Browsing by Author "JUICA, F"

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    APICAL SECRETION OF HEPATITIS-B SURFACE-ANTIGEN FROM TRANSFECTED MADIN-DARBY CANINE KIDNEY-CELLS
    (AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC, 1993) GONZALEZ, A; NICOVANI, S; JUICA, F
    Hepatitis B surface antigen (HBsAg), the major envelope component of human hepatitis B virus, during infection drives the assembly and basolateral secretion from hepatocytes of both virions and subviral lipoprotein particles into the bloodstream. We studied the sorting behavior of HBsAg in the heterologous epithelial Madin-Darby canine kidney cells permanently transformed with the hepatitis B virus S gene. These cells, forming tightly packed monolayers in permeable supports, secreted HBsAg apically through a mechanism not involving transcytosis. This suggests that molecular features acting as apical addressing information, seemingly unfunctional or less efficiently used by the exocytic machinery of hepatocytes, could be contained in short hydrophilic regions of HBsAg. Lipids also could play a role in this asymmetric sorting because HBsAg is known to be secreted by forming macromolecular lipoprotein complexes rather than as a soluble protein. Together with available data, our results would imply not only the existence of tissue-specific variations in handling constitutively secreted proteins but also that these variations are strikingly dependent on the kind of protein examined. On the other hand, pulse-chase experiments with tunicamycin showed that the expression of apical information in HBsAg particles does not require N-linked glycosylation, contrasting with the known gp80 Madin-Darby canine kidney-endogenous apical secretory marker. This is the first experimental evidence that carbohydrate moieties in secretory proteins do not hold domain-specific sorting signals, a fact previously shown exclusively for membrane proteins. Thus, HBsAg provides a novel model system for the analysis of the molecular mechanisms of constitutive apical secretion.
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    DEVELOPMENT OF ANTI-HUMAN-B BLOOD GROUP MONOCLONAL-ANTIBODIES SUITABLE AS A BLOOD TYPING REAGENT
    (1994) BECKER, MI; JUICA, F; JAMETT, A; TZICHINOVSKY, S; BARROS, S; AGUAYO, J; DEIOANNES, AE
    An improved procedure for the generation of high-avidity anti-human B blood group monoclonal antibodies (MAbs) was developed. One of them, termed 7A1-2, showed excellent qualities of titer, avidity, and intensity required For use as human B blood typing reagent. Hemagglutination inhibition studies with monosaccharides and oligosaccharides were carried out to determine the specificity of the MAb 7A1-2. These studies indicate that the antibody reacts with the immunodominant region of the antigen which is known to confer the serologic specificity of this blood group.