Function Of Virus Concentration Research Articles

A plasmon-assisted fluoro-immunoassay using gold nanoparticle-decorated carbon nanotubes for monitoring the influenza virus

A plasmon-assisted fluoro-immunoassay (PAFI) was developed for the detection of the influenza virus by using Au nanoparticle (Au NP)-decorated carbon nanotubes (AuCNTs) that were synthesized using phytochemical composites at room temperature in deionized water. Specific antibodies (Abs) against the influenza virus were conjugated onto the surface of AuCNTs and cadmium telluride quantum dots (QDs), which had a photoluminescence intensity that varied as a function of virus concentration and a detection limit of 0.1pg/mL for all three types of influenza viruses examined. The clinically isolated influenza viruses (A/Yokohama/110/2009 (H3N2)) were detected in the range of 50–10,000PFU/mL, with a detection limit of 50PFU/mL. From a series of proof-of-concept and clinical experiments, the developed PAFI biosensing system provided robust signal production and enhancement, as well as an excellent selectivity and sensitivity for influenza viruses. This nanoparticle-based technique could be potentially developed as an efficient detection platform for the influenza virus.

Chiral Smectic C Structures of Virus-Based Films

Long-range ordered virus-based films were fabricated using M13 phages (viruses) which were aligned and assembled using the meniscus phenomena. Their ordered structures and morphologies were studied and characterized using polarized optical microscopy (POM), atomic force microscopy (AFM), and scanning electron microscopy (SEM). M13 virus particles which are 880 nm in length were the basic building block of the fabricated films. Due to the unique micrometer length scale of viruses, the smectic ordering of virus particles could be easily visualized using conventional microscopy techniques and compared with a theoretical model of chiral liquid crystal structures. From the results of POM, AFM, and SEM, the viral films were determined to have a chiral smectic C structure. By a comparison of the ordering of film formation as a function of virus concentration and the formation of bundle-like domain structure found in viral thin films, a mechanism of film formation is suggested. These virus-based film structures are organized on multiple length scales, easily fabricated, and allow integration of aligned semiconductor and magnetic nanocrystals. These self-assembled hybrid materials may have applications in miniaturized self-assembled electronic devices.

Rotavirus interaction with isolated membrane vesicles.

To gain information about the mechanism of epithelial cell infection by rotavirus, we studied the interaction of bovine rotavirus, RF strain, with isolated membrane vesicles from apical membrane of pig enterocytes. Vesicles were charged with high (quenching) concentrations of either carboxyfluorescein or calcein, and the rate of fluorophore release (dequenching) was monitored as a function of time after mixing with purified virus particles. Purified single-shelled particles and untrypsinized double-shelled ones had no effect. Trypsinized double-shelled virions induced carboxyfluorescein release according to sigmoid curves whose lag period and amplitude were a function of virus concentration and depended on both temperature and pH. The presence of 100 mM salts (Tris Cl, NaCl, or KCl) was required, since there was no reaction in isoosmotic salt-free sorbitol media. Other membrane vesicle preparations such as apical membranes of piglet enterocyte and rat placenta syncytiotrophoblasts, basolateral membranes of pig enterocytes, and the undifferentiated plasma membrane of cultured MA104 cells all gave qualitatively similar responses. Inhibition by a specific monoclonal antibody suggests that the active species causing carboxyfluorescein release is VP5*. Ca2+ (1 mM), but not Mg2+, inhibited the reaction. In situ solubilization of the outer capsid of trypsinized double-shelled particles changed release kinetics from sigmoidal to hyperbolic and was not inhibited by Ca2+. Our results indicate that membrane destabilization caused by trypsinized outer capsid proteins of rotavirus leads to fluorophore release. From the data presented here, a hypothetical model of the interaction of the various states of the viral particles with the membrane lipid phase is proposed. Membrane permeabilization induced by rotavirus may be related to the mechanism of entry of the virus into the host cell.

Reverse transcriptase activity per virion for avian myeloblastosis virus and Rauscher murine leukemia virus.

We have measured reverse transcriptase enzyme activity per virus particle for samples of avian myeloblastosis virus (BAI strain) and murine leukemia virus (RAUSCHER) USing the synthetic template poly(rC)-oligo(dG). Absolute virus concentrations were determined directly by laser beat frequency spectroscopy. Enzyme activity per virion was determined from the slope of the activity plotted as a function of virus concentration. With this reverse transcriptase assay, the minimum activity (expressed as picomoles of dGTP incorporated/virion per hour) is estimated at (28.1 +/- 4.2) X 10(-7) for avian myeloblastosis virus and (1.1 +/- 0.2) X 10(-7) for murine leukemia virus. The sensitivity of this assay, which is determined by the level of incorporated radioactivity measurable above background, is 2.5 X 10(-4) virions for avian myeloblastosis virus (with dGTP specific activity of 8.9 Ci/mmol) and 88 X 10(-4) virions for murine leukemia virus (with dGTP specific activity of 6.52 CI/mmol). These results show that although reverse transcriptase assays can obviously be used to measure relative virus concentrations of equally purified samples of the same virus, they can be very misleading when used to compare the concentrations of different virus species.

The infection of leafhoppers by western X-disease virus: I. Frequency of transmission after injection or acquisition feeding

Western X-disease virus (WXV) was transmitted to healthy Colladonus montanus Van Duzee by injection of hemolymph or clarified extracts from infected vectors. Virus was first transmitted to healthy celery 11–14 days after the insects were injected with infectious hemolymph. The inoculativity of vectors injected with all inocula reached a peak, then declined rapidly. When tenfold dilutions of extract from infected vectors were injected, the position of the transmission curve for each dilution with respect to the time scale was a function of virus concentration. The latent period in the vector and time of peak transmission were therefore extended when dilutions of extract were injected. Transmission curves obtained from leafhoppers acquiring WXV by feeding on diseased celery were similar to those obtained after injection of a 10 −3 dilution of extract from infected vectors. Percentages of insects transmitting WXV in 2- and 4-day inoculation access periods could be converted to single-day percentages by binomial probability calculations.

Time of symptom response in Datura tatula L. to potato virus X as a function of virus concentration

Serial dilutions of potato virus X in either clarified sap or in a highly purified suspension of the virus were mechanically inoculated to leaves of Datura tatula L. Test plants which were inoculated with high concentrations of the virus developed systemic symptoms within the expected minimum time limits. As the virus concentration was decreased, time required for symptom development increased correspondingly and incubation periods in some cases were as long as 22 days. Delayed symptoms were also obtained when very restricted leaf areas were inoculated. In this respect, the results were similar to those obtained at low virus concentrations. The influence of low virus concentration in increasing the incubation period was least pronounced at high temperatures and was greatest at low temperatures. At the lower virus concentrations, variation in incubation periods of individual plants was considerably greater than when virus inoculum was more concentrated. In two tests where known amounts of virus X were inoculated to leaves of D. tatula and to leaves of Gomphrena globosa L., the former test plant was approximately 100 times more sensitive than the latter.