Expression Levels of the Attachment Protein G differ Between Strains of a Murine Pneumovirus and Determine the Virulence
Pneumonia virus of mice (PVM), the mouse homolog to respiratory syncytial virus (RSV), is increasingly used as surrogate model to study pneumovirus pathogenesis in a more natural pathogen-host relation. Two major strains of PVM, strain 15 and J3666 are currently used in laboratories, with preferences for either one or the other based on the well-documented isolation history of strain 15 or the suggested higher virulence of strain J3666. Using conventional and long read sequencing, we found that the PVM strain J3666 represents two distinct virus populations, which are defined by the sequence and structure of the G and SH genes encoding the putative attachment and small hydrophobic proteins, in addition to further nucleotide polymorphisms. Specifically, a nucleotide polymorphism at position 65 in the G gene results in either an upstream open reading frame (uORF) preceding the main ORF in frame, or an extension of the major G ORF by 18 codons. The impact of the different forms of the J3666-G genes on PVM was examined by generating recombinant PVMs that differed exclusively in the distinctive 5' portion of the respective G gene. This revealed that the population expressing a G protein with an extended main G ORF was more virulent, whereas the presence of an uORF attenuated virulence. The virulence of PVM correlated with increased expression levels of G, whereas attenuation was rather associated with downregulated expression of G due to the presence of an uORF. Thus, modulation of G protein levels may be an important mechanism by which pneumoviruses modulate virulence.
Pneumonia virus of mice (PVM), the mouse homolog to respiratory syncytial virus (RSV), is increasingly used as surrogate model to study pneumovirus pathogenesis in a more natural pathogen-host relation. Two major strains of PVM, strain 15 and J3666 are currently used in laboratories, with preferences for either one or the other based on the well-documented isolation history of strain 15 or the suggested higher virulence of strain J3666. Using conventional and long read sequencing, we found that the PVM strain J3666 represents two distinct virus populations, which are defined by the sequence and structure of the G and SH genes encoding the putative attachment and small hydrophobic proteins, in addition to further nucleotide polymorphisms. Specifically, a nucleotide polymorphism at position 65 in the G gene results in either an upstream open reading frame (uORF) preceding the main ORF in frame, or an extension of the major G ORF by 18 codons. The impact of the different forms of the J3666-G genes on PVM was examined by generating recombinant PVMs that differed exclusively in the distinctive 5' portion of the respective G gene. This revealed that the population expressing a G protein with an extended main G ORF was more virulent, whereas the presence of an uORF attenuated virulence. The virulence of PVM correlated with increased expression levels of G, whereas attenuation was rather associated with downregulated expression of G due to the presence of an uORF. Thus, modulation of G protein levels may be an important mechanism by which pneumoviruses modulate virulence.
Institut de Biologie Moleculaire et Cellulaire