Paramyxoviridae

File:Paramyxovirus genome structure.png

Paramyxovirus genome structure

File:Paramyxoviridae-Schema.png

Paramyxoviridae-Schema

Phylogenetic tree based on the N protein sequences of selected paramyxoviruses.

Paramyxoviridae is a family of viruses in the order Mononegavirales. This family includes several significant human and animal pathogens. Members of this family are characterized by their non-segmented, negative-sense RNA genomes and their ability to cause a range of diseases, from mild respiratory infections to severe systemic illnesses.

Structure

Paramyxoviridae viruses are enveloped and have a helical nucleocapsid. The envelope is derived from the host cell membrane and contains two types of glycoprotein spikes: the hemagglutinin-neuraminidase (HN) or hemagglutinin (H) and the fusion protein (F). These proteins are essential for the virus's ability to attach to and enter host cells.

Genome

The genome of Paramyxoviridae is a single strand of negative-sense RNA, typically ranging from 15,000 to 19,000 nucleotides in length. The genome encodes six to ten proteins, including the nucleocapsid protein (N), the phosphoprotein (P), the matrix protein (M), the fusion protein (F), the hemagglutinin-neuraminidase (HN) or hemagglutinin (H), and the large protein (L), which is the RNA-dependent RNA polymerase.

Replication Cycle

The replication cycle of Paramyxoviridae begins with the attachment of the virus to the host cell via the HN or H protein. The F protein then mediates the fusion of the viral envelope with the host cell membrane, allowing the nucleocapsid to enter the cytoplasm. The RNA genome is transcribed and replicated by the viral RNA polymerase. New viral particles are assembled in the cytoplasm and bud from the host cell, acquiring their envelope from the host cell membrane.

Pathogenesis

Paramyxoviridae includes several important human pathogens, such as the measles virus, the mumps virus, and the respiratory syncytial virus (RSV). These viruses can cause a range of diseases, from mild respiratory infections to severe systemic illnesses. For example, measles can lead to complications such as encephalitis and pneumonia, while RSV is a leading cause of severe respiratory illness in infants and young children.

Classification

The family Paramyxoviridae is divided into two subfamilies: Paramyxovirinae and Pneumovirinae. The Paramyxovirinae subfamily includes genera such as Morbillivirus, Rubulavirus, and Respirovirus. The Pneumovirinae subfamily includes the genus Pneumovirus.

Prevention and Treatment

Vaccination is the most effective method of preventing diseases caused by Paramyxoviridae viruses. For example, the MMR vaccine protects against measles, mumps, and rubella. There are also antiviral drugs available for the treatment of some Paramyxoviridae infections, such as ribavirin for RSV.

Related Pages

• Measles virus
• Mumps virus
• Respiratory syncytial virus
• RNA virus
• Viral replication
• Vaccination