Detection of in vivo hepatitis B virus surface antigen mutations-A comparison of four routine screening assays.

An important requirement for a state-of-the-art hepatitis B surface antigen (HBsAg) screening assay is reliable detection of mutated HBsAg. Currently, there is a striking shortage of data regarding the detection rates of in vivo HBsAg mutations for these clinically important assays. Therefore, we compared the detection rates of four commercial HBsAg screening assays using a global cohort of 1553 patients from four continents with known HBV genotypes. These samples, which represent the broadest spectrum of known and novel HBsAg major hydrophilic region (MHR) mutations to date, were analyzed for the presence of HBsAg using the Roche Elecsys® HBsAg II Qualitative, Siemens ADVIA Centaur XP HBsAg II, Abbott Architect HBsAg Qualitative II and DiaSorin Liaison® HBsAg Qualitative assays, respectively. Of the 1553 samples, 1391 samples could be sequenced; of these, 1013 (72.8%) carried at least one of the 345 currently known amino acid substitutions (distinct HBsAg mutation) in the HBsAg MHR. All 1553 patient samples were positive for HBsAg using the Elecsys® HBsAg II Qual assay, with a sensitivity (95% confidence interval) of 99.94% (99.64%-100%), followed by the Abbott Architect 99.81% (99.44%-99.96%), Siemens ADVIA 99.81% (99.44%-99.96%) and DiaSorin Liaison® 99.36% (98.82%-99.69%) assays, respectively. Our results indicate that the Elecsys® HBsAg II Qual assay exhibits the highest sensitivity among the commercial HBsAg screening assays, and demonstrate that its capacity to detect HBV infection is not compromised by HBsAg MHR mutants.

Mutation screening for the prothrombin variant G20210A by melting point analysis with the Light Cycler system: atypical results, detection of the variant C20209T and possible clinical implications.

In the differential diagnosis of thrombophilic disorders genotyping of prothrombin and factor V are nowadays performed as a routine analysis. In the following we describe the unusual results of the mutation screening using melting point analysis for two patients and the consecutive detection of the mutation C20209T by sequencing the corresponding gene fragments. The molecular result is discussed with special respect to the medical history, ethnic background and clinical findings of both patients.

Limited proteolysis of gamma II-crystallin from calf eye lens. Physicochemical studies on the N-terminal domain and the intact two-domain protein.

Gamma II-crystallin from calf eye lens consists of two homologous domains, connected by a six-residue linker peptide. In order to study the intrinsic properties of the domains and their mutual stabilization, limited proteolysis was applied. Optimum conditions providing a homogeneous 10-kDa fragment at high yield were pepsin cleavage in 0.1 M NaCl/HCl pH 2.0, in the presence of 3.0 M urea. Determination of the N-terminus and the C-terminal sequence showed that cleavage occurred at the Phe88-Arg89 peptide bond, giving rise to the complete N-terminal domain including the connecting hexapeptide. The C-terminal part of the polypeptide chain is cleaved to small fragments. Comparing the spectral properties of the isolated N-terminal domain and intact gamma II-crystallin proved the structure of the fragment to be closely similar to that of the native domain. Small differences in absorbance, fluorescence emission and circular dichroism point to alterations caused by the increase in surface area as a consequence of domain separation. The resistance of the 10-kDa fragment toward thermal and alkaline denaturation, as well as unfolding in the presence of urea or guanidine . HCl is decreased, due to the lack of domain interactions stabilizing the intact protein. Unfolding/folding kinetics of the 10-kDa fragment coincide with the second phase of the bimodal transition of intact gamma II-crystallin, in agreement with independent sequential folding and modular assembly of the domains within the native molecule.