An effective, simple and low-cost pretreatment for culture clarification in tetanus toxoid production.

Chemically inactivated tetanus toxin (tetanus toxoid, TT), purified from cultures of a virulent Clostridium tetani strain, is the active pharmaceutical ingredient of anti-tetanus vaccines. Culture clarification for TT production and is usually performed by filtration-based techniques. Final clarification of the culture supernatant is achieved by passage through 0.2 µm pore size filtering membranes. Large particles removal (primary clarification) before final filtration (secondary clarification) reduces costs of the overall clarification process. With this aim, chitosan-induced particle aggregation was assessed as an alternative for primary clarification. Three chitosan variants were tested with similar results. Optimal clarification of culture supernatant was achieved by the addition of 8 mg chitosan per l of culture. Extrapolation analysis of filter sizing results indicate that 100 l of chitosan-treated supernatant can be finally filtered with a 0.6 m2 normal filtration cartridge of 0.45 + 0.2 µm pore size. The clarified material is compatible with current standard downstream processing techniques for TT purification. Thus, chitosan-induced particle aggregation is a suitable operation for primary clarification.

Global DTP manufacturing capacity and capability. Status report: January 1995.

A recently completed survey of 63 manufacturers of diphtheria-tetanus-pertussis (DTP) vaccine and its components in 42 countries shows that there is potentially a large excess installed capacity for DTP production. However, many manufacturers are not producing to capacity, and demand and supply for this vaccine are not matched in individual countries. About half of all countries producing DTP vaccine and its components do not have fully functional national control systems, and some countries are performing none of the critical functions for an effective control of quality. Thus, potential for export of excess capacity is limited. The data collected indicate much homogeneity in the preparation of diphtheria and tetanus toxoids. Nearly all manufacturers use the same seeds and similar purification methods, but there is variability in whether purification is done before or after conversion of toxin to toxoid. About 10% of all manufacturers do not meet WHO-defined standards of purity for these toxoids. There is much more heterogeneity in the pertussis seed strains and the methods of purification used. The formulation of DTP vaccine differs considerably among producers. Potency testing is not being done by the WHO-recommended method by about 50% of manufacturers on lots of diphtheria and tetanus toxoids for release. Testing of irreversibility of conversion of toxin to toxoid, a WHO-specified safety test, is also not being done on each lot of diphtheria toxoid by 15% of manufacturers surveyed nor on each lot of tetanus toxoid vaccine by 30% of manufacturers surveyed. Access to technology to develop new DTP-based combination vaccines will be delayed if these manufacturers cannot ensure consistent high quality vaccine for their target populations. The results and conclusions suggest areas for future activities to strengthen the supply and quality of DTP and DTP-based combination vaccines.

Inactivated poliovirus vaccine: current production methods and new developments.

The biotechnologic developments during the last decade have led to the production of inactivated poliovirus vaccine (IPV) on an industrial scale and at economically acceptable costs. Replacement of primary monkey kidney cells by subcultured monkey kidney, Vero, or human diploid cells as substrate for virus multiplication as well as the introduction of the microcarrier culture technique have made cell and virus cultivation in large fermentors of 100-1,000 liters feasible. Procedures for processing virus harvests into highly concentrated purified vaccines were developed; also, the safety and potency control tests were improved and simplified. It has been demonstrated that these more potent poliovirus vaccines, either alone or in combination with diphtheria-tetanus-pertussis vaccine, induce a high immunity with reduced vaccination schedules. The overall costs of vaccination will be reduced considerably in this way. In addition, the results of biochemical and immunologic studies indicate that neutralizing antibodies can be induced by the viral proteins alone. These findings open up promising perspectives for production of subunit poliovirus vaccines with use of recombinant DNA and synthetic antigen, a method that has already proved feasible for producing vaccine against foot and mouth disease. These new techniques may lead to a further reduction of production costs and will improve the safety of the vaccine.