Specialization of Hepatitis C Virus Envelope Glycoproteins for B Lymphocytes in Chronically Infected Patients

Abstract

Hepatitis C virus (HCV) productively infects hepatocytes. Virion surface glycoproteins E1 and E2 play a major role in this restricted cell tropism by mediating virus entry into particular cell types. However, several pieces of evidence have suggested the ability of patientderived HCV particles to infect peripheral blood mononuclear cells. The viral determinants and mechanisms mediating such events remain poorly understood. Here, we aimed at isolating viral determinants of HCV entry into B lymphocytes. For this purpose, we constructed a library of full E1E2 sequences isolated from serum and B lymphocytes of four chronically infected patients. We observed a strong phylogenetic compartmentalization of E1E2 sequences isolated from B lymphocytes in one patient, indicating that E1E2 glycoproteins can represent important mediators of the strong segregation of two specialized populations in some patients. Most of the E1E2 envelope glycoproteins were functional and allowed transduction of hepatocyte cell lines using HCV-derived pseudoparticles. Strikingly, introduction of envelope glycoproteins isolated from B lymphocytes into the HCV JFH-1 replicating virus switched the entry tropism of this nonlymphotropic virus from hepatotropism to lymphotropism. Significant detection of viral RNA and viral proteins within B cells was restricted to infections with JFH-1 harboring E1E2 from lymphocytes and depended on an endocytic, pH-dependent entry pathway. Here, we achieved for the first time the isolation of HCV viral proteins carrying entry-related lymphotropism determinants. The identification of genetic determinants within E1E2 represents a first step for a better understanding of the complex relationship between HCV infection, viral persistence, and extrahepatic disorders. IMPORTANCEHepatitis C virus (HCV) mainly replicates within the liver. However, it has been shown that patient-derived HCV particles can slightly infect lymphocytes in vitro and in vivo, highlighting the existence of lymphotropism determinants within HCV viral proteins. We isolated HCV envelope glycoproteins from patient B lymphocytes that conferred to a nonlymphotropic HCV the ability to enter B cells, thus providing a platform for characterization of HCV entry into lymphocytes. This unusual tropism was accompanied by a loss of entry function into hepatocytes, suggesting that HCV lymphotropic variants likely constitute a distinct but parallel source for viral persistence and immune escape within chronically infected patients. Moreover, the level of genetic divergence of B-cell-derived envelopes correlated with their degree of lymphotropism, underlining a long-term specialization of some viral populations for B-lymphocytes. Consequently, the clearance of both hepatotropic and nonhepatotropic HCV populations may be important for effective treatment of chronically infected patients.

A role for B cells to transmit hepatitis C virus infection

“…In contrast, CD19 + B cells from chronic infected patients established infection in the mice whereas B cells from recently infected patients were non-infectious; highlighting a dichotomy in the infectious sources of HCV. Comparing HCV QS-diversity in the sera and B cells of these infected subjects con rmed previous reports of viral compartmentalization (nonrandom phylogenetic distribution) in B cells (48,49). The intracellular B cell compartment carried a unique population of pauci-or monoclonal viral variants that closely resembled replicating virus isolated from mice infected via B cell transfer.…”

Hepatitis C virus has a genetically determined lymphotropism through co-receptor B7.2

“…To further ascertain the importance of E1-E2 proteins in the lymphotropism of SB virus, we produced HCVpp using an envelope-defective HIV-1 proviral vector495051. This HCVpp bears the E1 and E2 envelope proteins of HCV and contains a luciferase reporter gene in the lentivector.…”

HCV Lymphotropism and Its Pathogenic Significance

“…lymphotropism was recently provided which showed that a distinct virus subpopulation capable of encoding particular E1E2 (envelope) epitopes might be responsible for the infection of B lymphocytes [86]. Isolated HCV E1E2 glycoproteins from patient B cells were able to confer the ability to enter and replicate in B cells to a non-lymphotropic HCV JFH-1 strain, as demonstrated by the detection of viral RNA and proteins within those cells.…”