Persisting viruses, such as HCV (a single strand RNA virus causing chronic hepatitis in 60–80% of infected individuals, depending on the geographical areas), HIV-1 (a lentivirus belonging to the Retroviridae family, infecting human immune cells and causing AIDS in the majority of infected individuals without treatment), and to a lesser extent HBV (a double strand DNA virus causing chronic hepatitis in less than 3% of infected individuals), provide different mutation rates that can have equally different impact on BCR or TCR diversity. This evidence concerns the gene BCR and chronic hepatitis.