Performance of Various Commercial Assays for the Detection of Toscana Virus Antibodies

Abstract

Introduction: Sandfly fever virus (SFV) serotypes sandfly fever Naples virus, sandfly fever Sicilian virus, and sandfly fever Cyprus virus cause febrile diseases, whereas Toscana virus (TOSV) is responsible for aseptic meningoencephalitis. Diagnosis and surveillance of TOSV depend heavily on virus serology, and various commercial assays utilizing various antigen sources and formats have been available. The aim of this study was to perform comparative evaluation of commercially available serological assays for anti-TOSV immunoglobulins. Materials and Methods: A collection of 120 sera from healthy blood donors from an endemic region, previously identified to be reactive for antibodies against various SFV serotypes by indirect immunofluorescence test (IIFT), was reevaluated for IgG/IgM via IIFT, enzyme-linked immunosorbent assay, and an immunoblot assay manufactured by Euroimmun, Diesse, and Mikrogen, respectively. Virus neutralization test (VNT) was performed for 99 sera using standard TOSV, sandfly fever Sicilian virus, and sandfly fever Naples virus strains. Results: A total of 89 samples (74.2%) were reactive for TOSV IgG in at least one of the commercial assays, and 31 samples (31.3%) were reactive in VNT for various SFV serotypes. Average percentage agreements among commercial assays and between VNT and the commercial assays were noted as 57.8% and 62.6%, respectively. No significant correlation between assay results and VNT titers was observed. SFV IgM antibodies were detected in a total of eight samples (6.7%) via IIFT, which were nonreactive in enzyme-linked immunosorbent assay and VNT. Discussion: Commercial diagnostic immunoassays displayed slight to fair agreement for TOSV IgG as assessed via kappa and percentage agreement values. The results could only be confirmed via virus neutralization in a portion of the samples, and overall agreement between the commercial assays and VNT was slight. Commercial assays such as immunoblot can be used in addition to VNT for confirmation of TOSV exposure.

Clinic–Epidemiologic Study of Human Infection by Granada Virus, a New Phlebovirus within the Sandfly Fever Naples Serocomplex

“…This lack of agreement among serologic assays for phleboviruses has been reported before. 12 In addition, in 2008, we recovered a TOSV isolate from a cerebrospinal fluid (CSF) sample of a patient with meningitis, and the neutralization assay to detect anti-TOSV IgM antibodies was negative (personal communication).…”

First report of sandfly fever virus infection imported from Malta into Switzerland, October 2011

“…Viral neutralisation tests (VNT) using early convalescent sera remain the serological reference method to identify these viruses or to assess the specificity of the antibody response [8]. Although generally regarded as the gold standard assay for specificity, the VNT is relatively labour-intensive and only established in few laboratories.…”

“…SFV-specific commercial assays such as IIFT, enzyme-linked immunoassay and IB are much more commonly used. For the diagnosis of the cases described here, we used IIFT for screening purposes and the IB as confirmatory assay [8].…”

Serological Investigation of Phlebovirus Exposure in Blood Donors from the Mediterranean Province of Mersin, Turkey

“…TOSV VNT Vero hücreleri (ATCC CCL81) ve standart TOSV genotip A izolatı (ISS.Phl.3) kullanılarak, 1:40 son serum dilüs-yonunda önceden tarifl endiği şekilde uygulandı ve 37°C'de 96 saatlik inkübasyon sonucu sitopatik etki gözlenerek yorumlandı 9 .…”