Biology subjects

Tachedjian, M.

Publications and source records attributed to Tachedjian, M..

7 recordsLinked to original sources

bioRxiv2024

Use of Stem Cell-Derived Cardiomyocyte and Nasal Epithelium Models to Establish a Multi-Tissue Model Platform to Validate Repurposed Drugs Against SARS-CoV-2 Infection

The novel coronavirus disease (COVID-19) and any future coronavirus outbreaks will require more affordable, effective and safe treatment options to complement current ones such as Paxlovid. Drug repurposing can be a promising approach if we are able to find a rapid, robust and reliable way to down-select and screen candidates using in silico and in vitro approaches. With repurposed drugs, ex vivo models could offer a rigorous route to human clinical trials with less time invested into nonclinical animal (in vivo) studies. We have previously shown the value of commercially available ex vivo/3D airway and alveolar tissue models, and this paper takes this further by developing and validating human nasal epithelial model and embryonic stem cells derived cardiomyocyte model. Five shortlisted candidates (fluvoxamine, everolimus, pyrimethamine, aprepitant and sirolimus) were successfully compared with three control drugs (remdesivir, molnupiravir, nirmatrelvir) when tested against key variants of the SARS-CoV-2 virus including Delta and Omicron, and we were able to reconfirm our earlier finding that fluvoxamine can induce antiviral efficacy in combination with other drugs. Scalability of this high-throughput screening approach has been demonstrated using a liquid handling robotic platform for future Disease-X outbreaks.

microbiology↗

bioRxiv2022

Highly Thermotolerant SARS-CoV-2 Vaccine Elicits Neutralising Antibodies Against Delta and Omicron in Mice

As existing vaccines fail to completely prevent COVID-19 infections or community transmission, there is an unmet need for vaccines that can better combat SARS-CoV-2 variants of concern (VOC). We have previously developed highly thermo-tolerant monomeric and trimeric receptor binding domain derivatives that can withstand 100{degrees}C for 90 minutes and 37{degrees}C for four weeks, and help eliminate cold chain requirements. We show that mice immunised with these vaccine formulations elicit high titres of antibodies that neutralise SARS-CoV-2 variants VIC31 (with Spike: D614G mutation), Delta and Omicron (BA.1.1) VOC. Compared to VIC31, there was an average 14.4-fold reduction in neutralisation against BA.1.1 for the three monomeric antigen-adjuvant combinations, and 16.5-fold reduction for the three trimeric antigen-adjuvant combinations; the corresponding values against Delta were 2.5 and 3.0. Our findings suggest that monomeric formulations are suitable for the upcoming Phase I human clinical trials, and that there is potential for increasing efficacy with vaccine matching to improve responses against emerging variants. These findings are consistent with in silico modelling and AlphaFold predictions which show that while oligomeric presentation can be generally beneficial, it can make important epitopes inaccessible, and also carries the risk of eliciting unwanted antibodies against the oligomerisation domain.

immunology↗

bioRxiv2021

Novel Hendra virus variant detected by sentinel surveillance of Australian horses.

A novel Hendra virus (HeV) variant, not detected by routine testing, was identified and isolated from a Queensland horse that suffered acute, fatal disease consistent with HeV infection. Whole genome sequencing and phylogenetic analysis demonstrated the variant to have ~83% nucleotide identity to the prototype HeV strain. An updated RT-qPCR assay was designed for routine HeV surveillance. In silico and in vitro comparison of the receptor-binding protein with prototypic HeV showed that the human monoclonal antibody m102.4 used for post-exposure prophylaxis, as well as the current equine vaccine, should be effective against this variant. Genetic similarity of this virus to sequences detected from grey-headed flying-foxes suggests the variant circulates at-least in this species. Studies determining infection kinetics, pathogenicity, reservoir-species associations, viral-host co-evolution and spillover dynamics for this virus are urgently needed. Surveillance and biosecurity practices should be updated to appreciate HeV spillover risk across all regions frequented by flying foxes.

molecular biology↗

bioRxiv2021

Live virus neutralisation of the 501Y.V1 and 501Y.V2 SARS-CoV-2 variants following INO-4800 vaccination of ferrets

The ongoing COVID-19 pandemic has resulted in significant global morbidity and mortality on a scale similar to the influenza pandemic of 1918. Over the course of the last few months, a number of SARS-CoV-2 variants have been identified against which vaccine-induced immune responses may be less effective. These "variants-of-concern" have garnered significant attention in the media, with discussion around their impact on the future of the pandemic and the ability of leading COVID-19 vaccines to protect against them effectively. To address concerns about emerging SARS-CoV-2 variants affecting vaccine-induced immunity, we investigated the neutralisation of representative G614, 501Y.V1 and 501Y.V2 virus isolates using sera from ferrets that had received prime-boost doses of the DNA vaccine, INO-4800. Neutralisation titres against G614 and 501Y.V1 were comparable, but titres against the 501Y.V2 variant were approximately 4-fold lower, similar to results reported with other nucleic acid vaccines and supported by in silico biomolecular modelling. The results confirm that the vaccine-induced neutralising antibodies generated by INO-4800 remain effective against current variants-of-concern, albeit with lower neutralisation titres against 501Y.V2 similar to other leading nucleic acid-based vaccines.

immunology↗

bioRxiv2020

Bats Possess Unique Variants of the Antiviral Restriction Factor Tetherin

Bats are recognised as important reservoirs of viruses deadly to other mammals, including humans. These infections are typically non-pathogenic in bats raising questions about host response differences that might exist between bats and other mammals. Tetherin is a restriction factor which inhibits the release of a diverse range of viruses from host cells, including retroviruses, coronaviruses, filoviruses, and paramyxoviruses, some of which are deadly to humans and transmitted by bats. Here we characterise the tetherin genes from 27 species of bats, revealing that they have evolved under strong selective pressure, and that fruit bats and vesper bats express unique structural variants of the tetherin protein. Tetherin was widely and variably expressed across fruit bat tissue-types and upregulated in spleen tissue when stimulated with Toll-like receptor agonists. The expression of two computationally predicted splice isoforms of fruit bat tetherin was verified. We identified an additional third unique splice isoform which includes a C-terminal region that is not homologous to known mammalian tetherin variants but was functionally capable of restricting the release of filoviral virus-like particles. We also report that vesper bats possess and express at least five tetherin genes, including structural variants, a greater number than any other mammal reported to date. These findings support the hypothesis of differential antiviral gene evolution in bats relative to other mammals.

evolutionary biology↗

bioRxiv2019

Filoviruses Can Efficiently Infect Human Neuron-Like Cells Without Genetic Adaptation

Recent large-scale Ebola outbreaks, combined with improved follow-up of survivors, has permitted the observation of common long-term neurological sequelae in patients that have survived Ebola virus infection. To date there have been few studies into neurological infections by Ebola or related filoviruses, however, recent studies have isolated infectious virus from patients cerebrospinal fluid months after being discharged from the treatment facility. In order to determine whether different filoviruses were capable of infecting human neurons, the human neuroblastoma cell lines, SH-SY5Y and M17, were chemically-differentiated into more neuron-like cells using established protocols. The neuron-like profiles of the differentiated cells were confirmed by the determination of expression of a range of neuron-specific markers. Zaire ebolavirus, Reston ebolavirus, and Marburg virus were serially-passaged in both cell lines to determine permissiveness of the cells, as well as permit the acquisition of adaptive mutations in the viral genomes. Whilst Marburg virus grew to high titres in both cell lines, Zaire ebolavirus only grew in SH-SY5Y cells, and Reston ebolavirus rapidly died out in both cell lines. Whole-genome sequencing of the passaged viruses revealed two consensus-level non-coding mutations in the SH-SY5Y-passaged Marburg virus. Viral growth kinetics were determined for pre- and post-passaging Zaire ebolavirus and Marburg virus in both human neuronal cell lines, as well as the human hepatocyte cell line, Huh7. Growth kinetics were similar for both the pre- and post-passaged viruses, suggesting that adaptive mutations were not required for efficient growth in these cells. This study is the first to demonstrate that filoviruses are capable of infecting human neuron-like cells in a species-specific manner. Marburg virus-infected cells remained alive up to Day 21 post-infection, suggesting that long-term neurological sequelae following filovirus infection may be a result of direct neuronal infection, and that infection of neurons might contribute to viral persistence in survivors. Author SummaryFiloviruses, including Ebola and Marburg viruses, have been traditionally considered "haemorrhagic fever" viruses, with infections causing bleeding and frequently death. Recent large-scale outbreaks in Africa have challenged these assumptions due to a significant number of patients reporting neurological symptoms sometimes months after infection. In many of these patients, virus was present at detectable levels in the fluid surrounding the brain. There has been significant debate about the ability of Ebola and Marburg viruses to infect and grow in human neurons (brain cells), and evidence has been lacking due to the lack of feasibility in taking brain samples. Our study demonstrates that both Zaire ebolavirus and Marburg virus are capable of infecting cells derived from human brains without needing to change, and without killing the cells. Reston ebolavirus, a related virus that appears not to cause disease in humans, was not able to grow efficiently in these cells. Our findings show that these viruses might be capable of living in the brains of survivors for long periods of time, similar to previous observations in the eye and testes. In addition, the response of the body to these infected cells might account for the neurological symptoms described by patients.

microbiology↗

bioRxiv2018

RNASeq analysis of Aedes albopictus mosquitoes during chikungunya virus infection

Chikungunya virus (CHIKV), preferentially transmitted by Aedes mosquitoes, is an emerging pathogen around the world and causes significant morbidity in patients. A single amino acid mutation in the envelope protein of CHIKV has led to shift in vector preference towards Aedes albopictus, an invasive mosquito. Previous studies have shown that after infection, mosquitoes mount an antiviral immune response. However, molecular interactions during the course of infection at different tissues and time-points remain largely uncharacterised. Here we performed whole transcriptome analysis on dissected midguts and head/thorax of CHIKV (Indian Ocean strain) infected Aedes albopictus to identify differentially expressed genes compared with uninfected controls. For this, RNA was extracted at two days post-infection (D2) from pooled midguts and eight days post-infection (D8) from heads and the anterior 1/3rd of the thorax. We identified 25 and 96 differentially expressed genes from the D2 and D8 samples respectively (p-value <0.05). Custom de novo transcriptomes were assembled for the reads that did not align with the reference genome and an additional 225 and 4771 differentially expressed genes from D2 and D8, respectively, were identified. Twenty-two of the identified transcripts, possibly involved in immunity, were validated by qRT-PCR. Interestingly, we also detected changes in viral diversity, as shown by number of mutations in the viral genome, with increase in number of mutations in the midgut compared with mammalian host (Vero cell culture), followed by reduction in the number of mutations in head and thorax at D8, indicating a possible genomic bottleneck. Taken together, these results will help in understanding Aedes Albopictus interactions with CHIKV and can be utilised to reduce the impact of this viral infection.\n\nAuthor SummaryChikungunya virus has caused several outbreaks around the world in the last decade. Once a relatively unknown virus, it now causes seasonal infections in tropical and some temperate regions. This change in epidemiology is attributed to vector switch from Aedes aegypti to Aedes albopictus, an invasive pest leading to spread and causing infections in temperate regions. Although recent research has identified mosquito factors influencing infections, our understanding of interaction between chikungunya virus and its vector is limited. Using whole transcriptome sequencing of chikungunya infected mosquitoes, we identified differentially expressed genes in the midgut and head and thorax, over the course of mosquito infection. We also detected changes in the viral genome during mosquito infection and a possible genetic bottleneck event with reduction in viral variants at the head and thorax region of mosquito in the later stages of infection. These results will lead to improving our understanding of mosquito-virus interactions with Aedes albopictus as a vector and in turn lead to development of novel disease control strategies.

microbiology↗