Family - Paramyxoviridae

Abstract

This chapter focuses on Paramyxoviridae family whose member genuses include Rubulavirus, Avulavirus, Respirovirus, Pneumovirus, and Metapneumovirus. The virions of this family consist of a lipid envelope surrounding a nucleocapsid, and the envelope is derived directly from the host cell plasma membrane by budding, and contains two or three transmembrane glycoproteins. The virions contain a single molecule of linear, negative sense, ssRNA that is not infectious alone, but is infectious in the form of the nucleocapsid. Genome lengths for all viruses in the subfamily Paramyxovirinae are multiples of 6, which is a requirement for the efficient replication of the members of the subfamily Paramyxovirinae, but does not apply to the members of the subfamily Pneumovirinae. Some virions may contain positive sense RNA and thus, partial self-annealing of extracted RNA may occur. Members of the subfamily Paramyxovirinae encode 7–10 proteins (5–250 kDa) of which 2–4 (or more) are derived from the 2–3 overlapping ORFs in the P locus. Pneumoviruses encode 9–11 proteins of 4.8–250 kDa, including two proteins encoded by overlapping ORFs in the M2 locus. The virions are composed of 6% carbohydrate by weight which is again dependent on the host cell. Fusion and attachment proteins are glycosylated by N-linked carbohydrate side chains and in the subfamily Pneumovirinae, the attachment protein (G) is heavily glycosylated by O-linked as well as N-linked carbohydrate side chains.