Evaluation of human antimycobacterial immunity using recombinant reporter mycobacteria

A novel in vitro whole blood model was developed to study human antimycobac terial immunity. Recombinant reporter mycobacteria were used to enumerate t he bacteria, and interactions between host immune cells and mycobacteria we re studied using whole blood rather than cell fractions, The ability of hea lthy tuberculin-positive and tuberculin-negative individuals to restrict my cobacterial growth was compared. Growth of luminescent mycobacteria was sig nificantly lower in blood samples of tuberculin-positive individuals than i n blood samples of tuberculin-negative individuals (P = .005). Restricted m ycobacterial growth was associated with significantly higher production of tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma (P = .01 and . 004, respectively). Inhibition of the TNF-alpha and IFN gamma response path ways by neutralizing monoclonal antibodies increased mycobacterial growth i n whole blood. This model is the first functional assay in which individual variations in cell-mediated immunity are shown to correlate with differenc es in ability to control mycobacterial growth. It provides a new tool for s tudying human mycobactericidal mechanisms and, potentially, for the evaluat ion of improved vaccines.