The novel tuberculosis vaccine, AERAS-402, induces robust and polyfunctional CD4⁺and CD8⁺ T cells in adults

Rationale: AERAS-402 is a novel tuberculosis vaccine designed to boost immunity primed by bacillus Calmette-Guérin (BCG), the only licensed vaccine. Objectives: We investigated the safety and immunogenicity of AERAS-402 in healthy Mycobacterium tuberculosis-uninfected BCG-vaccinated adults from a tuberculosis-endemic region of South Africa. Methods: Escalating doses of AERAS-402 vaccine were administered intramuscularly to each of three groups of healthy South African BCG-vaccinated adults, and a fourth group received two injections of the maximal dose. Participants were monitored for 6 months, with all adverse effects documented. Vaccine-induced CD4+ and CD8 + T-cell immunity was characterized by an intracellular cytokine staining assay of whole blood and peripheral blood mononuclear cells. Measurements and Main Results: AERAS-402 was well tolerated, and no vaccine-related serious adverse events were recorded. The vaccine induced a robust CD4+ T-cell response dominated by cells coexpressing IFN-γ, tumor necrosis factor-α, and IL-2 ("polyfunctional" cells). AERAS-402 also induced a potent CD8+ T-cell response, characterized by cells expressing IFN-γ and/or tumor necrosis factor-α, which persisted for the duration of the study. Conclusions: Vaccination with AERAS-402 is safe and immunogenic in healthy adults. The immunity induced by the vaccine appears promising: polyfunctional T cells are thought to be important for protection against intracellular pathogens such as Mycobacterium tuberculosis, and evidence is accumulating that CD8+ T cells are also important. AERAS-402 induced a robust and durable CD8+ T-cell response, which appears extremely promising. Clinical trial registered with www.sanctr.gov.za (NHREC no. 1381).