Diversity of amino acid sequences within the HCV E2 protein in serum and PBMC

Introduction: HCV infects hepatocytes, but is a potential lymphotropic virus either. Interaction between the HCV envelope (E) protein 2 and CD81 is essential for cell entry. Two putative CD81 binding regions (CD81-1/-2) within HCV E2 have been described. Variants with enhanced binding affinity to CD81 may be identified by analysis of inter- and intra-patient variability of CD81–1/2 in PBMC and serum derived HCV-RNA. Patients and Methods: 37 patients (f=20, m=17; mean age, 44 years) chronically infected with HCV genotype (GT) 1a (n=21, mean viral load [mvl] 6.0 logIU/ml) or 1b (n=16, mvl 5.9 logIU/ml) were investigated. A segment of 285 nucleotides coding for 95 aminoc acids (aa) containing CD81–1/-2 was amplified from PBMC and serum derived HCV-RNA and sequenced. A detailed mutational analysis of the deduced aa was performed. Results: The overall mutational frequency (MF) within CD81–1 was 13% (GT1a) and 28% (GT1b) in PBMC derived HCV-RNA, and 5% (GT1a) and 22% (GT1b) in serum derived HCV-RNA, respectively. Within CD81–2, the MF was 5% (GT1a) and 11% (GT1b) in PBMC derived HCV-RNA, and 10% (GT1a) and 11% (GT1b) in serum derived HCV-RNA. Compared to the consensus sequence at different (60, 80, 100%) consensus levels 76%, 52%, 32%, and 80%, 73%, and 60% of aa positions were conserved within CD81–1 and CD81–2, respectively. To investigate the intra-individual aa diversity, CD81–1/-2 sequences from corresponding PBMC and serum derived HCV RNA samples were compared. Divergences between PBMC and serum derived aa sequences were seen in 4 patients at 8 positions. Discussion: Overall, CD81–1/-2 binding regions are conserved between PBMC and serum derived HCV RNA samples. Highly conserved amino acid patterns at the 100% consensus level might be functionally important for cell attachment and entry of HCV. The importance of the identified aa patterns as well as their use as potential anti-HCV targets is currently investigated with an in vitro HCV infection model.

CD81 - HCV-E2 - PBMC - viral fitness