In Vivo Suppression of HIV by Antigen Specific T Cells Derived from Engineered Hematopoietic Stem Cells

Abstract

The HIV-specific cytotoxic T lymphocyte (CTL) response is a critical component in controlling viral replication in vivo , but ultimately fails in its ability to eradicate the virus. Our intent in these studies is to develop ways to enhance and restore the HIV-specific CTL response to allow long-term viral suppression or viral clearance. In our approach, we sought to genetically manipulate human hematopoietic stem cells (HSCs) such that they differentiate into mature CTL that will kill HIV infected cells. To perform this, we molecularly cloned an HIV-specific T cell receptor (TCR) from CD8+ T cells that specifically targets an epitope of the HIV-1 Gag protein. This TCR was then used to genetically transduce HSCs. These HSCs were then introduced into a humanized mouse containing human fetal liver, fetal thymus, and hematopoietic progenitor cells, and were allowed to differentiate into mature human CD8+ CTL. We found human, HIV-specific CTL in multiple tissues in the mouse. Thus, genetic modification of human HSCs with a cloned TCR allows proper differentiation of the cells to occur in vivo , and these cells migrate to multiple anatomic sites, mimicking what is seen in humans. To determine if the presence of the transgenic, HIV-specific TCR has an effect on suppressing HIV replication, we infected with HIV-1 mice expressing the transgenic HIV-specific TCR and, separately, mice expressing a non-specific control TCR. We observed significant suppression of HIV replication in multiple organs in the mice expressing the HIV-specific TCR as compared to control, indicating that the presence of genetically modified HIV-specific CTL can form a functional antiviral response in vivo . These results strongly suggest that stem cell based gene therapy may be a feasible approach in the treatment of chronic viral infections and provide a foundation towards the development of this type of strategy.

Engineering HIV-Specific Immunity with Chimeric Antigen Receptors

“…28 We further demonstrated that these HIV-specific CTLs could effectively lower viral loads following HIV infection. These cells underwent normal developmental processes, including their maturation into T cells in the human thymus, and responded to HIV infection in vivo in a highly active and normal manner.…”

“…[27][28][29] We determined that the modification of a human HSC with a lentiviral vector containing an anti-HIV TCR can direct the differentiation of mature, polyfunctional HIV-specific T cells in human thymic tissue in vivo in the SCID-hu mouse, a humanized mouse model that recapitulates human T cell development and thymic selection. 27 These cells, carrying the transgenic anti-HIV TCR, survived hematopoietic differentiation and thymopoiesis and developed into cells capable of killing HIV-infected cells ex vivo.…”

“…28 In this approach, we utilized the surrogate humanized bone marrow, fetal liver, and thymus (BLT) mouse model to demonstrate that human CD34…”

“…(B) Untransduced (control) mice or mice transduced with the CD4f CAR were then infected with HIV-1 NLHSA-HA , which is a variant of HIV NL4-3 that contains the murine heat-stable antigen containing the hemagglutinin (HA) epitope from influenza cloned into the vpr gene to allow cell surface detection of viral expression. 28,43 The data represent the % of HSA-HA-expressing cells 2 and 4 weeks following infection (n = 4). This proof of principle establishes the ability of CD4f CAR expression to allow hematopoietic development into function T cells from early progenitor cells without deleterious effects and functionally inhibit viral replication in vivo.…”

Novel Prospective Treatment Options

“…Nevertheless, few of these techniques have entered into clinical trials and give hope for a promising future [152]. Apart from their use in therapeutic strategies, techniques of gene therapy are being evaluated in DNA vaccines for prophylactic use and also in some of the strategies of 'immune therapy' [156].…”