Mutant identifying a third recombination group in a bunyavirus

Area of Science:

• Virology
• Molecular Biology
• Genetics

Background:

• Bunyaviridae family viruses possess a tripartite genome, suggesting three expected recombination groups.
• Previous genetic analyses of bunyavirus temperature-sensitive (ts) mutants reported only two recombination groups.
• This discrepancy indicated potential gaps in understanding bunyavirus genome structure and reassortment.

Purpose of the Study:

• To investigate the genetic reassortment of bunyaviruses and identify potential new recombination groups.
• To characterize a temperature-sensitive (ts) Maguari virus mutant (MAGts23(III)) and determine its recombination group.
• To analyze the genetic composition and phenotypic properties of resulting recombinants.

Main Methods:

• Genetic crosses were performed between ts mutants of Maguari virus and Bunyamwera virus in both vertebrate (BHK-21) and invertebrate (Aedes albopictus) cells.
• Recombination assays were conducted using MAGts23(III) with mutants from established recombination groups I and II.
• Phenotypic analysis of wild-type recombinants and isolated clones was performed, including protein analysis (G and N proteins).

Main Results:

• A Maguari virus ts mutant, MAGts23(III), was identified and demonstrated recombination with mutants from groups I and II, establishing a third recombination group.
• MAGts23(III) exhibited unique phenotypic characteristics, including growth restriction in BS-C-1 cells.
• Recombination occurred between MAGts23(III) and a group II Bunyamwera virus mutant, yielding recombinants with Maguari G protein and Bunyamwera N protein.

Conclusions:

• The identification of MAGts23(III) as representing a third bunyavirus recombination group provides crucial evidence for the expected tripartite genome structure.
• Recombination analysis, while successful in generating reassortants, presented challenges in gene assignment for group III due to unequal recovery of phenotypes.
• Further genetic studies are needed to fully elucidate the gene assignment for the newly identified third recombination group in bunyaviruses.