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Some vaccines can protect us not only from the infections that they were designed to target but also from other unrelated infections. This effect is known as cross-protection. One of them is the Bacille Calmette-Guerin (BCG) vaccine, one of the oldest vaccines, developed to protect against tuberculosis but also gives non-specific benefits against non-tuberculous infections and is used as immunotherapy for certain malignancies. Recently, its non-specific benefits were linked to the memory responses of innate immune cells called “trained immunity”. Trained immunity differs from the adaptive immune memory responses mounted by B cells and T cells in their specificity. But can T cells also develop trained immunity characteristics? And if yes, what does it mean for the development of new vaccination strategies?
Researchers Suen et al. went out to investigate whether BCG vaccine can induce trained immunity in a non-conventional T cell, namely gamma delta (γδ) T cells. The research group led by Mihai G. Netea from department of Internal Medicine at the Radboud University Medical Center and Katarzyna Placek from the Department of Immunology and Metabolism at the Life and Medical Science Institute at the University of Bonn in collaboration with Yang Li from Department of Computational Biology of Individualized Medicine at Centre for Individualized Infection Medicine in Hannover published the results in Journal of Leukocyte Biology on 6th September 2023.
A clinical study was conducted, in which they recruited 300 healthy human volunteers who were then vaccinated with BCG. The blood samples were collected from the volunteers before, 2- and 12-weeks after the vaccination and submitted to analysis by single cell RNA-sequencing technology and immune functional assays. They showed that although the total number of γδ T cells were not affected, the cytotoxic molecule production and the transcriptional programs and immune responsiveness of γδ T cells significantly increased after the vaccination. This is to their knowledge, the first ever announced discovery of trained immunity in γδ T cells and suggest that γδ T cells can contribute to the protective effect of BCG vaccination in humans. This opens new avenues for the design of the next generation vaccines where targeting γδ T cells and their memory responses might bring a non-specific benefits.
Read the study here
Suen TK, Moorlag SJCFM, Li W, de Bree CLJ, Koeken VACM, Mourits VP, Dijkstra H, Lemmers H, Bhat J, Xu CJ, Joosten LAB, Schultze JL, Li Y, Placek K, Netea MG. BCG vaccination induces innate immune memory in gamma delta T cells in humans. J Leukoc Biol. 2023 Sep 6:qiad103. doi: 10.1093/jleuko/qiad103. Epub ahead of print. PMID: 37672677.
