Quantitative Measurement of the Concentration of Active Recombinant Retrovirus

Recombinant retroviruses are among several virus vectors currently being tested in clinical trials for purposes of gene therapy. As the number of clinical studies increases, accurate quantitation of retrovirus stocks and comparisons between different laboratories and clinical trials will become increasingly important. However, work from our laboratory as well as others has shown that the most commonly used quantitative retrovirus measures (i.e., titer and multiplicity of infection [MOI]) cannot be used to make accurate comparisons (1 –3 ).