Wind-mediated spread of Rice yellow mottle virus (RYMV) in irrigated rice crops

A study was carried out to demonstrate that Rice yellow mottle virus (RYMV), a virus known to be transmitted by beetles, can spread between rice plants by direct leaf contact caused by wind. Almost all healthy plants surrounding an infected plant became infected when exposed to a fan blowing for 15 min at a distance of 50 cm. Spread of RYMV by plant contact, mediated by wind, was also demonstrated in field experiments, the extent of spread depending on plant density. Infection was almost 10 times higher in plots with a density of 33 plants m⁻² than in plots with 16 plants m⁻². Less spread was observed in plots protected by 1·5 m high windscreens. It is suggested that wind-mediated spread of RYMV may result from abrasive contact between leaves of plants.     

Biology of a new virus isolated from Lupinus nootkatensis plants in Alaska

A new virus named Nootka lupine vein-clearing virus (NLVCV) was isolated from Lupinus nootkatensis plants that were confined to a relatively small area in the Talkeetna mountains of south-central Alaska. Annual surveys (2000–03) consistently found leaf symptoms of pronounced vein clearing and mosaic on 3- to 4-week-old plants in late June. Spherical particles ≈30 nm in diameter were isolated from these leaves. Virions contained a single-stranded RNA of ≈4·0–4·2 kb and one species of capsid protein estimated to be ≈40 kDa. The double-stranded RNA profile from naturally infected leaves consisted of three major bands ≈4·2, 1·9 and 1·5 kbp. Protein extractions from either sap or virions of diseased plants reacted to polyclonal antiserum made against the virions in Western blot assays. A predicted PCR product ≈500 bp was synthesized from virion RNA using primers specific to the carmovirus RNA-dependent RNA polymerase (RDRP) gene. The nucleotide sequence of the amplified DNA did not match any known virus, but contained short regions of identity to several carmoviruses. Only species belonging to the Fabaceae were susceptible to NLVCV by mechanical inoculation. Based on dsRNA profile, size of virion RNA genome and capsid protein, and similarity of the RDRP gene to that of other carmoviruses, it is suggested that NLVCV is a member of the family Tombusviridae , and tentatively of the genus Carmovirus . As the host range, RDRP gene and dsRNA profile of NLVCV are different from those of known viruses, this is a newly described plant virus.     

猪繁殖与呼吸综合征病毒缺失变异株的基因组特征

对猪繁殖与呼吸综合征病毒(PRRSV)分离株HB2(sh)／2002的全基因组序列进行了测定与分析。该毒株基因组全长为15373nt(不包括PolyA尾)，与国内外美洲型PRRSV分离株全序列相似性介于88．7％～95．1％之间。序列分析表明，该毒株是1个天然存在缺失的变异毒株，其ORFla的Nsp2存在编码12个氨基酸的连续36个核苷酸的缺失，ORF、3存在编码1个氨基酸的3个核苷酸的缺失。这是国内外首次发现PRRSV存在缺失变异现象，研究结果补充和丰富了PRRSV毒株的基因组信息数据，为深入研究该毒株的遗传与变异及其与生物学特性的关系奠定了基础。     

水泡性口炎病毒人工感染小白鼠的组织学和免疫组织化学观察

水泡性口炎病毒（VSV）具有广泛的宿主范围，临床血清学调查发现，许多动物表现为血清阳性[1]，可以感染多种试验动物和禽类。感染动物大多数表现为阴性感染和持续性感染，本试验以小白鼠为攻毒对象，探讨VSV在体内的致病作用，进一步了解病毒在机体内的分布及其所引起的组织病理学变化。     

西尼罗热病毒RT-PCR检测方法的建立

参考Genebank发表的西尼罗热病毒(West Nile virus，WNV)E糖蛋白基因序列，自行设计合成一对引物，对WNV进行RT—PCR扩增，产物经琼脂糖电泳分析，呈现一条约400bp的条带，将其克隆入pMD18-T—Vector载体中，并进行序列测定，与已发表的WNV基因比较发现，核苷酸的同源性为99．7％，证实为WNV的E基因，通过对样品多次检测，都能扩增出一条约400bp的条带，表明该方法比较稳定。     

我国部分地区猪繁殖与呼吸综合征病毒分离株ORF5基因的遗传变异分析

参考Genbank发表的猪繁殖与呼吸综合征病毒（PKRSV）ATCC VR-2332的ORF5基因序列，设计并合成了一对引物．对来自福建、浙江、山东等地的PRRSV分离毒株进行RT-PCR扩增．获得约748bp的DNA片断，将其分别克隆入pMD18-T载体中，并进行测序。应用DNAStar软件分析所测序列，并与ATCCVR-2332、CH-1a、MLV、Lv等毒株的ORF5序列进行比较，结果表明：SHDl与F114、MLV、ATCCVR-2332同源性高达98．5％，与CH-1a同源性为91．0％，与其它毒株同源性为86．6％~88．4％；F114与MLV、ATCCVR-2332同源性为99．3％～99．7％．其余分离毒株在遗传关系上和CH-1a又分为明显的两个群．显示近年来各地PRRSV分离毒株与cH-1a株的遗传差异越来越大。     

血清中IBV特异性IgG及总IgG含量变化规律的研究

本研究采用间接酶联免疫吸附试验对人工感染鸡传染性支气管炎病毒的SPF鸡血清中特异性抗体及总IgG含量进行检测并比较其相关性.结果表明感染IBV-M41第1 d、3 d、5 d、7 d、10d、14d、21 d、28 d的血清中特异性抗体水平随感染天数增加而升高,于第14天达到最高,之后略呈降低趋势,与健康对照比较差异显著(P＜0.01);总IgG含量较健康对照组增幅小,差异显著(P＜0.01).同时,两者的消长趋势基本一致.     

禽网状内皮组织增生病病毒和马立克氏病病毒共感染对鸡的致肿瘤作用

用禽网状内皮组织增生病病毒(REV)和马立克氏病病毒(MDV)共感染肉鸡，研究这2种病毒对鸡的致瘤作用，结果表明肉鸡共感染MDV和REV后13d即可发生死亡．接种后100d死亡率达84％。死亡鸡的肝脏、脾脏、肾脏和心脏等可以形成2种外观明显不同的散在的大肿瘤结节和弥漫性的小肿瘤结节。取发病鸡的肝脏、脾脏、肾脏、心脏和腺胃等组织样品做连续石蜡切片，HE染色后发现这些脏器均存在2种不同类型的肿瘤细胞增生。对这些连续切片分别用MDV和REV的单克隆抗体进行间接荧光试验，则同1份样品存在可以与REV和MDV分别呈现阳性反应的肿瘤细胞团，结果表明REV和MDV可以在感染鸡的体内分别诱发形成肿瘤。在接种后14、21、28和42d随机采集3只鸡的全血分离MDV和REV，均可以同时分离到MDV和REV。表明REV和MDV的共感染延长了病毒血症的时间。     

H1N1猪流感广东株血凝素基因的克隆与序列分析

用RT-PCR方法扩增H1N1亚型猪流感病毒广东分离株A／Swine／GuangDong／711／2001HA基因，对其进行了克隆和测序。结果显示，HA基因全长1771bp．共编码579个氨基酸。A／Swine／Guang Dong／711／2001HA基因编码的氨基酸序列中有8个糖基化位点，5个位于HAl基因的第27、28、40、104和287位点，3个位于HA2基因的21、153和213位点。与H1N1亚型猪流感经典毒株比较后发现，血凝素糖基化位点并不是高度保守的。将A／Swine／Guang Dong／711／2001与自Gen Bank读取的1918年人流感毒株A／South Carolina／1／18、1991年人流感毒株A／MD／12／91和1997年猪流感毒株A／Swine／Wisconsin／238／97等进行核苷酸同源性比较分析，A／Swine／Guang Dong／711／2001与A／SouthCarolina／1／18、A／MD／12／91和A／Swine／Wisconsin／238／97等毒株的核苷酸同源性分别为93．9％、94．7％和93．9％。从系统发生树来看，A／Swine／Guang Dong／711／2001与A／South Carolina／1／18和A／Swine／Wisconsin／238／97的亲缘关系相近。     

表达H3N2亚型猪流感病毒HA基因重组伪狂犬病病毒的构建

将SV40启动子控制下的LacZ基因表达盒和CMV启动子控制下的H3N2亚型猪流感病毒（SIV H3N2）的HA基因插入到伪狂犬病病毒（PRV）通用转移载体pBdTK-Uni中，获得转移载体pLTK-HA。将该载体与PRV Bartha-K61株基因组DNA通过脂质体法共转染Vero细胞，经过10代蓝斑筛选、纯化和PCR鉴定获得了一株插入SIV HA基因的重组伪狂犬病病毒，命名为rPRV-HA。Western blotting和间接免疫荧光试验证实HA基因在重组病毒感染的细胞中获得了表达。用不同的细胞（PK-15、IBRS-2、Vero和鸡胚成纤维细胞）对该重组病毒与亲本病毒的增殖滴度和致细胞病变进行比较，未见显著差异，对第30代重组病毒的HA基因进行序列分析，表明该重组病毒遗传性状稳定。