Stuart, C. | bioRxiv Science

bioRxiv2025

ACE2 utilization of HKU25 clade MERS-related coronaviruses with broad geographic distribution

Dipeptidyl peptidase-4 (DPP4) is a well-established receptor for several MERS-related coronaviruses (MERSr-CoVs) isolated from humans, camels, pangolins, and bats (1-6). However, the receptor usage of many genetically diverse bat MERSr-CoVs with broad geographical distributions remains poorly understood. Recent studies have identified angiotensin-converting enzyme 2 (ACE2) as an entry receptor for multiple merbecovirus clades. Here, using viral antigen and pseudovirus-based functional assays, we demonstrate that several bat merbecoviruses from the HKU25 clade previously thought to utilize DPP4 (7), employ ACE2 as their functional receptor. Cryo-electron microscopy analysis revealed that HsItaly2011 and VsCoV-a7 recognize ACE2 with a binding mode sharing similarity with that of HKU5 but involving remodeled interfaces and distinct ortholog selectivity, suggesting a common evolutionary origin of ACE2 utilization for these two clades of viruses. EjCoV-3, a strain closely related to the DPP4-using MERSr-CoV BtCoV-422, exhibited relatively broad ACE2 ortholog tropism and could utilize human ACE2 albeit suboptimally. Despite differences in entry mechanisms and spike proteolytic activation compared to MERS-CoV, these viruses remain sensitive to several broadly neutralizing antibodies and entry inhibitors. These findings redefine our understanding of the evolution of receptor usage among MERSr-CoVs and highlight the versatility of ACE2 as a functional receptor for diverse coronaviruses. SignificanceRecent studies unexpectedly revealed that several merbecoviruses convergently evolved ACE2 receptor usage with distinct binding modes across three continents, challenging the dogma that DPP4 is their primary receptor. Here, we demonstrate that HKU25 clade MERS-related coronaviruses broadly distributed across Eurasia utilize ACE2 as host receptor through a binding mode shared with HKU5, challenging prior findings. These findings reveal a prevalence of ACE2 usage in diverse MERS-related coronaviruses in bats and show that EjCoV-3 is preadapted to use human ACE2, suggesting a potential for spillover. Our data provide a blueprint of host receptor barrier determinants which will facilitate global surveillance and development of countermeasures against these poorly characterized merbecoviruses.

microbiology↗

bioRxiv2023

EX VIVO GENE EDITING AND CELL THERAPY FOR HEREDITARY TYROSINEMIA TYPE 1

Background & AimsWe previously demonstrated the successful use of in vivo CRISPR gene editing to delete 4-hydroxyphenylpyruvate dioxygenase (HPD) to rescue mice deficient in fumarylacetoacetate hydrolase (FAH), a disorder known as hereditary tyrosinemia type 1 (HT1). The goal of this study was to develop an ex vivo gene editing protocol and apply it as a cell therapy for HT1. MethodsWe isolated hepatocytes from wild-type (C57BL/6) and Fah-/- mice and then used an optimized electroporation protocol to deliver Hpd-targeting CRISPR-Cas9 ribonucleoproteins (RNP) into hepatocytes. Next, hepatocytes were transiently incubated in cytokine recovery media that we formulated to block apoptosis, followed by splenic injection into recipient Fah-/- mice. ResultsWe observed robust engraftment and expansion of transplanted gene-edited hepatocytes from wild-type donors in the liver of recipient mice when transient incubation with our cytokine recovery media was used after electroporation and negligible engraftment without the media (mean 46.8% and 0.83%, respectively, p = 0.0025). Thus, the cytokine recovery media was a critical component of our electroporation protocol. When hepatocytes from Fah-/- mice were used as donors for transplantation, we observed 35% and 28% engraftment for Hpd-Cas9 RNPs and Cas9 mRNA, respectively. Tyrosine, phenylalanine, and biochemical markers of liver injury normalized in both Hpd-targeting Cas9 RNP and mRNA groups independent of drug induced-inhibition of Hpd through nitisinone, indicating correction of disease indicators in Fah-/- mice. ConclusionsThe successful liver cell therapy for HT1 validates our protocol and, despite the known growth advantage of HT1, showcase ex vivo gene editing using electroporation in combination with liver cell therapy to cure a disease model. These advancements showcase the impacts of electroporation combined with transplantation as a cell therapy.

bioengineering↗