How does the mumps virus replicate?

The mumps virus, a member of the Paramyxoviridae family, exhibits a specific replication process within host cells. Here's how the mumps virus replicates:

Attachment:

1. The mumps virus initially attaches to the surface of susceptible host cells, such as epithelial cells of the respiratory tract or salivary glands. This attachment is mediated by the virus's glycoproteins, particularly the hemagglutinin-neuraminidase (HN) protein.

Entry:

2. Following attachment, the virus enters the host cell through fusion of the viral envelope with the host cell membrane. This process depends on the fusion (F) protein, another glycoprotein on the viral envelope.

Uncoating:

3. Once inside the host cell, the viral envelope fuses with the cell membrane, releasing the viral nucleocapsid, which contains the viral RNA genome. This leads to the uncoating of the virus.

Transcription and Translation:

4. The viral RNA genome, which is single-stranded and non-segmented, serves as a template for transcription. Viral RNA-dependent RNA polymerase, encoded by the viral genome, transcribes the RNA genome into viral messenger RNA (mRNA).

5. The viral mRNA is translated by the host cell's ribosomes to produce viral proteins, including structural proteins (for forming new virus particles) and non-structural proteins (involved in viral replication and evasion of host defenses).

Replication:

6. Replication of the viral RNA genome occurs in the cytoplasm of the host cell. The viral RNA-dependent RNA polymerase synthesizes new copies of the viral RNA genome using the negative-sense RNA as a template.

Assembly:

7. Newly synthesized viral RNA genomes and structural proteins come together to form new viral particles. The matrix (M) protein plays a crucial role in the assembly and budding process.

Budding:

8. The assembled viral particles acquire their envelope as they bud from the host cell membrane. During budding, viral glycoproteins (HN and F proteins) are incorporated into the viral envelope.

Release:

9. The newly formed mumps virions are released from the host cell through budding without causing cell lysis (cell rupture). This allows the virus to spread to neighboring cells and continue the replication cycle.

Throughout the replication process, the mumps virus evades host immune responses and establishes infection. Infected individuals may develop symptoms such as fever, swollen parotid glands (mumps), facial swelling, and complications like meningitis, encephalitis, or orchitis in some cases.