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Paired specimens of serum from patients from whom Bacteroides fragilis had been isolated were tested by complement fixation against a crude B. fragilis antigen. A high titre or a rise in titre to B. fragilis was obtained in each of five patients with infection after abdominal surgery but in none of 11 patients with postpartum pyrexia nor in nine with vaginitis.
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The complement fixation (CF) procedure has played a significant role in the diagnosis of infectious diseases for almost a century. It has accomplished this by functioning in serodiagnosis and by antigen identification particularly in clinical virology. Although it has been replaced by newer, more sensitive and rapid techniques for serodiagnosis, the CF assay is still important as a reference standard for clinical laboratories.
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Sera from patients suspected of having rickettsial infections were tested in the complement fixation test with antigens prepared from the rickettsiae of Rocky Mountain spotted fever (SF), rickettsial pox (RP), murine typhus, epidemic typhus, and from Rickettsia canada (RC). Eight units of antigen were used in all cases and two units in man. Only those patients with antibody titers of 1:16 or higher were included in the study. Largely on the basis of comparative titers, the patients were divided into two groups: 102 with SF and 35 with infections by one of the members of the typhus group. The antibody titers were higher with SF antigen than RP antigen in 72% of the SF patients, and in only two SF patients was the RP titer higher, and then by only one tube (twofold dilution). There seemed little advantage in including the RP antigen in the battery of rickettsial antigens. Cross-reaction with at least one of the typhus antigens was observed in the sera from 64% of the SF patients. It was extensive enough to be confusing (within one tube) in 17% with eight units of antigen, but the differentiation was more distinct with two units of antigen. The cross-reaction with typhus antigens was as frequent in children with SF as it was in adults; thus, it is unlikely that these cross-reactions resulted from previous typhus vaccination. The serological differentiation between murine typhus and epidemic typhus was frequently difficult, but the epidemiological background was distinct. Five patients had higher titers to RC antigen, and four of these may possibly have had RC infections.
The complement-fixation test may be used to detect rotaviral antigens directly in clinical specimens. However, a certain number of specimens tested for human rotaviruses by the complement-fixation test show an anti-complementary activity. By comparing eight techniques we analysed this anti-complementary activity and identified the best method for its reduction. Pretreatment of clarified supernatant of stool suspensions by some methods resulted in a reduction of anti-complementary activity, without reducing the sensitivity of the method. Clarified supernatants of 8/36 (22.2%) specimens were anti-complementary; this anti-complementary activity was best removed by absorption with fetal calf serum or calf albumin. Such treatment offers practical means of increasing the specificity of complement-fixation test. Some observations suggest that the anti-complementary activity of stool suspensions may be frequently due to presence of one or more chelating agents that may be in faecal specimens.
Several automatic methods have been described for complement-fixation tests. However, each of these methods presents some inconvenience either due to cross contamination or to limited sensitivity. The new method consists basically in separating clearly the fixation stage from the haemolytic stage by using two different sampler plates placed on the same sampler. By this procedure, it becomes possible to obtain a very high sensitivity. The serologist may set the temperature and the duration of the reaction according to the properties of the tests under study. In addition, the sampling rate can be raised to 120 analyses per hour.
A solid-phase, indirect, enzyme-linked immunosorbent assay (ELISA) was compared with the microtitre complement fixation test for detecting Brucella ovis antibodies in 220 ram sera. The ELISA was more sensitive than the complement fixation test; it demonstrated antibodies in 11 sera from known infected or vaccinated rams that were complement fixation test negative. No false positives were recorded with the ELISA and, in 36 sera positive to both tests, the ELISA titres were consistently higher than the corresponding complement fixation test titres.
The complement-fixation test was investigated as a means of detecting hog cholera virus in spleen from experimentally infected swine. Various methods of extracting the tissue for production of antigen are described and emphasis is placed on the necessity of using the modified direct complement-fixation test to obtain reactions. The tissue should be obtained from animals showing advanced clinical manifestations of the disease. Preferably, the tissue should be maintained frozen or at least well refrigerated. The results indicate that tissue from dead animals or from breeding sows should be avoided. The 77 per cent positive reactions obtained suggest the test could be of diagnostic value provided two or three samples are obtained from the same herd.
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BACKGROUND: The complement fixation test (CFT) is the basic method in the diagnosis of toxoplasmosis. Despite its standard and reproducible results, it is rarely used in routine diagnosis of toxoplasmosis where the detection of IgG by means of EIA tests is widely used. OBJECTIVE: The study is focused on the verification of CFT value within the spectrum of specific classes of immunoglobulins IgG, IgM, IgA antibodies and avidity of IgG antibodies, as well as on the clinical diagnosis of toxoplasmosis. METHOD: The study analysed 1705 samples of serum from patients suspected to be infected by Toxoplasma gondii. Out of these patients 451 suffered from acute lymphadenopathic toxoplasmosis (6 with seroconversion of both CFT and IgG antibodies) and 1254 serum samples were collected from patients with latent infection, out of whom 176 were with long-term persistence of IgM, or IgA antibodies after the elimination of disease. CONCLUSION: CFT is a reliable indicator of Toxoplasma infection and as opposed to IgG antibodies its levels enable a more objective determination of its course. However from the aspect of the determination of the stage of toxoplasmosis from a single sample of serum, the combination of CFT with IgM or IgA antibodies with quantitative order or test of avidity of IgG antibodies must be performed. (Tab. 4, Fig. 4, Ref. 30.).
A gel diffusion test with sonicated Brucella ovis antigen and an enzyme-linked immunosorbent assay based on heat-extracted antigen were used to distinguish false from true reactions in a complement fixation test based on heat-extracted antigen. Of 142 complement fixing reactors (occurring in supposedly Brucella ovis-free, accredited flocks), the gel diffusion test correctly identified the status of 139 animals as compared to 128 with the enzyme-linked immunosorbent assay. A combination of the two methods resulted in a correct identification of 141 animals. The procedures provide an easy, cheap and quick way to determine the true status of reactors that show up during routine use of the complement fixation test in Brucella ovis re-accreditation procedures.
The presence of complement-fixing antibody to an early herpes simplex virus type 2 (HSV-2) antigen (the AG-4 antigen) was correlated with HSV-2 infection in the sera of patients with genital herpes. Eighty-eight per cent of sera taken two weeks after clinical diagnosis of a primary or recurrent herpes infection in patients, confirmed to have HSV-2 by virus isolation and typing, contained the anti-AG-4 complement-fixing antibody. None of the patients with genital HSV-1 had the antibody, and only 9% of controls or patients with facial HSV-1 infection had positive results for the antibody. This correlation was used to identify genital HSV-2 infections when either no virus sample had been taken or when virus isolations had been unsuccessful. Thus, a simple complement-fixation test can confirm an HSV-2 virus infection without isolation of the virus from the herpetic lesion.
The practical value of the indirect fluorescent antibody technique (I FAT), the micro complement fixation test (M CFT) and the agar gel immunodiffusion test (AGIDT) for the detection of antibodies to bovine leucosis virus (BLV) was investigated. For this purpose 1495 serum samples were examined. There was a remarkably good agreement between the three tests in the demonstration of antibodies to BLV especially if sera with a sufficient high concentration of antibodies ("late serum") were under investigation. These positive sera were derived only from farms which exploited one or more imported animals. A disagreement of results of the three tests was observed in 38 (2.5%) cases. This was due to: (1) difficulties in reading of the test; (2) presumably by the demonstration of different classes of antibody and (3) the fact that in the AGIDT sera could be used undiluted. This discrepancy was especially evident with sera with a low concentration of antibodies ("early or incubation sera"). A drawback for the M CFT is the anticomplementary activity found in 17% of the bovine serum samples.
The direct, the modified direct and the indirect complement-fixation tests were investigated as methods for the detection of antibodies for the enzootic pneumonia mycoplasma and for Mycoplasma hyorhinis in the serum of infected pigs and of immunized rabbits. Only the modified direct complement-fixation test in which the guinea-pig complement is supplemented with fresh, normal unheated calf serum was suitable for the detection of mycoplasma antibodies in sera of infected swine. Based on the close correlation between the production of typical lung lesions in experimentally infected pigs and the appearance of significant serum antibody titres, the modified direct complement-fixation test provides for the first time a sensitive, specific in vitro method for the detection of enzootic pneumonia in the live pig. This test also permitted the in vitro differentiation of the mycoplasma causing enzootic pneumonia from M. hyorhinis which causes polyserositis. Antibodies in the sera of rabbits were demonstrable by the ordinary direct complement-fixation test. However, in contast to the observation made with swine sera, only a slight quantitative antigenic difference between the enzootic pneumonia mycoplasma and M. hyorhinis was seen when the tests were performed with rabbit serum antibodiies.
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