Bram Van Holm

Filoviruses, particularly those of the Orthoebolavirus genus, pose ongoing public health threats due to their increasing frequency and geographic spread. However, research has been impeded by the biosafety level 4 classification of filoviruses. We previously reported the generation of biologically contained Ebola, Marburg and Sudan virus as lower biosafety level-compatible filovirus systems. In the present study, we expanded this repertoire to include biologically contained Taï Forest, Bundibugyo and Reston virus, thereby creating a near-complete toolkit for currently recognized human-relevant orthoebolaviruses. VP30-deficient viruses were generated with matching VP30 expressing cell lines. More specifically, we developed and optimized a dual-reporter system in VeroE6, Huh-7 and A549 cells, combining a virus-encoded enhanced green fluorescent protein reporter as readout for viral replication with a stably cellular-expressed nuclear mCherry marker for cytotoxicity assessment. Next, we screened two repurposing-oriented compound libraries comprising 640 small molecules against Taï Forest, Bundibugyo and Sudan virus, and subsequently cross-validated against Reston and Ebola virus. This approach identified multiple candidates with broad-spectrum activity across orthoebolaviruses, while also revealing virus-specific antivirals, with robust activity observed in both primate- and human-derived cell lines. Together, this work establishes a versatile and experimentally tractable lower biosafety level-compatible platform for the study of human-relevant orthoebolaviruses and the systematic discovery of broad-spectrum antiviral countermeasures against filoviruses.

Nipah virus is a highly lethal, zoonotic paramyxovirus that has caused recurring outbreaks in several South and Southeast Asian countries since its discovery in Malaysia in 1998. Symptoms of infection include severe respiratory and neurological disease, often resulting in death. As no approved vaccines or antivirals are currently available to reduce the burden of this virus, it is classified as a biosafety level 4 pathogen. There is an urgent need for systems that enable research in a lower biocontainment setting, especially since the World Health Organization declared Nipah virus a priority pathogen for pandemic concern. In the past, several minigenome systems have already been developed as safe alternatives to working with infectious virus; however, these systems remain relatively inefficient and lack robustness and reliability for further applications. Therefore, we developed novel optimized RNA polymerase II-driven minigenomes with nanoluciferase or enhanced green fluorescent protein reporter genes. Both systems outperform previously designed Nipah virus minigenomes, are easily operable, and can be implemented for antiviral compound screenings.

Coronavirus Disease 2019 (COVID-19) vaccination has resulted in excellent protection against fatal disease, including in older adults. However, risk factors for post-vaccination fatal COVID-19 are largely unknown. We comprehensively studied three large nursing home outbreaks (20–35% fatal cases among residents) by combining severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) aerosol monitoring, whole-genome phylogenetic analysis and immunovirological profiling of nasal mucosa by digital nCounter transcriptomics. Phylogenetic investigations indicated that each outbreak stemmed from a single introduction event, although with different variants (Delta, Gamma and Mu). SARS-CoV-2 was detected in aerosol samples up to 52 d after the initial infection. Combining demographic, immune and viral parameters, the best predictive models for mortality comprised IFNB1 or age, viral ORF7a and ACE2 receptor transcripts. Comparison with published pre-vaccine fatal COVID-19 transcriptomic and genomic signatures uncovered a unique IRF3 low/IRF7 high immune signature in post-vaccine fatal COVID-19 outbreaks. A multi-layered strategy, including environmental sampling, immunomonitoring and early antiviral therapy, should be considered to prevent post-vaccination COVID-19 mortality in nursing homes.