儿童急性呼吸道感染病例样本中腺病毒感染特征及遗传进化研究

Detection and genetic evolution of adenovirus from children with acute respiratory tract infections

目的：对不同类型的儿童急性呼吸道感染病例的呼吸道样本中腺病毒的感染及其遗传进化特征进行研究。方法收集2011年3月至2013年2月浙江大学医学院附属儿童医院散发急性呼吸道感染病例样本1178份，其中上呼吸道感染病例咽拭子513份，下呼吸道感染病例气管吸取物665份；同时收集2011至2014年9起腺病毒聚集性发病病例。采用荧光聚合酶链式反应（ PCR ）进行腺病毒检测，扩增阳性样本的六联体（hexon）基因高可变（HVR）7区并测序，鉴定腺病毒基因型别并构建系统进化树。采用荧光PCR对腺病毒阳性样本进行其他常见呼吸道病毒的检测，并对下呼吸道感染阳性病例进行临床特征分析。采用χ2检验和Fisher确切概率法进行数据统计分析。结果1178份散发病例样本中共检出104份腺病毒，检出率为8．83％，其中上呼吸道感染组腺病毒检出率为13．65％（70／513），高于下呼吸道感染组检出率（34／665，5．11％），差异具有统计学意义（χ2＝26.193，P＜0．05），且在0～1岁和＞3岁年龄组腺病毒检出率上呼吸道高于下呼吸道（χ2＝6．575和7.334，P＜0．05或＜0．01）。腺病毒散发病例全年均有检出，流行高峰为春夏季。所有散发病例样本中54份鉴定出腺病毒型别，其中1型4株，2型6株，3型26株，4型2株，7型15株，31型1株。在9起聚集性发病疫情中，1起为腺病毒4型，其余8起均为腺病毒3型。腺病毒 hexon基因HVR 7区高度同源，与Genbank中序列比对发现高可变7区基因序列具有一定的地域性。上呼吸道感染组腺病毒合并其他病毒的感染率为12．86％（9／70），下呼吸道为58．82％（20／34），差异具有统计学意义（χ2＝24．045，P＜0．05）。此外，下呼吸道腺病毒单一感染和合并感染病例在临床特征上差异没有统计学意义（P＞0．05），但合并感染病例中出现2例死亡。结论腺病毒在上呼吸道感染中的检出率高于下呼吸道，腺病毒散发病例中以3型和7型为主，而聚集性发病病例中以3型为主。

Objective To detect adenovirus from children with acute upper/lower respiratory tract infections and to investigate the genetic evolution of virus .Methods A total of 1 178 clinical specimens were collected from the Children ’ s Hospital , Zhejiang University School of Medicine during March 2011 and February 2013, including 513 throat swabs from children with acute upper respiratory tract infection and 665 nasopharyngeal aspirates from children with acute lower respiratory tract infections .Besides, 9 specimens in an outbreak of adenovirus infection during 2011 and 2014 were also collected .Adenovirus was identified by real-time fluorescent polymerase chain reaction （RT-qPCR）.The hypervariable region （HVR）-7 region of hexon gene in positive samples was amplified and sequenced for typing and phylogenetic analysis .Other＆amp;nbsp;respiratory viruses were also detected with RT-qPCR in adenovirus positive samples .Clinical characteristics of adenovirus infection were analyzed in children with lower respiratory tract infections .Chi-square test and Fisher exact probability were used for data analysis .Results Among 1 178 samples from sporadic cases , 104 samples （8.83%） were adenovirus positive .The rates of adenovirus infection in upper respiratory tract infection group and lower respiratory tract infection group were 13.65%（70/513） and 5.11%（34/665）, respectively （χ2 =26.193, P〈0.05）.Compared with that in lower respiratory tract infections , positive rates of adenovirus were higher in upper respiratory tract infections in children aged 0-1 year and 〉3 years （χ2 =6.575 and 7.334, P〈0.05 or 〈0.01）.Adenovirus infection might occur throughout the year and peaked in spring and summer .Among 54 adenovirus-positive samples from 104 sporadic cases , adenovirus types 1, 2, 3, 4, 7 and 31 were identified in 4, 6, 26, 2, 15 cases and 1 case, respectively.While among 9 adenovirus-positive samples from outbreak cases , type 4 and type 3 were identified in 1 and 8 cases, respectively .The HVR-7 region of hexon gene was highly homologous in the same type , and the sequence alignment indicated that the sequence of HVR-7 might have regional differences .Nine out of 70 children （12.86%） were co-infected with other virus in upper respiratory tract infection group , while the rate of co-infection in lower respiratory tract infection group was much higher [58.82%（20/34）, χ2 =24.045, P〈0.05 ].There was no significant difference in clinical manifestations between children infected with adenovirus only and those with co-infection in lower respiratory tract infection group （P〉0.05）, but two children with co-infection died.Conclusions Adenovirus infection is more common in upper respiratory tract infection .Adenovirus type 3 and type 7 are the most prevalent serotypes in sporadic cases , while type 3 is the most prevalent serotype in outbreak cases .