Eleven novel human polyomaviruses (PyVs) and various animal PyVs have been identified during the last ten years. Basic characteristics like tissue tropism, cellular entry and infection mechanisms of these viruses will be the subject of future studies. The present thesis deals with the partial characterization of two novel human PyVs, the human polyomaviruses 9 (HPyV9) and 12 (HPyV12). Both were recently discovered, HPyV9 in the serum of a renal transplant recipient and HPyV12 in metastatic liver tissue. Here, genoprevalence and seroprevalence of HPyV9 and HPyV12 were analysed in different subject groups, cell lines were searched that support their replication, and HPyV9 and HPyV12 tumor antigens (TAg) were identified on the mRNA level. In tissue samples of patients suffering from malignant diseases of the gastro-intestinal tract (GIT), quantitative PCR yielded genoprevalences of 0 % for HPyV9 and 2.8 % for HPyV12. In ELISA based on viral major capsid protein (VP1), seroprevalence of HPyV9 was significantly higher in sera from patients with non-malignant diseases of the GIT (59 %) than that in sera of patiens with malignant diseases of the GIT (37 %, p = 0.02), and in sera of blood donors (32 %, p=0.04). VP1 seroprevalences of HPyV12 (8 % in blood donors, 20 % in patients with malignant diseases of the GIT, 25 % in patients with non-malignant diseases of the GIT) were generally lower and without significant differences (p>0.05). Similarly, ELISA based on the common N-terminus (78 amino acids) of T antigens of either PyV revealed sero-reactivities of 17 %–39 %. These data did not indicate any clear association of HPyV9 and HPyV12 with diseases of the GIT. Among the 12 cell lines tested to support HPyV9 and HPyV12 replication by transfection of synthetic genomes, the Vero cell line allowed the strongest increase in VP1 mRNA copies. Occasionally, cytopathic effects were observed, and viral proteins detected in immunofluorescence assay. Analysis of the early gene region of both viruses on the mRNA level resulted in identification of spliced LTAg- and small TAg-encoding mRNAs. In addition, so far unknown alternative TAgs (HPyV9-145T and HPyV12-84T) were identified. The results presented here contribute to the partial characterization of HPyV9 and HPyV12. Future studies concerning geno- and seroprevalence of the two PyV with alternative and larger sample panels are needed as the present results gave only first insights. The limitations of the protocol to test cell lines as potential in vitro replication systems might be overcome by further optimization and inclusion of primary cell lines. Characterization of the transforming potential of the identified LTAg splice variants will be of specific interest as they can be assumed to play a role in the oncogenic transformation of host cells and in pathogenesis.
|Commitee:||Kurreck, Jens, Rappsilber, Juri, Mankertz, Annette|
|School:||Technische Universitaet Berlin (Germany)|
|Source:||DAI-C 81/1(E), Dissertation Abstracts International|
|Keywords:||Human polyomaviruses, HPyV9, HPyV12|
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