The Fixation of Complement by Virus-Antibody Complexes: Equivalence and Inhibition in the Reactions of the Viruses of Tomato Bushy Stunt and Foot-and-Mouth Disease with Rabbit and Guinea-Pig Antisera

Abstract

SUMMARYA sensitive and simply calculated complement-fixation test is described in which viral antigen and antibody react to completion for up to 90 min. a t 37' before the addition of one 70 yo haemolysis unit of complement. The test has been applied to reactions between the components of the virus system of foot-and-mouth disease, tomato bushy stunt virus, bovine plasma albumin and their rabbit or guinea-pig hyperimmune sera. In the restricted region of proportional fixation each pl. of complement represents about 3 x lo9 virus particles and 6 x loll molecules of albumin.In suspensions of foot-and-mouth disease virus of highest infectivity (1010 mouse ID50/ml.), probably less than 1 in 30 of the characteristic 25 mp particles are infective.Quantitative data define the regions of antibody excess, equivalence and antigen excess, and show that complement is bound as a secondary process to that of antigen/antibody complex formation, that complement is bound only by relatively massive complexes and that the independent formation of unrelated complexes in the same system may be sensitively detected. The location of the optimum reaction and the confirmation of equivalence allow fixation data to be related closely to parallel data on the neutralization of infectivity. Since the concentrations of antigen and of antibody for optimal fixation are almost independent, it is concluded that the maintenance of equivalence in terms of a constant antigen/antibody ratio is not a valid principle for the interpretation of such data.

Vaccination of Pigs with Formaldehyde Inactivated Aluminium Hydroxide Foot-and-Mouth Disease Vaccines, Potentiated with Diethylaminoethyldextran (DEAE-D)

“…The quantitative complement-fixation test used in this laboratory, based on the method of BRADISH et al (1964), has been described (TERPSTRA et al, 1976). The number of complement-fixing units (CFU) remaining after centrifugation of the virus suspension for 90 min at 56,000 rpm (MSE, Sw 56) was subtracted from that obtained with the uncentrifuged suspension in order to evaluate the complement-fixing activity of the 1 4 0 s particles.…”

Foot‐and‐mouth disease vaccine production and research in the Netherlands

“…This technique provides a reproductible and flexible titration system. Immunological tests A semi-quantitative complement fixation (CF) test was described in 1943 (87) and a quantitative CF test in 1964 (26). This test enabled the estimation of total antigenic mass, i.e.…”