Background. Induction of innate immune memory, also termed trained immunity, by the anti-tuberculosis vaccine Bacillus Calmette-Guérin (BCG) contributes to protection against heterologous infections. However, the overall impact of BCG vaccination on the inflammatory status of an individual is not known: while induction of trained immunity may suggest increased inflammation, BCG vaccination has been epidemiologically associated with a reduced incidence of inflammatory and allergic diseases. Methods. We investigated the impact of BCG (BCG-Bulgaria, InterVax) vaccination on systemic inflammation in a cohort of 303 healthy volunteers, as well as the effect of the inflammatory status on the response to vaccination. A targeted proteome platform was used to measure circulating inflammatory proteins before and after BCG vaccination, while ex vivo Mycobacterium tuberculosis and Staphylococcus aureus induced cytokine responses in peripheral blood mononuclear cells were used to assess trained immunity. Results. While BCG vaccination enhanced cytokine responses to restimulation, it reduced systemic inflammation. This effect was validated in three smaller cohorts, and was much stronger in men than in women. In addition, baseline circulating inflammatory markers were associated with ex vivo cytokine responses (trained immunity) after BCG vaccination. Conclusion. The capacity of BCG to enhance microbial responsiveness while dampening systemic inflammation should be further explored for potential therapeutic applications. Funding. This study was funded by a Spinoza grant of the Netherlands Organization for Scientific Research and an ERC Advanced Grant (TRAIN-OLD nr. 833247).
Valerie A. C. M. Koeken, L. Charlotte J. de Bree, Vera P. Mourits, Simone J.C.F.M. Moorlag, Jona Walk, Branko Cirovic, Rob J.W. Arts, Martin Jaeger, Helga Dijkstra, Heidi Lemmers, Leo A.B. Joosten, Christine Stabell Benn, Reinout van Crevel, Mihai Netea