| Summary: | 碩士 === 國立臺灣大學 === 醫事技術學研究所 === 87 === Respiratory syncytial virus (RSV), an enveloped virus, is classified within the genus Pneumovirus of the family Paraxoviridae. RSV is the most important cause of lower respiratory tract infection in infants and vulnerable adults. The RSV genome is a single strand negative sense of RNA composed of approximately 15000 nucleotides that are transcribed into 10 major mRNA. Each of the mRNA encodes a major viral protein. Three of these proteins are transmembrane surface proteins ( G, F and SH).
On the basis of monoclonal antibody studies in 1985, RSV has been classified into two major subgroups, A and B. The G protein is the most variable gene product between RSV isolates. Sequence identity at the amino acid level is only 53% between the G protein of the prototype strains of subgroup A and B. Sequence variation has been observed among the G proteins of HRSV isolates of the same antigenic group. Our laboratory found that 11% sequence variation at amino acid level in Taipei RSV subgroup A isolates. To elucidate the variation of G gene of subgroup B RSV isolated in Taipei area, 43 strains of subgroup B from 1984-1998 were enrolled in this study. G protein genes of subgroup B RSV were amplified by RT-PCR. The nucleotide sequence of G gene was determined by dye termination autosequencing method. The identity of nucleotide and amino acid sequence of 43 RSV isolates in Taipei from 1984-1998 were compared and three subgroup B reference strain (8/60: 1960; CH18537: 1962; 9320: 1977) were used as reference. Nucleotide sequences homology and amino acid homology of 43 strains of subgroup B RSV were 93-99% and 87-99% respectively. The deduced amino acids sequence in cytoplasmic and transmembrane domains are conserved. Variation was found in two regions of extracellular domain; amino acid 80-154 and amino acid 198-300 region, separated by a highly conserved region (amino acid 155-197). The conserved region of G protein gene of subgroup B RSV in Taipei was smaller than the same region in strains isolated in other countries. The phylogenic tree of Taipei strains and some strains isolated in other countries was established by Neighbor-joining method. We find that most strains of Taipei isolates from 1984-1998 are grouped into one cluster (cluster I) and only three strains (840085, 840196, and 981480) are grouped into another cluster (cluster II).
RSV infection of the lower respiratory tract in infants typically causes acute bronchiolitis and pneumonia but may result in persistent abnormalities in pulmonary function and syndrome of wheezing and respiratory distress. Hospitalized and death causes are estimated very high in each year. Syndrome of infection of RSV in alveolar is more serious than in bronchus. Subgroup A RSV causes disease more severe than subgroup B virus causes. The correlations of clinical manifestation in different part of respiratory tract infected with different RSV subgroups are an interested issue. Dose cytokine production among these areas between RSV subgroup A and B infection plays another important role in the pathogenesis of RSV infection? In order to elucidate these questions, the IL-6, IL-8, and RANTES production in the human alveolar epithelial cell (A549), and human bronchial epithelial cell (BEAS-2B) infected with RSV A and B were compared. The results indicate that both subgroup A and B can induce all these three cytokines in A549 and BEAS-2B cells. In general, the production of cytokines by subgroup A and B was usually found higher in A549 than BEAS-2B. We compared the amount of cytokines production, RSV subgroup A produces more amounts of cytokine than subgroup B. This finding may explain the pathogenicity of subgroup A is higher than subgroup B.
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