Circulating CXCR3 Tfh Cells Positively Correlate with Neutralizing Antibodies Responses During HCV Infection

Abstract

OBJECTIVE: Circulating T follicular helper (cTfh) cells have been identified as counterparts of germinal center Tfh (GC Tfh) cells in humans and can support T-dependent B cell maturation and antibody production in vitro. However, the role of cTfh cells in neutralizing antibody responses during HCV infection remains unclear. Here, we characterized the phenotype and function of cTfh cells and demonstrated associations of cTfh cells and their subsets with neutralizing antibody responses during HCV infection. METHODS: A total of 38 HCV-infected individuals and 28 healthy controls were enrolled from a pool of injection drug users (IDUs). The frequency and function of blood Tfh cells were analyzed by flow cytometry. The titers and breadths of serum neutralizing antibodies were measured using HCV pseudo-particle neutralization assays. RESULTS: Herein, we report several key observations. First, HCV infection skewed cTfh toward CXCR3 cTfh cell differentiation. Second, the frequency of CXCR3 cTfh cells was positively correlated with HCV neutralizing antibody titers and breadths. Third, CXCR3 cTfh cells showed higher expression of Tfh-associated molecules (PD-1, ICOS, IL-21, Bcl-6) compared with CXCR3- cTfh cells from individuals with HCV infection. Coculture of cTfh cells and autologous memory B cells in vitro indicated that CXCR3 cTfh cells show a superior ability to support HCV E2-specific B cell expansion compared with CXCR3- cTfh cells from individuals with HCV infection. CONCLUSION: HCV infection skews cTfh cells toward CXCR3-biased Tfh cell differentiation, which positively correlates with the magnitude and breadth of the HCV neutralizing antibody response. It is our hope that these findings will provide insights for the rational design of a neutralizing antibody-based HCV vaccine. FUNDING STATEMENT: This study was supported in part by the Natural Science Foundation of China (grant numbers 81471959 and 81501746) and the foundation of The First People’s Hospital of Chenzhou (grant number N2018-001). DECLARATION OF INTERESTS: The authors who participated in this study declare that they have nothing to disclose regarding funding or conflicts of interest related to this manuscript. ETHICS APPROVAL STATEMENT: This study was approved by the Ethics Committee of The First People’s Hospital of Chenzhou (No. 2015002) and followed the principles established by the Declaration of Helsinki. All participants enrolled in the study provided written informed consent.