Adoptively Transferred Vɣ2Vδ2 T cells Protect Against the Dissemination of M. Tuberculosis in Macaques

Scientific Background: Despite the discovery of γδ T cells for 30 years, there is still no definitive in vivo evidence indicating that phosphoantigen specific Vγ2Vδ2 T cells can protect against Mycobacterium tuberculosis (MTB) infection in humans. Here, we aimed at exploring the role of Vγ2Vδ2 T cells in protection against TB using the adoptive cell transfer approach in macaque TB model. Approach: Peripheral blood mononuclear cells (PBMCs) were collected from cynomologus macaques and frozen down over time. Prior to the adoptive transfer, PBMCs were thawed and cultured for expansion of Vγ2Vδ2 T cells using a modified stimulation/expansion protocol. Expanded autologous Vγ2Vδ2 T cells were transferred to infected macaques on early time points after MTB infection. Animals were evaluated for immune responses and infection status over time after adoptive transfer. At 8 weeks after infection, macaques were subjected to complete necropsy for evaluation of gross pathology and bacterial burdens. Results: Infused Vγ2Vδ2 cells could be detected in the bronchoalveolar lavage (BAL) cells of monkeys 6 hours after infusion, peaked at 24-48 hours and still measurable at 7 days, suggesting pulmonary trafficking/accumulation of infused γδ T cells. The Vγ2Vδ2 T cell-infused group showed significantly less occurrence of weight loss and lymphocytopenia, and lower bacilli CFU counts in BAL fluid compared to the PBL-infused control group. At necropsy, Vγ2Vδ2 T cell-infused group showed significantly lower MTB burdens in right caudal lobe (infection site) and other lung lobes than the control group. Notably, the Vγ2Vδ2 T cell-infused group displayed significantly milder TB pathology or lesions in lungs, and much lower frequency of extrapulmonary TB dissemination than the control group. These results strongly support the hypothesis that Vγ2Vδ2 T effector cells are protective against TB. Conclusions: We are the first to expand macaque Vγ2Vδ2 T cells to large scales and adoptively transfer them into MTB-infected individuals. This study provides the first in vivo evidence that Vγ2Vδ2 T cells confer protection against TB. Findings support the concept that Vγ2Vδ2 T cells should be included for the design of new TB vaccine and immunotherapeutic.