Establishment of a Chikungunya virus pseudotype system strictly dependent on viral protein expression

Chikungunya virus (CHIKV) is an enveloped RNA virus that causes Chikungunya fever in humans. It is classified as an arbovirus (arthropod-borne virus) and is transmitted by mosquitoes. Therefore, CHIKV can replicate in many types of cells derived from mammals or insects. In this study, we tried to establish the widely useable CHIKV pseudotype system, adapting various viral species, and we demonstrated the production of Chikungunya pseudotype virus bearing the envelope protein from two different viral families, <i>Coronaviridae</i> or <i>Rhabdoviridae</i>, i.e. severe acute respiratory syndrome coronavirus 2 spike protein or vesicular stomatitis virus glycoprotein, respectively. We found that the capsid protein of CHIKV is not always necessary in the formation of CHIKV-based pseudotypes, but that the capsid protein increases the efficiency of expression of the sub-genomic RNA which codes the labelled genes. Our established pseudotype virus-producing system supplied a sufficient titre of virions for application to most virological experiments that showed more than 10⁴ focus-forming units per millilitre. The pseudotype infections were strictly dependent on compatibility between the viral envelope protein and its receptor, and there was no false-positive background infection. Our established pseudotype virus system can be used as a robust platform to study various virus infections and for screening and in-depth evaluation of neutralizing antibodies and antiviral agents.