Induction of plasmablasts by follicular helper T cell-CXCL13 axis upon occurrence of herpes zoster.

Herpes zoster (HZ) is a recurrent varicella zoster virus (VZV) infection. Follicular helper T (Tfh) cells produce IL-21 and CXCL13, which contributes to the differentiation of plasmablasts. Plasmablasts are involved in the VZV-specific antibody production. We investigated the kinetics of circulating plasmablasts and circulating Tfh (cTfh) cells in 43 HZ patients. Plasma IL-21 and CXCL13 levels were also measured. We found an increase of circulating plasmablasts during the clinical course of HZ. The frequency of circulating plasmablasts positively correlated with VZV-specific IgG titers, frequency of activated cTfh cells, and plasma CXCL13 levels, but did not correlate with plasma IL-21 levels. In a representative case, the kinetics peaked in the order of cTfh cells, CXCL13, plasmablasts, and VZV IgG titer. These results suggest that cTfh-CXCL13 may have a crucial role in the differentiation of B cells into VZV-specific IgG-producing plasmablasts, resulting in boosting immunity against VZV reactivation.