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. STUDY DESIGN AND METHODS: Three blood samples that had shown discordant results between the serologic and molecular typing for k were investigated by DNA sequencing. Two of these samples were also subjected to studies of adsorption and elution. RESULTS: After sequencing the whole KEL gene, we found three new missense mutations: c.455A>G (p.Tyr152Cys) at Exon 5, c.2111A>C (p.Pro704His) at Exon 19, and c.1726G>C (p.Gly576Arg) at Exon 16. So far, no known clinical implications are associated with these mutations. Further investigation by adsorption and elution methods has defined that c.455A>G and c.1726G>C resulted in K0 phenotype, while c.2111A>C encoded a K(mod) phenotype. CONCLUSION: Molecular investigation is an important complement to routine serologic analyses of Kell antigens. Discrepancies between genotype and phenotype may reveal the presence of K(mod) or K0 phenotypes. Our description of three new KEL alleles suggests a role for a wider diagnostic approach to typing of the Kell 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. The reasons for this phenomenon were investigated in a group of chronic hepatitis B treatment-naive patients. METHODS: Out of 23 treatment-naive patients starting entecavir, the 5 with the best and those with the worst viral load decay curves were selected for the study. Quasispecies analysis was performed for the reverse transcriptase/hepatitis B surface antigen (HBsAg) open reading frame (ORF) by ultra-deep pyrosequencing. For each patient, the analysis was performed at baseline (T0) and when viraemia reached between 15,000 and 200 IU/ml (T1). RESULTS: The few resistance mutations present at T0 were not selected by treatment; no other resistance mutations or suggestive mutational patterns were selected at T1. Selective pressure analysis indicated that both at T0 and T1 the HBsAg ORF was subjected to a significantly higher pressure in rapid responders, especially in a region rich in cytotoxic T-lymphocyte (CTL) epitopes. CONCLUSIONS: The results did not provide evidence that a slower response to entecavir is due to the emergence of less sensitive variants. Rather, the lower selective pressure and variability in humoral and CTL epitopes in slow responders suggests that their immune response might be at odds in rapidly clearing infected cells from the liver.