Bacteriostatic Effect of Human Sera on Group a Streptococci

Abstract

Although the presence in convalescent human sera of type-specific antibodies to group A streptococci has been reported by several workers (1-10), the specificity has not always been supported by unequivocal evidence. The newer knowledge of the different types of group A streptococci provided by Lancefield (11,12) and Griffith (13), and of the antigenic structure by the former, has made possible a new approach to the problem.A reliable and sensitive method of determining type-specific circulating antibodies would help greatly in solving the question of type-specific immunity; it would also provide a technique for investigating epidemiological and clinical problems resulting from streptococcal infections and their sequelae. Typespecific antibodies in the blood of patients recovering from group A streptococcal infections have been investigated by a variety of methods: agglutination, precipitation I complement fixation, mouse protection, opsonic, and bacteriostatic techniques. Both slide and macroscopic agglutination reactions have proved unsatisfactory because of non-type-specific reactions and also because of the difficulty in obtaining uniformly stable bacterial suspensions. Precipitin and complement fixation tests with human sera and M extracts reveal many cross-reactions with extracts of heterologous types. The mouse protection test requires strains of high mouse virulence which are infrequent in streptococci freshly isolated from human sources; this test apparently requires a higher antibody content than that usually found in convalescent human sera; moreover, large amounts of sera are necessary. The opsonic index technique is frequently difficult to interpret. The ba~teriostatic test, although dependent upon the opsonization by the serum and phagocytosis of the streptococcal cell byleukocytes, has yielded reliable and easily interpreted information concernLug the presence of type-specific antibodies. In conformity with previous investigators, the term bacteriostasis used in this report implies not merely the inhibition of bacterial growth but also the destruction of microorganisms by sensitization with convalescent serum and their subsequent phagocytosis by leukocytes.

Studies on the Bacteriophages of Hemolytic Streptococci

“…Experiments are now in progress to demonstrate that the protein isolated here is antigenic, inducing the formation in rabbits of type-specific precipitins and protective antibodies. The need for elucidating the characteristics of M protein is obvious, since the evidence strongly suggests that it contributes to the virulence of Group A hemolytic streptococci in natural infections of man (28)(29)(30)(31), and in experimental infections of animals (32)(33)(34)(35).…”

Streptococcal M protein: molecular design and biological behavior

“…This limited protection was based on the development of type-specific opsonic antibodies to the M molecule which were found to persist years after a streptococcal infection (128). However, after such an infection, measurable amounts of opsonic antibodies are usually delayed when compared with the response to other streptococcal antigens (124,125,176). In more recent studies with competitive inhibition assays with purified M protein, it was discovered that type-specific opsonic sera contained antibodies directed to a majority of the immunodeterminants on the M molecule while nonopsonic sera did not (64).…”

Long Chain Formation by Strains of Group a Streptococci in the Presence of Homologous Antiserum: A Type-Specific Reaction

“…Some additional antisera that were tested were prepared in other laboratories. 4 Assays for type-spedtic antibody in these sera were made by the bactericidal test described above, by capillary precipitin tests (2) and, in some instances, by mouse protection tests (7). Typespecific antisera were made by absorption of crude rabbit antisera with equal volumes of sedimented organisms from cultures of heterologous types.…”