Antibodies to cytomegalovirus class IgM and IgG in blood

IgM antibodies to CMV are normally absent in the blood serum.

Cytomegalovirus infection is a viral disease predominantly affecting young children, characterized by a variety of clinical symptoms and a specific morphological picture with the presence of cytomegalic cells against the background of lymphohistiocytic infiltrates. The causative agent of the infection belongs to the Herpesviridae family (human herpes virus type 5). Features of cytomegalovirus: large DNA genome (nucleocapsid diameter 100-120 nm), the ability to replicate without damaging cells, slow replication, relatively low virulence, and a sharp suppression of cellular immunity. Like other viruses of this family, cytomegalovirus is capable of causing persistent and latent infection and reactivating under conditions of weakened immunity. Cytomegalovirus is widespread. From 0.5% to 2.5% of newborns are infected with it during the period of intrauterine development.

The nature of the fetal damage depends on the timing of cytomegalovirus infection. Infection in early pregnancy leads in some cases to intrauterine fetal death and miscarriages, stillbirths, and the birth of children with malformations (for example, narrowing of the pulmonary trunk and aorta, defects of the interatrial and interventricular septum, myocardial fibroelastosis, microcephaly, pulmonary hypoplasia, esophageal atresia, renal malformations, etc.). Malformations do not form with infection in late pregnancy. However, from the first days after birth, the child develops jaundice, hepatosplenomegaly, and hemorrhagic syndrome. Damage to other organs and systems is also noted: lungs (interstitial pneumonia), central nervous system (hydrocephalus, meningoencephalitis), gastrointestinal tract (enteritis, colitis, polycystic pancreas), kidneys (nephritis).

In case of intranatal and early postnatal infection, clinical signs of the disease are detected in the first 1-2 months after birth.

Cytomegalovirus affects many types of blood cells and can persist in monocytes, macrophages, megakaryocytes, which in some cases leads to thrombocytopenia.

Laboratory diagnostics of cytomegalovirus infection is based on the detection of specific antibodies in the blood serum of infected individuals or viral DNA in biological fluids of the body (e.g. blood, saliva, urine, ejaculate, liver punctures, lymph nodes) using the PCR method, as well as viral antigens in lymphocytes of a peripheral blood smear using the indirect immunofluorescence method (a fast and sensitive method).

Serological diagnostics of cytomegalovirus infection uses many reactions, but those that can detect antibodies of the IgM and IgG classes are truly useful. Recently, the ELISA method has been most widely used.

Antibodies to cytomegalovirus class IgM appear within 1-2 weeks after the onset of the disease and indicate a fresh infection or reactivation of latent and persistent infection. However, it should be borne in mind that in some patients, an increase in the content of IgM antibodies may not occur during the first 4 weeks after the onset of the disease. An increased content of IgM antibodies to cytomegalovirus can persist for 12 months in 24% of patients. The presence of IgM antibodies in pregnant women is an indication for cordocentesis and testing of fetal blood for the presence of IgM antibodies. If IgM antibodies are present, the fetus is considered infected. In congenital cytomegalovirus infection, the titer of IgM antibodies is high, it gradually decreases, and they may be absent in the 2nd year of the child's life. When assessing the results of detecting IgM antibodies, it should be borne in mind that the presence of rheumatoid factor can lead to false-positive test results.

Antibodies to cytomegalovirus class IgG appear 2-4 weeks after infection, and in those who have recovered they persist for up to 10 years. The presence of infection is indicated only by a 4-fold or more increase in the titer of IgG antibodies in the study of paired sera. The frequency of detection of IgG antibodies can reach 100% among various population groups.

The group at greatest risk for cytomegalovirus infection includes individuals with artificial or natural immunosuppression: HIV-infected individuals, recipients of organs, tissues, cells, and cancer patients.

Detection of IgM and IgG antibodies to cytomegalovirus is used to diagnose the acute period of cytomegalovirus infection, including in immunodeficiency states, HIV infection, lymphoproliferative diseases and to determine the period of convalescence of cytomegalovirus infection.

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