Molecular characterization and genetic variation of the VP7 gene of human rotaviruses isolated in Paraguay

Rotavirus is the main cause of acute diarrhea in infants and young children worldwide. In Paraguay, acute diarrhea ranks fourth among the causes of mortality in children under 4 years of age. Rotavirus was detected in 93 out of 410 patients admitted to three main hospitals in Asunción, Paraguay from August 1998 to August 2000. Samples from 64 patients were analyzed by RT-PCR for G and P typing. G4P[8] (46.9%; 30/64) was the most common strain detected, followed by G9P[8] (17.2%; 11/64) and G1P[8] (10,9%; 7/64). Since G4 was predominant during the epidemiological peaks of 1998 and 1999, four samples were sequenced and all grouped into sublineage Ic. This sublineage was reported for the first time in 1998 in Argentina, southern border of Paraguay, and it was shown to be responsible for the increased prevalence of G4 during the epidemiological season of 1998 in that country. In addition, Paraguayan G1 strains grouped in different lineages (I and II). However, G9 was predominant during the rotavirus epidemiological peak of 2000, and phylogenetic analysis of five samples grouped into a common emergent/reemergent lineage that circulates worldwide. Since vaccination could reduce the severity and the number of cases of rotavirus disease, this study suggests that a vaccine containing recently isolated variants of the most prevalent types (G1-G4) together with the emerging G9 type, might be sufficient to elicit a protective immune response against the rotavirus types circulating currently in Paraguay.     

Characterization and phylogenetic analysis of a neurovirulent Zika virus isolated from Cambodia in 2019

The geographic range of Zika virus (ZIKV) has expanded from Asia to the Americas, leading to the 2015–2016 pandemic with enhanced neurovirulence. At present, ZIKV is continuously circulating in many Southeast Asian countries. Unfortunately, the persistent evolution of ZIKV in Southeast Asia and its influence on the biological characteristics of the virus remain incompletely understood. In this study, the in vitro and in vivo properties of a new ZIKV isolate obtained from Cambodia in 2019 (CAM/2019) were characterized and compared with those of the Cambodian strain (CAM/2010). Compared with CAM/2010, the CAM/2019 virus showed similar plaque morphology and growth curves in cell cultures and induced comparable viremia and organ viral loads profiles in both BALB/c and A129 (IFNAR1^−/−) mice upon intraperitoneal (i.p.) inoculation. Remarkably, the CAM/2019 virus exhibited enhanced neurovirulence in neonatal mice compared with CAM/2010, with a 74-fold reduction in the 50% lethal dose (LD₅₀). Consistently, CAM/2019 produced higher viral loads in the brains of BALB/c neonatal mice than CAM/2010 did. Sequence alignment showed that the CAM/2019 virus has acquired 12 amino acid substitutions, several of which were found to be associated with neurovirulence. In particular, the CAM/2019 virus shared an A1204T substitution in NS2A with the Thai isolate SI-BKK02 that was isolated from a microcephaly case. Taken together, our results indicate that a ZIKV strain isolated with specific mutations has emerged in Cambodia, highlighting the need for extensive molecular and disease surveillance in Cambodia and other Asian countries.     

Definition and pathology of primary sclerosing cholangitis

Although primary sclerosing cholangitis (PSC) is not a common disease, it is important in the differential diagnosis of hepatobiliary tract diseases in clinical practice. A diagnosis of PSC should be made only after the exclusion of similar diseases with well known etiologies or pathogeneses. In this review, the pathology of classical PSC and its variants or related diseases is highlighted. PSC is histologically characterized by progressive periductal fibrosis with luminal stenosis or obliteration, along with the formation of a fibrous core, as well as dilatation (cholangiectasis). Its etiology is unknown. Bacterial ascending cholangitis is superimposed on its long clinical course. Such a heterogeneous distribution of biliary lesions with biliary obliteration and cholangiectasis is responsible for the radiological demonstration of biliary abnormalities, particularly the beaded appearance. Sampling variability is common in needle or wedge biopsied specimens. As a result of biliary damage, the liver shows progressive cholestatic change followed by biliary fibrosis and cirrhosis, and this hepatic progression is divisible into four stages. There are several variants of PSC or related diseases, such as localized biliary sclerosis and stenosis, sclerosing cholangitis associated with inflammatory pseudotumor, and PSC-autoimmune hepatitis overlapping syndrome. Cholelithiasis, including secondary hepatolithiasis and, to a lesser degree, biliary carcinoma and dysplasia, are also known to develop at the perihilar bile ducts as a late complication of PSC. Received for publication on March 8, 1999; accepted on April 30, 1999     

"树皮年轮"质疑

目的：评述“树皮年轮”的概念及其应用于判断树龄的科学性。方法：在广泛查阅相关文献资料的基础上，对“树皮年轮”的概念及其在判断树龄方面应用的科学性问题进行了综合分析。结果：虽然韧皮部纤维存在分层排列的现象，但是不能称其为“年轮”。因为呈带状排列的纤维束的数目，在每个生长季节不总是固定的，有的甚至缺乏韧皮部纤维；并且次生韧皮部在次生生长过程中的数量有限，还会随着树皮逐渐剥落。结论：因此，认为“树皮年轮”的提法缺乏科学性，也不能作为判断树龄的依据。     

乙肝核心抗原DNA疫苗的构建及其免疫原性分析

构建ＨＢＶ核心抗原ＤＮＡ疫苗,并探讨基实验动物内的表达及其免疫原性。方法：采用ＰＣＲ法从ＨＢＶ全基因ＤＮＡ中获得核心抗原ＤＮＡ片段,并将其重组到ｐｃＤＮＡ３载体。以此为候选疫苗分别免疫小鼠和树Ｊｕ,并检测其抗ＨＢｃＩｇＧ。结果：构建了乙肝核心抗原候选核酸疫苗ｐｃＤＮＡ３－ＨＢｃ。免疫接种该疫苗后第２周抗ＨＢｃＩｇＧ水平开始升高,小鼠至第９周,树Ｊｕ至第７周升至峰值。结论：构建ｐｃＤＮＡ３－ＨＢＣｄ     

全球历年人甲型流感病毒H3A1抗原的分子进化研究

目的应用生物信息学数据库和工具，对现有的H3N2亚型人甲型流感病毒全球分离株的H3A1抗原序列进化规律进行分析研究。方法下载NCBI Genbank和流感病毒数据库中全部的甲型流感病毒H3A1序列，首先用两步聚类法进行样本拆分，随后分类绘制出完整的进化树。结果人H3A1序列呈现出单一主干的进化趋势，随着时间的推移，进化树结构和进化模型相关参数均呈现出一定的变化规律，关键变异株的出现则无明显的地域分布特征。结论人流感病毒H3A1抗原的进化主要是病毒抗原漂移和人类免疫选择相互作用的结果，新变异株的出现并未出现明显的地域倾向性，中国华南地区不应当被认为是H3亚型新变异株的发源地。     

浙江省HIV-I流行毒株GAG基因序列测定和亚型分析

〔目的〕利用分子生物学方法了解浙江省境内HIV -I流行毒株的亚型。〔方法〕采集 14份浙江省检出的HIV -I抗体阳性者的抗凝全血 ,从中提取前病毒DNA作为PCR扩增的模板 ,设计特异性引物对gag基因区进行扩增并测定其序列。所得序列与国际标准或参考序列进行比较 ,确定亚型。〔结果〕14份样本中有 9份扩增阳性并得到相应序列 ,扩增率为 6 4 .3%。经过离散率计算和系统树分析后证实 4份样本为A/E流行重组模式 ,3份样本为B亚型 ,1份样本为B/C流行重组模式 ,1份样本为G亚型。〔结论〕目前浙江省境内有多种亚型的HIV -I毒株存在。迫切需要对高危人群进行宣传教育和行为干预措施以阻断HIV/AIDS的流行和传播。     

生存树方法及其在预后分析中的应用

目的 针对临床随访资料，利用生存树方法进行预后分组，进一步完善预后分析的内容。方法 从生存树建立的主要过程——树的生长、剪枝以及子树的选择来介绍生存树方法，并对一乳腺增生症复发资料进行分析。结果 生存树方法显示：疗效、疗程以及增生程度作为对预后影响最大的因素用来预后分组，得到5个预后子群，其中位生存期分别为30．3月、21．4月、17．3月、11．0月、7．3月。结论 应用生存树方法进行预后分析，不但可以得到具有不同临床特征的预后子群（预后分组）。同时可以获得顶后相关因素。     

基因表达数据判别分析的随机森林方法

目的探讨随机森林算法在基因表达数据分类研究中的应用。方法通过实际基因表达数据考核其应用效果，并通过模拟试验进一步验证和研究在存在大量无差异表达基因情况下对分类产生的影响。结果随机森林算法对基因表达数据的分类具有较高的准确性，但随着基因数量的增加其判别效果呈下降的趋势，在差异表达基因之间具有相关性时，下降趋势明显减慢，能够获得较理想的分类效果。结论随机森林算法对基因表达数据的分类研究有较好的判别效果。     

深圳地区HBsAg阳性人群TTV核酸序列分析

目的 分析HBsAg阳性和阴性人群输血传播肝炎病毒（TTV）感染率的差异及TTV病毒核酸序列。方法应用套式PCR扩增TTV病毒核酸序列，将扩增的TTV核酸片段进行核酸测序，构建进化树分析TTV核酸序列的同源性。结果 HBsAg阳性和阴性人群TTV感染率比较，差异无统计学意义，深圳TTV病毒株与日本TTV病毒株的核酸序列同源性较大。结论人群中TTV病毒株携带率与HBsAg的携带率无相关性。