Monodelphis domestica as a fetal intra-cerebral inoculation model for Zika virus pathogenesis

Monodelphis domestica, also known as the laboratory opossum, is a marsupial native to South America. At birth, these animals are developmentally equivalent to human embryos at approximately 5 weeks of gestation which, when coupled with other characteristics including the size of the animals, the development of a robust immune system during juvenile development, and the relative ease of experimental manipulation, have made M. domestica a valuable model in many areas of biomedical research. However, their suitability as models for infectious diseases, especially diseases caused by viruses such as Zika virus (ZIKV), is currently unknown. Here, we describe the replicative effects of ZIKV using a fetal intra-cerebral model of inoculation. Using immunohistochemistry and in situ hybridization, we found that opossum embryos and fetuses are susceptible to infection by ZIKV administered intra-cerebrally, that the infection persists long term, and that the infection and viral replication consistently results in neural pathology and may occasionally result in global growth restriction. These results demonstrate the utility of M. domestica as a new animal model for investigating ZIKV infection in vivo. This new model will facilitate further inquiry into viral pathogenesis, particularly for those viruses that are neurotropic, that may require a host with the ability to support sustained viral infection, and/or that may require intra-cerebral inoculations of large numbers of embryos or fetuses.\n\nAUTHOR SUMMARYHere we show that the laboratory opossum (Monodelphis domestica) is a valuable new model for studying Zika virus pathogenesis. Newborns are at the developmental stage of 5-week human embryos. Zika virus inoculated on a single occasion into the brains of pups at the human developmental stages of 8-20 weeks post conception replicated in neuronal cells and persisted as a chronic infection until the experimental endpoint at 74-days post infection. In addition, we observed global growth restriction in one of 16 inoculated animals; global growth restriction has been observed in humans and other animal models infected with Zika virus. The results illustrate great potential for this new animal model for high throughput research on the neurological effects of Zika virus infection of embryos and fetuses.