Morphometric estimation of viral burden in cell culture material by TEM

Abstract

A major concern in the manufacture of cell culture-derived biotechnology products is the contamination of the cultures by potentially pathogenic agents such as retroviruses. Cell lines may have retroviral particles visible by TEM even when viral burden can not be demonstrated by infectivity assays or reverse transcriptase activity. The supernatant of the post-production cell cultures, therefore, must be evaluated by TEM for viral burden. An important question, however, is how to establish a quantitative viral load estimate for the evaluation of a purification process. The FDA recommends that a purification process for viral contaminants remove or inactivate 3-5 logs over the estimated viral burden.