| TT virus is a newly described DNA virus with high genetic heterogeneity. To investigate the novel variants of the virus, blood samples were collected from subjects who lived in various parts of China, and a PCR was carried out to amplify a 3244-bp fragment using primers deduced from the prototype TTV (TA278). Twelve entire ORFI nucleotide (nt) sequences were aligned and an unrooted phylogenetic tree was constructed. According to the genetic distances, these variants could be classified into eight groups of A to H, isolate TCHNHI belonged to genotype Ia, isolate TCHNA related to TUS01 and isolate TCHNG2 related to SANBAN. The distances of variant groups were more than 0.41 to TA278(except TCHNHI); The distances of TCHNA and TCHNB were 0.22, 0.41 to TUSO1, respectively; The distances ofTCHNF,TCHNGI and TCHNG2 were 0.36, 0.30, 0.11 to SANBAN, respectively. The distances between inter-groups were very different, 0.30 between TCHNCI and TCHNC2, 0.22 between TCI-INDI and TCI-1N02, 0.04 between TCHNEI and TCHNE2, and 0.30 between TCHNGI and TCHNG2. The ORFI encoded 426?80 amino acids (an) and ORF2 encoded 141?56 an. The nucleotide sequence surrounding the first ATG codon in ORFI possessed the consensus sequence (ACCATGG) for initiation of eukaryotic protein translation and a polyadenylation signal sequence AATAAA, was identified downstream from the ORF I termination codon. The homology of entire ORFI nt sequences between TA278 and novel variant groups was 49.7-55.0% (except TCHNH 1), that of an sequences was 36.2-48.9% (except TCI-INH 1), and the homology of entire ORF2 an sequence between TA278 and novel variant groups was 40.0%-46.2% (except TCHNH 1), the an sequence homology of ORF1 and ORF2 was lower than the nt homology. The first 65 an of ORF1 were rich in arginine and most conserved with homology of 56.5 ~/o?0.0%; There was a hypervariable region from an 286 to 403 of ORF I with merely 1 7.7%-~-27.0% of identity. Besides, compared 2 to TA278 there were multiple codon insertions/deletions spreading at many sites, and only fragment of aa 65-273, aa 401491, and 611-674 of ORFI sequences without these variations. Despite a low identity between TA278 and variants, there have similar hydrophilicity profiles of both ORFI and ORF2. There were one to nine asparagine-linked glycosylation motifs, but only one Rep motif, and many kinase phosphorylation sites at different regions in ORFI of these variants, so the ORF1 protein was presumed to be a coat protein. The an sequence W-X7-H-X3-C-X I -C-X5-H, a motif shared by chicken anemia virus (CAV ), was also present in ORF2 of these variants. In conclusion, despite divergence, sequences of all these isolates were collinear with that of TTV prototype, and share common genome organization, ORF structure, hydrophilicity patterns and some potential motifs. It is suggested that various TTV and TTV-like isolates belong to a very new and complex family, which remains to be studied. In the second part, we have reported that TI?virus could cause outbreak of hepatitis-like disease via enteric transmission and that the virus was identified to be able to transmit fecal-orally by experimental infection of Rhesus monkey. To examine its tissue-specific tropism, various tissues were collected from 5 experimentally infected monkeys during the viremic period for testing the viral DNA by dot blot hybridization with double or anti-sense probe. As the viral genome was negative polarity, the plus-stranded...
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