Hepatitis C virus (HCV)-driven stimulation of subfamily-restricted natural IgM antibodies in mixed cryoglobulinemia.
Hepatitis C virus (HCV) infection has been closely related to mixed cryoglobulinemia (MC). During HCV infection, cryoglobulins derive from the restricted expression of few germline genes as VH1-69, a subfamily highly represented in anti-HCV humoral response. Little is known about the self-reacting IgM component of the cryoprecipitate. In the present study, the IgM/K repertoire of an HCV-infected cryoglobulinemic patient was dissected by phage-display on well-characterized anti-HCV/E2 VH1-69-derived monoclonal IgG1/Kappa Fab fragments cloned from the same patient. All selected IgM clones were shown to react with the anti-HCV/E2 antibodies belonging to VH1-69 subfamily. More than 60% of selected clones showed a bias in VH gene usage, restricted to two VH subfamilies frequently described in autoimmune manifestations (VH3-23; VH3-21). Moreover, all selected clones showed an high similarity (>98.5%) to germline genes evidencing their natural origin. A possible hypothesis is that clones belonging to some subfamilies are naturally prone to react against other VH gene subfamilies, as VH 1-69. An antigen-driven stimulation of these subfamilies, and their overexpression as in HCV infection, could lead to a breaking of humoral homeostatic balance exposing the patients to the risk of developing autoimmune disorders.
Laboratorio di Microbiologia e Virologia, Università Vita-Salute San Raffaele, Milan, Italy.
Mario
M
Perotti
Nadia
N
Ghidoli
Raffaele
R
Altara
Roberta A
RA
Diotti
Nicola
N
Clementi
Donata
D
De Marco
Monica
M
Sassi
Massimo
M
Clementi
Roberto
R
Burioni
Nicasio
N
Mancini
D001323:Autoantibodies / Q000235:genetics / Q000276:immunology*; D003001:Cloning, Molecular; D003449:Cryoglobulinemia / Q000235:genetics / Q000276:immunology* / Q000821:virology*; D016174:Hepacivirus / Q000276:immunology; D006526:Hepatitis C / Q000235:genetics / Q000276:immunology*; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000235:genetics / Q000276:immunology; D007075:Immunoglobulin M / Q000235:genetics / Q000276:immunology*; D017422:Sequence Analysis, DNA; D014759:Viral Envelope Proteins / Q000276:immunology
D001323:Autoantibodies; D007140:Immunoglobulin Fab Fragments; D007075:Immunoglobulin M; D014759:Viral Envelope Proteins; C091015:glycoprotein E2, Hepatitis C virus