The determination of the total 5,224 base-pair DNA sequence of the virus SV40 has enabled us to locate precisely the known genes on the genome. At least 15.2% of the genome is presumably not translated into polypeptides. Particular points of interest revealed by the complete sequence are the initiation of the early t and T antigens at the same position and the fact that the T antigen is coded by two non-contiguous regions of the genome; the T antigen mRNA is spliced in the coding region. In the late region the gene for the major protein VP1 overlaps those for proteins VP2 and VP3 over 122 nucleotides but is read in a different frame. The almost complete amino acid sequences of the two early proteins as well as those of the late proteins have been deduced from the nucleotide sequence. The mRNAs for the latter three proteins are presumably spliced out of a common primary RNA transcript. The use of degenerate codons is decidedly non-random, but is similar for the early and late regions. Codons of the type NUC, NCG and CGN are absent or very rare.

A reverse-hybridization assay, the line probe assay (LiPA), based on variations found in the 5' untranslated regions of the different hepatitis C virus (HCV) genotypes was developed, permitting simple and fast determination of four HCV genotypes and their subtypes. Using this assay, 61 PCR-positive Brazilian HCV sera were typed. Of the sera, 33% had a type 1 HCV infection, 38 % had type lb (related to HCV-J), 1.5 % had type 2a (related to HC-J6), 24.5 % had type 3 (related to E-bl and HCV-T), and 3 % of the sera were co-infected. This assay format was further evaluated using 13 sera from Belgium and the Netherlands, and all of these could be classified. Two pools of Japanese sera were classified as either type 2a or were co-infected with types lb and 2a, but no type 2b sequences were detected. Another eight PCR-positive sera were obtained from Burundi and Gabon. The sequence of the 5' untranslated region of these African viruses was strongly divergent from the three previously described types. Therefore, these isolates were tentatively classified as type 4. These and some of the other non-type 1 sera often demonstrated weaker reactivities than type 1 isolates in currently used second generation antibody confirmation assays.

INTRODUCTIONThe antitumour effect of endotoxins has been known for over a century because of remarkable observations regarding spontaneous regression of

The sequences of two minicircles from the kinetoplast DNA of the CL strain and one of the Y strain of Trypanosoma cruzi are reported. These 1.4 kb molecules have a peculiar sequence organization, the most distinctive feature being the occurrence of a 120 bp sequence repeated four times, located at 0, 90, 180 and 270 degrees along each circle. We have termed these conserved regions in this species 'minirepeats'. Minirepeats have a 3-fold higher concentration of cytosine residues in comparison with the variable regions and contain the universal 12-mer motif GGGGTTGGTGTA present in all sequenced minicircles and which was shown to be involved in DNA replication. A consensus sequence of T. cruzi minirepeats was determined using the 20 minirepeats present in five known T. cruzi minicircle sequences. This consensus sequence contains regions which have been remarkably well preserved in strains which show great biological diversity. In addition a low level of intraminicircle sequence similarity was also observed within the variable region, but this similarity did not extend between strains. The abundance of conserved minirepeat sequences containing invariant restriction sites in T. cruzi cells may prove valuable for the development of new direct diagnostic methods for Chagas' disease based on DNA probe technology.