Redirection of Cord Blood T Cells and Natural Killer Cells for Elimination of Autologous HIV-1-Infected Target Cells Using Bispecific DART® Molecules

Abstract

Mother-to-child transmission of HIV-1 remains a major global health challenge. Currently, HIV-1-infected infants require strict lifelong adherence to antiretroviral therapy to prevent replication of virus from reservoirs of infected cells, and to halt progression of disease. There is a critical need for immune interventions that can be deployed shortly after infection to eliminate HIV-1-infected cells in order to promote long-term remission of viremia, or to potentially cure pediatric HIV-1-infection. Bispecific HIV × CD3 DART ® molecules able to co-engage the HIV-1 envelope protein on the surface of infected cells and CD3 on cytolytic T cells have been previously shown to eliminate HIV-1 infected cells in vitro and are candidates for passive immunotherapy to reduce the virus reservoir. However, their potential utility as therapy for infant HIV-1 infection is unclear as the ability of these novel antibody-based molecules to work in concert with cells of the infant immune system had not been assessed. Here, we use human umbilical cord blood as a model of the naïve neonatal immune system to evaluate the ability of HIV x CD3 DART molecules to recruit and redirect neonatal effector cells for elimination of autologous CD4 + T cells infected with HIV-1 encoding an envelope gene sequenced from a motherto-child transmission event. We found that HIV × CD3 DART molecules can redirect T cells present in cord blood for elimination of HIV-infected CD4 + T cells. However, we observed reduced killing by T cells isolated from cord blood when compared to cells isolated from adult peripheral blood-likely due to the absence of the memory and effector CD8 + T cells that are most cytolytic when redirected by bispecific DART molecules. We also found that newly developed HIV × CD16 DART molecules were able to recruit CD16-expressing natural killer cells from cord blood to eliminate HIV-infected cells, and the activity of cord blood natural killer cells could be substantially increased Pollara et al. DART-Molecule Recruitment of Neonatal Cells by priming with IL-15. Our results support continued development of HIV-specific DART molecules using relevant preclinical animal models to optimize strategies for effective use of this immune therapy to reduce HIV-1 infection in pediatric populations.

In utero human cytomegalovirus infection expands NK cell-like FcγRIII-expressing CD8+ T cells that mediate antibody-dependent functions

“…Both markers of ADCC activity were enhanced when NK cells were preincubated with IL-15 ( Fig. 8C-D ), consistent with prior literature indicating that IL-15 augments neonatal NK cell cytotoxicity (Pollara et al, 2020). Next, we assessed the capacity of cord blood CD8+ T cells to mediate Fc-dependent antibody effector functions.…”

In Utero Activation of Natural Killer Cells in Congenital Cytomegalovirus Infection

“…However, NKG2C + NK-cell expansion also requires costimulation in the form of proinflammatory cytokines, particularly IL-12 [ 16 , 45 ]. IL-12 is under tight epigenetic control in the tolerogenic immune environment maintained throughout gestation [ 46 ], and stimulation of cord blood NK cells with IL-12 and IL-15 has been shown to rapidly increase their functional capacity to levels approaching that of adult NK cells [ 29 , 47 , 48 ]. Thus, it is possible that the restricted cytokine environment in utero hinders expansion of fetal NKG2C + NK cells.…”

Bispecific antibody-derived molecules to target persistent HIV infection

“…7B2 x anti-CD16A DART molecules were tested for ability to redirect adult PBMCs or cord blood mononuclear cells (CBMCs) to lyse HIV-1-infected CD4 + T cells. 66 The subset of cytotoxic CD56 dim CD16 + NK cells was the dominant population of NK cells in both cord blood and adult PBMC and treatment with IL-15 increased the activation (upregulated HLA-DR and CD69) of NK cells in adult PBMC and cord blood. However, NK cells in cord blood are less mature, less lymphoid homing, less active and produce less granzyme B compared to NK cells in adult PBMCs.…”

“…To explore the possibility that DART molecules could be utilized early after birth to eliminate HIV-infected cells and, ultimately, impact persistent infection, Pollara and collaborators evaluated the potency of A32 x anti-CD3 and 7B2 x anti-CD3 DART molecules in the newborn population by analyzing the killing capacity of cytotoxic T cells isolated from the cord blood. 55 Their study revealed that DART molecules were indeed capable of redirecting CD3 + cytotoxic T cells to kill HIV-infected CD4 + T cells. However, cellular subsets acquired from cord blood were less potent than those isolated from the adult peripheral blood, indicating a possible limitation of this strategy.…”