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Introduction to Cytomegalovirus

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Some kinds of antibodies are frequently seen in the biology world, such as recombinant mouse anti-CMV antibody (DDG9 and CCH2) , a mouse monoclonal antibody that is capable of binding to CMV and recombinant mouse anti-CMV 65 kDa LA antibody (5E250), a mouse monoclonal antibody that is capable of binding to CMV 65 kDa LA.

So, what is CMV?

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Figure 1. Cytomegalovirus

Cytomegalovirus (CMV) is a DNA virus of herpesvirus group which also known as cell inclusion body virus for causing the enlargement of the infected cells which will develop a huge nuclear inclusion body. Cytomegalovirus is widely distributed in animals, which can cause infection in various systems, including genitourinary system, central nervous system and liver diseases, from mild asymptomatic infection to severe defects or death.

 

Biological character

CMV has the typical herpesvirus morphology, and its DNA structure is similar to herpes simplex virus (HSV), but 5% larger than HSV. Human CMV (HCMV) can only infect human and proliferate in human fibrocytes. The virus proliferates slowly in cell culture, and the replication cycle is long. It takes 30-40 days for the first isolation and culture to develop cytopathy. It is characterized by cell enlargement and rounding, nuclear enlargement, and a round of "halo" of large eosinophils around the nucleus.

 

Type

  1. According to the order of its infection, it can be divided into: (1) Primary infection: the host first infects CMV, but lacks any specific antibody to CMV before the infection (infants 6 months ago can have IgG antibody passively obtained from the mother); and (2) Recurrent infection, because the latent virus in the host is reactivated and replicated to proliferate; or to reinfect with different exogenous strains or larger doses of the same virus. CMV infection occurs when CMV invades the host and replicates or lurks in the host.
  2. According to the time when the host acquires the infection, it can be divided into: (1) Congenital infection: it refers to the child born by the mother with CMV infection, and it is confirmed that CMV infection is caused by intrauterine infection within 14 days (including 14 days) after birth;(2) Perinatal infection: for the children of CMV infected mothers, no CMV infection was found within 14 days of birth, and those confirmed to be infected within 3-12 weeks after birth were mainly infected through the birth canal or breast milk. The above two types are primary infection. (3) Postnatal infection or acquired infection: it refers to the infection confirmed after 12 weeks of birth (no evidence of CMV infection within 12 weeks of birth), which can be primary infection or reinfection.
  3. According to the presence or absence of symptoms, it can be divided into: (1) Symptomatic infection: It refers to the presence of symptoms and signs related to CMV infection. In symptomatic infection, there are virus activities in children's bodies, which are in the stage of virus producing infection.(2) Asymptomatic infection: there are two conditions of virus replicationin vivo: if it is enough to cause target organ or tissue damage, and the clinical manifestations have signs and organ function changes, it is called subclinical infection; if it does not cause target organ damage, there is no corresponding sign and function change, it is asymptomatic Epizootic infection.

 

Seeding way

CMV infection is very widespread in the population, and the infection is usually occult, which causes no clinical symptoms on the infected people, but under certain conditions, it can invade multiple organs and systems leading to serious diseases. The virus can invade lung, liver, kidney, salivary gland, other glands of mammary gland, as well as multinucleated leukocytes and lymphocytes, and can be discharged from saliva, milk sweat blood, urine, semen, and uterine secretion for a long time or intermittently, usually by oral, reproductive, placental, blood transfusion or organ transplantation and other multi-channel transmission.

(1) Congenital infection

CMV infection in pregnant women can invade the fetus through placenta and cause congenital infection, and a few cases show premature delivery, abortion, stillbirth or postnatal death. Jaundice, hepatosplenomegaly, thrombocytopenic purpura and hemolytic anemia may occur in children. Living children often suffer from permanent mental retardation, neuromuscular dyskinesia, deafness and chorioretinitis.

(2) Perinatal infection

When CMV is discharged from the urinary tract and cervix of the parturient, the infants can be infected through the birth canal. Most of them are of subclinical bed infections with mild or no clinical symptoms. Some of them suffer from slight respiratory disorders or liver function damage.

(3) Infection in children and adults

Sucking, kissing, sexual contact, blood transfusion and other infections, usually subclinical, can also lead to heterophilic antibody negative mononucleosis. Due to pregnancy, immunosuppressive therapy, organ transplantation, tumor and other factors, the virus is activated in monocytes and lymphocytes, causing mononucleosis, hepatitis, interstitial pneumonia, retinitis, encephalitis and so on.

(4) Cell transformation and possible carcinogenic effect

The CMV inactivated by UV can be transformed into mouse embryonic fibroblasts. In some tumors, such as cervical cancer, colon cancer, prostate cancer, CMV DNA detection rate is high, and CMV antibody titer is also higher than that of normal people, with virus particles being found in the cell lines established by the above tumors, suggesting that CMV, like herpesvirus, has the potential to cause cancer.

 

Preventive health care

(1) Physical training is necessary. In order to reduce the serious harm of cytomegalovirus to the fetus, we should improve the immune function and disease resistance of the body, especially in women of childbearing age.

(2) Pregnant women or patients with chronic consumptive diseases and low immunity should be protected to keep them away from infection.

(3) Pay attention to environmental health and food hygiene.

(4) Those with positive cytomegalovirus in milk should not be breastfed.

(5) Immune treatment is still under research and exploration. After CMV’s causing intracellular infection, the inactivated vaccine has no significant preventive effect. If CMV infection is found in the early stage of pregnancy and/ or there is CMV antigen in amniotic fluid cells, the pregnancy should be stopped. Live attenuated vaccine can make the vaccinated person produce antibody and activate cell immunity to CMV, reducing the occurrence of symptomatic CMV infection. CMV high titer immunoglobulin can protect symptomatic CMV infection in CMV negative bone marrow transplant recipients, but it cannot prevent reinfection. Wash hands carefully after contacting with urine or saliva to prevent CMV infection.

To prevent CMV infection caused by fresh blood transfusion, the following methods can be used: (1) using frozen blood or washed blood; (2) storing blood for more than 48 hours before transfusion; (3) using irradiated blood; (4) using blood filter to remove giant cells in the blood.


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