A COMPARATIVE STUDY OF THE POTENCY AND POLYVALENCY OF ANTISTREPTOCOCCUS SERUM USED IN THE TREATMENT OF SCARLET FEVER*

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Abstract
In treatment of severe toxemias of scarlatina, serum of highest potency and broad polyvalency is essential. The present study was undertaken (1) to acquire information regarding therapeutic sera available and (2) to secure data relative to serum production and standardization. Besides comparative tests of products from 7 laboratories, sera from horses under immunization by different methods and with various strains were tested by toxin-antitoxin neutralization tests on man and on goats, in comparison with federal control serum, against federal standard toxin (Dick-II strain) and New York State standard toxin (Dochez N. Y. No. 5 strain). A routine therapeutic New York State serum, unconcentrated, produced with the Dochez N. Y. No. 5 strain, was also used as a basis for comparisons. Many of the 18 monovalent and polyvalent sera from individual horses had little or no demonstrable antitoxic action against one or both standard toxins. Therapeutic sera in general were also of low potency and limited polyvalency, although in some instances a substantial gain in titer by concentration was indicated. The titer of unconcentrated New York State serum was equal with both toxins and appeared to be at least twice that of the other samples, concentrated or unconcentrated. Thus were brought out wide differences in antigenic activity of streptococcus strains, and the importance of their careful selection and of elimination from therapeutic material of sera from unproductive animals by more frequent testing during immunization. The superiority of the Dochez N. Y. No. 5 strain to others now in use was indicated by both laboratory findings and clinical results. A higher minimum standard of potency for therapeutic material is recommended and also the designation of a higher and more convenient unit value of 100 instead of the present 50 skin test doses. Discrepancies were found between original titers of several of the concentrated sera and titers based on the present tests, suggesting rapid loss of neutralizing value in certain concentrated sera upon ageing. Doubts are raised as to the practical value of concentration. The present time limit and method of control by potency tests only at time of issue may be an insufficient safeguard for a new therapeutic product before uniform stability is proved.

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