Adjuvant type
PharmTech: Can certain types of adjuvants (e.g., surfactant-containing solutions) cause fewer problems with regard to filters' bacterial
retention?
Bromm (Sartorius Stedim): A review of validation studies and field tests for a broader variety of fluid formulations indicates that low surface tension
formulations, such as many adjuvants or adjuvanted vaccines, present a higher risk for bacterial penetration of sterilizing-grade
membrane filters. Among such formulations, according to the data analyzed, liposome formulations present a higher risk than
surfactant containing solutions. Therefore, the use of such formulations may be a suitable alternative to replace more critical
formulations where applicable.
Martin (Pall): It is possible that certain adjuvants and related low surface tension fluids may be intrinsically less likely than others
to cause reduced retention efficiency by membrane filters. However, there is insufficient data at this time to draw firm conclusions
and make recommendations. In addition, awareness among vaccine producers that selection of surfactant-containing adjuvants
and processing conditions can influence bacterial retention efficiency of sterilizing filters is not yet widespread. Until
then, filter manufacturers must continue to work with vaccine developers to define appropriate membranes and optimize reasonable
processing conditions to sterilize any vaccine formulation. Certainly, elaboration of an optimum adjuvant with such a goal
would require an extensive amount of work and a very close partnership between filter manufacturers and vaccine producers.
Koklitis (3M): The choice of adjuvant is dependent on meeting the requirements of the process under consideration. The pros and cons of using
a particular type of adjuvant must be considered and compared. When liposomes are selected as adjuvants their role as antigen
carriers is utilized along with their immunological enhancement effect.
Powell (Asahi): These issues should be discussed with the membrane supplier's technical support teams and if they can't help, the filters
must be screened to choose the best solution for the filter application. The answer depends on the membrane chemistry, but
for large porosity filters, surfactant-containing solutions are typically not that large of a problem. Smaller porosity filters
can be dramatically impacted in a negative way.
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