Anti-CMV IgG and IgG avidity ELISA Kit

Human cytomegalovirus (HCMV) is a human infectious disease caused by cytomegalovirus infection. Research shows that human cytomegalovirus infection is relatively widespread, and primary infection often occurs in infants and young children. Once infected, it will last for life. HCMV is a weak pathogenic factor. It has no obvious pathogenicity in people with normal immune function and most of the infections are asymptomatic. However, it can cause disease in people with pathological and physiological immunodeficiency, such as fetuses and newborns with developmental immunodeficiency. It can also cause serious illness in HIV or organ transplant patients, manifested as damage to multiple organs. The digestive system is most commonly affected, followed by the nervous system, urinary system, blood system, respiratory system, etc. Human cytomegalovirus belongs to the subfamily Herpesvirinae and is officially known as human herpesvirus type 5 (HHA-5). The virus particles are difficult to distinguish under an electron microscope. The diameter of the particles is 150-200 nm. The capsid has 20-sided cubic symmetry with 162 particles. The virus has a molecular weight of 100×10⁶-150×10⁶ and is a double-stranded linear DNA virus with a genome length of 240 Kb and a high degree of species specificity. Viruses produce typical giant cell inclusions as they replicate within infected cells.

Figure 1. Overview of human cytomegalovirus entry into target cells and the establishment of latency in non-permissive myeloid cells.(Sources: Griffiths P, et al. 2021)

Depending on the time of infection, HCMV infection in infants and young children is classified as congenital, perinatal or postnatal infection. Congenital infection refers to infants born to CMV-infected mothers who are confirmed to have CMV infection within 14 days of birth; perinatal infection refers to infants born to CMV-infected mothers who are not confirmed to have CMV infection within 14 days of birth but are confirmed to have CMV infection within 3 to 12 weeks of birth; postnatal infection or acquired infection refers to CMV infection detected after 12 weeks of age. The rate of congenital CMV infection is 0.2%~2.0% worldwide. Infected newborns are transmitted from mother to newborn through three routes: placenta, birth canal and breast milk. Symptomatic clinical manifestations of infection include jaundice, hepatosplenomegaly, cough, respiratory distress, pneumonia, microcephaly and hydrocephalus. Fetuses infected with cytomegalovirus intrauterine during the first half of pregnancy are more likely to have threatened abortion, stillbirth, microcephaly and intracranial calcifications than uninfected fetuses. The mechanism may be that CMV DNA integrates into the normal genome of the cells of the villous tissue, affecting protein synthesis under the control of the transcription and translation of the normal genome, causing alterations in the synthesis and secretion of steroid hormone proteins (particularly hCG) and causing abortion, whereas fetuses with late infection often present with hepatitis, pneumonia, purpura and severe thrombocytopenia or are asymptomatic.

Early and accurate selection of sensitive indicators is crucial for diagnosing HCMV infection. Currently, commonly used diagnostic indicators and methods include serological testing and pathogen testing. 1. Serological testing; ELISA method is used to detect CMV-specific antibodies IgM and IgG in serum. CMV infection can stimulate the human body to produce specific IgM, IgG, IgA and IgE. The presence of CMV in the body can be indirectly confirmed by detecting CMV-IgM and IgG in serum. A positive result indicates that CMV infection has been acquired. IgM positive indicates recent infection or latent virus may be activated, and IgM positive in newborns indicates intrauterine infection. However, due to the absence of IgM in the initial stage of infection and the small number of antibodies in recurrent infection, IgM is not easy to detect, resulting in a false negative diagnosis. For pregnant women with negative CMV serology, when CMV infection is suspected after pregnancy, virus-specific antibodies should be rechecked. If the antibody changes from negative to positive, it indicates primary CMV infection. In addition, the changes in specific antibody levels before and after suspected CMV infection in pregnant women are also very meaningful for diagnosis. Pregnant women who have not undergone serological testing before pregnancy, if they have CMV-specific IgM and mild or moderate CMV-specific IgG affinity after pregnancy, can increase the detection rate of primary CMV infection in pregnant women. If the above antibodies are positive before 12 to 16 weeks of pregnancy, the possibility of symptoms after CMV infection in newborns is very high. 2. Pathogen detection; Virus isolation: Isolation of CMV from blood, urine, saliva, and tissues is the gold standard for diagnosing CMV infection. Cytomegalovirus inclusion bodies: Typical cytomegalovirus inclusion bodies are seen in the cells of the examined tissues (note that other viral infections are excluded). Antigen detection: For example, pp65, CMV antigens in tissues, cells, and blood are detected using specific monoclonal antibodies. As the main structural protein of viral particles, pp65 is related to viral gene expression, host immune evasion, and cellular metabolism. Its detection is currently considered one of the "gold standards" for diagnosing active cytomegalovirus infection, and its antigen level is positively correlated with the clinical symptoms of HCMV infection. CMV mRNA detection: Detected by molecular hybridization or PCR methods. CMV gene transcription has a time phase and can be divided into immediate early (IE), early (E) and late (L). IE-mRNA can be detected 1 hour after virus infection. Therefore, the detection of CMV IE-mRNA can detect CMV infection earlier than other traditional methods.

HCMV
Human Cytomegalovirus