Zika Virus Causes Persistent Infection in Porcine Conceptuses and may Impair Health in Offspring

Abstract

Outcomes of Zika virus (ZIKV) infection in pregnant women vary from the birth of asymptomatic offspring to abnormal development and severe brain lesions in fetuses and infants. There are concerns that offspring affected in utero and born without apparent symptoms may develop mental illnesses. Therefore, animal models are important to test interventions against in utero infection and health sequelae in symptomatic and likely more widespread asymptomatic offspring. To partially reproduce in utero infection in humans, we directly inoculated selected porcine conceptuses with ZIKV. Inoculation resulted in rapid trans-fetal infections, persistent infection in conceptuses, molecular pathology in fetal brains, fetal antibody and type I interferon responses. Offspring infected in utero showed ZIKV in their fetal membranes collected after birth. Some in utero affected piglets were small, depressed, had undersized brains, and showed seizures. Some piglets showed potentially increased activity. Our data suggest that porcine model of persistent in utero ZIKV infection has a strong potential for translational research and can be used to test therapeutic interventions in vivo.

Persistent Zika virus infection in porcine conceptuses is associated with elevated in utero cortisol levels

“…We have recently developed a fetal pig model which partially reproduces persistent in utero ZIKV infection and neonatal clinical pathology in humans [13]. Pigs share a close similarity in anatomy, growth and brain development with humans [14], and are often used in neuroscience and cortisol studies [12,14], including hypothalamic-pituitary-adrenal (HPA) axis [12,[15][16][17] and 11β-hydroxysteroid dehydrogenase (11β-HSD) research [18][19][20].…”

“…Additionally, pigs can bear more than 21 fetuses with each fetus possessing an individual placenta and amniotic membranes, providing an ample number of replicates. Here, samples from our previous ZIKV studies [13] and additional challenge experiments were tested to assess in utero cortisol levels in amniotic fluids (AF) from conceptuses inoculated at early and midgestation.…”

“…In a recently published study [13], three selected conceptuses (fetuses with fetal membranes) from each of four experimental gilts (G296, G313 -intramniotic + intraperitoneal (IA+IP) inoculation; G295, G314 -intracerebral (IC); a gilt is a pig pregnant for the first time) were directly inoculated in utero (2015). Conceptuses from two control gilts (G270 and G312) were inoculated with virus-free media in the same manner.…”

“…Inoculations were done at midgestation (50 gestation days (gd), the total duration of pregnancy in pigs is 114 days) and all inoculated and non-manipulated conceptuses and their mothers were sampled at 78 gd (36 days before birth). A detailed description of inoculation methods, sampling, and results from these animals has been published [13].…”

“…We used 10 6.0 TCID 50 /fetus (10 6.6 TCID 50 /litter) of ZIKV because abundant fluids in the allantoic cavity do not directly contact fetuses separated by amniotic membranes. Conceptuses and gilts were sampled at 110 gd following the previously published protocol [13]. Samples were tested with ZIKV specific quantitative RT-PCR, virus isolation and titration on VERO E6 cells, and histological and serological assays as previously described [13,21].…”