Establishing a Yellow Fever Serological Testing Method
2003 Vol.19 NO.3
For the rapid diagnosis and early detection of cases, and early control of disease outbreaks, a plan for the establishment of a laboratory testing system for yellow fever was reviewed. Serum specimens were collected from voluntary acceptors of yellow fever vaccine before immunization, and seven, 14 and 48 days after immunization for testing with ELISA (enzyme-linked immunosorbent assay), HI (hemagglutination-inhibition test), PRNT (plaque reduction neutralization test), and virus isolation methods to decide on the most optimum laboratory testing method for yellow fever. The results showed that, by ELISA method, serum collected 14 days after immunization showed ELISA-IgM positive, indicating that both the sensitivity and specificity of the ELISA-IgM system were relatively high. No viruses were detected by virus isolation in sera collected and cultured seven and 14 days after immunization. By using the HI test for testing virus antibodies, it was found that though serum specimens collected before immunization and 14 days after immunization showed cross-reactions of other viruses of the flavivirus genus, antibodies had increased by four-folds. The HI test was thus considered a tool good only for initial screening. When the pairing serum specimens collected before immunization and 14 days after immunization were compared with the PRNT method, it was found that the neutralizing antibodies of yellow fever had increased by four-folds, and their titers were high, particularly in the case of primary infection or early infection. The type of the flaviviruses that has caused the infection can be detected by using the PRNT to test the titers of the neutralizing antibodies; its sensitivity and specificity are both high, and even higher than those of other serological testing methods are. Results obtained from different experimental methods showed that both the ELISA-IgM and the PRNT were similar in result. They could clearly detect the types of the flaviviruses that had caused the infections. They were higher in sensitivity and specificity than other laboratory testing methods.