呼吸道合胞病毒G蛋白基因序列分析

Sequence Analysis of G Glycoprotein Gene of Human Respiratory Syncytial Virus

目的了解2010年四川地区呼吸道合胞病毒(HRSV)G蛋白基因特征和优势型别。方法 RTPCR方法扩增18例呼吸道感染HRSV阳性患儿样本HRSVG蛋白基因,测序并分析G蛋白基因特征,构建系统进化树鉴定基因型,分析选择压力。结果所测G蛋白基因第二个高变区序列7例A亚型和11例B亚型核苷酸基因距离分别为0.022±0.005和0.073±0.010,碱基转换率大于颠换率,A和B亚型分别主要是GA+AG和UC+CU转换。系统进化分析A亚型全部为GA2基因型,B亚型为BA基因型和GB2基因型;A亚型G蛋白基因长度都为298aa,B亚型为295aa、312aa和315aa3种长度。A、B亚型的选择压力为净化选择占主导,第二个高变区A亚型有9个正选择位点,B亚型有1个正选择位点。结论 2010年四川18例HRSV以GA2、GB2和BA基因型为主要型别,G蛋白基因长度变化、碱基替换、选择压力是HRSV逃避免疫反应的原因。

l Objective To understand the variation of G glycoprotein gene of human respiratory syncytial virus （HRSV） obtained from Sichuan in 2010 and determine the dominant genotypes. Methods G glycoprotein gene of seven cases of subtype A and eleven cases of subtype B of HRSV were amplified by RT-PCR and sequenced. The phylogenetic trees were constructed to determine the subtype of samples. And then, the genetic variations of the second hypervariable region of G glycoprotein gene were studied. Results The nucleotide genetic distances of G glycoprotein gene in subtype A and subtype B HRSV were 0. 022 ±0. 005 and 0. 073±0. 010, respectively. Transitions were more prevalent than transversions, GA＋ AG were the most frequent transitions detected among group A viruses, while UC＋CU transitions were the most among group B. Phylogenetic analyses demonstrated that 7 subtype A virus could be clustered into one genotype, genotype GA2, and 11 subtype B virus could be clustered into two genotypes, GB2 and BA. The length of G protein gene in group A was all 298aa, but in group B included 295aa, 312aa and 315aa. Selective pressure was purifying selection in both subtypes. 9 positively selected sites in group A and i in group B on the second hypervariable region of G protein were identified. Conclusion GA2, GB2 and BA were the main genotype. The changes may favor virus escape from the host immune response including the variation of the G protein gene length, frequency of nucleotide changes and selective pressure.