This involvement is also confirmed by the data showing that a long-lasting memory CD4 and CD8 cell responses against HBV antigens are still detectable several years after recovery from acute hepatitis B possibly because during the occult phase of the infection, HBV is still able to synthesize minute amounts of antigens, which are undetectable by available technical approaches but are sufficient enough to maintain an HBV-specific T cell response [8, 10]. This evidence concerns the gene CD4 and infection.