Research Article: Utilization of an Eilat Virus-Based Chimera for Serological Detection of Chikungunya Infection

Date Published: October 22, 2015

Publisher: Public Library of Science

Author(s): Jesse H. Erasmus, James Needham, Syamal Raychaudhuri, Michael S. Diamond, David W. C. Beasley, Stan Morkowski, Henrik Salje, Ildefonso Fernandez Salas, Dal Young Kim, Ilya Frolov, Farooq Nasar, Scott C. Weaver, Brian Bird.

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.

Partial Text: The genus Alphavirus in the family Togaviridae is comprised of small, enveloped viruses with single-stranded, positive-sense RNA genomes 11–12 kb in length [1]. The genus includes 31 recognized species classified into eleven complexes based on antigenic and/or genetic similarities [2–4], with most utilizing mosquitoes as vectors [1–7]. Mosquito-borne alphaviruses can infect mosquito species encompassing at least eight genera as well as many vertebrate taxa [8–12]. This ability to infect vertebrates and mosquitoes enables the maintenance of alphaviruses in endemic cycles with sporadic spillover events into human populations. Infections by Old World alphaviruses including chikungunya (CHIKV), o’nyong-nyong, Sindbis, and Ross River viruses can produce rash and debilitating arthralgia [13]. In contrast, New World alphaviruses such as western (WEEV), eastern, and Venezuelan equine encephalitis (VEEV) viruses can cause fatal encephalitis [13].

Our results indicate that EILV/CHIKV serves as a cost effective ELISA antigen for serological detection of CHIKV infection. In mosquito cells, this chimera replicates to exceptionally high titers (1010 PFU/mL), including in serum-free medium. Using a highly sensitive, newborn mouse model, we have demonstrated the replication-incompetence and safety of EILV/CHIKV following IC inoculation. The safety characteristics of EILV/CHIKV eliminate the need for high-level biosafety containment facilities for antigen production, and chemical or physical inactivation, thus maximally preserving native antigens. When applied either in capture- or indirect-ELISA formats using control MIAFs and acute and convalescent human serum samples from the Caribbean and Bangladesh, respectively, we determined that the EILV/CHIKV-based assay provides extremely sensitive indication of infection, outperforming traditional antigens with very high signal-to-noise ratios.



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