Studies on Complement-Fixation Reaction in Equine Infectious Anemia

The substances responsible for inhibiting complement-fixation (CF) reaction of the late-stage serum of an equine infectious anemia (EIA)-infected horse were investigated. It was found that the IgG and IgG(T) classes in the late-stage serum were responsible for the CF inhibition. IgA could not be detected in partially purified IgG(T) by an immunodiffusion test using rabbit anti-human IgA serum. Other serum components could not be demonstrated in purified IgG by immunoelectrophoresis using rabbit anti-horse serum. The IgG class simultaneously showed CF and CF-inhibiting (CFI) activities, whereas the IgG(T) class showed only CFI activity. The IgG(T) class could exert CFI activity only when it had been reacted with the EIA antigen before addition of the reference CF serum and complement. In contrast, the IgG class converted the CF-active reference serum into a non-CF-reactive one irrespective of whether it was simultaneously reacted with the EIA antigen and the reference CF serum, whether it was added to the reaction mixture of the EIA antigen and the reference CF serum, or whether it was sensitized with the EIA antigen before addition of the reference CF serum. Inhibitory activities of the IgG and IgG(T) classes seemed to be different from each other in their reaction pattern as far as tested under our experimental conditions. Their CFI activities seemed to be specific for EIA, being negative in CFI activity in reaction with other antigens.     

Studies on Complement-Fixation Reaction in Equine Infectious Anemia

Complement-fixing (CF) and complement fixation-inhibiting (CFI) antibodies were investigated sequentially in three horses infected with equine infectious anemia (EIA) virus. The CF activity was first demonstrated 6 or 8 days after onset of the first pyrexia. The CFI activity developed a short period later, and caused a decrease of apparent CF titer of the whole serum. However, both antibodies tended to increase with advance of the disease course in two persistently infected horses, whereas they became completely undetectable during the late-stage in the remaining horse which showed no evidence for recurrence of pyrexia or persistence of viremia. The CF activities determined with varying dilutions of serum were distinctly different in pattern between the early-stage serum having the CF activity alone and the late-stage serum having both the CF and the CFI activities. The CF antibody was precipitated by 27–30% saturation with ammonium sulfate (SAS) while the CFI activity distributed in a wider range of precipitates formed by 26–32% SAS. The CFI activity was demonstrated to a higher titer when a relatively small amount of antigen was sensitized with CFI antibody prior to addition of reference CF antibody than when the three reagents were mixed at one time. The late-stage serum with a strong CFI activity against EIA antigen had no effect on the CF reaction of other viral antigen–antibody systems such as equine influenza and equine rhinopneumonitis.     

Toxoplasmosis II. Studies of Animal Sera Using Complement-Fixation Tests

Serological studies were performed in guinea pigs, a sheep, calf, goat and two pigs experimentally infected with toxoplasmosis. The direct complement-fixation method was effective in detecting antibodies in guinea-pig, goat and sheep sera. The modified complement-fixation technique supplementing complement with normal bovine serum fraction, was required when testing bovine serum. With swine sera best reactions occurred in the indirect complement-fixation test and definite but low grade reactions were produced in the direct test after pro-complementary activity was removed by pH treatment of the sera. Allergic skin reactions were produced in the experimental animals but improvement in the antigen is necessary before the test could be used generally in the field as a diagnostic method for animal toxoplasmosis.     

Complement-Fixation Analysis of Four Subtypes of Foot-and-Mouth Disease Virus Type A

Complement-fixation patterns were established for four subtypes of foot-and-mouth disease virus by block assays against homologous and heterologous antiserum. Inhibition of fixation by excess antigen was observed in most homologous systems but rarely in the heterologous systems. The heterologous antibody titers were, in all instances, considerably lower than those for the homologous systems. Although relatively high dilutions of antiserum may be desirable for subtyping, higher concentrations of antibody should be used for determining serological types.     

Complement-Fixation Test for Detection of Herpes-like Viruses in Cell Cultures of Burkitt''s Lymphoma

Although biopsies of Burkitt's tumors contained no detectable complement-fixing (CF) antigen or antigens, tumor cell lines contained CF antigen or antigens related to the presence of a herpes-like virus particle.     

Toxoplasmosis III. Studies Using the Complement-Fixation Test and Fluorescence-Inhibition Test with Sera of Experimentally Exposed Birds

The direct, modified direct and indirect complement-fixation tests and the fluorescence-inhibition test were investigated using sera from pigeons, chickens and turkeys which had been exposed to Toxoplasma gondii. The direct CF test was suitable for use with pigeon sera. The indirect CF method effectively demonstrated antibodies in chicken and turkey sera. FI tests were less sensitive than the CF methods.     

Comparison of the Complement-Fixation Test and the Microscopic-Agglutination Test (Agglutination-Lysis) for the Detection of Leptospiral Serogroup Antibodies

The MA and CF tests using alcohol extracted antigens have been compared with sera from infected rabbits and calves. The MA test was highly serotype specific with serum from both animal species. The CF test was broadly reactive with serum from rabbits infected with various serotypes. However, when bovine serum was used cross reactivity was reduced and it was necessary to use pooled antigens to detect heterologous serotypes.