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SUMMARYThere are few data about the distribution ofneutralizing antibodies (NA) against adenovirus types in the Italian population, especially the high-numbered ones. We tested the sera from 453 children and 51 young adults to evaluate NA against adenovirus prototypes 1-33. Using the microneutralization test, 338 (74-6 %) of the children's sera were positive for at least one adenovirus type. Antibody to type 2 was the most frequently detected followed, in descending order, by antibody to types 5, 1 and 3. All these types are known to be associated with disease but antibody to type 7, a type also associated with disease, was less frequent than that to other serotypes such as 18 and 31, the pathogenicity of which in man is not clearly established. The antibody positivity rate rose with age for the more frequent types while it did not vary for the less frequent ones. The number of sera with NA against more than one adenovirus type increased with age. With regard to types 1-8, we found that their frequencies in Italy were similar to those found in the U.S.A.

AAT.ATT is the most abundant and also the most frequently polymorphic class of trinucleotide repeats in the human genome. To characterize its structural properties and conformational changes induced by minor groove ligands, (AAT)(6) and (ATT)(6) oligomers as well as their complexes with DAPI were investigated by electrophoretic mobility and UV thermal stability as well as fluorescence and NMR spectroscopy. The results show that individual (AAT)(6) and (ATT)(6) strands exist principally as monomeric non-hydrogen-bonded structures. Their individual interaction with DAPI induces the formation of base-paired structures with different thermal stabilities by quite spectroscopically distinct binding mechanisms. In the presence of DAPI, (ATT)(6) forms a monomeric hairpin structure stabilized by two ligands located in the minor groove with a strong apparent binding constant of 3.4 x 10(6) M(-)(1). The DAPI-induced (ATT)(6) hairpin is characterized by well-stacked A.T Watson-Crick and T.T wobble base pairs, a high electrophoretic mobility, and a melting temperature of 41 degrees C. Interaction of DAPI with the complementary (AAT)(6) strand favors less stable base-paired structures, and the results are consistent with electrostatic and hydrogen-bond interactions of the ligand with the phosphodiester backbone of (AAT)(6) by minor involvement of DNA bases.

A fast-growing strain of human hepatitis A virus was selected and characterized. The virus has the unusual property of developing a strong cytopathic effect in tissue culture in 7 to 10 days. Sequences of the viral genome were cloned into recombinant plasmids with the double-stranded replicative form as a template for the reverse transcription of cDNA. Restriction analysis and direct sequencing indicate that this strain is different from that described by Ticehurst et al. (Proc. Natl. Acad. Sci. USA 80:5885-5889, 1983) in the region that presumptively codes for the major capsid protein VP1, but both isolates have conserved large areas of homology in the untranslated 5'-terminal sequences of the genome.

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