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 into the arboviruses (arthropod-borne viruses) and is transmitted by mosquitoes. Therefore, mosquitoes can replicate many types of cells derived from mammals or insects. In this study, we tried to establish the widely useable Chikungunya virus pseudotype-system adapting various viral species, and we demonstrated the production of Chikungunya pseudotype virus baring the envelope protein from two different viral families, Coronaviridae or Rhabdoviridae i.e., severe acute respiratory syndrome coronavirus 2 spike protein (CoV-2-S) or vesicular stomatitis virus glycoprotein (VSV-G), respectively. We found that the capsid protein of Chikungunya virus is not always necessary in the formation of Chikungunya virus-based pseudotypes, but that the capsid protein increases the efficiency of expression of the sub-genomic RNA which codes the labeled genes. Our established pseudotype virus-producing system supplied a sufficient titer of virions for application to most virological experiments that showed more than 10 4 focus forming units (FFU)/ml. 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.