A collaborative study on the testing of rabies immune globulin (human) by the mouse neutralization test (MNT) and the rapid fluorescent focus inhibition test (RFFIT).
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Biomedical subjects
Publications and source records attributed to E A Fitzgerald.
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Eleven laboratories from eight countries and four continents took part in a collaborative study to evaluate experimental procedures to be used in selecting the new standard reference rabies vaccine prepared in human diploid cell cultures. The following procedures were used : (a) the NIH potency test in mice, (b) the antibody binding technique (by either mouse inoculation or the tissue culture method), (c) virus-neutralizing antibody levels in mice used for the NIH test, and (d) antibody induction in human volunteers treated with vaccine alone and in combination with human rabies gamma globulin. The four methods used for determination of rabies antibodies were mouse inoculation, rapid fluorescent focus inhibition, plaque reduction and complement fixation techniques. All results were expressed in International Units as compared to the standard WHO serum and vaccine preparations. In general, a close correlation was noted in results from different laboratories, and it was recommended that the future rabies standard vaccine should be evaluated by three testing procedures, the NIH test, the antibody-binding technique, and antibody levels in mice used for the NIH test.
At present, the NIH potency test is the most widely used method for determining the potency of rabies virus vaccines. The drawbacks of this test are well known and include significant test variability as well as the use of an unnatural challenge route. The antibody assay in immunized mice involves the assay of sera from mice immunized with serial dilutions of rabies vaccine. The amount of antibody in the sera is expressed in International Units per ml (IU/ml). Sera from identical dilutions of different vaccines are compared for potency with serum from the same dilution of U.S. Reference Rabies Vaccine. A "unit ratio" is calculated by dividing the serum potency value for the test vaccine by that for the reference vaccine at each dilution tested. This unit ratio may then be compared to the antigenic value generated by the NIH test performed on the same vaccines. In this study, results are reported for both duck embryo and human diploid cell culture vaccines using the Serum Neutralization Test in mice as well as the Rapid Fluorescent Focus Inhibition Test to assay the antisera. Correlations are presented between the unit ratio and antigenic value for all vaccines tested. Also, practical applications and limitations of the test are discussed.