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PubMed2025

DHX15 inhibits mouse APOBEC3 deamination.

APOBEC3 family proteins are critical host factors that counteract and prevent the replication of retroviruses and other viruses through cytidine deamination. Human APOBEC3 proteins inactivate HIV-1 through the introduction of lethal mutations to viral genomes. In contrast, mouse APOBEC3 does not induce DNA hypermutation of murine retroviruses, although it retains functional cytidine deaminase activity. Why mouse APOBEC3 does not effectively deaminate murine retroviruses is still unknown. In this study, we found that the dead box helicase DHX15 interacts with mouse APOBEC3 and inhibits its deamination activity. DHX15 was packaged into murine leukemia virus (MLV) virions independent of its binding with APOBEC3. Moreover, DHX15 knockdown inhibited MLV replication and resulted in more G-to-A mutations in proviral DNA. Finally, DHX15 knockdown induced DNA damage in murine cells, suggesting that it plays a role in preserving genome integrity in cells expressing mouse APOBEC3 protein.

Animals↗

PubMed2025

Defining the genome-wide mutagenic impact of APOBEC3 enzymes.

Somatic mutations drive cancer initiation and tumor evolution. Therefore, the etiology of mutagenesis in cancer is important to preventative and treatment strategies. Somatic mutagenesis in cancer is a multifactorial process and includes both endogenous and exogenous sources of mutations. One recently recognized source of mutagenesis in cancer is the innate immune APOBEC3 family of enzymes, which catalyze cytosine deamination to restrict viral infection but can aberrantly act on the cellular genome, resulting in mutations. Single base substitution (SBS) signatures, or mutational patterns, identified in cancer genomes have demonstrated widespread mutagenesis caused by APOBEC3 enzymes throughout human tumors. To comprehensively define the consequences of APOBEC3 mutagenesis, we developed an experimental pipeline for prospective analysis of genome-wide mutations caused by APOBEC3 activity. This pipeline can be adapted to analyze additional sources of mutagenesis across a spectrum of cells.

Humans↗

PubMed2025

Quantifying the mutational landscape of retroviral and lentiviral vectors in gene therapy patients.

Adenosine deaminase severe combined immunodeficiency (ADA-SCID) is a monogenic disorder caused by mutations in the ADA gene. Gene therapy using γ-retroviral and lentiviral vector gene addition approaches have shown curative results. We sequenced the ADA transgene in transduced CD3+ T cells, and in peripheral blood cells from patients treated with autologous CD34+ cells transduced with either a γ-retroviral or lentiviral ADA gene vector to assess transgene mutational profiles. In both CD3+ T cells and ADA-SCID patients' cells treated with the lentiviral vector, we observed significantly higher occurrences of guanine (G)-to-adenosine (A) base substitutions than with the γ-retroviral vector. We hypothesized that this G-to-A mutational signature was due to the APOBEC3 cytosine deaminase protein family. By knocking out APOBEC3 genes in HEK239T packaging cells, APOBEC3-mediated mutagenesis decreased by 91.2% along the transgene in CD34+ transduced cells in comparison to CD34+ cells transduced with lentiviral supernatant packaged in parental HEK293T cells.

Humans↗

PubMed2026

Genomic Epidemiology and Clinical Characteristics of Mpox Lineage C.1 Outbreak in Thailand, 2023-2024.

Since 2022, human monkeypox virus (hMPXV) has emerged in non-endemic regions, including Thailand. However, the genomic dynamics and clinical correlates of local transmission remain incompletely defined. Whole-genome sequencing was performed on hMPXV from 16 patients in Thailand (2023-2024) using targeted amplicon NGS. Phylogenetic analyses integrated global reference sequences. Mutational profiles, specifically non-synonymous substitutions and APOBEC3-associated signatures, were analyzed in relation to clinical data. Phylogenetic reconstruction identified three temporal phases. Early 2022 cases (clade IIb lineages A and B) were interspersed with global sequences, consistent with multiple introductions. In contrast, 2023-2024 cases were dominated by lineage C.1. All 16 genomes belonged to C.1 (one C.1.1), and formed a distinct mid-2023 cluster, designated C.1/Thai/Cluster, supporting sustained local transmission. APOBEC3-associated mutations were pervasive across the C.1 lineage overall, including within C.1/Thai/Cluster, without evidence of significant enrichment specific to this cluster. The cohort comprised exclusively male patients (81% HIV-positive, MSM), with predominantly genital painful lesions and a median recovery time of 23 days. No significant associations were detected between viral genetic variation and clinical outcomes. Mpox transmission in Thailand evolved from multiple introductions to sustained C.1-dominated local spread, underscoring the importance of continued genomic surveillance.

Humans↗

PubMed2026

Early epidemiologic and genomic insights from Sierra Leone's first mpox cases, 2025.

INTRODUCTION: early characterization of outbreak cases supports rapid decisions. We conducted real-time analysis during the initial outbreak phase in mid-March 2025 of Sierra Leone's first 44 laboratory-confirmed Mpox cases (10th January to 5th March 2025) to generate epidemiologic and genomic intelligence for response. METHODS: we summarized surveillance data and sequenced 18 early cases with Oxford Nanopore. Firth-penalized logistic regression was employed to explore risk factors for severe disease. RESULTS: median age was 27 years (interquartile range 22 to 35); 68.2% were male. Most cases reported no recent international travel (95.5%). All cases presented with rash; fever occurred in 72.7%. Six cases (13.6%) met severe criteria; no deaths occurred (0 of 44; 95% confidence interval 0 to 8.0). Household secondary attack rate was 7.3% during the study window and 8.2% after completion of follow-up. Sequencing identified two co-circulating sub-lineages consistent with A.2.2 and B.1.6 and a strong APOBEC3 pattern (142 of 212 guanine-to-adenine in thymine-cytosine versus 70 of 212 cytosine-to-thymine in guanine-adenine; exact binomial p approximately 8.6x10-7; X2= 24.5, df = 1, p≈ 7.6x10-7). Root-to-tip analysis showed weak temporal signal (R2=0.31; date randomization p= 0.18), so we did not interpret clock estimates. CONCLUSION: real-time analysis during the initial outbreak phase showed community transmission, quantified household spread, documented two sub-lineages with an APOBEC3 signature, and generated severity hypotheses that immediately informed surveillance and vaccine prioritization. Findings require validation in larger cohorts.

Adult↗

PubMed2025

Nanobioreactor detection of space-associated hematopoietic stem and progenitor cell aging.

Human hematopoietic stem and progenitor cell (HSPC) fitness declines following exposure to stressors that reduce survival, dormancy, telomere maintenance, and self-renewal, thereby accelerating aging. While previous National Aeronautics and Space Administration (NASA) research revealed immune dysfunction in low-earth orbit (LEO), the impact of spaceflight on human HSPC aging had not been studied. To study HSPC aging, our NASA-supported Integrated Space Stem Cell Orbital Research (ISSCOR) team developed bone marrow niche nanobioreactors with lentiviral bicistronic fluorescent, ubiquitination-based cell-cycle indicator (FUCCI2BL) reporter for real-time HSPC tracking in artificial intelligence (AI)-driven CubeLabs. In month-long International Space Station (ISS) missions (SpX-24, SpX-25, SpX-26, and SpX-27) compared with ground controls, FUCCI2BL reporter, whole-genome and transcriptome sequencing, and cytokine arrays demonstrated cell-cycle, inflammatory cytokine, mitochondrial gene, human repetitive element, and apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like 3 (APOBEC3) deregulation together with clonal hematopoietic mutations. Furthermore, HSPC functionally organized multi-omics aging (HSPC-FOMA) analyses revealed reduced telomere maintenance, adenosine deaminase acting on RNA1 (ADAR1) p150 self-renewal gene expression, and replating capacity indicative of space-associated HSPC aging that may limit long-duration spaceflight.

Humans↗

PubMed2025

Biochemical assays for AID/APOBECs and the identification of AID/APOBEC inhibitors.

Activation-induced cytidine deaminase (AID) and apolipoprotein B-mRNA editing catalytic polypeptide 3 (APOBEC3 or A3) proteins belong to the AID/APOBEC family of cytidine deaminases. While AID mediates somatic hypermutation and class-switch recombination in adaptive immunity, A3s restrict viruses and retroelements by hypermutation. Mis-regulated expression and off-target activity of AID/A3 can cause genome-wide mutations promoting oncogenesis, immune evasion, and therapeutic resistance due to tumor and viral evolution. In these contexts, inhibition of AID/A3 represents a promising therapeutic approach. Competitive inhibition could be achieved with different strategies: one class would be small molecules that bind in the catalytic pocket (active site) and block access for the substrate cytidine. Another type of larger molecule inhibitor would bind the enzymes' surface more broadly and compete with the binding of the polynucleotide substrates prior to deamination catalysis. Several biochemical assays developed to assess AID/A3 activity can be employed to screen for potential inhibitors. These include in cellulo and in vitro activity-based as well as binding-based assays. In this chapter, we discuss the key considerations for designing robust enzyme assays and provide an overview of assays that we and others have established or modified for specific applications in AID/A3 enzymology, including measurement of inhibition. We provide detailed protocols for the two most widely used in vitro enzyme assays that directly measure the activities of purified AID/A3s on DNA and/or RNA substrates, namely, the gel-based alkaline cleavage assay and multiple variations of PCR/sequencing-based assays.

Cytidine Deaminase↗

PubMed2025

Genomic epidemiology of clade Ia monkeypox viruses circulating in the Central African Republic in 2022-24: a retrospective cross-sectional study.

BACKGROUND: The spread of monkeypox virus (Orthopoxvirus monkeypox) clade Ib from the Democratic Republic of the Congo to neighbouring countries has raised global concerns, leading to WHO declaring mpox a public health emergency on Aug 14, 2024. We applied genomic epidemiology to investigate the causes of recurrent mpox outbreaks in the Central African Republic. We aimed to determine whether frequent zoonotic spillovers or increased human-to-human transmissions are driving mpox epidemiology. METHODS: We performed a retrospective cross-sectional study of monkeypox virus genomic sequences among PCR-confirmed mpox cases detected in the Central African Republic between Feb 17, 2022, and Sept 17, 2024. We used hybridisation capture coupled to high throughput sequencing to analyse 46 samples from mpox outbreaks that occurred in eight of the 20 prefectures (14 of 35 health districts). Near-complete genomes were used for phylogenomic analyses. FINDINGS: Between Jan 10, 2022, and Sept 15, 2024, 89 mpox cases were confirmed, including 53 cases in the first 9 months of 2024. We generated 41 near-complete genomes from this period, including 33 from 2024. All new and already published monkeypox virus genomes from the Central African Republic belonged to clade Ia. These genomes spanned the phylogenetic diversity of clade Ia viruses, and most likely represented several dozen independent transmission events to humans. The monkeypox virus phylogenetic diversity was geographically structured within the country. Plausibly linked cases often showed indistinguishable genomes. Conversely, we detected identical genomes in cases that epidemiological information would suggest were independent outbreaks. Finally, we found that three distinct viruses caused cases in the capital city of Bangui in July, 2024, with all three detected on the same day (July 24, 2024). We did not detect substantial enrichment of APOBEC3 editing, suggesting limited human-to-human transmission. INTERPRETATION: The data indicate that mpox epidemiology in the Central African Republic is primarily driven by short-lived outbreaks resulting from many independent zoonotic spillover events, particularly in rural areas. Although evidence remains limited, in Bangui additional factors such as movement of people and importation of bushmeat from other regions might be introducing the virus into urban settings. Similar spillover patterns have been observed in the Democratic Republic of the Congo. The poorly understood nature of monkeypox virus reservoirs in both countries is a regional concern, as frequent spillovers increase the risk of outbreaks leading to sustained human transmission. Beyond strengthening surveillance and developing countermeasures, it is important to better understand the reservoirs and focus on reducing transmission opportunities to prevent further outbreaks. FUNDING: Pasteur Institute of Bangui, Africa CDC, AFROSCREEN, WHO, the Helmholtz Institute for One Health, and the Deutsche Forschungsgemeinschaft.

Humans↗

PubMed2026

Clinical, epidemiological, and genomic evidence on mpox in mainland China, 2022-2025: a scoping review.

BACKGROUND: Since 2022, mpox has expanded globally with sustained human-to-human transmission and increasing evidence of MPXV genomic diversification. In mainland China, mpox evidence has accumulated rapidly, but clinical, epidemiological, and genomic findings remain fragmented. METHODS: We conducted a scoping review of PubMed, CNKI, and WanFang databases up to March 2, 2026, and integrated literature-derived evidence with public MPXV sequences from GenBank, GenBase, and GISAID. Literature-derived data were used to map clinical-epidemiological characteristics, study-level genomic evidence, sequencing coverage, and reported lineage distribution. Curated public MPXV sequences were used for phylogenetic reconstruction, amino acid mutation profiling, and APOBEC-like substitution analysis. RESULTS: Fifty-eight studies were included: 32 addressed clinical or epidemiological evidence only, 25 addressed genomic evidence only, and one contributed to both domains. Fourteen hospital-based studies summarized 951 cases, showing that reported cases were concentrated among young adult men, with frequent MSM exposure (798/897, 89.0%; 95% CI 86.7-90.9%) and HIV co-infection (469/951, 49.3%; 95% CI 46.1-52.5%). Public sequence curation identified 231 unique mainland China MPXV sequences, of which 230 were used for phylogenetic and mutation analyses. Literature-based genomic evidence comprised 26 genomic studies, 37 study-level genomic records, and 31 reported-case units, including 414 sequenced cases among 530 reported cases (78.1%; 95% CI 74.4-81.4%). Clade IIb predominated among sequenced cases (412/414, 99.5%; 95% CI 98.3-99.9%), with C.1.1 and C.1 most frequently represented. Within the available dataset, public genomes represented multiple lineages and were unevenly distributed across regions and time. Mutation analysis revealed dispersed amino acid variation and a predominance of G>A and C>T transitions (73.0%). After collapsing recurrent substitutions to unique genomic sites, the proportion of G>A/C>T transitions decreased to 35.8% and further to 17.8% under a strict APOBEC3 motif definition, indicating that the observed mutation spectrum includes both shared lineage-associated substitutions and sequence-context-based APOBEC-like patterns. CONCLUSION: Available evidence indicates multi-lineage MPXV circulation and in mainland China, but interpretation remains constrained by uneven sequencing and lack of individual-level clinical-genomic linkage. Integrated genomic surveillance and standardized data linkage are needed to better characterize MPXV transmission and evolution.

APOBEC‑like substitutions↗