ABSTRACT
In December of 2013, chikungunya virus (CHIKV), an alphavirus in the family Togaviridae, was introduced to the island of Saint Martin in the Caribbean, resulting in the first autochthonous cases reported in the Americas. As of January 2015, local and imported CHIKV has been reported in 50 American countries with over 1.1 million suspected cases. CHIKV causes a severe arthralgic disease for which there are no approved vaccines or therapeutics. Furthermore, the lack of a commercially available, sensitive, and affordable diagnostic assay limits surveillance and control efforts. To address this issue, we utilized an insect-specific alphavirus, Eilat virus (EILV), to develop a diagnostic antigen that does not require biosafety containment facilities to produce. We demonstrated that EILV/CHIKV replicates to high titers in insect cells and can be applied directly in enzyme-linked immunosorbent assays without inactivation, resulting in highly sensitive detection of recent and past CHIKV infection, and outperforming traditional antigen preparations.
Subject(s)
Antibodies, Viral/blood , Antigens, Viral/immunology , Chikungunya Fever/diagnosis , Chikungunya virus/immunology , Serologic Tests/methods , Animals , Anopheles , Antigens, Viral/genetics , Caribbean Region/epidemiology , Cell Line , Chikungunya Fever/epidemiology , Enzyme-Linked Immunosorbent Assay/methods , Humans , Insect Viruses/genetics , Insect Viruses/growth & development , Mice , Recombinant Proteins/genetics , Recombinant Proteins/immunology , Sensitivity and SpecificityABSTRACT
Toscana virus (TOSV) is an arthropod-borne virus, transmitted to humans by Phlebotomus spp. Sandflies, which causes neurological diseases such as aseptic meningitis and meningoencephalitis. The commercial enzyme-linked immunosorbent assay (ELISA) is used widely to detect anti-TOSV IgG and IgM antibodies and to allow for rapid diagnosis of infection (Diesse Diagnostica Senese, Siena, Italy). Recently, an immunochromatographic assay (ICA) was developed for human anti-TOSV IgG or IgM detection by InBios International (Seattle, WA, USA). A comparison of the two diagnostic assays was performed on one hundred serum samples collected from patients hospitalized with suspected TOSV meningitis. Both assays were in excellent agreement, for both IgG and IgM detection. For IgM, 64/65 ELISA positive samples were positive by ICA. One serum, positive for specific IgM by ELISA but negative by ICA, was confirmed by direct diagnosis, with TOSV RNA detection in the patient's cerebrospinal fluid by PCR. For IgG, 64 samples were positive by ICA out of 71 ELISA positive samples. The discordant sera were positive by immunofluorescence and neutralization tests. Three out of these seven samples were also positive by IgM ICA. The sensitivity of these new assays compared to ELISA, which is used routinely, was 98.5% for IgM and 90.1% for IgG, while specificity was 100% in both cases. This data shows that ICA could be a reliable alternative test for serological diagnosis of TOSV infection in humans.
