Abstract
Dependent on the viral vector and the specific assay used, viral titers produced from commonly used retroviral packaging cell lines have an upper limit in the range of 105 to 107 infectious units/ml. We have developed a generally applicable method, using hollow-fiber filtration technology, which allows for the concentration of infectious virus derived from packaging lines. This method resulted in a reproducible 10- to 30-fold increase in viral titer and can readily be scaled to accommodate larger input volumes. Over 80% of the input virus is recovered in an infectious form in the concentrate. Concentrated virus containing media was seen to produce higher infection frequencies in Jurkat T cells as compared to unconcentrated virus containing media; however, this was not proportional to the differences in viral titer observed by limiting dilution analysis on NIH-3T3 cells. These results are discussed in relation to the importance of factors other than viral titer in determining transduction frequencies.
Overview summary
Currently, many gene therapy experiments and clinical protocols utilize vectors packaged by various retrovirus-based packaging cell lines. The viral titer produced by a given combination of vector and packaging line is highly variable. Often, the success of experiments in which this approach is used to transduce target cells hinges upon this titer being adequate. Paul et al. report a generally applicable method for increasing titer through concentration of virus-containing medium.
Get full access to this article
View all access options for this article.