Flavivirus replication kinetics in early-term placental cell lines with different differentiation pathways

Abstract

Background The uncontrollable spread of Zika virus (ZIKV) in the Americas during 2015–2017, and its causal link to microcephaly in newborns and Guillain-Barré syndrome in adults, led the World Health Organisation to declare it a global public health emergency. One of the most notable features of ZIKV pathogenesis was the ability of the virus to pass the placental barrier to infect the growing foetus. This pathogenic trait had not been observed previously for medically important flaviviruses, including dengue and yellow fever viruses. Methods In this study we evaluated the replication kinetics of ZIKV and the related encephalitic flavivirus West Nile strain Kunjin virus (WNVKUN) in early-term placental cell lines. Results We have observed that WNVKUN in fact replicates with a greater rate and to higher titres that ZIKV in these cell lines. Conclusions These results would indicate the potential for all flaviviruses to replicate in placental tissue but it is the ability to cross the placenta itself that is the restrictive factor in the clinical progression and presentation of congenital Zika syndrome.

Proposal of Model for Evaluation of Viral Kinetics of African/Asian/Brazilian—Zika virus Strains (Step Growth Curve) in Trophoblastic Cell Lines

“…Uninfected cells (BeWo, HTR-8, and HuH-7) were observed and compared with infected cells at each time point. Cell viability was considered visually, with the support from data published in the literature [ 14 , 16 , 19 , 33 , 34 , 35 ] and from cell banks. Images of mock and infected cells can be seen in the Supplementary Materials Figure S1 .…”

“…Regarding virus transmission by the placental barrier, the first 12 gestational weeks are the most critical, because the placenta is still developing and its protection depends on maternal antibodies [ 11 , 12 , 13 , 14 , 17 , 18 , 19 , 33 , 34 , 35 ]. Among the proposed routes, virus transmission can occur via trophoblasts [ 33 , 34 , 35 ], which are pluripotent cells that arise in the blastula stage and the beginning of the first cell differentiation and will originate from the embryo and embryonic annexes [ 36 ].…”

“…Our study is based on the models by Delbruck and Ellis, and Burleson and has as its mainly aims to bring about an improvement by applying mathematical calculations to quantify virus production originating from bench experiments. Carrera et al [ 19 ] compared ZIKV with WNV (West Nile virus), quantified each time point by PFU/mL, and built a curve graph with this result. In our work, we improved this method and established a relationship between C T values obtained by qRT-PCR and the plaque assay (PFU/mL).…”

“…Considering the viral detection in the amniotic fluid of pregnant women and in the female and male sexual organs, it is possible that ZIKV can be transmitted by means of sexual relations and maternal fetal attachment [ 13 , 14 , 15 , 16 , 17 , 18 ]. Among flaviviruses, there are cases of vertical transmission (maternal fetal) for CHIKV, DENV, and WNV [ 8 , 9 ], and WNV can infect trophoblast cells more efficiently when compared with ZIKV [ 19 ]. However, its relevance for the spread and disease of such viruses is still not conclusive.…”

Transmission of Zika virus by dendritic cell subsets in skin and vaginal mucosa

“…Consequently, the World Health Organization (WHO) labeled in 2016 the Zika virus pandemic in South America a public health emergency (9). Zika virus is the only Flavivirus that passes the maternal-placental barrier (10) and infects placental cells that include villous stromal macrophages, i.e. Hofbauer cells, and placental trophoblasts (11)(12)(13)(14).…”