Paramyxoviruses are enveloped viruses that range in size from 100-300 nanometers in diameter. They have a single-stranded, negative-sense RNA genome and can have spherical, oval, or bullet shapes. Paramyxoviruses attach to and fuse with the host cell membrane, releasing their genetic material. The RNA is then transcribed and the proteins are assembled into new viral particles, which bud from the cell to infect others. Common cell lines used to culture paramyxoviruses include Vero, HEL, and MDCK cells. Cytopathic effects include syncytia formation, cell rounding, death, and foci of infection.

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.

4. 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.

5. 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.

6. 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.

7. 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.

11. 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.