Certain vaccines such as BCG have non-specific effects, which modulate innate immune responses and lead to protection against mortality from unrelated infections (trained immunity). In contrast, diphtheria-tetanus-pertussis (DTP) vaccination eliminates these beneficial effects of BCG, but the mechanisms responsible were unknown.In a randomized trial Mihai Netea and colleagues, theme Infectious diseases and global health, aim to investigate the non-specific immunological effects of BCG and DTP-containing vaccines on the immune response to unrelated pathogens. They have published their findings in Clinical Infectious Diseases.
Tdap vaccination led to short-term potentiation and long-term repression of monocyte-derived cytokine responses, and short-term as well as long-term repression of T-cell reactivity to unrelated pathogens. BCG led to short-term and long-term potentiation of monocyte-derived cytokine responses. When given together with Tdap or after Tdap, BCG abrogated the immunosuppressive effects of Tdap vaccination.
Tdap induces immunotolerance to unrelated antigens, which is partially restored by concurrent or subsequent BCG vaccination. These data indicate that modulation of heterologous immune responses is induced by vaccination with Tdap and BCG, and more studies are warranted to investigate whether this is involved in the non-specific effects of vaccines on mortality.