Peter Balfe

The immune mechanisms responsible for protection and pathogenesis in pneumoviral infection are not well defined. We demonstrated that pharmacological activation of the hypoxic inducible factor (HIF) signaling axis using daprodustat limited viral replication through enhanced immune signaling. Transcriptomic analysis revealed HIF augmented activation of innate immune response genes, including interferon-stimulated gene 15 ( Isg15 ), in the lung and spleen of mice infected with pneumonia virus of mice (PVM). In human respiratory syncytial virus (hRSV)-infected airway epithelial cells, daprodustat inhibited viral replication and enhanced ISG15 expression in a HIF-dependent manner. Importantly, inhibition of type I interferon signaling or the RIG-I sensing pathway abrogated the antiviral activity of HIF. Moreover, daprodustat increased interferon signaling in response to viral RNA, suggesting that HIF inhibits pneumovirus replication through enhancing viral RNA sensing. Mechanistically, daprodustat reduced N ⁶ -methyladenosine modification of viral RNA through upregulation of RNA demethylases, promoting detection by innate immune sensors. This study highlights the intricate interplay between hypoxia and antiviral immunity and offers valuable insights into pneumovirus–host interactions and potential therapeutic interventions.

Hepatitis B virus (HBV) is a small DNA virus that establishes chronic infection and drives progressive liver disease and cancer; presenting a global health problem with more than 250 million infections. HBV replicates via an episomal covalently-closed-circular DNA (cccDNA) and integrated viral DNA fragments are linked to carcinogenesis. Current treatments only suppress HBV replication and there is a global initiative to develop genome targeting therapies, including siRNAs, antisense oligonucleotides and epigenetic modifiers specific for HBV cccDNA. However, our knowledge of the cccDNA and integrant transcriptomes is confounded by overlapping viral RNAs. Using targeted long-read sequencing we mapped the HBV transcriptome in liver biopsies from eleven treatment naïve patients. Probe enrichment yielded robust sequencing libraries and identified cccDNA-derived genomic and sub-genomic transcripts, and a repertoire of previously uncharacterised spliced, truncated and chimeric viral RNAs. Assigning viral transcripts to their respective DNA templates revealed differential promoter activity in cccDNA and integrants, with implications for the efficacy of epigenetic modifiers. Integrant-derived transcripts showed vast diversity in the viral-host junctions, posing a challenge for current nucleotide-targeting therapies. cccDNA was a source of genetic polymorphism, with distinct viral lineages present in the surface antigen encoding region, providing an insight into hepadnavirus evolution during chronic infection.

Respiratory syncytial virus (RSV) is a global healthcare problem, causing respiratory illness in young children and elderly individuals. However, our knowledge of the host pathways that define susceptibility to RSV infection and disease severity is limited. Hypoxia inducible factors (HIFs) define cellular metabolic processes in response to low oxygen and are recognised to play a key role in regulating inflammatory responses in the lower respiratory tract. We demonstrate a role for hypoxia inducible factors (HIFs) to suppress RSV entry and RNA replication. We show that hypoxia and HIF prolyl-hydroxylase inhibitors significantly reduce expression of the RSV entry receptor nucleolin and inhibit viral driven cell-cell fusion. We identify a HIF regulated microRNA, miR-494, that regulates nucleolin expression. In RSV-infected mice, treatment with the clinically approved HIF prolyl-hydroxylase inhibitor, Daprodustat, reduced the level of infectious virus and infiltrating monocytes and neutrophils in the lung. This study highlights a role for HIF-signalling to limit multiple aspects of RSV infection and associated inflammation and informs future therapeutic approaches for treating this respiratory pathogen.

Hepatitis B virus (HBV) is one of the smallest human DNA viruses and its 3.2 Kb genome encodes multiple overlapping open reading frames, making its viral transcriptome challenging to dissect. Previous studies have combined quantitative PCR and Next Generation Sequencing to identify viral transcripts and splice junctions, however the fragmentation and selective amplification used in short read sequencing precludes the resolution of full length RNAs. Our study coupled an oligonucleotide enrichment protocol with state-of-the-art long read sequencing (PacBio) to identify the repertoire of HBV RNAs. This methodology provides sequencing libraries where up to 25 % of reads are of viral origin and enable the identification of canonical (unspliced), non-canonical (spliced) and chimeric viral-human transcripts. Sequencing RNA isolated from de novo HBV infected cells or those transfected with 1.3 × overlength HBV genomes allowed us to assess the viral transcriptome and to annotate 5′ truncations and polyadenylation profiles. The two HBV model systems showed an excellent agreement in the pattern of major viral RNAs, however differences were noted in the abundance of spliced transcripts. Viral-host chimeric transcripts were identified and more commonly found in the transfected cells. Enrichment capture and PacBio sequencing allows the assignment of canonical and non-canonical HBV RNAs using an open-source analysis pipeline that enables the accurate mapping of the HBV transcriptome.

Human immunodeficiency virus 1 (HIV-1) is a life-threatening pathogen that still lacks curative therapies or vaccines. Circadian rhythms are endogenous daily oscillations that coordinate an organism’s response to its environment and invading pathogens. Recent reports of diurnal variation in peripheral viral load in HIV-1 infected subjects highlights the need for mechanistic studies. Here, we demonstrate rhythmic HIV-1 replication in circadian-synchronised model systems and show the circadian transcription factors, BMAL1 and REV-ERB, bind conserved motifs in the HIV-1 promoter. REV-ERB competes with ROR for binding to the same regulatory motif, and we uncover a role for ROR inhibitors to perturb rhythmic HIV-1 replication and host gene expression. We demonstrate that many HIV-1 host factors are circadian regulated and likely to define rhythmic viral replication. In summary, this study increases our understanding of the mechanisms underlying the circadian regulation of HIV that can inform HIV therapy and management.

Circadian rhythms influence and coordinate an organism’s response to its environment and to invading pathogens. We studied the diurnal variation in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA in nasal/throat swabs collected in late 2020 to spring 2021 in a population immunologically naïve to SARS-CoV-2 and prior to widespread vaccination. SARS-CoV-2 diagnostic PCR data from 1698 participants showed a significantly higher viral load in samples obtained in the afternoon, in males, and in hospitalised patients when linear mixed modelling was applied. This study illustrates the importance of recording sample collection times when measuring viral replication parameters in clinical and research studies.

Chronic hepatitis B virus (HBV) infection is a global health problem that presents as a spectrum of liver disease, reflecting an interplay between the virus and the host immune system. HBV genomes exist as episomal covalently closed circular DNA (cccDNA) or chromosomal integrants. The relative contribution of these genomes to the viral transcriptome in chronic hepatitis B (CHB) is not well-understood. We developed a qPCR method to estimate the abundance of HBV cccDNA- and integrant-derived viral transcripts and applied this to a cohort of patients diagnosed with CHB in the HBe antigen negative phase of disease. We noted a variable pattern of HBV transcripts from both DNA templates, with preS1/S2 mRNAs predominating and a significant association between increasing age and the expression of integrant-derived mRNAs, but not with inflammatory status. In contrast, cccDNA-derived transcripts were associated with markers of liver inflammation. Analysis of the inflammatory hepatic transcriptome identified 24 genes significantly associated with cccDNA transcriptional activity. Our study uncovers an immune gene signature that associates with HBV cccDNA transcription and increases our understanding of viral persistence.

The COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a global crisis with unprecedented challenges for public health. Vaccinations against SARS-CoV-2 have slowed the incidence of new infections and reduced disease severity. As the time-of-day of vaccination has been reported to influence host immune responses to multiple pathogens, we quantified the influence of SARS-CoV-2 vaccination time, vaccine type, age, sex, and days post-vaccination on anti-Spike antibody responses in healthcare workers. The magnitude of the anti-Spike antibody response associated with the time-of-day of vaccination, vaccine type, participant age, sex, and days post vaccination. These results may be relevant for optimizing SARS-CoV-2 vaccine efficacy.