What is the difference between genomic titer and infectious titer?
The infectious titer measures the number of vector particles that are actually infectious and this number will generally be lower than the genomic titer. Calculation of the infectious titer requires transduction of cells and transgene expression analysis (by FACSCAN analysis of protein expression for example). Given the assumption that all particles carrying the genome should be infectious, genomic titer and infectious titer should be the same for any given vector preparation. However investigators have performed comparisons and shown this is not always the case. The ratio appears to span a wide range from 1:2 to 1:200 (genomic to infectious titer) depending on the publication cited.
