The association between parental and neonatal BCG vaccination and neonatal T helper 17 cell expansion

Background: Bacille Calmette-Guérin (BCG) vaccination reduces the severity of neonatal infections; this effect appears enhanced if the mother has received BCG. We performed immunophenotyping of the T-cell subset and characterized T-cell proliferation responses to assess possible immune response pathways. Methods: Healthy BCG-vaccinated (n = 8) and unvaccinated (n = 9) neonates born by elective caesarean section were sampled 3 weeks after birth. We compared a wide panel of intracellular cytokine and cell surface expression markers as well as proliferation response in T-cells between BCG-vaccinated and unvaccinated neonates, stratified by parental BCG status. Results: For all BCG-vaccinated neonates and 3 of 9 unvaccinated neonates that served as controls, both parents had a BCG scar. Th17 (CD4 + IL-17+) prevalence as percentage of total CD4 + T-cells was expanded 4-fold in BCG-vaccinated compared to unvaccinated, being 11.6% [3.6–19.6%] vs 2.8% [1.0–6.6%]. Th17 counts for 3 unvaccinated neonates born to BCG-vaccinated parents was comparable to vaccinated neonates, and higher than remaining controls, parental BCG = 8.5% [4.4–8.9%] vs 1.8% [0.8–3.3%] for no parental BCG (median [interquartile range] for all data). Conclusion: Among neonates born to BCG-vaccinated parents, the prevalence of Th17 cells, important in the response against bacterial infections, was substantially elevated. The interaction between neonatal and parental BCG for Th17 responses and the importance remains to be further investigated.