Mouse models of Zika virus transplacental transmission

The HAVCR1-centric host factor network drives Zika virus vertical transmission

Zika virus (ZIKV) vertical transmission results in devastating congenital malformations and pregnancy complications; however, the specific receptor and host factors facilitating ZIKV maternal-fetal transmission remain elusive. Here, we employ a genome-wide CRISPR screening and identify multiple placenta-intrinsic factors modulating ZIKV infection. Our study unveils that hepatitis A virus cellular receptor 1 (HAVCR1) serves as a primary receptor governing ZIKV entry in placental trophoblasts. The GATA3-HAVCR1 axis regulates heterogeneous cell tropism in the placenta. Notably, placenta-specific Havcr1 deletion in mice significantly impairs ZIKV transplacental transmission and associated adverse pregnancy outcomes. Mechanistically, the immunoglobulin variable-like domain of HAVCR1 binds to ZIKV via domain III of envelope protein and virion-associated phosphatidylserine. Proteomic profiling and function analyses reveal that AP2S1 cooperates with HAVCR1 for ZIKV internalization through clathrin-mediated endocytosis. Overall, our work underscores the pivotal role of HAVCR1 in mediating ZIKV vertical transmission and highlights a therapeutic target for alleviating congenital Zika syndrome.

The first trimester human placenta responds to Zika virus infection inducing an interferon (IFN) and antiviral interferon stimulated gene (ISG) response

BACKGROUND

Zika virus (ZIKV) is a positive-strand RNA virus of the Flaviviridae family. Maternal ZIKV infection during pregnancy can spread to the placenta and fetus causing severe neurological defects and infants born with microcephaly. Here, we investigated ZIKV infection and the cellular innate antiviral immune response in first trimester human placental explant cultures and isolated primary villus cytotrophoblasts (CTBs).

METHODS

Placentas were obtained with informed consent from women undergoing elective pregnancy termination and either cultured as placental explants or used to isolate primary CTBs. Explants and CTBs were both infected with ZIKV (PRVABC59), and samples evaluated for infection by qRT-PCR, viral plaque and ELISA assays, and immunohistochemical or immunocytochemical staining.

RESULTS

We demonstrate robust infection and production of ZIKV in placental explant and CTB cultures. Both displayed delayed upregulation of interferons (IFN), most notably IFNβ and IFNλ2/3, and a panel of interferon stimulated genes (ISG) (IFI6, IFIT1, IFIT2, IFITM1, ISG15, MX1, RSAD). Stimulation of explants and CTBs with the dsRNA mimic poly(I: C), caused immediate IFN and ISG upregulation, demonstrating the first trimester placenta is innate immune competent. This suggests that either ZIKV blocks the early innate response, or the placental response is inherently hindered.

CONCLUSION

Together these data show that first trimester placenta is susceptible to ZIKV infection which induces a delayed type III IFN antiviral response. This delay likely creates an environment favourable to ZIKV replication and dissemination across the early gestation placenta to fetal tissue, causing pathologies associated with congenital ZIKV syndrome.

Efficacy of emergency maternal MVA-ZIKV vaccination in a rapid challenge model of lethal Zika infection

Zika virus (ZIKV) outbreak of 2015 was associated with microcephaly and congenital birth defects in children born to pregnant women infected with ZIKV. Using the highly susceptible Type I Interferon Receptor-deficient mouse-model, we demonstrate that a single emergency vaccination with a non-replicating MVA-ZIKV vaccine, when administered as early as 2-days before challenge fully protected non-pregnant and pregnant mice and fetuses against lethal ZIKV-infection. Early protection was associated with the rapid emergence of ZIKV-specific CD8+ T cell responses; depletion of CD8+ T cells resulted in the loss of protection supporting a critical role for CD8+ T cells in the early protective efficacy of MVA-ZIKV. Neutralizing antibody responses were induced later than the CD8+ T cell responses, suggesting that it may play a role in later stages of infection. Our results suggest that MVA-ZIKV induces potent anamnestic cellular immunity early after infection, contributing to its protective efficacy against rapid ZIKV challenge.

Silent risk: the vertical transmission of Oropouche virus

The Oropouche virus (OROV), a member of the Orthobunyavirus genus, poses a significant public health challenge due to its potential for vertical transmission and lack of approved vaccines or antiviral treatments. Recent outbreaks have highlighted the association of OROV infection in pregnant women with severe outcomes, including spontaneous abortions, congenital anomalies, and fetal deaths. This letter to the editor emphasizes the need for a multifaceted approach to address the potential for vertical transmission of OROV, including the use of small animal models, detailed pathological studies, and robust preventive measures. We stress the importance of increased clinician awareness, timely patient management, and a One Health surveillance program to mitigate the risks associated with OROV infection during pregnancy.

The inoculum dose of Zika virus can affect the viral replication dynamics, cytokine responses and survival rate in immunocompromised AG129 mice

Zika virus, a mosquito-borne arbovirus, has repeatedly caused large pandemics with symptoms worsening from mild and self-limiting diseases to Guillain-Barré syndrome in adults and fetal microcephaly in newborns. In recent years, Zika virus diseases have posed a serious threat to human health. The shortage of susceptible small animal models makes it difficult to study pathogenic mechanisms and evaluate potential therapies for Zika virus infection. Therefore, we chose immunocompromised mice (AG129 mice) deficient in IFN-α/β and IFN-γ receptors, which can abolish the innate immune system that prevents Zika virus infection early. AG129 mice were infected with the Zika virus, and this mouse model exhibited replication dynamics, tissue tropism, pathological lesion and immune activation of the Zika virus. Our results suggest that the inoculum dose of Zika virus can affect the viral replication dynamics, cytokine responses and survival rate in AG129 mice. By testing the potential antiviral drug favipiravir, several critical indicators, including replication dynamics and survival rates, were identified in AG129 mice after Zika virus infection. It is suggested that the model is reliable for drug evaluation. In brief, this model provides a potential platform for studies of the infectivity, virulence, and pathogenesis of the Zika virus. Moreover, the development of an accessible mouse model of Zika virus infection will expedite the research and deployment of therapeutics and vaccines.

The Antiviral Potential of AdipoRon, an Adiponectin Receptor Agonist, Reveals the Ability of Zika Virus to Deregulate Adiponectin Receptor Expression

Zika virus (ZIKV) is a pathogenic member of the flavivirus family, with several unique characteristics. Unlike any other arbovirus, ZIKV can be transmitted sexually and maternally, and thus produce congenital syndromes (CZS) due to its neurotropism. This challenges the search for safe active molecules that can protect pregnant women and their fetuses. In this context, and in the absence of any existing treatment, it seemed worthwhile to test whether the known cytoprotective properties of adiponectin and its pharmacological analog, AdipoRon, could influence the outcome of ZIKV infection. We showed that both AdipoRon and adiponectin could significantly reduce the in vitro infection of A549 epithelial cells, a well-known cell model for flavivirus infection studies. This effect was particularly observed when a pre-treatment was carried out. Conversely, ZIKV revealed an ability to downregulate adiponectin receptor expression and thereby limit adiponectin signaling.