Search

The development of acellular pertussis vaccines has raised a number of issues relevant to the control of these products. Of particular importance is the need for robust and accurate in vitro assays for the antigen content of the vaccines which might contain up to five different antigen components, each of which needs to be independently assayed. This paper describes a simple method for the quantification of three component antigens. Because relatively high doses of purified antigens are used in those preparations, the elimination of residual toxicity is a major concern. This is achieved by genetic modification of chemical treatment. The latter results in modification of the immunological reactivity of the antigens making direct assay by such methods as ELISA ineffective. A single radial diffusion technique using polyclonal antisera for the assay of pertussis toxoid (PTxd), chemically treated filamentous haemagglutinin (FHA) and pertactin (69 kDa) has been developed. The method uses low concentrations of antisera, allowing accurate and reproducible quantification of antigen content as low as 25 microg/ml of protein for pertussis toxoid and filamentous haemagglutinin and 5 microg/ml for pertactin. Since by the addition of detergent, diffusible subunits are produced irrespective of the original physical state of the antigens, the assay is suitable for assay of these antigens after detoxification/or stabilization by chemical treatment and is able to determine the differences between preparations which have the same protein concentration but different antigenic contents. This provides a means for assuring the consistency of the antigens after detoxification/or chemical stabilization which could be used as an in-process control method for acellular pertussis vaccines., (Copyright 1998 The International Association of Biological Standardization.)

The usefulness of cytopathic indicators for the titration of Cl perfringens beta and epsilon toxins has been investigated. Neutralization experiments with monoclonal antibodies have shown that the entities responsible for the lethal and dermonecrotic effects of Cl perfringens beta toxin preparations are identical. However, the cytopathic effects of the same preparations are caused by other entities. Therefore, titrations based upon lethal and dermonecrotic indicators of beta toxin are equally valid but those based on cytopathic effects are not. Similar experiments with Cl perfringens epsilon preparations have shown that their lethal, dermonecrotic and cytopathic activities are all caused by the same entity. It follows that all three activities can be valid indicators for toxin neutralization tests. Cell culture titrations of Cl perfringens epsilon antitoxin performed on rabbit sera at the levels of test prescribed by the European Pharmacopoeia have produced consistent results which agree closely with the dermonecrotic test. This test has, in turn, been shown to reflect the results of the mouse lethal test accurately. Titrations of cattle and sheep sera at lower levels of test have also produced results in close agreement with the in vivo test. It is concluded that cell culture titration offers a valid in vitro alternative to the use of mouse lethal and guinea-pig dermonecrotic indicators for the titration of sera generated in the course of potency tests and field trials of Cl perfringens epsilon vaccines.

Approximately 85 samples of injectable biological products regulated by the Center for Drugs and Biologics of the United States Food and Drug Administration were surveyed for the presence of 11 elements, namely aluminum, arsenic, barium, cadmium, chromium, lead, mercury, selenium, thallium and zinc, by flame and flameless methods of atomic absorption spectrometry and flame emission spectrometry. The range of products tested included whole blood, red cells, plasma, normal serum albumin, antihemophilic factor, and other products derived from blood; allergenic extracts including honey bee venom and house dust allergenic extracts; vaccines such as measles virus vaccine and typhoid vaccine; and tetanus toxoid. The metal concentrations found in the majority of these products were low or undetectable. The metal levels varied from manufacturer to manufacturer, product and lot-to-lot of the same manufacturer's products. House dust allergenic extracts had the highest concentrations of arsenic (2.4 ppm), cadmium (0.28 ppm), chromium (0.6 ppm) and lead (1.5 ppm) found in the study. A high zinc concentration (24 ppm) in an immune serum globulin was attributed to the zinc-containing rubber stopper in contact with the product. A range of 0.36-3.30 ppm aluminum was found for seven 25% normal serum albumin samples from seven manufacturers. Values of 8.2, 17 and 18 ppm aluminum were found in one manufacturer's 25% normal serum albumin. These aluminum values appeared to be the result of an anomaly in this manufacturer's production that has not been repeated to date.