臺灣本土禽流感病毒株血液凝集素重鏈異構物分析及其醣質表現圖譜

Abstract

許多低病原性禽類流感病毒 (avian influenza viruses, AIV) 已於臺灣本土農場分離出來，然而這些病毒蛋白質體之改變與毒性之關係尚未被研究清楚。在本研究中，使用二次元電泳 (2-DE) 並配合專一性之凝集素 (specific lectins) 分析比較，來自同一 H6N1 族群，但卻表現不同毒性程度之兩株 AIV：非毒性病毒株 (2838N) 及毒性病毒株 (2838V)。比較兩病毒株之二次元蛋白質圖譜發現，血液凝集素 1 (hemagglutinin, HA) 為差異最大之蛋白質，且兩株 AIV 之 HA1 皆有分子量相近，但等電點迥異之 6 種異構物。本研究發現，HA1 這些異構物形成之原因，並非因於蛋白質磷酸化，亦非 HA1 醣質之唾液酸修飾 (sialylation)。另外，我們使用介質輔助雷射脫附離子化質譜儀 (MALDI MS and MS/MS) 建構 HA1 各異構物之醣質圖譜。比較 HA1 各異構物之醣質表現圖譜發現，等電點越低之 HA1 異構物其 m/z 1867 之 X-醣質比例越高。而血液凝集素主要功能為辨識並和宿主之唾液酸受體結合，因此 HA1 本身特別之醣基化可能會影響 AIV 之宿主辨識，亦可能和病毒之組織趨性及免疫逃脫有關。

Several low pathogenic avian influenza viruses (AIV) had been isolated in local farms. However, the relationship between the protein change and the virulence of these AIV was not clear. In this study, two variants from a single H6N1 population with different virulence levels, the non-virulent strain (2838N) and the virulent strain (2838V), were analyzed by two-dimensional electrophoresis (2-DE) and then identified with specific lectins. Comparisons of the 2-DE patterns of these two strains showed major difference in hemagglutinin 1 (HA1) which contained six isoforms with similar molecular mass but showing variant isoelectric points (pI). We found that the difference in pI values was not due to either of phosphorylation and sialylation on HA1. In addition, we performed MALDI mass spectrometry (MS and MS/MS)-based glycomic profile analyses for the N-glycans of the HA1 isoforms. The results showed that the isoform with lower pI contained more m/z 1867 X-glycan. One of the major functions for hemagglutinin is the recognition and binding of sialic acid-containing receptors on the target cell. It is possible that the special glycosylation of HA1 might have effects on host recognition, as well as tissue tropism or immune escape.