Viral replication dynamics: Coinfection and superinfection of Vero cells with Zika virus and West Nile virus or Zika virus and Mayaro virus

Globalization and climate change have contributed to the emergence and spread of arboviruses, with the possibility of their cocirculation in the same geographic region at the same time. Understanding the effects of concurrent infections within a mosquito vector or human host is therefore an emerging focus in arboviral research. Studies using mosquito- and mammalian-derived cell lines provide a controlled framework for studying viral replication dynamics. In this study, Vero cells were infected with either Zika virus (ZIKV) and West Nile virus (WNV) or ZIKV and Mayaro virus (MAYV). In nature, concurrent infections can occur either simultaneously (i.e., coinfections) or sequentially (i.e., superinfections), and both conditions were studied here. Arbovirus replication was assessed 6 days post-infection using RT-qPCR, along with corresponding cytopathic effects on cells. Single infections were used as comparators to the coinfection and superinfection assays. Coinfections (ZIKV/WNV and ZIKV/MAYV) resulted in viral interference, with ZIKV RNA levels reduced when cells were coinfected with either WNV or MAYV. Viral accommodation was observed when ZIKV was the first to infect the cells during superinfections. In contrast, superinfection exclusion was observed when ZIKV was introduced to cells that were already infected with another virus. RNA production of WNV and MAYV was not affected by the presence of ZIKV in any of the conditions investigated. Understanding replication dynamics in in vitro coinfection and superinfection scenarios is the first step toward addressing the knowledge gap concerning cocirculating arboviruses.