Type: Evaluation Essays
Sample donated: Owen Gibbs
Last updated: September 22, 2019
A modelof a simple inactivation study could comprise evaluation of the titre of livevaccine before and after inactivation and measuring the log10 fallin titre during the inactivation process. This would give an indication of theefficacy of the inactivation process. There is evidence that virus titrationtests may not have satisfactory sensitivity to ensure complete inactivation. Inthese circumstances, a specific innocuity test would need to be developed andvalidated to be fit for increased sensitivity.
To increase sensitivity morethan one passage would be essential depending on the virus of concern (OIETerrestrial manual tests of sterility, 2017).Asample representing at least 200 doses of vaccine (final formulated product)should go through innocuity test to show absence of infectious virus by inoculation of sensitive cell culture monolayers. Thefollowing instructions should be considered for innocuity test:(1)The test method should be highly sensitive to the virus.(2) Alarge enough number of vaccine doses to satisfy statistical requirements shouldbe tested.(3)Under the selected conditions inactivated virus should not interfere with thereplication of non-inactivated virus (Barteling, 1983).
Inthe final product, antigen must be extracted from adjuvant following anappropriate validated method (OIE Terrestrial manual FMD, 2017). Antigen recoveryfrom oil-adjuvanted vaccines using n-butyl alcohol as nine volumes of anoil-emulsion vaccine was mixed thoroughly with one volume of n-butyl alcoholand centrifuged for 5 min at 4?, 5000g. Collection of the lower aqueous phasesto be tested (Feng et.
al, 2016).Concentrationof antigen may be necessary in which case it must be shown that theconcentrated does not affect with the sensitivity or reading of the assay. Inspectionof The cell sheets is done daily over a period of 2–3 days, after which the consumedmedium is transferred to fresh monolayers and the original monolayers are replenishedwith fresh medium. Using this method, traces of live virus can be amplified bythe passage procedure and detected on the basis of CPEobserved. Three passages of the original virus preparation are usually used. Avariant on this method is to freeze–thaw the old monolayers to releaseintracellular virus, which can be detected by additional passage (OIE Terrestrialmanual FMD, 2017).Aslong as the 146S antigen concentration was below 1 ?g per 106 cells,suspension cultures of baby hamster kidney cells is proved to be the mostsensitive detection system for traces of infective virus.
Above this levelinterference may cover the presence of non-inactivated virus (Barteling, 1983).