Virus concentration

CV) ranged from 17 to 39%. The %CV was highest near the quantification limit of the assay. The results from the first- and second-generation assays were highly correlated (r = 0.96), allowing meaningful comparisons of virus concentrations in specimens tested with either assay. 

In the clinically relevant concentration range56 the relation between the response of the sensor and the viral concentration is linear (a linear fit through the data points in Fig. 10.16a gives a correlation coefficient of 0.98) facilitating easy virus concentration predictions with a calibrated sensor. Furthermore, even at the lowest measured virus concentration (850 particles/ml) a high signal-to-noise ratio of... 

According to Eq. (4) (Table 1.2), the time required to halve the concentration of the virus particles in the suspension containing the virus particles only would be almost 200 days. In the presence of bentonite (kb = 3.1 10 10 cm3 sec1 and Nd2 = 7.35 106 cm 3) we find after integrating that the free virus concentration after 1 hour of contact is only 2.6 particles cm 3. This example illustrates that the presence of larger particles may aid significantly in the removal of smaller ones, even when Brownian diffusion is the predominant transport mechanism. 

Methods to Detect and Quantitate Viral Agents in Fluids. In order to assess the effectiveness of membrane filtration the ability to quantitate the amount of virus present pre- and post-filtration is critical. There are a number of techniques used. The method of choice for filter challenge studies is the plaque assay which utilizes the formation of plaques, localized areas in the cell monolayer where cell death caused by viral infection in the cell has occurred on the cell monolayer. Each plaque represents the presence of a single infectious virus. Virus quantity in a sample can be determined by serial dilution until the number of plaques can be accurately counted. The effectiveness of viral removal may be determined, as in the case of bacterial removal, by comparing the virus concentration in the input suspension to the concentration of virus in the effluent. 

A viral preparation was inactivated in a chemical bath. The inactivation process was found to be first-order in virus concentration, and at the beginning of the experiment 2.0% of the virus was found to be inactivated per minute. Evaluate k for the inactivation process in units (1/s). 

The probability of detecting a small number of virus particles must, however, be always taken into consideration.239 For instance, virus concentrations as low as 10-1000 particles per liter may not be detected, resulting in a wrong analytical conclusion. 

Because vT is a function of particle size, Eq. 19.1 must be solved for a number of particle diameters. By using 11 size increments, Table 19.1 can be constructed and a plot of C versus droplet diameter for various times is shown in Fig. 19.3. Then Fig. 19.4 shows the relative decrease in virus concentration as a function of time for the summed data. 

Type of laboratory Industrial and research laboratories are more likely to work with large quantities of concentrated viral preparations, which increases the risk of infection following a spillage. Exposure to high virus concentrations may also result in infection by other routes than the natural route of infection. 

In the equilibrium studies, tests were conducted with various initial concentrations of adsorbents and viruses to determine the amount of virus adsorbed per unit gram of adsorbent and the virus concentration remaining in the solution at equilibrium. The time required to reach equilibrium was determined by periodically sampling over a 24-hour period. In the kinetic studies, samples were withdrawn at predetermined time intervals and assayed for virus titer. 

Table V. Influenza Virus Concentration (Whole Virus Vaccine) Performance Data...

Virus Concentration. In large scale virus production, concentration of the virus or its proteins is frequently necessary to obtain workable volumes for subsequent processing. Often continuous-flow zonal centrifuges are used for this purpose but with a significant loss in biological activity. Most viruses are larger than 0.01 n and can be safely (closed system) concentrated with a 80,000 MWCO membrane without loss of activity. 

Fig. 13.5.1. Diffusion coefficient Z>2 0 of R-17 virus as a function of virus concentration in 1, 0.15, and 0.015M NaCl. (From Pusey, et al., 1972.)...

A low-level sensitivity is required for viral test methods to maximize reduction factors [5]. However, the ability to detect low virus concentrations is limited by... 

The volume (about 20 mL) of the recovery medium is too large to allow for the detection of infectious virus in all or most of it without a virus concentration step. 

Surface decontamination of BSCs can be carried out using 70-85% ethanol or isopropanol. These alcohols are effective against most microbiological organisms except for spores or nonlipid viruses. Concentrations of these alcohols below 50% are not effective. It is important to limit the use of these alcohols in BSCs due to their flammability and the fact that components of the BSCs are not spark-proof. 

Shapiro, M. Farrar, Jr, R. R. Domek, J. Javaid, I. Effects of virus concentration and ultraviolet irradiation on the activity of com earworm and beet armyworm (Lepidoptera Noctuidae) nucleopolyhedrovirases. J. Econ. Enrowo/. 2002.95.243-249. 

Fig. 3. Effect of virus concentration on the sedimentation constant of the E. colt bacteriophages (254).

---