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PubMed1987

Preliminary studies of the complement fixation test to confirm the diagnosis of bovine ephemeral fever.

A strain of bovine ephemeral fever (BEF) virus isolated in China in 1976 was adapted to growth in tissue cultures. A baby hamster kidney complement fixing (CF) antigen, stable at -20 degrees C for at least 120 days, was prepared from the BEF virus grown in tissue culture and used to test bovine sera for antibodies to that virus. CF antibodies were detected in all of 31 cattle after convalescence from experimental infection with BEF virus, in 208 (98%) of 213 cattle observed to have shown clinical ephemeral fever in an epidemic, in 96 cattle in these herds which did not show clinical signs of ephemeral fever and 16 cattle from herds in northern China outside the epidemic area. The CF antibodies to BEF virus were found to persist in 34 (89%) of 38 cattle which were bled 6 years after natural exposure to ephemeral fever. The CF antigen is economical to prepare and is suitable to differentiate ephemeral fever from other viral infections with which it could possibly be confused on clinical appearance.

Animals↗
PubMed2005

Comparison of fluorescence polarization assay with card and complement fixation tests for the diagnosis of goat brucellosis in a high-prevalence area.

An evaluation of fluorescence polarization assay (FPA) to detect antibodies against Brucella melitensis according to the Mexican Official Norm (NOM) was performed. In this study, a total of 2582 goat serum samples from a high-prevalence area in northeast Mexico where vaccination is applied, were used. Of these, 1094 were classified as NOM negatives (card test (CT) negatives or CT positives/complement fixation test (CFT) negatives) and 1488 as NOM positives (CT and CFT positives). The receiver operator characteristics (ROC) curve analysis was used to obtain the FPA sensitivity (83.5%), specificity (82.2%) and accuracy (88.2%) compared with NOM criteria, using a cut-off value of 89mP for positive samples. In addition, FPA produced 84.1% of negative results versus 65.7% of CT using 1094 CFT negative samples, which indicated that FPA performance was better than CT to detect negative samples or differentiate samples from vaccinated animals. Finally, FPA showed 95.8% sensitivity when using 702 negative non-vaccinated samples. Taken together, these results suggested that FPA might replace CT as a screening test for its better performance compared with CFT, its adjustable cut-off useful in different epidemiological situations, and for its reliability, ease of performance, comparable cost with CT regimen, and potential application in field and high-throughput laboratories. The use of FPA as screening test will help to reduce the percentage of goats wrongly slaughtered because of brucellosis misdiagnosis. More studies on FPA are required for its approval as diagnostic tool for goat brucellosis.

Agglutination Tests↗
PubMed1980

Limitations of the complement-fixation test for distinguishing naturally acquired from vaccine-induced yellow fever infection in flavivirus-hyperendemic areas.

On the basis of previous studies, it has long been stated that 17D yellow fever (YF) vaccine generally does not induce complement-fixing (CF) antibodies, and that the presence of CF antibodies could be used in epidemiological studies to distinguish individuals infected with wild YF virus from vaccinated persons. In January 1979, seroepidemiological investigations were conducted during a YF epidemic in The Gambia, West Africa. Since a mass vaccination campaign was also in progress, it was important to confirm that the CF test could be used for serodiagnosis and determination of the incidence of natural YF infections. The serological responses of 58 individuals who received 17D YF vaccine were studied. The vaccinees fell into three gorups: 1) those with prevaccination YF neutralizing (N) antibodies; 2) immunological virgins without prevaccination YF-N antibody or hemagglutination-inhibiting (HI) antibodies to heterologous flaviviruses (Zika, West Nile, dengue 1, Uganda S, Spondweni, or Ntaya; and 3) those without prevaccination YF-N antibodies but with heterologous flaviviral HI antibodies. Vaccination of persons without prior flaviviral immunological experience resulted in monotypic YF HI and/or N antibody seroconversions, but no CF antibody response. The presence of prevaccination YF N antibodies blocked serological response to the vaccine in a high proportion of the cases; however, 24% of vaccinees in this group had a marked rise in log2 YF CF antibody titer (mean increase of 3.9). Thirteen (46%) of 28 persons without prevaccination YF N, but with heterologous flaviviral HI antibodies demonstrated YF CF antibody seroconversion or increase in titer following vaccination; in this group the mean increase in log2/ YF CF antibody titer was 2.1. The CF antibody response was generally broadly cross-reactive; but in a few individuals, the YF CF antibody response was homotypic. Nine different patterns of HI and CF homologous and heterologous antibody responses were defined and are discussed. The practical significance of these studies is that they demonstrate that in a high percentage of persons with prior flavivirus exposure, anamnestic serological responses to YF vaccine result in CF antibodies similar to those induced by natural YF virus infection. In Africa and tropical America, where the background of flaviviral immunity is high, it is imperative that seroepidemiologic investigations during or after YF outbreaks be conducted prior to vaccination.

Adolescent↗