Evaluation of fluorescence microsphere immunoassay for the detection of antibodies to Rift Valley Fever nucleocapsid protein and glycoproteins

Authors: RAGAN, IZABELLA - Kansas State University; DAVIS, SALLY - Kansas State University; McVey, David; RICHT, JUERGEN - Kansas State University; ROWLAND, ROBERT - Kansas State University; Wilson, William - Bill

Submitted to: Journal of Clinical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2018
Publication Date: 6/1/2018
Citation: Ragan, I., Davis, S.A., McVey, D.S., Richt, J., Rowland, R.R., Wilson, W.C. 2018. Evaluation of fluorescence microsphere immunoassay for the detection of antibodies to Rift Valley Fever nucleocapsid protein and glycoproteins. Journal of Clinical Microbiology. 56(6):e01626-17. http://doi.org/10.1128/JCM.01626-17.
DOI: https://doi.org/10.1128/JCM.01626-17

Interpretive Summary: Rift Valley Fever virus (RVFV) is a virus that infects humans and ruminants including cattle, sheep, goats, camels and buffalo. In this study we improved and evaluate a multiplex diagnostic assay that can simultaneously detect antibodies against multiple parts of the RVFV offers a high throughput test for disease surveillance and vaccine evaluations. This design allows for detection and confirmatory assays to run in a single assay. The assay is also compatible with a differentiate infected from vaccinated animal (DIVA) control strategy.

Technical Abstract: Rift Valley Fever virus (RVFV) is a zoonotic virus that infects ruminants including cattle, sheep, goats, camels and buffalo. Multiplexing diagnostic assays that can simultaneously detect antibodies against multiple RVFV antigens offer a high throughput test for disease surveillance and vaccine evaluations. We describe the improvement and evaluation of a previously developed fluorescence microsphere immunoassay (FMIA) for the detection of IgG and IgM antibodies against the RVFV glycoproteins (Gn) and the immunodominant nucleocapsid protein (Np). Well-characterized vaccinated and experimentally infected ruminant sera were used for the evaluation of the assay. Recombinant viral proteins were produced then coupled to polystyrene magnetic beads for analysis using the Luminex MAGPIX'system with xMAP technology. The FMIA was performed in parallel with virus neutralization tests. Our results revealed the highest MFI (Median Fluorescence Intensity) values for the detection of IgG antibodies against the RVFV Np, indicating that this antigen would be a good candidate for a screening assay. The Np and Gn targets could differentiate infected from vaccinated animals (DIVA) when tested with a candidate subunit vaccine formulation based on the RVFV Gn and Gc proteins. The results presented in this report demonstrate that FMIA provides a rapid and robust serological diagnostic tool for the detection of antibodies against RVFV. The targets developed in this assay provide the basis for the development of a companion diagnostic test for a DIVA compliant RVFV Gn/Gc subunit vaccine, as well as a multiplex sero-diagnostic assay that can simultaneously screen for several ruminant diseases.