Selective, efficient modulation of activated CD4+ alpha beta T cells by the novel humanized antibody GZ- alpha beta TCR targeting human alpha beta TCR

Allograft rejection and immunosuppression are two major issues in transplantation medicine. The specific targeting of alloreactive T cells, the initiators and promoters of allograft rejection, would be a promising strategy to reduce unwanted T-cell responses and side effects of lifelong immunosuppression. The novel humanized monoclonal antibody GZ- alpha beta TCR, specific for the human alpha beta T-cell receptor, was tested in vitro and in vivo for its specificity and efficacy to modulate the alpha beta T-cell compartment. GZ- alpha beta TCR moderately induced apoptosis in resting alpha beta T cells in vitro, an effect considerably amplified in activated T cells. A single dose of GZ- alpha beta TCR significantly reduced human CD45 super(+)CD3 super(+) T cells in vivo, with a preferential modulation of CD4 super(+) alpha beta T cells. Importantly, naive T cells, the T-cell subset from which alloreactivity emanates, were significantly reduced. Simultaneously, a significant, compensatory increase of gamma delta T cells was observed in vitro and in vivo in both humanized mouse models examined. GZ- alpha beta TCR did not induce cytokines and was well tolerated. Thus, specificity and high efficacy make GZ- alpha beta TCR a powerful tool to selectively eliminate putatively detrimental T-cell subsets, a major goal in transplantation medicine. At the same time, GZ- alpha beta TCR spares gamma delta and natural killer cells, thus leaving the recipient's immune system competent for cell-mediated immunoregulation and cell-mediated immunity.