PD-1 directed immunotherapy alters Tfh and humoral immune responses to seasonal flu vaccine

Anti-PD-1 (aPD1) immunotherapy likely affects other immune cells including follicular helper CD4 T cells (Tfh) involved in germinal center (GC) responses. Little is known, however, about the effects of anti-PD-1 immunotherapy on non-cancer immune responses in humans. To investigate this question, we examined the impact of aPD1 immunotherapy for cancer on the Tfh-B cell axis responding to unrelated viral antigens. Following influenza vaccination, a subset of adults receiving aPD1 had more robust circulating Tfh (cTfh) responses than adults not receiving immunotherapy, and cTfh responses correlated with plasmablasts. PD-1 pathway blockade also resulted in transcriptional signatures of increased cellular proliferation in cTfh and responding B cells compared to controls. Overall design: Comparison of 4 immune subsets before and after influenza vaccination in the setting of anti-PD1 immunotherapy