for a humoral response, a T-helper cell response, a T-cytotoxic cell response, a NK cell-mediated cytotoxic cell response, NK cell-mediated production of cytokines and/or chemokines, a DC-mediated cytotoxic response, a DC-mediated production of cytokines and/or chemokines, or an innate lymphocyte inflammatory response in the mouse. 
     
     
         11 . The method of  claim 9  further comprising the administration of Flk2L to the transgenic animal. 
     
     
         12 . A method for analysing the capacity of the immune response of a xenogenic species to be modified by an adjuvant in vivo comprising the steps of:
 (i) contacting a Rag −/− , γc −/− , Flk2 −/−  transgenic mouse transplanted with xenogenic hematopoietic progenitor cells with an antigen of interest in the presence of an adjuvant to be tested; and   (ii) assaying for the presence of an immune response.   
     
     
         13 . The method of  claim 12  wherein the presence of an immune response is detected by assaying for a humoral response, a T-helper cell response, a T-cytotoxic cell response, a NK cell-mediated cytotoxic cell response, NK cell-mediated production of cytokines and/or chemokines, a DC-mediated cytotoxic response, a DC-mediated production of cytokines and/or chemokines, or an innate lymphocyte inflammatory response in the mouse. 
     
     
         14 . The method of  claim 12  further comprising the administration of Flk2L to the transgenic animal. 
     
     
         15 . A method for analysing the capacity of pathogens to modify immune responses of a xenogenic species in vivo, characterized in that it comprises the steps of:
 (i) contacting a Rag −/− , γc −/− , Flk2 −/−  transgenic mouse transplanted with xenogenic hematopoietic progenitor cells with a pathogen; and   (ii) assaying for the presence of an immune response.   
     
     
         16 . The method of  claim 15  wherein the presence of an immune response is detected by assaying for a humoral response, a T-helper cell response, a T-cytotoxic cell response, a NK cell-mediated cytotoxic cell response, NK cell-mediated production of cytokines and/or chemokines, a DC-mediated cytotoxic response, a DC-mediated production of cytokines and/or chemokines, or an innate lymphocyte inflammatory response in the mouse. 
     
     
         17 . The method of  claim 16  further comprising the administration of Flk2L to the transgenic animal. 
     
     
         18 . (canceled) 
     
     
         19 . A method for identifying a compound that modulates Flk2 expression or activity, such as an agonist, thereby inducing DC development, homeostasis, maturation or function, comprising:
 (i) engrafting xenogenic hematopoietic progenitor cells into a Rag −/− , γc −/− , Flk2 −/−  transgenic mouse;   (ii) contacting said Rag −/− , γc −/− , Flk2 −/−  transgenic mouse with a test compound; and   (iii) measuring the level of DC development, homeostasis, maturation or function in the presence of the test compound, wherein an inducement of DC development, homeostasis., maturation or function indicates the presence of a test compound that induces DC development, homeostasis, maturation or function.   
     
     
         20 . The method according to  claim 6 , wherein the xenogenic hematopoietic progenitor cells are human hematopoietic progenitor cells. 
     
     
         21 . The method according to  claim 7 , wherein the xenogenic hematopoietic progenitor cells are human hematopoietic progenitor cells. 
     
     
         22 . The method according to  claim 9 , wherein the xenogenic hematopoietic progenitor cells are human hematopoietic progenitor cells. 
     
     
         23 . The method according to  claim 12 , wherein the xenogenic hematopoietic progenitor cells are human hematopoietic progenitor cells. 
     
     
         24 . The method according to  claim 15 , wherein the xenogenic hematopoietic progenitor cells are human hematopoietic progenitor cells. 
     
     
         25 . The method according to  claim 19 , wherein the xenogenic hematopoietic progenitor cells are human hematopoietic progenitor cells.