AUTHOR=Khanam Arshi , Ayithan Natarajan , Tang Lydia , Poonia Bhawna , Kottilil Shyam 

TITLE=IL-21–Deficient T Follicular Helper Cells Support B Cell Responses Through IL-27 in Patients With Chronic Hepatitis B

JOURNAL=Frontiers in Immunology

VOLUME=11

YEAR=2021

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2020.599648

DOI=10.3389/fimmu.2020.599648

ISSN=1664-3224

ABSTRACT=<p>Chronic Hepatitis B (CHB) affects over 350 million people worldwide. Current treatment does result in reduced complications; however, a cure (development of antibodies to the S antigen) is not achieved, requiring life-long therapy. Humoral responses contribute to viral elimination by secreting neutralizing antibodies; though, effective induction of humoral immunity require CD4T cell differentiation into T follicular helper (T<sub>FH</sub>) cells that support B cell response through interleukin-21 (IL-21). In CHB, mechanism of T<sub>FH</sub>-B interactions is seldom described. During CHB, T<sub>FH</sub> cells are defective in producing IL-21 in response to hepatitis B surface antigen (HBsAg). However, regardless of low IL-21, T<sub>FH</sub> cells efficiently support B cell responses by producing interleukin-27 (IL-27), which directs the formation of plasmablasts and plasma cells from memory and naïve B cells by enhancing B lymphocyte-induced maturation protein-1. IL-27 not only improved total antibody production but HBsAg-specific IgG and IgM secretion that are essential for viral clearance. Importantly, IL-27+T<sub>FH</sub> cells were significantly associated with HBV DNA reduction. Therefore, these findings imply a novel mechanism of T<sub>FH</sub> mediated B cell help in CHB and suggest that IL-27 effectively compensate the function of IL-21 by supporting T<sub>FH</sub>-B cell function, required for protective antibody response and may contribute to viral clearance by providing potential target for achieving a functional cure.</p>