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Directed Evolution of Seneca Valley Virus in Tumorsphere and Monolayer Cell Cultures of a Small-Cell Lung Cancer
Shakeel Waqqar1, Kai Lee1, Blair Lawley1
1Department of Microbiology and Immunology, University of Otago, Dunedin 9016, New Zealand.
Abstract:
The Seneca Valley virus (SVV) is an oncolytic virus from the picornavirus family, characterized by a 7.3-kilobase RNA genome encoding for all the structural and functional viral proteins. Directed evolution by serial passaging has been employed for oncolytic virus adaptation to increase the killing efficacy towards certain types of tumors. We propagated the SVV in a small-cell lung cancer model under two culture conditions: conventional cell monolayer and tumorspheres, with the latter resembling more closely the cellular structure of the tumor of origin. We observed an increase of the virus-killing efficacy after ten passages in the tumorspheres. Deep sequencing analyses showed genomic changes in two SVV populations comprising 150 single nucleotides variants and 72 amino acid substitutions. Major differences observed in the tumorsphere-passaged virus population, compared to the cell monolayer, were identified in the conserved structural protein VP2 and in the highly variable P2 region, suggesting that the increase in the ability of the SVV to kill cells over time in the tumorspheres is acquired by capsid conservation and positively selecting mutations to counter the host innate immune responses.
Insights
Seneca Valley virus (SVV) adapted through serial passaging in tumorspheres showed enhanced tumor-killing efficacy. Genomic analysis revealed mutations in structural protein VP2 and the P2 region, suggesting adaptation to overcome host immune responses.
Area of Science:
- Virology
- Oncolytic Virus Therapy
- Cancer Research
Background:
- Seneca Valley virus (SVV), a picornavirus, is explored for oncolytic virotherapy.
- Directed evolution via serial passaging is a strategy to enhance oncolytic virus efficacy.
- Tumorspheres offer a more representative model of tumor microenvironments than cell monolayers.
Purpose of the Study:
- To adapt SVV for increased efficacy against small-cell lung cancer using tumorsphere culture.
- To investigate genomic changes in SVV following adaptation in a tumorsphere model.
- To identify viral adaptations contributing to enhanced oncolytic activity.
Main Methods:
- Propagation of SVV in small-cell lung cancer cells under monolayer and tumorsphere conditions.
- Serial passaging of SVV for ten passages in tumorspheres.
- Deep sequencing analysis of SVV populations to identify genomic variants and amino acid substitutions.
Main Results:
- SVV passaged in tumorspheres demonstrated increased cell-killing efficacy compared to monolayer-passaged SVV.
- Genomic analysis revealed 150 single nucleotide variants and 72 amino acid substitutions in adapted SVV.
- Key genomic differences were observed in the conserved structural protein VP2 and the variable P2 region.
Conclusions:
- SVV adaptation in tumorspheres enhances its oncolytic potential against small-cell lung cancer.
- Mutations in VP2 and P2 regions likely contribute to improved viral fitness and immune evasion.
- Capsid conservation and specific mutations are critical for SVV's enhanced killing ability.
