浙江省野生动物鼬獾狂犬病毒全基因组序列测定分析

目的 测定浙江省分离的2株野生动物鼬獾狂犬病毒株全基因组序列,从分子水平进行遗传变异特征分析,了解狂犬病毒在浙江省的流行和变异情况.方法 RT-PCR测定鼬獾狂犬病毒株全基因组核苷酸序列,并进行基因序列和编码蛋白相似性比较及种系发生分析.结果 测序获得2株鼬獾狂犬病毒全基因组核苷酸序列信息:基因组全长11 923 nts,leader长58 nts,由5个编码区组成:NP(1353 nts)、PP(894 nts)、MP(609 nts)、GP(1575 nts)、LP(6386 nts),N-P-M-G间隔序列长2、5、5 nts;G-L基因间伪基因ψ长423 nts;trailer长70 nts.核酸BLAST及多序列比对显示,浙江省鼬獾狂犬病毒株全基因组序列的组成和结构符合弹状病毒科狂犬病毒属特征;鼬獾病毒株负链RNA基因组5个基因编码氨基酸的长度没有变异,编码区基因没有发生重组,编码蛋白仅表现较少的序列变化,多数只发生碱基的替代;中国病毒株之间特别是同种动物狂犬病毒之间各个基因区域核苷酸与氨基酸序列相似性最高,鼬獾狂犬病毒基因组序列相似性在氨基酸水平明显高于核苷酸水平,蛋白质编码基因的核苷酸变异大多属于同义突变.结论 鼬獾狂犬病毒与研究中选择的代表性疫苗株或者街毒株的变异位点和变异类型相似,多序列相似性比较和N基因种系发生分析显示,鼬獾狂犬病毒均属于基因1型,具有中国地域性特点,2株野生动物鼬獾狂犬病毒极有可能是存在于自然界中固有的街毒株.     

浙江省野生动物鼬獾和家犬狂犬病病毒L基因序列测定分析

目的测定浙江省野生动物鼬獾和家犬狂犬病病毒L基因序列,在分子水平分析转录酶大蛋白(LP)的变异特点和遗传进化特征。方法对实验室检测阳性的狂犬病病毒标本进行L基因编码区核酸序列测定,通过生物分析软件比较L基因核苷酸序列和氨基酸序列,并与GenBank的36个参考序列编码区进行比对分析。结果测序获得野生动物鼬獾(F02、F04)和家犬(D01、D02)二种宿主来源的狂犬病病毒街毒株L基因核苷酸全长序列并递交GenBank,开放读码框(ORF)均为6 387 bp,编码区均以2个连续的起始密码子ATG起始,编码2 128个氨基酸。在LP保守结构域上的特异功能短序列几乎完全保守,各结构域之间的序列保守性略差,对存在的变异位点绝大多数极性并没有变化,系统进化分析显示浙江省鼬獾、犬街毒株均归属于传统的狂犬病病毒Asian谱系,与我国广泛传播的狂犬病病毒同属一种系。结论浙江省狂犬病病毒L基因的构成与传统狂犬病病毒一致,所构建进化树的分析作用与N基因相同,鼬獾病毒依然具有本土狂犬病病毒的基因特点,家犬病毒可能与我国多种宿主动物病毒来源相同或者具有新近的相互传播,不同宿主动物狂犬病病毒具有种群多样性的进化特点和地域性流行特征。     

Waning of measles maternal antibody in infants in measles elimination settings – A systematic literature review

IntroductionMost infants are born with immunity to measles through maternal antibodies transferred in pregnancy, which decay over time. However, in measles elimination settings, where measles does not circulate endemically and most immunity is from immunization rather than infection, maternal antibody levels are lower. This results in infant immunity that wanes earlier, and a wider susceptibility gap between maternal antibody decay and infant immunization than in non-eliminated settings. We aimed to systematically quantify the extent and duration of protection from measles in infants in settings that have sustained measles elimination.MethodsWe conducted a systematic review of studies of measles maternal antibody waning in infants in measles elimination settings. We searched MEDLINE, Embase, CINAHL, Scopus, BIOSIS Previews, and Global Health databases for relevant studies. Studies were included if they were set in countries that had eliminated measles for ≥3 years, and if the study cohort included healthy, full-term, unvaccinated infants ≤12 months, born to healthy mothers, and reported a relevant measure of measles maternal antibody in infants. We assessed study quality using the MetaQAT tool.ResultsWe identified 4692 unique citations, eight of which met inclusion criteria. One study reported anti-measles antibody in cord blood, six reported antibody in infant sera, and one reported both. Two studies reported that 80 and 100% of infants were protected from measles at birth. One study reported no protection amongst 3–7 month old infants, and another reported limited protection in infants >4 months. The remaining studies reported the proportion of infants with detected antibody, but not the proportion immune.ConclusionAlthough limited, these data suggest that in settings that have sustained measles elimination, some infants are susceptible to measles well before the age of routine measles immunization. Setting-specific seroprevalence and vaccine effectiveness studies are required to evaluate this in different jurisdictions.