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Simplified Reverse Genetics Method to Recover Recombinant Rotaviruses Expressing Reporter Proteins
Published on: April 17, 2020
VP4 Mutation Boosts Replication of Recombinant Human/Simian Rotavirus in Cell Culture
Roman Valusenko-Mehrkens1, Katja Schilling-Loeffler1, Reimar Johne1
1Department of Biological Safety, German Federal Institute for Risk Assessment, 10589 Berlin, Germany.
Insights
Developing new Rotavirus A vaccines is crucial. A specific mutation in the VP4 protein significantly improved the rescue and replication of reassortant rotaviruses in cell culture, aiding vaccine development.
Area of Science:
- Virology
- Vaccinology
- Molecular Biology
Background:
- Rotavirus A (RVA) is a major cause of severe diarrhea and mortality in children, particularly in Sub-Saharan Africa.
- Current vaccine development aims to target diverse African RVA genotypes.
Purpose of the Study:
- To generate next-generation RVA vaccines against African genotypes using a reverse genetics system.
- To enhance the rescue and replication efficiency of reassortant RVA strains in cell culture.
Main Methods:
- A simian rotavirus reverse genetics system was employed to exchange VP4, VP7, and VP6 genes with those from African human RVA strains.
- Reassortant viruses were rescued, passaged, and analyzed via whole-genome sequencing.
- Site-directed mutagenesis was used to introduce specific VP4 mutations.
Main Results:
- A G9-P[6]-I2 triple-reassortant RVA initially showed poor replication but improved upon passaging.
- Whole-genome sequencing identified a single point mutation (A797G) in VP4 (E263G) responsible for enhanced replication.
- Introducing this mutation into the VP4 plasmid significantly increased the replication of both mono-reassortant and triple-reassortant viruses.
- The beneficial effect of the mutation was strain-specific.
Conclusions:
- Specific point mutations in the VP4 protein can substantially enhance the rescue and replication of recombinant RVA reassortants in cell culture.
- This finding is valuable for developing novel RVA vaccine strains, particularly against prevalent African genotypes.
Abstract:
Rotavirus A (RVA) is the leading cause of diarrhea requiring hospitalization in children and causes over 100,000 annual deaths in Sub-Saharan Africa. In order to generate next-generation vaccines against African RVA genotypes, a reverse genetics system based on a simian rotavirus strain was utilized here to exchange the antigenic capsid proteins VP4, VP7 and VP6 with those of African human rotavirus field strains. One VP4/VP7/VP6 (genotypes G9-P[6]-I2) triple-reassortant was successfully rescued, but it replicated poorly in the first cell culture passages. However, the viral titer was enhanced upon further passaging. Whole genome sequencing of the passaged virus revealed a single point mutation (A797G), resulting in an amino acid exchange (E263G) in VP4. After introducing this mutation into the VP4-encoding plasmid, a VP4 mono-reassortant as well as the VP4/VP7/VP6 triple-reassortant replicated to high titers already in the first cell culture passage. However, the introduction of the same mutation into the VP4 of other human RVA strains did not improve the rescue of those reassortants, indicating strain specificity. The results show that specific point mutations in VP4 can substantially improve the rescue and replication of recombinant RVA reassortants in cell culture, which may be useful for the development of novel vaccine strains.
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