A majority of SARS-CoV-2 recoverees develop only mild-to-moderate symptoms, while some remain completely asymptomatic. Although viruses, including SARS-CoV-2, may evade host immune responses by epigenetic mechanisms including DNA methylation, little is known about whether these modifications are important in defence against and healthy recovery from COVID-19 in the host. To this end, epigenome-wide DNA methylation patterns from COVID-19 convalescents were compared to uninfected controls from before and after the pandemic. Peripheral blood mononuclear cell (PBMC) DNA was extracted from uninfected controls, COVID-19 convalescents, and symptom-free individuals with SARS-CoV-2-specific T cell-responses, as well as from PBMCs stimulated in vitro with SARS-CoV-2. Subsequently, the Illumina MethylationEPIC 850K array was performed, and statistical/bioinformatic analyses comprised differential DNA methylation, pathway over-representation, and module identification analyses. Differential DNA methylation patterns distinguished COVID-19 convalescents from uninfected controls, with similar results in an experimental SARS-CoV-2 infection model. A SARS-CoV-2-induced module was identified in vivo , comprising 66 genes of which six ( TP53, INS, HSPA4, SP1, ESR1, and FAS ) were present in corresponding in vitro analyses. Over-representation analyses revealed involvement in Wnt, muscarinic acetylcholine receptor signalling, and gonadotropin-releasing hormone receptor pathways. Furthermore, numerous differentially methylated and network genes from both settings interacted with the SARS-CoV-2 interactome. Altered DNA methylation patterns of COVID-19 convalescents suggest recovery from mild-to-moderate SARS-CoV-2 infection leaves longstanding epigenetic traces. Both in vitro and in vivo exposure caused epigenetic modulation of pathways thataffect odour perception. Future studies should determine whether this reflects host-induced protective antiviral defense or targeted viral hijacking to evade host defence.

Post-acute COVID-19 syndrome (PACS) has been defined as symptoms persisting after clearance of a COVID-19 infection. We have previously demonstrated that alterations in DNA methylation (DNAm) status persist in individuals who recovered from a COVID-19 infection, but it is currently unknown if PACS is associated with epigenetic changes. We compared DNAm patterns in patients with PACS with those in controls and in healthy COVID-19 convalescents and found a unique DNAm signature in PACS patients. This signature unravelled modified pathways that regulate angiotensin II and muscarinic receptor signalling and protein–protein interaction networks that have bearings on vesicle formation and mitochondrial function.

Tuberculosis (TB), caused by Mycobacterium tuberculosis, spreads via aerosols and the first encounter with the immune system is with the pulmonary-resident immune cells. The role of epigenetic regulations in the immune cells is emerging and we have previously shown that macrophages capacity to kill M. tuberculosis is reflected in the DNA methylome. The aim of this study was to investigate epigenetic modifications in alveolar macrophages and T cells in a cohort of medical students with an increased risk of TB exposure, longitudinally. DNA methylome analysis revealed that a unique DNA methylation profile was present in healthy subjects who later developed latent TB during the study. The profile was reflected in a different overall DNA methylation distribution as well as a distinct set of differentially methylated genes (DMGs). The DMGs were over-represented in pathways related to metabolic reprogramming of macrophages and T cell migration and IFN-γ production, pathways previously reported important in TB control. In conclusion, we identified a unique DNA methylation signature in individuals, with no peripheral immune response to M. tuberculosis antigen who later developed latent TB. Together the study suggests that the DNA methylation status of pulmonary immune cells can reveal who will develop latent TB infection.

Host innate immune cells, including alveolar macrophages, have been identified as key players in the early eradication of Mycobacterium tuberculosis and in the maintenance of an anti-mycobacterial immune memory, which is believed to be induced through epigenetic changes. The aim of the study was to elucidate whether exposure to M. tuberculosis induced a different DNA methylation pattern of alveolar macrophages and pulmonary T lymphocytes. Alveolar macrophages and T lymphocytes were isolated from induced sputum obtained from individuals living in Lima, which is an area high endemic for tuberculosis. To determine the latent tuberculosis infection status of the subjects, an interferon-γ release assay was performed. We evaluated the DNA methylomes of the alveolar macrophages and T lymphocytes using the Illumina Infinium Human Methylation 450K Bead Chip array, revealing a distinct DNA methylation pattern in alveolar macrophages allowing the discrimination of asymptomatic individuals with latent tuberculosis infection from non-infected individuals. Pathway analysis revealed that cell signalling of inflammation and chemokines in alveolar macrophages play a role in latent tuberculosis infection. In conclusion, we demonstrated that DNA methylation in alveolar macrophages can be used to determine the tuberculosis infection status of individuals in a high endemic setting.

Tuberculosis (TB), caused by Mycobacterium tuberculosis, spreads via aerosols and the first encounter with the immune system is with the pulmonary resident immune cells. The role of epigenetic regulations through DNA methylation in the immune cells is emerging. We have previously shown that capacity to kill M. tuberculosis is reflected in the DNA methylome. The aim of this study was to investigate epigenetic modifications in the pulmonary immune cells in a cohort of medical students with a previously documented increased risk of TB exposure, longitudinally. Sputum samples containing alveolar macrophages (AMs) and T cells were collected before and after study subjects worked in hospital departments with a high-risk of TB exposure. DNA methylome analysis revealed that a unique DNA methylation profile was present already at inclusion in subjects who developed latent TB during the study. The profile was both reflected in different overall DNA methylation distribution as well as more profound alterations in the methylation status of a unique set of CpG-sites. Over-representation analysis of the DMGs showed enrichment in pathways related to metabolic reprograming of macrophages and T cell migration and IFN-γ production. In conclusion, we identified a unique DNA methylation signature in individuals, while still IGRA-negative and who later developed latent TB. Epigenetic regulation was found in pathways that have previously been reported to be important in TB. Together the study suggests that DNA methylation status of pulmonary immune cells can predict IGRA conversion.