Biology subjects

Bailey, D.

Publications and source records attributed to Bailey, D..

3 recordsLinked to original sources

bioRxiv2019

Murine norovirus virulence factor 1 (VF1) protein contributes to viral fitness during persistent infection

BackgroundMurine norovirus (MNV) is widely used as a model for studying norovirus biology. While MNV isolates vary in their pathogenesis, infection of immunocompetent mice mostly results in persistent infection. The ability of a virus to establish a persistent infection is dependent on its ability to subvert or avoid the host immune response. Previously, we described the identification and characterization of virulence factor 1 (VF1) in MNV, and established that it acts as an innate immune antagonist. Here, we explore the role of VF1 during persistent MNV infection in an immunocompetent host.\n\nMethodsUsing reverse genetics, we generated VF1-knockout MNV-3 that contained a single or a triple termination codon inserted in the VF1 open reading frame.\n\nResultsVF1-knockout MNV-3 replicated to comparable levels to the wildtype virus in tissue culture. Comparative studies between MNV-3 and an acute MNV-1 strain show that MNV-3 VF1 exerts the same functions as MNV-1 VF1, but with reduced potency. Mice infected with VF1-knockout MNV-3 showed significantly reduced replication kinetics during the acute phase of the infection, but viral loads rapidly reached the levels seen in mice infected with wildtype virus after phenotypic restoration of VF1 expression. Infection with an MNV-3 mutant that had three termination codons inserted into VF1, in which reversion was suppressed, resulted in consistently lower replication throughout a three-month persistent infection in mice, suggesting a role for VF1 in viral fitness in vivo.\n\nConclusionOur results indicate that VF1 expressed by a persistent strain of MNV also functions to antagonise the innate response to infection. We found that VF1 is not essential for viral persistence, but instead contributes to viral fitness in mice. These data fit with the hypothesis that noroviruses utilise multiple mechanisms to avoid and/or control the host response to infection and that VF1 is just one component of this.

microbiology↗

bioRxiv2019

Viral infection enhances vomocytosis of intracellular fungi via Type I interferons

Cryptococcus neoformans is an opportunistic human pathogen, which causes serious disease in immunocompromised hosts. Infection with this pathogen is particularly relevant in HIV+ patients, where it leads to around 200,000 deaths per annum. A key feature of cryptococcal pathogenesis is the ability of the fungus to survive and replicate within the phagosome of macrophages, as well as its ability to escape via a novel non-lytic mechanism known as vomocytosis. We have been exploring whether viral infection affects the interaction between C. neoformans and macrophages. Here we show that viral infection enhances cryptococcal vomocytosis without altering phagocytosis or intracellular proliferation of the fungus. This effect occurs with distinct, unrelated human viral pathogens and is recapitulated when macrophages are stimulated with the anti-viral cytokine interferon alpha (IFN). Importantly, the effect is abrogated when type-I interferon signalling is blocked, thus underscoring the importance of type-I interferons in this phenomenon. Our results highlight the importance of incorporating specific context cues while studying host-pathogen interactions. By doing so, we found that acute viral infection may trigger the release of latent cryptococci from intracellular compartments, with significant consequences for disease progression.\n\nNon-Technical Author SummaryInfectious diseases are typically studied in the laboratory in isolation, but in real life people often encounter multiple infections simultaneously. Here we investigate how the innate immune response to the fatal fungus Cryptococcus neoformans is influenced by viral coinfection. Whilst virally-infected macrophages retain a normal capacity to engulf and kill Cryptococci, they demonstrate a dramatically enhanced propensity to expel them via the process known as non-lytic expulsion or vomocytosis. Activation of vomocytosis is independent of the type of virus encountered, since both HIV and measles (two entirely unrelated viral pathogens) trigger the same effect. Instead it is driven by interferon-, a generic antiviral response, which signals back to the infected macrophage, triggering expulsion of the fungus. We propose that this hitherto unobserved phenomenon represents a reprioritisation pathway for innate immune cells, by which they can alter the frequency with which they expel one pathogen (Cryptococcus) depending on the level of threat from a secondary viral infection.

microbiology↗

bioRxiv2018

Clinical diagnosis of TIA or stroke and prognosis in patients with neurological symptoms: a rapid access clinic cohort

BackgroundThe long-term risk of stroke or MI in patients with minor neurological symptoms who are not clinically diagnosed with transient ischaemic attack (TIA) or minor stroke is uncertain.\n\nMethodsWe used data from a rapid access clinic for patients with suspected TIA or minor stroke and follow-up from four overlapping data sources for a diagnosis of ischaemic or haemorrhagic stroke, myocardial infarction, major haemorrhage and death. We identified patients with and without a clinical diagnosis of TIA or minor stroke. We estimated hazard ratios of stroke, MI and death in early and late time periods.\n\nResults5,997 patients were seen from 2004-2013, who were diagnosed TIA or minor stroke (n=3604, 60%) or with other diagnoses (n=2392, 40%). By 5 years the proportion of patients who had a subsequent ischaemic stroke or MI, in patients with a clinical diagnosis of minor stroke or TIA was 19% [95% confidence interval (CI): 17-20%], and in patients with other diagnoses was 10% (95%CI: 8-15%). Patients with clinical diagnosis of TIA or minor stroke had three times the hazard of stroke or MI compared to patients with other diagnoses (HR 2.83 95%CI:2.13-3.76, adjusted age and sex) by 90 days post-event; however from 90 days to end of follow up, this difference was attenuated (HR 1.52, 95%CI:1.25-1.86). Older patients and those who had a history of vascular disease had a high risk of stroke or MI, whether or not they were diagnosed with minor stroke or TIA.\n\nConclusionsCareful attention to vascular risk factors in patients presenting with transient or minor neurological symptoms not thought to be due to stroke or TIA is justified, particularly those who are older or have a history of vascular disease.

epidemiology↗