Mutations in the putative HCV‐E2 CD81 binding regions and correlation with cell surface CD81 expression

Abstract

The hepatitis C virus (HCV) envelope (E)2 protein interacts with the cellular receptor CD81 leading to modulation of B and T cell function. Recently, a higher binding affinity of subtype 1a in comparison with 1b derived E2 proteins for CD81 in vitro was described. The importance of mutations within the putative CD81 binding regions of different HCV geno-/subtypes in correlation with CD81 expression is unknown. In the present study, CD81 expression on blood lymphocytes of patients with chronic hepatitis C infected with different HCV geno-/subtypes were analysed by fluorescence activated cell sorter analyses. In addition, the putative CD81 binding regions on the E2 gene comprising the hypervariable region (HVR)2 were analysed by direct sequencing. CD81 expression on CD8(+) T-lymphocytes from patients infected with subtype 1a (n = 6) was significantly higher in comparison with subtype 1b (n = 12) and 3 (n = 5) infected patients before and during antiviral therapy (P = 0.006; P = 0.021, respectively). Sequencing of the putative CD81 binding regions in the E2 protein comprising the HVR2 (codon 474-495 and 522-552 according to the HCV-1a prototype HCV-H) showed a highly conserved motif within HVR2 for subtype 1a isolates and an overall low number of mutations within the putative CD81 binding regions, whereas numerous mutations were detected for subtype 1b isolates (12.0 vs 23.6%). HCV-3 isolates showed an intermediate number of mutations within the putative binding sites (19.2%; P = 0.022). In conclusion, the highly conserved sequence within HVR2 and putative CD81 binding sites of subtype 1a isolates previously associated with a high CD81 binding affinity in vitro is correlated with high CD81 expression on CD8(+) T-lymphocytes in vivo.

Virological analysis and phenotypic characterization of peripheral blood lymphocytes of hepatitis C virus-infected patients with and without mixed cryoglobulinaemia

“…The factors responsible for HCV enrichment in PBL preparations from cryoglobulinaemic patients are unknown, but may be related to the higher density and/or genetic polymorphism of the putative (co)receptor gene for HCV binding [37,38]. The connection between HCV cells enrichment and cryoglobulin production is also unclear.…”

Tetraspanins in Viral Infections: a Fundamental Role in Viral Biology?

“…Thus, it appears that formation of the CD81-E2 complex does not necessarily confer susceptibility to the virus. It has also been observed that different HCV strains utilize CD81 to different extents (70,94,131); E2 subtype 1b, for instance, shows a lower binding affinity to CD81-LEL than E2 subtype 1a. The CD81-LEL Phe186Leu mutation has been shown to abolish the binding of CD81 LEL to soluble E2 strain H but not to strain Con 1, even though this mutation has no effect on the ability of transfected HepG2 cells to support infection by pseudotype viruses expressing either Con 1 or strain H E2 (175).…”

Hepatitis C Virus Infection and Mixed Cryoglobulinemia

“…MC patients are distinctly characterized by higher levels of cell-associated viral load, because a significant enrichment of HCV RNA in PBL has been demonstrated [61]. This peculiar feature may be considered as the result of a higher density [62] and/or polymorphism of receptor genes [63, 64], whereas direct infection and replication of HCV in B cells may promote lymphocyte proliferation [65]. …”