Multiple-bead assay for the differential serodiagnosis of neglected human cestodiases: Neurocysticercosis and cystic echinococcosis

Abstract

Background Neurocysticercosis (NCC), and cystic echinococcosis (CE) are two neglected diseases caused by cestodes, co-endemic in many areas of the world. Imaging studies and serological tests are used in the diagnosis of both parasitic diseases, but cross-reactions may confound the results of the latter. The novel multiplex bead-based assay with recombinant antigens has been reported to increases the diagnostic accuracy of serological techniques. Methodology We set-up an immunoassay based on the multiplex bead-based platform (MBA), using the rT24H (against Cysticercus cellulosae, causing cysticercosis) and r2B2t (against Echinococcus granulosus sensu lato, causing CE) recombinant antigens, for simultaneous and differential diagnosis of these infections. The antigens were tested on 356 sera from 151 patients with CE, 126 patients with NCC, and 79 individuals negative for both diseases. Specificity was calculated including sera from healthy donors, other neurological diseases and the respective NCC or CE sera counterpart. The diagnostic accuracy of this assay was compared with two commercial ELISA tests, Novalisa and Ridascreen, widely used in the routine diagnosis of cysticercosis and CE, respectively. Main findings For the diagnosis of NCC, sensitivity ranged from 57.94–63.49% for the rT24H-MBA, and 40.48–46.03% for Novalisa ELISA depending on exclusion or inclusion of sera having equivocal results on ELISA from the analysis; specificities ranged from 90.87–91.30% and 70.43–76.96%, respectively. AUC values of the ROC curve were 0.783 (rT24H) and 0.619 (Novalisa) (p-value Conclusions/Significance Overall, the recombinant antigens tested with the bead-based technology showed better diagnostic accuracy than the commercial assays, particularly for the diagnosis of NCC. The possibility of testing the same serum sample simultaneously for the presence of antibodies against both antigens is an added value particularly in seroprevalence studies for cysticercosis linked to control programs in endemic areas where these two parasites coexist. Author summary Cysticercosis and cystic echinococcosis are caused by infection with the larval stages of Taenia solium and Echinococcus granulosus sensu lato, respectively, and their distribution largely overlaps in many areas of the world. Currently, the WHO is calling for the need to map endemic areas for cysticercosis, where control programs should be applied. Serosurveys may serve this scope, but cross-reactivities may be an issue. This study evaluated the accuracy of two recombinant antigens (rT24H and r2B2t) specific for each parasite used together applying a novel multiple bead technology assay (MBA), and compared the results with two commercial ELISA tests for the diagnosis of these infections. We found that this method, although not 100% specific, provides better results than those obtained with the commercially available tests, with the added advantage of testing simultaneously for both infections using just one sample, and could prove an efficient and rapid support for serological screening studies to map areas of cysticercosis transmission. Importantly, this novel method based on MBA technology is open and flexible, allowing continuous improvement due to its ability to simultaneously introduce new recombinant antigens as they are discovered/defined.