CD8 Depletion

Cell-mediated immunity is critical for control of M. tuberculosis infection. Although the importance of CD4 T cells in control of tuberculosis is well-established, the importance of CD8+ lymphocytes is less clear. Here, we investigated the requirement for all CD8+ lymphocytes (innate and adaptive) or just CD8 alpha/beta adaptive T cells in control of initial and early infection in cynomolgus macaques, using anti-CD8alpha or anti-CD8beta depleting antibodies in vivo. Flow cytometry and single-cell RNA-sequencing analysis of lung granulomas from control (undepleted) macaques at 6 weeks post-infection revealed a rich landscape of cytotoxic CD8+ lymphocytes. Anti-CD8alpha antibody resulted in susbstantial loss of all CD8+ lymphocytes from granulomas, while anti-CD8beta antibody selectively depleted classical CD8alpha beta T cells. In CD8-depleted granulomas, CD4 T cells and gamma delta T cells had increased expression of certain cytotoxic effectors, such as granzymes. However, these cells had reduced expression of perforin, granulysin, and/or CCL5, and thus displayed an incomplete cytotoxic profile. At 6 weeks post-infection, CD8 alpha depleted macaques had increased granuloma numbers, lung inflammation, and total thoracic bacterial burden, while CD8beta-depleted macaques showed increased lymph node bacterial burden. Mtb barcode analysis revealed that depletion of all CD8+ lymphocytes resulted in greater initial establishment of Mtb in the lungs, indicating a loosening of the airway bottleneck for infection, and increased dissemination of Mtb within lungs, to lymph nodes and to extrapulmonary sites. These data suggest that the total CD8+ lymphocyte population is critical for early control of Mtb infection in macaques and support the importance of targeting CD8+ lymphocytes in a vaccine strategy.