Trafficking mechanism of West Nile (Sarafend) virus structural proteins

Previous studies have shown that West Nile (Sarafend) virus matured by budding at the plasma membrane, which differs from the usual intracellular maturation of other flaviviruses. The present study investigated the trafficking mechanism of the envelope (E) and capsid (C) proteins of West Nile (Sarafend) virus during the replication cycle. The use of time-based double-immunofluorescence labelling coupled with the Triton X-100 extraction procedure revealed that both the E and C proteins were transported from the perinuclear region towards the plasma membrane along the microtubules simultaneously. The strong association of these virus proteins with the microtubules was demonstrated further with Triton X-100 extraction procedure coupled with double immunogold-labelling. Extraction of infected cells with Triton X-100 in high salt also revealed that virus E proteins were associated with the microtubules via protein-protein interaction. The disruption of microtubules with vinblastine sulphate inhibited the trafficking of both the virus E and C proteins. Both virus structural proteins were observed to co-localise and retained within vinblastine sulphate-induced microtubulin paracrystals. Extracellular virus production was also reduced drastically by vinblastine sulphate at non-cytotoxic concentration. Subsequent studies revealed that the transportation of virus E protein was associated with the microtubules-based motor protein, kinesin.     

Conformationally dependent epitopes of bluetongue virus neutralizing antigen

The neutralizing epitopes of Bluetongue virus serotype 17 (BTV 17) were evaluated by virus neutralization assay, flow cytometry, radioimmuno-precipitation, and Western blot. We showed that neutralizing monoclonal antibodies (MABs) raised to BTV 17 bound to viral proteins on intact virus when examined by virus neutralization and by an indirect binding assay analyzed by flow cytometry. In contrast, when the viral proteins were solubilized, a loss in reactivity with some of the neutralizing MABs was observed. Additionally, when the viral proteins were subjected to denaturing conditions, none of the neutralizing MABs reacted with the viral proteins. The results indicate that these neutralizing MABs bind conformationally dependent epitopes.     

Enhanced detection of infectious airborne influenza virus

Current screening methodologies for detecting infectious airborne influenza virus are limited and lack sensitivity. To increase the sensitivity for detecting infectious influenza virus in an aerosol sample, the viral replication assay was developed. With this assay, influenza virus is first amplified by replication in Madin-Darby canine kidney (MDCK) cells followed by detection with quantitative PCR (qPCR). Spanning a 20-h replication period, matrix gene expression levels from infectious virus were measured at several time points using qPCR and found to exponentially increase. Compared with the traditional culture-based viral plaque assay, the viral replication assay resulted in a 4.6 × 10(5) fold increase in influenza virus detection. Furthermore, viral replication assay results were obtained in half the time of the viral plaque assay. To demonstrate that the viral replication assay is capable of detecting airborne influenza virus, dilute preparations of strain A/WS/33 were loaded into a nebulizer, aerosolized within a calm-air settling chamber and subsequently collected using NIOSH Two-Stage Bioaerosol Samplers. At the most diluted concentration corresponding to a chicken embryo infectious dose 50% endpoint (CEID(50)) of 2.8E+02/ml, the viral replication assay was able to detect infectious influenza virus that was otherwise undetectable by viral plaque assay. The results obtained demonstrate that the viral replication assay is highly sensitive at detecting infectious influenza virus from aerosol samples.     

Structural proteins of Marek's disease virus

Marek's disease virus (MDV) was propagated in roller-bottle cultures of duck embryo fibroblasts and partially purified by sucrose gradient centrifugation. Analysis of viral protein by polyacrylamide gel electrophoresis revealed that at least eight proteins (designated VPI-VPVIII) were present in MDV. The VPI is the major viral protein. At least two viral proteins, VPII and VPIV, with glucosamine label could be detected. These two peaks may represent viral glycoprotein and may be associated with the viral envelope. No host cell proteins coelectrophoresed with any viral proteins. Similar electropherograms were obtained by coelectrophoresis of MDV and herpes simplex virus proteins and of MDV and pseudorabies virus proteins.     

Entry of human immunodeficiency virus (HIV) into MT-2, human T cell leukemia virus carrier cell line

Summary The ultrastructural features of early events in human immunodeficiency virus (HIV) infection of HTLV-I-carrying MT-2 lymphocytes were investigated by electron microscopy. Within 10 min after virus inoculation at 37°C, the virus entered the cell in two ways; (1) the virus attached to the lymphocyte membrane and the viral core entered the cell after fusion of the viral envelope with the cell membrane, and (2) part of the cell membrane to which the virus was attached became invaginated, the virus became trapped in a phagosome and the viral core entered after the fusion of viral membrane with the vacuolar membrane. Thereafter, some cells were observed to form syncytia with multiple nuclei. When the proportion of anti-HIV antibody-reactive cells present exceeded 90%, virus production was strongly activated, and budding on the cell membrane was frequently observed.     

Cell surface changes associated with mutation of visna virus in antibody-treated cell cultures.

Sheep cells inoculated with a portion of a plaque suspension of visna virus developed acute cytopathic changes and produced progeny virus which was antigenically identical to the parental strain. In contrast, cultures inoculated with other portions of the same suspension and maintained in medium containing specific viral antiserum developed cytopathic changes more slowly and yielded genetically stable mutant strains of virus which were poorly neutralized by the same antiserum. Scanning and transmission electron microscopy showed that, in the absence of antibody, cell surfaces of infected cells were covered diffusely with viral buds, whereas in the presence of antibody, viral buds were often grouped in caps and progressive aggregation of released virus occurred. Viral aggregates were strongly anchored to viral buds or long villi and sometimes became engulfed by infected cells. In addition, single maturing virions were continuously detected close to large aggregates. These morphological events suggest that selective replication of mutant virus in antibody-treated cells is favored by (1) elimination of parental virus through aggregation and endocytosis and (2) patching and capping of viral buds, which leave free cell surface areas for maturation of mutant virus.     

Monoclonal antibodies with neutralizing activity segregate isolates of bovine viral diarrhea virus into groups

Summary Isolates of bovine viral diarrhea (BVD) virus were differentiated by monoclonal antibodies (MoAbs) reactive with the 56kD viral polypeptide. Patterns of neutralizing activity of the MoAbs indicate that multiple epitopes are involved in virus neutralization.     

Molecular screening by polymerase chain reaction detects panleukopenia virus DNA in formalin-fixed hearts from cats with idiopathic cardiomyopathy and myocarditis.

Viral myocarditis has been suggested as an etiology for cardiomyopathy in several mammalian species. Myocarditis and idiopathic cardiomyopathy have been reported in the domestic cat, although a viral etiology has not been demonstrated. Because of the continuing interest in the potential relationship between viral myocarditis and cardiomyopathy, we evaluated hearts from cats with spontaneous, idiopathic cardiomyopathy for viral genomic material within myocytes by polymerase chain reaction, and for the presence of myocarditis by light microscopy. Thirty-one (31) formalin-fixed hearts from domestic cats who died of idiopathic cardiomyopathy were randomly selected from pathology archives. Seventeen (17) formalin-fixed hearts from healthy cats were similarly selected as normal controls. The polymerase chain reaction (PCR) was used to evaluate myocardial tissue for the presence of viral genome from feline panleukopenia virus, herpes virus, calici virus, and corona virus. Hearts were examined using light microscopy for histologic evidence of myocarditis according to the Dallas criteria. Panleukopenia virus was identified by PCR in 10 of 31 cats with cardiomyopathy but in none of the controls. Neither cardiomyopathic or control cats tested positive by PCR for herpes virus, calici virus, and corona virus. Myocarditis was detected by histologic examination in 18 of 31 cardiomyopathic cats and in none of 17 control cats. Myocarditis and or feline panleukopenia virus genome was detected in felines with idiopathic hypertrophic, dilated, and restrictive cardiomyopathy, suggesting a possible role of viral infection and inflammation in the pathogenesis of cardiomyopathy in this species.     

Spontaneous and induced herpesvirus genome expression in Marek''s disease tumor cell lines.

We incubated 31 newly established Marek's disease tumor cell lines at 41 degrees C for 48 h after subculturing and then examined them to determine the spontaneous rates of expression of viral internal antigen(s), viral membrane antigen(s), and virus isolation. All but two of the lines were isolated from tumors induced by clone-purified Marek's disease virus strain JM-10, GA-5, RB-1B, and BC-1A in nine different genetic strains of chickens with defined histocompatibility antigens. The line-to-line variations in the rates of spontaneous expression for the antigens or virus rescue were great, but the levels of expression were very low in most cases. The median rates of expression for viral internal antigen, viral membrane antigen, and virus isolation were 32, 8, and 2 positive cells per 10(5) cells, respectively (ranges, 0 to 20,280, 0 to 22,990, and 0 to 220 positive cells per 10(5) cells, respectively). The ratio of viral internal antigen expression to virus isolation was extremely variable and often high, whereas the ratio of viral internal antigen to viral membrane antigen expression was more consistent and generally low. The virus strain which induced the cell line influenced the level of virus genome expression, but the cell genotype did not. Cell lines transformed by JM-10 virus, which exhibited low oncogenicity, had significantly (p less than 0.01) higher rates of expression than cell lines transformed by CA-5 and RB-1B viruses, which exhibited high oncogenicity. Treatment with iododeoxyuridine or incubation at 37 degrees C induced increased rates of expression in most lines but not in all lines. The degree of enhanced expression was inversely proportional to the rate of spontaneous expression.     

Toll-like receptor 4 is not involved in host defense against respiratory tract infection with Sendai virus

Toll-like receptors (TLR) induce innate immune responses upon stimulation by a wide variety of pathogens. TLR4 has been implicated in innate immunity against respiratory syncytial virus (RSV) by an interaction with the viral envelope fusion (F) protein. Sendai virus (mouse parainfluenza type 1) shares many features with RSV, including a structurally and functionally similar F protein. To determine the role of TLR4 in host defense against Sendai virus respiratory tract infection, TLR4 mutant and wildtype mice were intranasally infected with Sendai virus. Sendai infection resulted in an increase in viral RNA copies in lung homogenates peaking on day 4. Pulmonary viral loads, histopathology, cytokine levels and leukocyte influx were similar in TLR4 mutant and wildtype mice. In spite of the structural similarities shared by the F proteins of Sendai virus and RSV, TLR4 is not involved in host defense against respiratory tract infection with Sendai virus.     

Comparative study of nasopharyngeal aspirate and nasal swab specimens for diagnosis of acute viral respiratory infection

Paired nasopharyngeal aspirate (NPA) and nasal swab (NS) samples from 475 children hospitalized for acute respiratory infection were studied for the detection of influenza virus, parainfluenza virus, respiratory syncytial virus, and adenovirus by immunofluorescence test, viral culture, and multiplex PCR assay. The overall sensitivity of viral detection with NPA specimens was higher than that obtained with NS specimens.     

Persistence of hepatitis B virus DNA after reduction of viral replication in serum and liver.

Liver and serum samples from 67 children with hepatitis B chronic infection, whether or not treated with recombinant interferon, were analyzed for the presence of hepatitis B virus DNA. After follow-up, 44/67 (66%) still had serum and liver viral DNA; 23/67 (34%) were negative for serum hepatitis B virus DNA. Of the 23 children in the latter group, liver biopsy was available in 21 and viral DNA was not detected by Southern-blot in 20. In the remaining patient, viral DNA was in an episomal nonreplicative form. Polymerase chain reaction was performed in the 21 serum samples negative for viral DNA by conventional techniques and in the 21 liver samples (20 negative for hepatitis B virus DNA and 1 with episomal nonreplicative form). All liver samples resulted in a positive reaction to viral DNA by this technique. Serum viral DNA by polymerase chain reaction was detected in 15/21 (71%) of these patients. The mean of alanine aminotransferase values was similar in patients with or without hepatitis B virus DNA in serum by polymerase chain reaction. In summary, in the majority of the patients who respond to the therapy, there is a persistence of viral replication detected by polymerase chain reaction. This fact explains the persistence of serum HBsAg in these patients. However, more studies are necessary to determine the meaning of the presence of hepatitis B virus DNA that is only detectable by polymerase chain reaction.     

A Live Attenuated Human Metapneumovirus Vaccine Strain Provides Complete Protection against Homologous Viral Infection and Cross-Protection against Heterologous Viral Infection in BALB/c Mice

A live attenuated vaccine candidate strain (M2) of human metapneumovirus (hMPV) was generated by removing the N-linked carbohydrate at amino acid 172 in the fusion (F) protein. Previously, replication of M2 in mouse lungs could be detected by molecular assays but not by viral titration. In the present study, the protective effects of M2 against infection by homologous or heterologous viruses were evaluated in BALB/c mice. Immunization with M2 produced a high titer of serum virus-neutralizing antibodies in BALB/c mice at 4 and 8 weeks postimmunization, with the titers against the homologous virus being higher than those against the heterologous virus. Challenges at 4 and 8 weeks postinoculation with M2 or wild-type virus led to no replication when mice were challenged with a homologous virus and extremely reduced replication when mice were challenged with a heterologous virus, as determined by the detection of viral genomic RNA copies in the lungs, as well as significantly milder pulmonary pathology. Thus, M2, with only one N-linked carbohydrate removed in the F protein, provides complete protection from homologous virus infection and substantial cross-protection from heterologous virus infection for at least 56 days after inoculation. This vaccine strain may therefore be a candidate for further preclinical study. Furthermore, this attenuating strategy (changing the glycosylation of a major viral protein) may be useful in the development of other viral vaccines.     

A pathogenetic study of the early connective tissue lesions of viral caprine arthritis-encephalitis.

Experiments were designed to correlate morphologic lesions with the presence of caprine arthritis-encephalitis virus (CAEV). Twenty-one cesarean-derived goat kids were infected with 10(6) to 10(7) TCID50 of virus, killed sequentially, and examined for viral antigens by immunofluorescence, viral infectivity by isolation and titration, and morphologic changes by light microscopy. Fluorescent viral antigens were detected from 1 to 10 days postinoculation (DPI) and only in synovial cells. Virus was reisolated from several joints and from brain 0.5 to 79 DPI. Increases in synovial fluid cell counts were noted by 1 DPI, and morphologic changes in synovial membranes were present from 3 to 45 DPI. Joint lesions progressed from mild synovial cell hyperplasia and perivascular mononuclear cell infiltration to severe synovial cell hyperplasia and mononuclear cell infiltration with villous hypertrophy. Lesions elsewhere were mild, consisting only of perivascular mononuclear cell infiltrates. Eleven cesarean-derived control goats were negative for viral antigens, virus, and morphologic lesions.     

肠道病毒EV71及CA16在不同细胞系中细胞病变作用的研究

目的研究CA16和EV71在4种细胞系中细胞病变作用的差异.方法随机选择滴度相似的EV71轻症、EV71重症和CA16轻症毒株各1株,分别感染RD、Vero、U251和SY5Y细胞,比较3株病毒在细胞病变的形态及程度、感染后的细胞存活率、病毒在细胞中的复制水平和病毒所致凋亡蛋白相关mRNA的表达水平等方面的差别.结果3株病毒的感染在同一细胞系中表现相似.镜下从形态学上无法对三株病毒加以区别;感染后病毒载量均表现为从高到低依次为Vero、RD、SY5Y细胞到U251细胞的顺序;病毒感染后细胞存活率的顺序与细胞内复制水平与相反,两者之间存在类似负相关的趋势.3株病毒的感染在3种细胞系中均有凋亡蛋白caspase-8、9和3相关mRNA的表达,提示可能3种细胞系中凋亡启动的途径相同.结论细胞水平的感染,提示这两种病毒感染所致临床表现的差异性并非单独由病毒所决定.     

我国部分地区病毒性脑炎标本的实验室检测

目的 初步了解我国病毒性脑炎的病原种类及其分布特征.方法用ELISA方法对2004年至2006年从我国6个省份收集的771例临床诊断为病毒性脑炎患者的急性期血清和脑脊液标本检测乙脑病毒IgM抗体,然后对乙脑IgM抗体阴性的所有血清标本检测其他7种常见病毒IgM抗体.此外,用PCR方法对54例脑脊液标本检测肠道病毒、版纳病毒和辽宁病毒的基因.结果经血清学检测,771例患者中的567例(73.5%)检测出病毒特异性IgM抗体,构成顺序为乙脑病毒(47.0%)、腮腺炎病毒(10.6%)、肠道病毒(8.8%)、单纯疱疹病毒(5.7%)、麻疹病毒(0.4%)、水痘-带状疱疹病毒(0.4%)、EB病毒(0.4%)、巨细胞病毒(0.3%);经分子生物学检测,在54例脑脊液中检测到8例(14.8%)肠道病毒基因阳性标本,未检测到版纳病毒与辽宁病毒基因阳性标本.结论乙脑病毒是我国病毒性脑炎的首要病原,腮腺炎病毒次之,肠道病毒和单纯疱疹病毒也是重要的病原.