| Summary: | 博士 === 國立陽明大學 === 公共衛生研究所 === 98 === Previously, it has been reported that there was an outbreak of human immunodeficiency virus type 1 (HIV-1) circulating recombinant form (CRF) 07_BC among injection drug users (IDUs) in Taiwan in 2004. The objectives of the present study were to conduct a molecular epidemiological analysis and to characterize the full-length genome and biological and properties of the Taiwanese CRF07_BC. Therefore, the specific aim of this study was 1) to conduct a molecular epidemiological analysis of HIV-1 infection in Taiwan in 2004; 2) to characterize the full-length genome of the Taiwanese CRF07_BC; 3) to characterize the biological and virological properties of HIV-1 CRF07_BC strains and 4) to study the effects of the truncated p6gag and p6pol in the virus life cycle.
Patients with HIV-1/AIDS from hospitals and from detention centers were recruited for molecular epidemiological analysis. Longitudinal data of treatment-naïve IDUs from AIDS clinics were collected retrospectively to evaluating the rate of disease progression. DNA sequencing and phylogenetic analysis were conducted to determine subtypes and evolutionary relationships. Recombination breakpoints of two full-length CRF07_BC strains were elucidated using a bootscanning method. The replicative capacity and biological phenotype were investigated in PBMCs and MT-2 cells. Assembly and processing of HIV-1 Gag proteins and infectivity of virus particles with 7 and 11 aa deletions in p6 region were analyzed using immunoblotting and single-cycle-infection assay.
Of 206 HIV-1-infected patients who received a diagnosis in 2004, 44.7% were infected with subtype B, 53.4% with CRF07_BC, and 1.5% with CRF01_AE. Ninety-eight percent of IDUs were infected with CRF07_BC. There was no difference in the rate of CD4+ T cell loss between subtype B and CRF07_BC (p=0.7101, Mann-Whitney test), and regression analysis revealed higher CD4+ T cells and lower viral load over time in CRF07_BC group (p=0.7481 and p=0.1659 respectively, GEE model). The Taiwanese CRF07_BC strains belonged to 2 phylogenetic clusters, and the first cluster contained only CRF07_BC strains from the southern part of Taiwan. Full-length genomic analysis showed that Taiwanese CRF07_BC strains clustered with other CRF07_BC strains from mainland China, with a bootstrap value of 100. The bootscan of the Taiwanese CRF07_BC strain revealed that it was mainly composed of subtype C, with 5 inserted segments of subtype B’. There were 10 recombination breakpoints in Taiwanese CRF07_BC and that they were almost identical to those of the CRF07_BC prototype (97CN54) from China. Deletions of 7-11 aa in both p6gag and p6pol proteins were noted among the Taiwanese CRF07_BC strains which were non-syncytium inducing (NSI) and R5 phenotypes and replicated less efficiently in the cellular environment. Eleven aa deletions in p6 severe reduced the virion production from transfection, while seven amino acid deletions in p6 had no major effect on protease-mediated particle processing. The infectivity of the released pseudotyped viruses carrying either 7 or 11 aa deletions in p6 region in the context of a HXB2 molecular clone were significant reduced.
The Taiwanese CRF07_BC strains had 97% full-length sequence homology with the prototype from mainland China. Furthermore, the appropriate Gag processing and decreased replicative capacities of the CRF07_BC strains may be related to reduced virulence and slow disease progression.
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