鸡红细胞吸附H5N1病毒超薄切片的形态学观察

目的应用电子显微镜对鸡胚分离的高致病性H5N1病毒进行观察鉴定。方法分别用不同浓度的甲醛和戊二醛灭活H5N1病毒,超速离心浓缩病毒分离物后,负染观察病毒形态;用鸡红细胞吸附H5N1病毒后超薄切片观察病毒形态。结果负染观察可见1‰的甲醛处理的禽流感病毒呈多形性,表面有许多突起,超薄切片观察可见鸡红细胞表面存在有囊膜的病毒颗粒,多为椭圆形,表面有许多突起,直径为80～120nm。结论鸡红细胞似可代替传代细胞吸附H5N1病毒进行超薄切片的形态学观察,该法安全、简便。     

鸡胚法分离福建省甲型H1N1流感病毒及分离株特征

目的建立甲型H1N1流感病毒鸡胚分离方法,了解病毒分离株特征,为疫苗制备和开展实验室常规监测等奠定基础。方法呼吸道标本接种鸡胚尿囊腔;血凝(HA)法测定收获的尿囊液中病毒滴度;逆转录PCR法检测病毒亚型特异性。使用甲醛灭活鸡胚分离物,灭活效果采用鸡胚接种法评价。血凝抑制(HI)实验检测急性期和恢复期血清,评价检测病毒感染后的免疫应答情况。结果从13份患者的呼吸道标本中分离出12株甲型H1N1流感病毒。多数病毒可在第二次传代鸡胚中分离到。病毒分离株的血凝滴度较低,为1∶1～16。阳性分离物再次接种鸡胚无法显著提高其HA效价。同鸡和人"O"型红血球比较,使用豚鼠红细胞可得到更高的血凝滴度。1‰甲醛可在24h内完全灭活病毒,但同时病毒的HA效价显著降低。病毒感染后,恢复期的HI滴度较急性期有2～16倍升高,HI抗体4倍增长需要约3w时间。结论鸡胚分离可应用于甲型H1N1流感病毒的分离,病毒的HA滴度较低。尽管甲醛可迅速灭活病毒,但灭活后病毒抗原血凝效价难以维持。病毒感染后,特异性血凝抗体产生较慢,同时滴度较低。基层实验室采用豚鼠血球更适合于病毒的HA滴度测定。     

人感染高致病性禽流感病毒A/Fujian/1/2007(H5N1)株基因组序列测定及分析

目的对福建省分离的高致病性禽流感病毒A/Fujian/1/2007(H5N1)株进行全基因组序列测定,了解病毒序列及进化特征。方法SPF鸡胚分离法分离A/Fujian/1/2007(H5N1)株病毒,并提取病毒RNA。病毒RNA经通用引物逆转录后,应用特异性引物分别扩增病毒各节段,产物经TA克隆到载体中进行测序并对结果进行排列、拼接成完整的病毒基因组。分析病毒重要位点特征,并参照已发表的病毒序列,对A/Fujian/1/2007(H5N1)株作系统进化分析。结果应用自行设计的引物,扩增并获得完整的A/Fujian/1/2007(H5N1)株基因组序列。病毒重要位点的分析表明,该株病毒为禽源高致病性禽流感病毒,病毒对达菲敏感而对金刚烷胺类药物则具有耐药性。病毒特征有待进一步的生物学验证。系统进化分析显示,在亚洲各国引起人类感染的高致病性禽流感病毒具有明显的地理分布特征,A/Fujian/1/2007(H5N1)病毒与国内以往毒株属同一进化分支。结论获得人感染高致病性禽流感病毒A/Fujian/1/2007株全基因组序列,了解病毒重要的氨基酸位点特征以及亚洲人感染病毒间的亲缘关系,为进一步探讨福建省禽流感病毒变异、传播机制等奠定基础。     

新疆出血热病毒反向被动血凝和血凝抑制试验的改进研究

本文报道采用戊二醛、丙酮醛和戊二醛-甲醛双醛化绵羊红细胞;不同株新疆出血热病毒和不同方法免疫家兔;不同方法纯化IgG和用不同方法以抗体致敏血球进行反向血凝和血凝抑制试验。结果表明采用本文报道的方法,以戊二醛处理的绵羊红细胞经鞣酸化后优于丙酮醛或戊二醛-甲醛双醛化的血球。用病毒悬液(感染鼠脑悬液)加福氏完全佐剂,经淋巴结注射免疫的方法所获免疫血清的抗体效价最高(补体结合抗体滴度达1∶1024)。用50%饱和硫酸铵沉淀一次和33%沉淀3次后,再经DEAE纤维素提取的IgG效果优于低温酒精法和SephadexG100及SephadexG200分筛提取法。鞣酸化后用这种IgG致敏的血球效果最好,冻干后在4℃下可保持原效价至少一年以上。作者讨论了本试验方法应用中需注意的各种细节问题,并推荐用反向被动血凝试验检测病毒抗原,用反向被动血凝抑制试验检测抗体具有稳定可靠,操作方便和可以直接检测各种动物标本的优点。可广泛用于临床诊断和流行病学调查研究。     

2009-2011年环洞庭湖区主要活禽批发市场低致病禽流感监测情况

目的 了解环洞庭湖区主要活禽批发市场低致病性禽流感病毒的分布和流行情况,为该地区活禽批发市场低致病性禽流感的防控措施提供一些依据。方法 对在活禽批发市场上采集的拭子样品先由尿囊腔接种SPF鸡胚,然后用血凝试验(HA)测定所收集的尿囊液,对HA测定有滴度的再进行血凝抑制试验(HI)和RT-PCT方法相结合鉴定病毒的亚型。结果 2009-2011年冬春季节,我们在环洞庭湖地区主要活禽批发市场上共分离到627株低致病性禽流感病毒,总的分离率为22.2%,其中鸭拭子低致病性禽流感病毒的分离率最高,达到24.6%,其次是鸡拭子,达到21.5%,鹅拭子为11%。在所监测的5家活禽批发市场中共分离到H3、H4、H6、H9、H10型和H11等 6种亚型的低致病性禽流感病毒,其中H9、H6和H4亚型比较高,其分离率分别可达到11％、6.3％和3.4％。结论 活禽批发市场中低致病性禽流感隐性带毒的情况普遍存在,其发生禽流感疫情的威胁较大。建议整顿规范市场经营管理,特别是要建立活禽交易市场定期休市制度。     

疫苗保护小鼠免遣多种H5N1型禽流感病毒侵袭

据Medscape．com 2月1日报道（原载Lancet 2006），美国研究已经研制了一种依赖腺病毒载体的疫苗可用来有效地预防禽流感，与过去的同类疫苗相比，它具有多种优点，包括易于大规模生产和可针对不同抗原型的H5N1禽流感病毒株产生保护功效。对高致病性H5N1型禽流感病毒在人与人之间传播可能会造成流感大流行的惧怕反而刺激了人们努力去研制一种新的预防此病毒的疫苗。以前的此类疫苗都是依赖受精鸡胚生产的减毒疫苗。     

2016-2018年广州市H6亚型禽流感病毒外环境分离株HA基因遗传特征分析

目的 对广州禽类市场外环境H6亚型禽流感病毒进行分离和测序,分析HA基因遗传进化特点。方法 通过接种鸡胚分离H6亚型禽流感病毒,采用RT-PCR方法扩增HA基因全长序列并测序,通过DNA Star7.1和MEGA 4.0软件,分析HA基因遗传特征。结果 2016-2018年广州禽类市场外环境分离到6株H6亚型禽流感病毒,HA基因核苷酸同源性在81.0%~99.1%之间。基因序列特征分析显示,所有分离株裂解位点序列相对保守,只有1个碱性氨基酸插入,呈现低致病性禽流感病毒分子特点。受体结合位点均为226Q和228G,为禽类呼吸道上皮受体结合位点。2016年分离株发现183-NNT糖基化位点的缺失。进化分析显示,广州早期分离株属于广东常见的ST2853-like分支,但2018年监测发现了ST339-like新流行分支病毒。结论 广州地区H6亚型禽流感病毒尚为禽类低致病性病毒,本研究毒株HA基因变异较大, 2018年毒株出现多遗传分支进化趋势,因此需要继续监测H6亚型禽流感病毒的流行和变异。     

福建省人感染HSN1禽流感病毒血凝素基因测定和分析

目的了解我省人感染高致病性禽流感H5N1亚型病毒血凝素基因的特点以及和其他毒株序列间的关系。方法从采集自两例福建省感染者的标本中扩增H5N1禽流感病毒血凝素基因并作序列测定，获得的序列同其他H5N1禽流感病毒的血凝素基因进行比较并作进化分析。结果获得福建省的两例感染者中的H5N1禽流感病毒血凝素基因，并推导出该基因的氨基酸序列。结果表明，两株病毒的血凝素基因在蛋白酶水解位点均含有多个连续的碱性氨基酸，符合高致病性禽流感病毒的特征。经Blast程序检索发现，我省两例感染者与国内其他省份的感染者携带的病毒血凝素基因具有很高的相似性，提示国内的H5N1禽流感病毒感染者的病毒来源可能有一定的关系。结论通过对两例福建省感染者标本中的H5N1禽流感病毒血凝素基因进行序列测定，了解病毒基因的部分特点。通过序列比较分析为分子流行病学调查提供线索，但还需对其他基因序列以及病毒的致病性等生物学特征作进一步分析。     

福建省人感染H5N1禽流感病毒血凝素基因测定和分析

目的了解我省人感染高致病性禽流感H5N1亚型病毒血凝素基因的特点以及和其他毒株序列间的关系。方法从采集自两例福建省感染者的标本中扩增H5N1禽流感病毒血凝素基因并作序列测定,获得的序列同其他H5N1禽流感病毒的血凝素基因进行比较并作进化分析。结果获得福建省的两例感染者中的H5N1禽流感病毒血凝素基因,并推导出该基因的氨基酸序列。结果表明,两株病毒的血凝素基因在蛋白酶水解位点均含有多个连续的碱性氨基酸,符合高致病性禽流感病毒的特征。经Blast程序检索发现,我省两例感染者与国内其他省份的感染者携带的病毒血凝素基因具有很高的相似性,提示国内的H5N1禽流感病毒感染者的病毒来源可能有一定的关系。结论通过对两例福建省感染者标本中的H5N1禽流感病毒血凝素基因进行序列测定,了解病毒基因的部分特点。通过序列比较分析为分子流行病学调查提供线索,但还需对其他基因序列以及病毒的致病性等生物学特征作进一步分析。     

云南森林脑炎病毒生物学性状研究

1989年从云南省怒江州捕获的两组卵形硬蜱和一高热患者血中分离到3株病毒,对乳小白鼠和鸡胚敏感,并能在多种组织培养细胞上增殖产生病变。能凝集多种动物红细胞,血凝最适pH为6.2和6.6。电镜观察病毒呈球形,有包膜,直径40～62nm.不耐酸,不耐乙醚,属RNA病毒。保护力试验表明森林脑炎病毒免疫血清对新分离株有保护作用,经交叉血抑试验、交叉中和试验鉴定属披膜病毒科黄病毒属蜱媒脑炎亚组中的森林脑炎病毒。     

Avian Influenza: Mixed Infections and Missing Viruses

A high prevalence and diversity of avian influenza (AI) viruses were detected in a population of wild mallards sampled during summer 2011 in California, providing an opportunity to compare results obtained before and after virus culture. We tested cloacal swab samples prior to culture by matrix real-time PCR, and by amplifying and sequencing a 640bp portion of the hemagglutinin (HA) gene. Each sample was also inoculated into embryonated chicken eggs, and full genome sequences were determined for cultured viruses. While low matrix Ct values were a good predictor of virus isolation from eggs, samples with high or undetectable Ct values also yielded isolates. Furthermore, a single passage in eggs altered the occurrence and detection of viral strains, and mixed infections (different HA subtypes) were detected less frequently after culture. There is no gold standard or perfect reference comparison for surveillance of unknown viruses, and true negatives are difficult to distinguish from false negatives. This study showed that sequencing samples prior to culture increases the detection of mixed infections and enhances the identification of viral strains and sequences that may have changed or even disappeared during culture.     

Influenza Viruses Suitable for Studies in Syrian Hamsters

Several small animal models, including mice, Syrian hamsters, guinea pigs, and ferrets are used to study the pathogenicity, transmissibility, and antigenicity of seasonal and pandemic influenza viruses. Moreover, animal models are essential for vaccination and challenge studies to evaluate the immunogenicity and protective efficacy of new vaccines. However, authentic human influenza viruses do not always replicate efficiently in these animal models. Previously, we developed a high-yield A/Puerto Rico/8/34 (PR8-HY) vaccine virus backbone that conferred an increased virus yield to several seasonal influenza vaccines in eukaryotic cells and embryonated chicken eggs. Here, we show that this PR8-HY genetic backbone also increases the replication of several seasonal influenza viruses in Syrian hamsters compared to the authentic viruses. Therefore, the PR8-HY backbone is useful for animal studies to assess the biological properties of influenza viral HA and NA.     

Analysis of Single Nucleotide Variants (SNVs) Induced by Passages of Equine Influenza Virus H3N8 in Embryonated Chicken Eggs

Vaccination is an effective method for the prevention of influenza virus infection. Many manufacturers use embryonated chicken eggs (ECE) for the propagation of vaccine strains. However, the adaptation of viral strains during subsequent passages can lead to additional virus evolution and lower effectiveness of the resulting vaccines. In our study, we analyzed the distribution of single nucleotide variants (SNVs) of equine influenza virus (EIV) during passaging in ECE. Viral RNA from passage 0 (nasal swabs), passage 2 and 5 was sequenced using next generation technology. In total, 50 SNVs with an occurrence frequency above 2% were observed, 29 of which resulted in amino acid changes. The highest variability was found in passage 2, with the most variable segment being IV encoding hemagglutinin (HA). Three variants, HA (W222G), PB2 (A377E) and PA (R531K), had clearly increased frequency with the subsequent passages, becoming dominant. None of the five nonsynonymous HA variants directly affected the major antigenic sites; however, S227P was previously reported to influence the antigenicity of EIV. Our results suggest that although host-specific adaptation was observed in low passages of EIV in ECE, it should not pose a significant risk to influenza vaccine efficacy.     

The effect of temperature and UV light on infectivity of avian influenza virus (H5N1, Thai field strain) in chicken fecal manure

Normal chicken fecal manure (pH 8.23 and 13.7% moisture) was investigated for infectivity of the avian influenza virus (AIV; H5N1). The manure was divided into three groups; each group was inoculated with AIV at 2.38 x 10(5.25) ELD50. After viral inoculation, the first group was incubated at 25 degrees C. The second group was kept at 40 degrees C, and the last group was exposed to ultraviolet light at 4-5 microw/cm2 at room temperature. After incubation, a 20% suspension of manure was filtered and the filtrates were inoculated into 9-11 day-old embryonated chicken eggs per WHO protocol (2002). The results showed that at 25 degrees C the virus lost its infectivity within 24 hours, and at 40 degrees C within 15 minutes. UV light, however, could not destroy the infectivity of the virus even after exposure for 4 hours.     

Matrix and Backstage: Cellular Substrates for Viral Vaccines

Vaccines are complex products that are manufactured in highly dynamic processes. Cellular substrates are one critical component that can have an enormous impact on reactogenicity of the final preparation, level of attenuation of a live virus, yield of infectious units or antigens, and cost per vaccine dose. Such parameters contribute to feasibility and affordability of vaccine programs both in industrialized countries and developing regions. This review summarizes the diversity of cellular substrates for propagation of viral vaccines from primary tissue explants and embryonated chicken eggs to designed continuous cell lines of human and avian origin.