Common mutations in immunoglobulin VK3 light chain sequences from B-cells of HCV-related disorders

It has been proposed that persistent HCV infection drives the proliferation of B cells through an antigen-selective stimulation, mediated by B-cell receptor (BCR) involvement that preferentially includes a IgL Vk-3 chain. The aim of this study is to characterize IgL Vk rearrangements from different setting of HCV-related disorders to investigate if there is a preferential subset of BCR repertoire among 5 clinical groups. 26 HCV+ve patients (HBV-ve; HIV-ve) were studied: 2 MC, 12 NHL without clinical manifestation of MC, 6 HCV spontaneously resolved (SR), 6 HCV chronic infected (CE). Six blood donors (BD) were used as controls. VK3 gene region was amplified using VK3 specific and a mixture of JK primers. In the present study VK3-20, VK3-15 and VK3-11 subfamilies were the most represented (>90% of total clones). IGKV3-15 gene was over represented in both NHL and MC groups (67%) vs CE+SR+BD (22%, p<0.001). IGKV3-20 gene was the most represented gene in BD and IGKV3-11 in CE, SR. An higher mutation frequency was detected both in BD (media of mutations 2,62%) and NHL (2,41%) with respect to CE (2,04%), MC (1,75%) and SR (1,55%) groups. The higher and the lower levels of R mutations were detected in SR, respectively in FR1 region (1,52%) and in the CDR2 (0,06%). Both in FR1 and FR2, the R:S ratio of SR was the highest (35%), in CDR2 was the lowest (1,5%). In FR3 and in CDR1 the R:S ratio was similar between groups, while in CDR2 BD had the highest value (10,5%). Multiple alignments of amino acid sequences obtained (472 clones) were carried to produce a consensus sequence Data highlighted that FR2 and CDR2 VK3-regions were conserved in all the 5 groups. FR1, CDR1 and CDR3 were commonly shared by CE, SR and BD. FR3 distinguish SR from these other groups in the in the first residue (Thr vs Asn). MC and NHL shared a consensus sequence among them that was more similar to VK3-15 chain mainly in the hypervariable CDR3 (Asn93), FR1 (Val13) and FR3 (Thr54, Glu71; Gln80 and Ser81) regions. In addition, Asn residue in pos32 in MC and in pos33 in NHL, distinguishes MC from NHL in CDR1. A 3D structural modelling is now in course to evaluate the potential impact on antibody-HCV antigen interactions (Leukemia, 2006). In conclusion we described common mutations in HCV-related lymphoproliferative diseases that should be useful to corroborate the molecular insights of HCV outcomes and to better define targets for potential anti-idiotype therapeutic approaches.