Analytical and clinical evaluation of a duplex RT-qPCR assay for the detection and identification of o’nyong-nyong and chikungunya virus

Abstract

The mosquito-borne alphavirus o’nyong-nyong virus (ONNV) has proven its potential to cause major human outbreaks. On the African continent, ONNV causes unspecific febrile illness and co-circulates with the close relative chikungunya virus (CHIKV). The true scale of ONNV burden is poorly understood in Africa, because of the scarce availability of molecular in-house and commercial assays, strong cross-reactivity between ONNV and CHIKV in serological assays and a lack of surveillance. We designed a new RT-qPCR assay targeting the E1 gene for the detection of ONNV that can be used in monoplex or in duplex format, combined with a previously published CHIKV monoplex assay targeting the nsp1. The lower limit of detection with 95% positivity rate was determined to be <10 RNA copies/µL in monoplex and duplex format for both ONNV and CHIKV. Both monoplex assays and the duplex assay proved to be linear within the tested range of approximately 10 8 to 10 2 RNA copies/µl, and showed 100% specificity against a wide panel of arbovirus supernatants as well as several other pathogens in clinical samples. Testing of CHIKV positive serum and ONNV-spiked plasma samples confirmed the suitability of the assays in a clinical setting. The new assays provide a robust tool for molecular ONNV as well as ONNV/CHIKV simultaneous detection and may contribute to clarify the true burden of the two viruses, to improve arbovirus surveillance and to strengthen epidemics preparedness in Africa.