title: Validation of an indirect ELISA based on a recombinant nucleocapsid protein of Rift Valley fever virus for the detection of IgG antibody in humans.
abstract: An indirect enzyme-linked immunoassay (I-ELISA) based on the recombinant nucleocapsid protein (rNp) of Rift Valley fever virus was validated for the detection of specific IgG antibody in human sera. Validation data sets derived from testing sera collected in Africa (n=2967) were categorized according to the results of a virus neutralisation test. The assay had high intra- and inter-plate repeatability in routine runs. No detectable cross-reactions between IgG antibodies generated from mice experimentally infected with viruses representing genus Phlebovirus, Nairovirus, Orthobunyavirus and Bhanja virus of the family Bunyaviridae were observed. At a cut-off optimised by the two-graph receiver operating characteristics analysis at 95% accuracy level, the diagnostic sensitivity of the I-ELISA was 99.72% and diagnostic specificity 99.62% while estimates for the Youden's index (J) and efficiency (Ef) were 0.993 and 99.62%. When cut-off values determined by mean plus two and by mean plus three standard deviations derived from I-ELISA readings in an uninfected reference population were used, the diagnostic sensitivity was 100% but estimates of Y, Ef and other combined measures of diagnostic accuracy were lower. The I-ELISA based on rNp is highly sensitive, specific and robust and can be applied for diagnosis of infection of Rift Valley fever and disease-surveillance studies in humans.
authors.affiliation: Special Pathogens Unit, National Institute for Communicable Diseases of the National Health Laboratory Service, Sandringham 2131, South Africa. januszp@nicd.ac.za
authors.forename: Janusz T
authors.initials: JT
authors.lastname: Paweska
authors.forename: Petrus
authors.initials: P
authors.lastname: Jansen van Vuren
authors.forename: Robert
authors.initials: R
authors.lastname: Swanepoel
mesh_terms: D000349:Africa; D000914:Antibodies, Viral / Q000097:blood* / Q000276:immunology; D003429:Cross Reactions; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D019251:Nucleocapsid / Q000276:immunology*; D011994:Recombinant Proteins / Q000276:immunology; D015203:Reproducibility of Results; D012295:Rift Valley Fever / Q000821:virology; D012296:Rift Valley fever virus / Q000276:immunology* / Q000302:isolation & purification; D012680:Sensitivity and Specificity
chemical_list: D000914:Antibodies, Viral; D007074:Immunoglobulin G; D011994:Recombinant Proteins