Current antiretroviral therapies (ART) dramatically improve quality of life and survival for HIV patients. Unfortunately, many ART-treated individuals continue to harbor latently infected CD4+ T cells and display low levels of detectable viral RNA, and once ART is withdrawn, the virus rapidly rebounds. These observations highlight the inability of ART treatment alone to eradicate HIV; therefore, new and complementary therapies are needed to detect and eliminate rare populations of ART-resistant, latently infected cells. Julia Sung, Joy Pickeral, Liquin Liu, and colleagues at the University of North Carolina, Duke University, and MacroGenics, Inc., respectively, developed Dual-Affinity-Re-Targeting (DART®) proteins that simultaneously target HIV-infected cells and cytolytic effector T cells and thus facilitate T cell-mediated lysis of HIV-infected cell populations. These HIVxCD3 DARTs consist of two effector arms; an HIV-1 Env-binding domain, which targets HIV-infected cells, and a CD3ε-binding arm, which targets activated T cells. The binding of each arm to its cell-surface antigen brings HIV-infected cells into direct contact with activated T cells, thereby redirecting T cells to engage and kill HIV-infected cells. Critically, in lymphocytes isolated from HIV-infected donors on suppressive ART, HIVxCD3 DARTs promoted clearance of both autologous reservoir-infected CD4+ T cells from seronegative donors and latently infected CD4+ T cells from seropositive patients that had been treated to induce latent virus expression. Collectively, these findings suggest that DARTs should be further explored for the treatment of HIV-1. The accompanying image illustrates the mechanism of action for HIVxCD3 DARTs. The anti-CD3 arm (orange) binds to T-cells, whereas the anti-HIV arm (blue) binds HIV-infected cells, thus directing T cell lysis of HIV-infected cells following target recognition by both DART arms.
Enhancement of HIV-specific immunity is likely required to eliminate latent HIV infection. Here, we have developed an immunotherapeutic modality aimed to improve T cell–mediated clearance of HIV-1–infected cells. Specifically, we employed Dual-Affinity Re-Targeting (DART) proteins, which are bispecific, antibody-based molecules that can bind 2 distinct cell-surface molecules simultaneously. We designed DARTs with a monovalent HIV-1 envelope-binding (Env-binding) arm that was derived from broadly binding, antibody-dependent cellular cytotoxicity–mediating antibodies known to bind to HIV-infected target cells coupled to a monovalent CD3 binding arm designed to engage cytolytic effector T cells (referred to as HIVxCD3 DARTs). Thus, these DARTs redirected polyclonal T cells to specifically engage with and kill Env-expressing cells, including CD4+ T cells infected with different HIV-1 subtypes, thereby obviating the requirement for HIV-specific immunity. Using lymphocytes from patients on suppressive antiretroviral therapy (ART), we demonstrated that DARTs mediate CD8+ T cell clearance of CD4+ T cells that are superinfected with the HIV-1 strain JR-CSF or infected with autologous reservoir viruses isolated from HIV-infected–patient resting CD4+ T cells. Moreover, DARTs mediated CD8+ T cell clearance of HIV from resting CD4+ T cell cultures following induction of latent virus expression. Combined with HIV latency reversing agents, HIVxCD3 DARTs have the potential to be effective immunotherapeutic agents to clear latent HIV-1 reservoirs in HIV-infected individuals.
Julia A.M. Sung, Joy Pickeral, Liqin Liu, Sherry A. Stanfield-Oakley, Chia-Ying Kao Lam, Carolina Garrido, Justin Pollara, Celia LaBranche, Mattia Bonsignori, M. Anthony Moody, Yinhua Yang, Robert Parks, Nancie Archin, Brigitte Allard, Jennifer Kirchherr, JoAnn D. Kuruc, Cynthia L. Gay, Myron S. Cohen, Christina Ochsenbauer, Kelly Soderberg, Hua-Xin Liao, David Montefiori, Paul Moore, Syd Johnson, Scott Koenig, Barton F. Haynes, Jeffrey L. Nordstrom, David M. Margolis, Guido Ferrari