Three missense mutations found in the KEL gene lead to K(mod) or K0 red blood cell phenotypes.

Background: The KEL gene is highly polymorphic. It presents two major alleles, KEL1(K) and KEL2(k), but a variety of mutations give rise to weakened (K(mod) phenotype) or lack (K0 phenotype) of Kell antigen expression. Recently, the use of advanced DNA-based techniques has greatly increased our understanding of the Kell blood group system.

Slow response to entecavir treatment in treatment-naive HBV patients is conditioned by immune response rather than by the presence or selection of refractory variants.

Background: Entecavir is the drug of choice as first-line treatment for treatment-naive HBV patients. As a result of the high genetic barrier to resistance, treatment failure remains rare, but occurs within 3 years of initiation, suggesting that viral genetic characteristics may provide a fast lane to resistance. One of the main concerns is the long time to viral suppression observed in some (even treatment-naive) patients.