Desgraupes, S. | Search bioRxiv

bioRxiv2025

In vivo risk assessment of yellow fever virus transmission through breastfeeding, and mechanistic insights

Yellow fever virus (YFV), a mosquito-borne flavivirus, remains a significant public health threat, especially in areas with low vaccine coverage. Since 2010, yellowfevervaccination is not recommended for breastfeeding women due to reported cases of vaccine strain transmission through breast milk, leading to neonatal meningoencephalitis. However, the efficiency of YFV vaccine strain transmission via breastfeeding remains unknown, and wild-type strains transmission may be suspected based on viral RNA detection in breast milk. Direct evidence of breastfeeding-related transmission in humans is challenging to obtain given the confounding presence of vector-borne transmission, making animal models crucial for evaluating this risk. In this study, the A129 mouse model was used to investigate YFV transmission via breastfeeding for both wild-type and vaccine strains. Results show that both strains can spread to mammary glands, leading to viral detection in breast milk as free viral particles and cell-associated virus, with similar viral loads for all strains. Mammary stromal and immune cells are primary targets of YFV in vivo, while mammary epithelial cells also support infection, suggesting two possible mechanisms of mammary epithelial crossing. Neonates are found to be susceptible to oral infection, with higher infection rates for the wild-type strain but evidence of neuroinvasion for both strains. Both strains can infect and cross an in vitro human intestinal barrier model, indicating this epithelium as a potential viral entry site for neonates. Finally, this study confirms the existence of YFV transmission through breastfeeding in an animal model, highlighting the need to consider it among transmission risks.

microbiology↗

bioRxiv2025

The genetic driver of Acute Necrotizing Encephalopathy, RANBP2, regulates the inflammatory response to Influenza A virus infection

Influenza virus infections can cause severe complications such as Acute Necrotizing Encephalopathy (ANE), which is characterised by rapid onset pathological inflammation following febrile infection. Heterozygous dominant mutations in the nucleoporin RANBP2/Nup358 predispose to influenza-triggered ANE1. The aim of our study was to determine whether RANBP2 plays a role in IAV-triggered inflammatory responses. We found that the depletion of RANBP2 in a human airway epithelial cell line increased IAV genomic replication by favouring the import of the viral polymerase subunits, PB1, PB2 and PA following viral transcription and translation. Additionally, RANBP2 knockdown enhanced the cytoplasmic export of viral RNA (vRNA) and disrupted segment stoichiometry, which associated with elevated production of the pro-inflammatory chemokines CXCL8, CXCL10, CCL2, CCL3 and CCL4 in human primary macrophages. Using CRISPR-Cas9 knock-in for the ANE1 disease variant RANBP2-T585M, we further demonstrate that this point mutation causes a loss-of-localisation phenotype that excludes RANBP2 from the nuclear envelope, which phenocopies RANBP2 knockdown by increasing IAV replication and driving pro-inflammatory cytokine expression following infection. Together, our results reveal that RANBP2 regulates influenza RNA replication and nuclear export, thereby restraining virus-induced hyperinflammation, and further suggest that ANE1 pathogenesis results from the impaired localisation of RANBP2 at the nuclear envelope.

immunology↗