Validation of an in vitro assay for the determination of rabies antigen.

The modified antibody binding test, an in vitro method, was validated by a number of studies and was used as a reliable method for in process controls in the manufacture of rabies vaccines for man and animals over the last 6 years. A calculation was made showing the number of laboratory mice which were not needed for animal experiments because these were substituted by the in vitro method mentioned above.

Purified chick embryo cell (PCEC) rabies vaccine for human use. Laboratory data.

A new inactivated rabies vaccine (Purified Chick Embryo Cell vaccine) for use in humans has been developed. The FLURY-LEP C25 strain of rabies virus was adapted to propagate in primary chick embryo cell cultures. The antigen was purified and concentrated by continuous density gradient centrifugation and inactivated by Betapropiolactone. The PCEC-rabies vaccine was tested for innocuity, tolerability and protective capacity in a series of laboratory tests and compared with Human Diploid Cell Strain rabies vaccine (HDCSV) of similar antigenicity. The results of the laboratory tests indicated that this new vaccine was excellently tolerated and that its protective activity met the high standard of HDCS-vaccine, conditions which were imposed on the PCEC-vaccine before clinical trials in man were initiated.

A new inactivated tissue culture rabies vaccine for use in man. Evaluation of PCEC-vaccine by laboratory tests.

A new inactivated rabies vaccine (purified chick embryo cell vaccine) has been developed using the Flury LEP-C 25 strain of rabies virus propagated in primary chick embryo cell cultures. The antigen was purified and concentrated by continuous density gradient centrifugation and inactivated by betapropiolactone. This vaccine was tested for innocuity, tolerability and protective capacity in a series of laboratory tests and compared with human diploid cell strain (HDC)-vaccines of similar antigenicity. The results indicated that this new vaccine was excellently tolerated and that its protective activity met the high standard of HDC-vaccine, conditions which were imposed on this vaccine before entering clinical trials in man.

Purification, concentration and evaluation of rabies virus antigen.

A number of concentration and purification procedures for rabies virus antigen have been developed during the last decades but only ultrafiltration and density gradient centrifugation have been found suitable for large scale production. The antibody binding test developed by Arko, Wiktor and Sikes was modified and was found useful for evaluation of inactivated antigen-concentrates. This test was used as an 'in process' control. Three examples of practical experience are reported and discussed.

Effectiveness of orally administered Bordetella pertussis vaccine in mice.

Oral administration of killed Bordetella pertussis organisms to mice results in increased resistance to an intracerebral infection with virulent B. pertussis cells. The rate of survival is dependent on the dose of antigen. But besides specific systemic immunity, which is persistent over a long period, also transient non-specific resistance is increased. These effects are evidently induced without penetration of bacterial substances into the circulation.

Studies on the immunizing capacity of orally administered particulate antigens. I. The efficiency of killed Bordetella pertussis cells.

The single i.p. injection of 2.5 times 10-8 killed B. pertussis cells protected 23 out of a group of 24 NMRI mice (95.8%) against the subsequent intracerebral infection, whilst 13 out of 24 mice (54.2%) survived the intracerebral challenge with virulent B. pertussis cells after prior oral administration of 2.5 times 10-11 killed B. pertussis cells, as demonstrated by the mouse protection test. Similar treatment with non-specific substances, such as egg white and saline, did not result in any increase of resistance. Systemic anaphylactic hypersensitivity to bovine serum albumin could also be achieved, when either both the protein antigen and the B. pertussis vaccine were given by the oral route or when the B. pertussis vaccine was injected intraperitoneally into mice which had received the soluble protein antigen by the oral route. Such effects were not produced at all in the reverse situation, when the B. pertussis vaccine was orally administered in mice, which were given the soluble protein antigen by the intraperitoneal route. After oral inoculation of 6 times 10-11 killed B. pertussis cells neither splenomegaly nor blood lymphocytosis became detectable. It is still unknown, in which manner the orally administered B. pertussis vaccine effects protection against the intracerebral infection with virulent bacteria as well as susceptibility for systemic anaphylaxis. The data presented do not favor the view that those effects are due to the phenomenon of persorption.