Academic Journal
Increased or decreased numbers of CpG dinucleotide motifs in the genome of influenza A virus do not affect in vitro virus phenotype.
| Τίτλος: | Increased or decreased numbers of CpG dinucleotide motifs in the genome of influenza A virus do not affect in vitro virus phenotype. |
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| Συγγραφείς: | Susma B; Department of Viroscience, Erasmus Medical Center, Rotterdam, the Netherlands., Spronken M; Department of Viroscience, Erasmus Medical Center, Rotterdam, the Netherlands., van Nieuwkoop S; Department of Viroscience, Erasmus Medical Center, Rotterdam, the Netherlands., Kalverda B; Department of Viroscience, Erasmus Medical Center, Rotterdam, the Netherlands., Gultyaev AP; Department of Viroscience, Erasmus Medical Center, Rotterdam, the Netherlands., Fouchier RAM; Department of Viroscience, Erasmus Medical Center, Rotterdam, the Netherlands., van den Hoogen BG; Department of Viroscience, Erasmus Medical Center, Rotterdam, the Netherlands. |
| Πηγή: | Journal of virology [J Virol] 2026 Jul 21; Vol. 100 (7), pp. e0004726. Date of Electronic Publication: 2026 Jun 22. |
| Τύπος έκδοσης: | Journal Article |
| Γλώσσα: | English |
| Στοιχεία περιοδικού: | Publisher: American Society For Microbiology Country of Publication: United States NLM ID: 0113724 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1098-5514 (Electronic) Linking ISSN: 0022538X NLM ISO Abbreviation: J Virol Subsets: MEDLINE |
| Imprint Name(s): | Publication: Washington Dc : American Society For Microbiology Original Publication: Baltimore, American Society for Microbiology. |
| Ιατρικοί όροι (MeSH): | Influenza A virus*/genetics , Influenza A virus*/physiology , CpG Islands*/genetics , Genome, Viral*, Virus Replication/genetics ; RNA, Viral/genetics ; Influenza, Human/virology ; Epithelial Cells/virology ; Humans ; Dogs ; Animals ; Madin Darby Canine Kidney Cells ; Mutation ; A549 Cells ; Phenotype ; Immunity, Innate ; RNA Replication ; Dinucleoside Phosphates |
| Περίληψη: | Cytosine-phosphate-guanine (CpG) dinucleotide motifs are the most underrepresented motifs in RNA virus genomes, including those of the influenza A viruses (IAV). Previous studies have indicated that increasing the number of CpG motifs in IAV genomes negatively impacts viral replication. However, outcomes of these studies have been inconsistent, most likely due to variations in experimental designs. Here, the impact of altered numbers of CpG motifs in the IAV genome was investigated by carefully designing mutants with either increased or decreased frequencies of CpG motifs. Importantly, CpG mutations were excluded from regions essential for viral replication, such as predicted RNA secondary structures and alternative open reading frames, and only mutations naturally occurring in viral isolates were introduced. The resulting mutant viruses showed no significant differences in replication efficiency in human respiratory epithelial cells, nor in their ability to activate the innate immune response. Furthermore, after repeated passage in both human respiratory epithelial (A549) and MDCK cells, the introduced mutations remained stable, indicating no selection pressure on CpG motifs in vitro. This is the first study to assess the effects of genome-wide increases and decreases in CpG content in IAV while preserving essential genomic structures. Under these controlled conditions, altering CpG motif frequency did not alter the viral phenotype.IMPORTANCECpG motifs are underrepresented in RNA virus genomes, including those of influenza A virus (IAV). Previous work suggested that increasing CpG content attenuates IAV and could be exploited to design live-attenuated vaccines. However, previous work focused on single IAV genes, did not control for secondary effects, nor included mutants with decreased CpG frequencies. Here, we engineered mutants with decreased or increased CpG frequencies across multiple viral genes. Only naturally occurring mutations were introduced, while regions involved in RNA secondary structures or alternative open reading frames were preserved. Altered CpG frequencies had no significant effect on IAV replication and did not alter innate immune responses. Repeated viral passaging in immune-competent cells revealed the absence of natural selection on CpG motifs. These results demonstrate that altering CpG content does not affect IAV phenotype and challenge the rationale of using CpG enrichment to design live-attenuated IAV vaccines. |
| Competing Interests: | The authors declare no conflict of interest. |
| Grant Information: | 813343 Horizon 2020 Framework Programme |
| Contributed Indexing: | Keywords: CpG motifs; evolutionary pressure; influenza virus |
| Substance Nomenclature: | 2382-65-2 (CpG dinucleotide) 0 (RNA, Viral) 0 (Dinucleoside Phosphates) |
| Entry Date(s): | Date Created: 20260627 Date Completed: 20260721 Latest Revision: 20260726 |
| Update Code: | 20260726 |
| PubMed Central ID: | PMC13386996 |
| DOI: | 10.1128/jvi.00047-26 |
| PMID: | 42363877 |
| Βάση Δεδομένων: | MEDLINE |
| ISSN: | 1098-5514 |
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| DOI: | 10.1128/jvi.00047-26 |