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Virus Titer (virus + titer)
Selected AbstractsEpidemiology of Plum pox virus strain M in GreeceEPPO BULLETIN, Issue 2 2006C. Varveri Plum pox virus has been endemic in Greece since 1967 causing important losses in apricot and to a lesser extent in peach crops. A survey undertaken in 1992 in public and private mother-tree plantations to estimate its incidence revealed that the virus was absent in isolated areas far from commercial stone-fruit crops. Virus titers decrease significantly during the hot months in the infected trees but re-increase in October,November permitting reliable detection. It is virulent M-type isolates which are effectively transmitted by aphids that are mostly recovered. Aphis gossypii and Hyalopterus pruni were the most abundant virus vectors captured during the small scale monitoring undertaken in apricot orchards in 1999 and 2000. Virus spread was monitored in two apricot orchards from 1996 to 2000 and analysed. Initial infections followed a completely random spatial pattern, while loose clusters appeared in succeeding years, to finally reach a uniform distribution representing high infection levels. The nearby ecological conditions greatly affected the rate of disease development. [source] Life history of the bird cherry-oat aphid, Rhopalosiphum padi, on transgenic and non-transformed wheat challenged with Wheat streak mosaic virusENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 1 2009Edgardo S. Jiménez-Martínez Abstract The life history of the bird cherry-oat aphid, Rhopalosiphum padi (L.) (Hemiptera: Aphididae), was studied via laboratory assays on Wheat streak mosaic virus (WSMV)-infected and non-infected transgenic and non-transformed wheat [Triticum aestivum L. (Poaceae)]. Although R. padi is not a WSMV vector, it is known to colonize WSMV-infected wheat plants. Two transgenic soft white winter wheat genotypes, 366-D03 and 366-D8, that express the WSMV coat protein gene, and the WSMV-susceptible non-transformed cultivar Daws were tested. All genotypes showed disease symptoms when infected with WSMV. Whereas plant height was significantly reduced on virus-infected compared to non-infected plants of all genotypes, virus-infected transgenic plants exhibited lower virus titer and lower disease rating scores than Daws. No significant effects of WSMV infection or genotypes were observed on the length of R. padi nymphal development period, nor on their pre-, and post-reproductive periods. Rhopalosiphum padi reproductive period was significantly longer on Daws infected with WSMV than on non-infected plants of this cultivar. In contrast, there were no significant differences in length of R. padi reproductive period between virus-infected and non-infected transgenic plants within a genotype. Rhopalosiphum padi daily fecundity was significantly lower and adult longevity significantly longer on virus-infected than on non-infected plants of all genotypes. Total aphid fecundity and intrinsic rate of increase were not significantly different among treatments. The percentage of winged aphids that developed was greater on WSMV-infected compared to non-infected plants within a genotype. Results indicate that both virus infection status of plants and wheat genotype influence the life history of R. padi. [source] Comparison of cell culture with RT-PCR for enterovirus detection in stool specimens from patients with acute flaccid paralysisJOURNAL OF CLINICAL LABORATORY ANALYSIS, Issue 4 2007Zabih-Ollah Shoja Abstract Since October 2000, Iran has been declared polio-free by the World Health Organization (WHO). Despite the fact that poliomyelitis caused by polioviruses has been eliminated from Iran, the number of acute flaccid paralysis (AFP) cases has not been reduced. Therefore, it is of great importance to investigate the other viral agents that may cause AFP (mainly nonpolio enteroviruses, which play a significant role in the etiology of neurological syndromes). Some enteroviruses do not grow in the conventional cell lines that are being used for enterovirus detection. Furthermore, the virus titer is an important factor in the sensitivity of cell culture to detect the virus. The fact that cell culture is a time-consuming procedure is another reason to find a more practical method for enterovirus detection. Therefore, a more sensitive and rapid method should be used to detect enteroviruses as efficiently as possible in the stool specimens of AFP cases. The aim of this study was to evaluate cell culture and RT-PCR in enterovirus detection. Findings have shown that RT-PCR can increase the rate of nonpolio enterovirus detection by up to 10% in comparison with cell culture. Also, the rapid detection of enteroviruses by RT-PCR can decrease both the unnecessary use of antibiotics and the costs in clinical practice. For this reason, we find that RT-PCR is a more practical technique for enterovirus detection. J. Clin. Lab. Anal. 21:232,236, 2007. © 2007 Wiley-Liss, Inc. [source] Neutralizing antibody against severe acute respiratory syndrome (SARS)-coronavirus spike is highly effective for the protection of mice in the murine SARS modelMICROBIOLOGY AND IMMUNOLOGY, Issue 2 2009Koji Ishii ABSTRACT We evaluated the efficacy of three SARS vaccine candidates in a murine SARS model utilizing low-virulence Pp and SARS-CoV coinfection. Vaccinated mice were protected from severe respiratory disease in parallel with a low virus titer in the lungs and a high neutralizing antibody titer in the plasma. Importantly, the administration of spike protein-specific neutralizing monoclonal antibody protected mice from the disease, indicating that the neutralization is sufficient for protection. Moreover, a high level of IL-6 and MCP-1 production, but not other 18 cytokines tested, on days 2 and 3 after SARS-CoV infection was closely linked to the virus replication and disease severity, suggesting the importance of these cytokines in the lung pathogenicity of SARS-CoV infection. [source] Safety and immunogenicity of live attenuated varicella vaccine in 9-month-old childrenPEDIATRICS INTERNATIONAL, Issue 6 2000Güler Kanra Background: The present study was conducted to evaluate the safety and immunogenicity of live attenuated varicella vaccine (Oka-strain) in 9-month-old infants. Methods: One hundred and fourteen infants were vaccinated once with live attenuated varicella vaccine (Valrix®; SmithKline Beecham Biologicals, Rixensart, Belgium) containing a mean virus titer of 104.0 plaque-forming units (p.f.u.) per dose. Signs and/or symptoms after vaccination were followed for 42 days. Home visits were made to detect solicited local reactions (0,3 days) and solicited general reactions (0,21 days), as well as unsolicited reactions. Specific varicella antibodies were determined by an indirect immunofluorescence method. The geometric mean titer and seroconversion rate were calculated. Results: Signs and/or symptoms were reported in 47.4% (54/114) of cases following vaccination. The only local symptom reported was pain on digital pressure at the injection site and this was reported in 28.1% (32/114) of infants. General symptoms were reported in 38.6% (44/114) of cases. The most frequently reported findings were fever (27.2%), which was mostly mild, restlessness (20.2%) and cough (11.4%). Only four unsolicited symptoms were reported and they were all unrelated to vaccination. No serious adverse event was reported. Of the 109 infants included in the immunogenicity analysis, 105 were seronegative and four were seropositive for antibodies against varicella before vaccination. The vaccine elicited seroconversion in 97.1% of initially seronegative cases. The post-vaccination geometric mean titer for these infants was 30.9 geometric mean titer (GMT). Conclusions: The vaccine was found to be safe and immunogenic when given to infants as young as 9 months of age. This may be of clinical significance during outbreaks of varicella and especially for developing countries. [source] Ex vivo hypothermic recirculatory adenoviral gene transfer to the transplanted pig heartTHE JOURNAL OF GENE MEDICINE, Issue 7 2006Keiji Oi Abstract Background To facilitate the application of adenoviral gene therapy in clinical heart transplantation, we developed an ex vivo hypothermic recirculatory adenoviral gene transfer method to the transplanted pig heart. Methods Experimental animals were assigned into three groups; controls, 1 × 108 plaque-forming units (pfu)/ml group and 1 × 109 pfu/ml group. During the 30 min gene transfer perfusion, 200 ml of University of Wisconsin solution containing the adenoviral vector was recirculated through the coronary vessels. The myocardial temperature was maintained below 4 °C and the perfusion pressure was adjusted at 50 mmHg. Results Cardiac myocyte transduction efficiencies in the 1 × 108 pfu/ml group were 0.04% and 0.07%, whereas transduction efficiencies in the 1 × 109 pfu/ml group were widely distributed from 0.45% to 22.62%. The gene transduction efficiency increased with the virus titer. Additionally, no difference in the transduction efficiency was observed between different segments of the left ventricle. The current gene transfer method at 1 × 109 pfu/ml of adenovirus titer enabled homogeneous gene transduction into the transplanted pig heart up to a maximum of 22.62%. Conclusions This model can be applied to a large isolated heart and will greatly facilitate the investigation of gene therapy in large animal models of heart transplantation. Copyright © 2006 John Wiley & Sons, Ltd. [source] The effect of Bcl-2, YAMA, and XIAP over-expression on apoptosis and adenovirus production in HEK293 cell lineBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2009Kalbinder Singh Sandhu Abstract Many viruses induce cell death and lysis as part of their replication and dissemination strategy, and in many cases features of apoptosis are observed. Attempts have been made to further increase productivity by prolonging cell survival via the over-expression of anti-apoptotic genes. Here, we extend the study to investigate the association between virus replication and apoptosis, pertinent to large-scale vector production for gene therapy. Infection of an HEK293 cell line with a replication defective type-5-adenovirus expressing a GFP reporter (Ad5GFP) resulted in rapid decline in viability associated with increased virus titer. The over-expression of bcl-2 resulted in improved cell resistance to apoptosis and prolonged culture duration, but reduced virus specific and total productivity. In contrast, the over-expression of pro-caspase-3 (Yama/CPP32/apopain) resulted in reduced cell survival but increased virus productivity. The treatment of infected cells with caspase inhibitors support the preposition that caspase-3 dependent apoptosis, and to a lesser degree caspase-9 dependent apoptosis, represent important steps in virus production, thus implicating the intrinsic apoptosis pathway in the production of adenovirus from HEK293 cells. The suppression of apoptosis by the over-expression of XIAP (inhibitors of caspase family cell death proteases) further shows that caspase-mediated activation plays an important role in virus infection and maturation. Biotechnol. Bioeng. 2009; 104: 752,765 © 2009 Wiley Periodicals, Inc. [source] 293 cell cycle synchronisation adenovirus vector productionBIOTECHNOLOGY PROGRESS, Issue 1 2009Tiago B. Ferreira Abstract As the market requirements for adenovirus vectors (AdV) increase, the maximisation of the virus titer per culture volume per unit time is a key requirement. However, despite the fact that 293 cells can grow up to 8 × 106 cell/mL in simple batch mode operations, for optimal AdV infection a maximum cell density of 1 × 106 cell/mL at infection time has usually been utilized due to the so called "cell density effect". In addition, AdV titer appears to be dependent upon cell cycle phase at the time of infection. To evaluate the dependence of AdV production upon cell cycle phase, 293 cells were chemically synchronised at each phase of the cell cycle; a 2.6-fold increase on AdV cell specific titer was obtained when the percentage of cells at the S phase of the cell cycle was increased from 36 to 47%; a mathematical equation was used to relate AdV cell specific productivities with cell synchronisation at the S phase using this data. To avoid the use of chemical inhibitors, a temperature shift strategy was also used for synchronisation at the S phase. S phase synchronisation was obtained by decreasing the culture temperature to 31°C during 67 h and restoring it to 37°C during 72 h. By using this strategy we were able to synchronise 57% of the population in the S phase of the cell cycle obtaining an increase of 7.3-fold on AdV cell specific titer after infection. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Synergistic antiviral effect of a combination of mouse interferon-, and interferon-, on mouse hepatitis virusJOURNAL OF MEDICAL VIROLOGY, Issue 2 2003Uichiro Fuchizaki Abstract Although interferon (IFN)-, and IFN-, have been reported to exhibit a synergistic antiviral effect through the different signaling pathways in vitro, their therapeutic efficacy is not well defined in vivo. The current study was carried out to investigate the combined antiviral effect in a model of mouse hepatitis virus Type 2 (MHV-2) infection, in which fulminant hepatitis is developed. MHV-2 was injected intraperitoneally into 4-week-old ICR mice, IFN or the vehicle was administered intramuscularly for 5 days, and the antiviral effect was evaluated based on survival periods, liver histology, serum alanine transaminase (ALT) levels, and MHV-2 virus titers in the liver tissues. The animals in the group treated with a combination of IFN-, and IFN-, survived for longer periods than the groups treated with IFN-, alone and IFN-, alone (IFN-, 103 (IU/mouse)/-, 103 vs. IFN-, 103, P,<,0.005; IFN-, 103/-, 103 vs. IFN-, 103, P,<,0.001). This is consistent with the lower levels of hepatocellular necrosis and serum ALT and the decreased titers of MHV-2 virus in the liver tissues (48 hr, P,<,0.001; 72 hr, P,<,0.001). These findings indicate that a combination of IFN-, and IFN-, exhibits a synergistic antiviral effect on MHV-2 infection. The biology of MHV-2 is quite different from that of human hepatitis viruses; however, these results suggest the beneficial combined therapy of IFN-, and IFN-, for the treatment of human viral hepatitis. J. Med. Virol. 69:188,194, 2003. © 2003 Wiley-Liss, Inc. [source] | |||||||||||||