Biology subjects

Smertina, E.

Publications and source records attributed to Smertina, E..

3 recordsLinked to original sources

bioRxiv2025

Inhibition of interferon signalling improves rabbit calicivirus replication in biliary organoid cultures

The Rabbit haemorrhagic disease virus (RHDV) was discovered 40 years ago. This highly pathogenic virus threatens the integrity of ecosystems in the European rabbits native range, while in Australia, it is used as a biocontrol tool to manage overabundant populations of feral rabbits (Oryctolagus cuniculus). Little is known about the life cycle of this virus due to the absence of a reliable cell culture system. In 2023, we developed a rabbit liver-derived organoid cell culture system that supports RHDV replication but is unable to sustain serial passaging in culture. Here, we report that the interferon signalling pathway inhibitor Ruxolitinib increases virus replication in organoid-derived monolayer cells and, for the first time, enables the serial passaging of RHDV in cell culture. Four consecutive passages were achieved with viral titres reaching the concentration of the initial virus stock as measured by RT-qPCR. Immunofluorescence analysis showed that more cells are infected in the presence of Ruxolitinib. Furthermore, we noted that cells grew faster and formed healthier monolayers in the presence of the interferon inhibitor. To determine the cellular composition of the monolayers, we used single-cell RNA-sequencing, revealing that our organoids consist largely of RHDV-permissive cholangiocytes. IMPORTANCEIn this work, we describe the use of interferon inhibitor to enhance the permissiveness of our recently developed rabbit liver-derived organoid cell culture to RHDV infection. Interferon inhibitors offer a simple and cost-effective approach to increase the replication of difficult-to-grow viruses in culture systems that are not interferon-deficient.

microbiology↗

bioRxiv2022

Hepatobiliary organoids derived from leporids support the replication of hepatotropic lagoviruses

Lagoviruses, family Caliciviridae, are some of the most virulent vertebrate viruses known. They infect leporids, i.e., rabbits (Oryctolagus spp.), hares (Lepus spp.) and cottontails (Sylvilagus spp.) and rapidly kill over 95% of susceptible animals. Pathogenic lagoviruses are hepatotropic and induce a fulminant hepatitis that typically leads to disseminated intravascular coagulation within 24-72 hours of infection. However, the pathophysiological mechanisms governing this extreme phenotype and other aspects of the fundamental biology of these viruses are poorly understood due to a lack of cell culture systems. Here, we report on a robust and reliable ex vivo model for the cultivation of hepatotropic lagoviruses. We show that three rabbit haemorrhagic disease virus (RHDV) variants, RHDV1, RHDV2 and RHDVa-K5, replicate in monolayer cultures derived from rabbit hepatobiliary organoids. Viral replication was demonstrated by a (i) increase in viral RNA levels of greater than one log10 over a 23-hour period, (ii) detection of viral structural and non-structural proteins, and (iii) detection of double-stranded RNA viral replication intermediates. Furthermore, we generated hepatobiliary organoids from a feral cat (Felis domesticus), a wild mouse (Mus musculus) and a European brown hare (Lepus europaeus) and showed that monolayer cultures derived from the cat and mouse organoids were not permissive for lagovirus infection, while those derived from the hare organoids only supported replication of RHDV2, recapitulating the species tropism that has been observed with these viruses. Our organoid culture system will facilitate future studies into the molecular biology of lagoviruses, which will have considerable import for the conservation of endangered leporid species in Europe and North America and the biocontrol of overabundant rabbit populations in Australia and New Zealand.

microbiology↗

bioRxiv2021

Frequent intergenotypic recombination between the non-structural and structural genes is a major driver of epidemiological fitness in caliciviruses

The diversity of lagoviruses (Caliciviridae) in Australia has increased considerably. By the end of 2017, five variants from three viral genotypes were present in populations of Australian rabbits, while prior to 2014 only two variants were known. To understand the interactions between these lagovirus variants we monitored their geographical distribution and relative incidence over time through a landscape-scale competition study, and from this, revealed potential drivers of epidemiological fitness. Within three years of the arrival of GI.1bP-GI.2 (RHDV2) into Australia, we observed the emergence of two novel recombinant lagovirus variants, GI.4eP-GI.2 (4e-recombinant) in New South Wales and GI.4cP-GI.2 (4c-recombinant) in Victoria. Although both novel recombinants contain the non-structural genes from benign, rabbit-specific, enterotropic viruses, these variants were recovered from the livers of both rabbits and hares that had died acutely. This suggests that determinants of host and tissue tropism for lagoviruses are associated with the structural genes, and that tropism is intricately connected with pathogenicity. Phylogenetic analyses demonstrated that the 4c-recombinant emerged independently on multiple occasions, with five distinct lineages observed. Both new recombinant variants replaced the previous dominant parental RHDV2 in their respective geographical areas, despite sharing an identical or near-identical (i.e., single amino acid change) major capsid protein with the parental virus. This suggests that epidemiological fitness of these recombinants was not driven by antigenic variation in the capsid, implicating the non-structural genes as key drivers of epidemiological fitness. Molecular clock estimates place the GI4.e recombination event in early to mid-2015, while the five GI.4c recombination events occurred from late 2015 through to early 2017. The emergence of at least six viable recombinant variants within a two-year period highlights an unprecedented frequency of these events, detectable only due to intensive surveillance, and demonstrates the importance of recombination in lagovirus evolution.

microbiology↗