Abstract
Protein vaccines combined with adjuvants have been widely used to induce immune responses, especially the humoral immune response, against molecular targets including parasites. Follicular T helper (Tfh) cells are the specialized providers of B-cell help, however, the induction of Tfh cells in protein vaccination has been rarely studied. Here, we report that the Schistosoma japonicum recombinant protein (SjGST-32) combined with tacrolimus (FK506) augmented the induction of Tfh cells, which expressed the canonical markers CXCR5, BCL6, and IL-21, and enhanced the humoral immune responses in BALB/c mice. Furthermore, the expression of IL-21R on germinal center (GC) B cells and memory B cells increased in immunized mice, which indicated that IL-21 from the induced Tfh cells interacted with IL-21R for activation of B cells and maintenance of long-lived humoral immunity. Our results suggest that helminth protein vaccine combined with FK506 induces Tfh cell for stimulating humoral immune responses and inducing long-lived humoral immunity.