Structure of Human Cytomegalo Virus
- Cytomegalovirus (CMV) is a member of the herpes virus family which fall under the beta herpes subfamily.
- CMV is spherical in shape with icosahedral symmetry.
Figure: Structure of Human Cytomegalo Virus, Source: Dr. Marko Reschke, Marburg, Germany
- The icosahedral protein capsid with average diameter 100 nm consists of 162 hollow hexagonal and pentagonal capsomeres with an electron-dense core containing the double stranded DNA genome with 230 kbp nucleotides together forming the nucleocapsid.
- The nucleocapsid is surrounded by an envelope which is lipoprotein in nature.
- Lipid part is derived from the nuclear membrane of the infected host cell.
- Projecting from the trilaminar lipid host-derived envelope are spikes of viral glycoproteins which bind to specific host receptor and mediate virus entry.
- gB is one of the major surface glycoproteins in CMV which influences virus binding to and entry into the cell and cell to cell transmission.
- gH is second relatively abundant glycoprotein which is a target for complement independent neutralizing antibodies.
- In mature virus particles, outside the capsid is an amorphous proteinaceous layer, the tegument, surrounded by a lipid envelope derived from host cell membranes.
- Atleast 25 proteins are located in the tegument layer.
- The tegument consist of enzymes such as VP16 which is responsible for subverting cellular proteins and enzymes to involve in viral nucleic acid replication and VHS (Virion Host Shut off ) protein which shut off the host cell protein synthesis in the cytoplasm.
Genome of Human Cytomegalo Virus
- The CMV genome consists of approximately 230kb of linear double stranded DNA.
- The genome is monopartite and contains terminal and internal reiterated sequences.
Figure: Genome of Human Cytomegalo Virus, Source: https://doi.org/10.3390/v4112448
- The genome is split into a unique long (UL) and a unique short (US) region, both flanked by inverted sequences.
- It contains approximately 150 open reading frames (ORFs) that encode proteins.
- Out of these, it has been found that 41 are essential and 117 are nonessential for CMV replication.