Zika virus outbreak in the Americas: Is Aedes albopictus an overlooked culprit?

Azeem Mehmood Butt; Izza Nasrullah; Raheel Qamar; Yigang Tong

The workflow of phylogenetic and codon based analyses followed was similar as reported previously by us for CHIKV (Butt et al., 2014) and Marburg viruses (Nasrullah et al., 2015) . The analyzed ZIKV genomes (n = 27) clustered into three separate groups of Asian, West African and East African genotypes where all of the recently reported outbreak sequences clustered into Asian genotype group. Although, we also noted that NS1 gene had the highest adaptation towards H. replicate successfully in multiple hosts therefore, a virus may have to create a dynamic balance of both codon adaptation and codon deoptimization that could enable efficient replication and survival possibilities in multiple hosts of variable codon usage patterns. In such cases, we suspect that a single CAI observation is not enough to completely decipher the evolutionary patterns for such multi-host pathogen. We therefore, conducted similarity index and relative codon deoptimization index (RCDI) analyses to further investigate magnitude of ZIKV evolution under the influence of multiple hosts. ZIKV coding sequence were found to have highest codon deoptimization towards Ae. albopictus whereas, lowest codon deoptimization trends were noted for Ae. aegypti and H. sapiens. As reported previously, a low RCDI might indicate high adaptation to a host that comes in agreement to overall high CAI of ZIKV coding sequences towards H. sapiens and Ae. aegypti. On the other hand, a low RCDI is indicative that some viral genes are expressed in latency phases or even that the virus might present a low replication rate for successful establishment in a host with alternative codon usage patterns (Puigbo et al., 2010) . Furthermore, according to the similarity index analysis, Ae. albopictus is probably the new preferred vector of ZIKV because the selection pressure exerted by Ae. albopictus on all three ZIKV genotypes is greater than the selection pressures imposed by Ae. aegypti or H. sapiens (Figure 1 ). The similarity index was found to be highest for Ae. albopictus whereas, lowest was noted for H. sapiens.