Expression of HLA Class II Molecules in Humanized NOD.Rag1KO.IL2RgcKO Mice Is Critical for Development and Function of Human T and B Cells

Abstract

BackgroundHumanized mice able to reconstitute a surrogate human immune system (HIS) can be used for studies on human immunology and may provide a predictive preclinical model for human vaccines prior to clinical trials. However, current humanized mouse models show sub-optimal human T cell reconstitution and limited ability to support immunoglobulin class switching by human B cells. This limitation has been attributed to the lack of expression of Human Leukocyte Antigens (HLA) molecules in mouse lymphoid organs. Recently, humanized mice expressing HLA class I molecules have been generated but showed little improvement in human T cell reconstitution and function of T and B cells.MethodsWe have generated NOD.Rag1KO.IL2RγcKO mice expressing HLA class II (HLA-DR4) molecules under the I-Ed promoter that were infused as adults with HLA-DR-matched human hematopoietic stem cells (HSC). Littermates lacking expression of HLA-DR4 molecules were used as control.ResultsHSC-infused HLA-DR4.NOD.Rag1KO.IL-2RγcKO mice developed a very high reconstitution rate (>90%) with long-lived and functional human T and B cells. Unlike previous humanized mouse models reported in the literature and our control mice, the HLA-DR4 expressing mice reconstituted serum levels (natural antibodies) of human IgM, IgG (all four subclasses), IgA, and IgE comparable to humans, and elicited high titers of specific human IgG antibodies upon tetanus toxoid vaccination.ConclusionsOur study demonstrates the critical role of HLA class II molecules for development of functional human T cells able to support immunoglobulin class switching and efficiently respond to vaccination.

Transgenic expression of human signal regulatory protein alpha in Rag2−/−γc−/−mice improves engraftment of human hematopoietic cells in humanized mice

“…These include transient approaches such as hydrodynamic injection of plasmid DNA (34), injections of cytokines, and infections of mice or CD34 + cells with lentiviruses (35)(36)(37). Alternatively, transgenic expression of human MHC molecules has been demonstrated to improve the development of antigen-specific immune responses in vivo (38)(39)(40). Nonetheless, overexpression of cytokines might also have detrimental side effects due to the unphysiological expression such as in mice transgenic for SCF, GM-CSF, and IL-3 (41).…”

“…Hence, the increased functionality in SIRP-DKO mice is likely the result of improved selection and differentiation of T cells in vivo due to overall higher numbers of human immune cells. Similarly, HLA-DR4 transgenic mice and humanized mice that are generated by cotransplantation of CD34 + cells and human fetal thymus pieces have improved HLA-restricted T cell responses and also improved antigen-specific antibody responses (40,46). However, further studies will be needed to characterize and quantify antigenspecific T cell responses in hSIRPa-DKO mice.…”

Current advances in humanized mouse models

“…Antigen-specific IgG was produced in HLA class II transgenic NSG mice. 43 Real humanized mice are expected to be generated in the near future by improving immunodeficient mice.…”

“…25 In addition, recent reports have shown that new mouse strains that express HLA-DR mounted an antigen-specific IgG response upon immunization. 43 Collectively, B cells in humanized mice maintain the ability to mediate humoral immune reactions.…”

Dendritic Cell–Mediated Immune Humanization of Mice: Implications for Allogeneic and Xenogeneic Stem Cell Transplantation

“…Factors that may impact in the inefficient lymphatic development in HIS mice include the absence of human histocompatibility molecules and a poor humanized cytokine environment. To overcome this deficiency, approaches including delivery of recombinant cytokines (32,33), transplantation of fetal lymphatic tissue along with HPCs (34,35) or the use of transgenic strains constitutively expressing the MHC class I (36) and II (37) or critical hematopoietic cytokines (38) have been described recently. Despite some improvement, these single strategies allowed a limited improvement in B and T cell responses against human viral challenges.…”