Paramyxovirus - Measles,Mumps and Respiratory Syncytial Virus

Paramyxovirus-Measles,Mumps and RSV

1. Paramyxovirus Dr Sumitha J Associate Professor JBAS College for Women,Teynampet,Chennai-18

2. Morphology Size: Paramyxoviruses are typically 100-300 nanometers in diameter. This is larger than most other viruses, such as the common cold virus (rhinovirus), which is 12-30 nanometers in diameter. Shape: Paramyxoviruses are pleomorphic, meaning they can have a variety of shapes. They can be spherical, oval, or bullet-shaped. Genome structure: Paramyxoviruses have a single-stranded, negative-sense RNA genome. This means that the RNA strand is complementary to the mRNA that is used to make proteins.

3. Replication The virus attaches to the surface of a cell using its hemagglutinin (HA) protein. The virus fuses with the cell membrane and releases its genetic material into the cell. The viral RNA is transcribed into positive-sense RNA by a viral enzyme called RNA-dependent RNA polymerase. The positive-sense RNA is used to make proteins. The proteins are then assembled into new virions. The new virions are released from the cell and can infect other cells.

4. Replication The replication of orthomyxoviruses can be divided into two phases: the transcription phase and the replication phase. Transcription phase: In the transcription phase, the viral RNA is transcribed into DNA by reverse transcriptase. The DNA is then integrated into the host cell genome. Replication phase: In the replication phase, the virus replicates and produces new virions. The new virions are released from the cell and can infect other cells.

5. Replication Measles virus: The measles virus has a unique feature called the fusion-associated protein (F protein). The F protein is responsible for mediating the fusion of the virus with the cell membrane. Mumps virus: The mumps virus has a unique feature called the mumps virus matrix protein (M protein). The M protein is responsible for the assembly of the virus particle. Respiratory syncytial virus (RSV): RSV has a unique feature called the RSV attachment protein (G protein). The G protein is responsible for mediating the attachment of the virus to the cell surface.

6. Cultivation The most commonly used cells are Vero cells, human embryonic lung (HEL) cells, and chick embryo cells. The virus can also be cultivated in animal models, such as chimpanzees, ferrets, and mice. Morbillivirus: Measles virus is the only member of this subfamily. It can be cultivated in cell culture, but it is more difficult to grow than other paramyxoviruses. The most commonly used cells are Vero cells and HEL cells. Pneumovirinae: Respiratory syncytial virus (RSV) is the only member of this subfamily. It can be cultivated in cell culture, but it is also more difficult to grow than other paramyxoviruses. The most commonly used cells are human embryonic lung (HEL) cells and rhesus monkey kidney (RMK) cells. Rubulavirus: Mumps virus is the only member of this subfamily. It can be cultivated in cell culture, but it is not as difficult to grow as measles virus or RSV. The most commonly used cells are Madin-Darby canine kidney (MDCK) cells and rhesus monkey kidney (RMK) cells.

7. CPE Syncytia: Syncytia are large, multinucleated cells that are formed when the virus fuses cells together. This is a common CPE of measles virus, mumps virus, and respiratory syncytial virus (RSV). Cell rounding: Cells infected with paramyxoviruses often become rounded and detached from the culture dish. This is because the virus disrupts the cytoskeleton of the cell. Cell death: Paramyxoviruses can cause cell death, which can be seen as the lysis of cells in the culture dish. Foci of infection: Paramyxoviruses can also cause foci of infection, which are areas of cells that are infected with the virus.