cytomegalovirus infection
Introduction
Introduction to cytomegalovirus infection Cytomegalovirus (CMV) infection has been paid more and more attention. Because the infected cells are giant cells, inclusion bodies are visible in the cytoplasm and nucleus, it is also known as cytomegalic inclusion disease (CID). After infection, the virus can be confined to the parotid gland, and some can cause systemic infection. Most CMV infections are subclinical, and those with dominant infections have diverse clinical manifestations, and severe cases can be fatal. Because cytomegalovirus can cause stillbirth, miscarriage, and premature birth through intrauterine infection, it can also lead to congenital malformation. Therefore, the prevention and treatment of this disease affects eugenics and population quality. basic knowledge The proportion of illness: 1.3% Susceptible people: no specific population Mode of infection: non-infectious Complications: retinitis pneumonia
Cause
Cause of cytomegalovirus infection
Effects on thymus and spleen (15%):
In the laboratory of acute CMV-infected newborn guinea pigs, thymus development is inhibited and the number of T cells is reduced. After adult mice are infected with CMV, CMV can be detected in 88% of thymus. The spleen function was affected by CMV infection, the proliferation of spleen lymphocytes stimulated by conA decreased, and the IL-2 produced by spleen cells was significantly decreased.
Effects on immune cells (15%):
The immunosuppression caused by CMV infection is related to the intracellular replication of the virus. CMV can replicate in mononuclear phagocytic cells, T cells, B cells and some unidentified monocytes. Mononuclear phagocytic cells are most susceptible to CMV, lymphoid cells. Cells have important regulatory and effector functions in immune response, and CMV infection can cause various immune functions of lymphocytes to be impaired.
CMV infection mostly manifested as acute mononucleosis, peripheral blood lymphocytes to mitogen, CMV antigen and HSV antigen proliferative response decreased, induced interferon levels decreased, CD4/CD8 ratio decreased from 1.7 ± 0.7 to 0.2 + 0.2, T Cellular activity is reduced. This change can be sustained for a long time. At 10 months after the disease, the proportion of T cell subsets in most patients has not fully recovered.
The immunosuppressive effect of CMV infection is mainly caused by the abnormal function of large mononuclear cells and CD8 cells infected by viruses. Mononuclear phagocytic cells play a pivotal role in anti-CMV immunity, which can not only directly phagocytose, kill viruses, but more importantly It can process, present antigen, secrete cytokines, regulate and expand immune response. When CMV is infected, mononuclear phagocytic function is affected. CMV-infected macrophages cause their phagocytic function to decrease and intracellular oxygen free radicals to decrease. FC receptor, the expression of complement receptor is changed, and its antigen-presenting function is reduced, IL-1 is decreased, and the response to IL-1 and IL-2 is also decreased. Moses and the like are detected by thymocyte proliferation test, IL- 1 decreased activity, decreased IL-1 production can cause imbalance in the proportion of TH / TS cells.
NK cells have an antagonistic effect on the spread of CMV. NK cells actively participate in the whole process of anti-CMV infection, but the presence of high NK activity is not necessarily a protective response, but a proof of active infection. NK cells can not prevent primary disease. The emergence of CMV infection, but once there is infection, NK cells can appear in the early stage of CMV infection, have limited diffusion, and limit the infection. NK cells, CTL cells are important effector cells against CMV, in the early stage of CMV replication, infectivity Before virion production, they can lyse infected cells and cause the virus to spread abortion between cells. In the mouse model, when the virus acts for 3-5 days, the antiviral effect is mediated by NK cells, and NK cell activity can be enhanced by IFN. -21 days, spleen, peripheral blood in the presence of CTL cell killing activity, NK cells, CTL cell activity determines the body's sensitivity to CMV infection and the ease of infection recovery, but CMV infection, NK cells and CTL cells The activity was also seriously affected. In addition, specific cellular immunity prevented the recurrence of CMV infection. Some people detected T cell responses in 20 CMV-infected kidney transplant recipients, and 14 of them were found to have CM. V cytotoxic response, and 6 patients without cytotoxic response have serious clinical consequences, therefore, the presence of specific T cells, has the effect of preventing the recurrence of CMV infection.
Antibodies have a virulence effect (10%) in reducing CMV infection:
After the body is infected with CMV, a variety of antibodies, milk, cervical secretions, and saliva can be detected despite the presence of specific antibodies, including neutralizing antibodies, indicating that antibodies do not prevent the spread of the virus. The passively obtained antibodies of the mother can not block the infection transmitted by intrauterine, birth canal or milk. Studies have shown that before the lethal CMV challenge, 0.2 ml of high-valent anti-CMV globulin is injected into the abdominal cavity or vein of the mouse to completely protect the animal from After death, after a second attack with CMV and other attacks, the animals still survived, indicating that the antibody has a virulence effect of lowering CMV.
After the initial infection, CMV will exist in the host cell indefinitely in a latent state, possibly involving a variety of tissues and organs. The autopsy suggests that the lung, liver, pancreas, salivary gland, central nervous system and intestine may also be viral latent sites, congenital infections. Severity is related to the lack of ability to produce precipitated antibodies and the response of T cells to CMV. In children and adults infected with CMV, activated T lymphocytes with cytotoxic phenotype are present in peripheral blood, if host T cell function Impaired, latent viruses may resurrect and cause a variety of syndromes. Chronic stimulation after tissue transplantation provides conditions for CMV activation and disease-inducing, and some strong immunosuppressive agents against T cells, such as anti-thymocyte globulin, It is related to the high incidence of clinical CMV syndrome. In addition, CMV can be used as a cofactor to functionally activate latent HIV.
Prevention
Cytomegalovirus infection prevention
Cytomegalovirus is very harmful to humans, so we should actively prevent it from happening.
(1) Carry out conscious physical exercise, improve the body's immune function and disease resistance, especially women of childbearing age, to reduce the serious harm of cytomegalovirus to the fetus.
(2) For pregnant women or patients with chronic wasting diseases, patients with low immunity should pay attention to protection and keep them away from the source of infection.
(3) Pay attention to environmental hygiene and food hygiene.
(4) Those who are positive for cytomegalovirus in milk should not breastfeed.
(5) Immunological control is still under research and exploration.
Complication
Cytomegalovirus infection complications Complications, retinitis, pneumonia
Vascular, retinitis, pneumonia, and digestive tract infections occur due to impaired immune function, and most patients have Gram-Pygmy syndrome.
Symptom
Symptoms of cytomegalovirus infection Common symptoms Fatigue, difficulty breathing, lethargy, hepatosplenomegaly
The clinical manifestations vary depending on the route of infection. 20% of those infected with congenital cytomegalovirus have no symptoms at birth, but also have drowsiness, difficulty breathing and convulsions shortly after birth, and die within days or weeks. Other symptoms are conscious dyskinesia, mental retardation, hepatosplenomegaly, deafness and central nervous system symptoms. Most of the perinatal infections have no symptoms, only a few have intermittent fever 3 months after birth, pneumonia and single In cytomegaloosis, cytomegalovirus mononucleosis in adults is more common in children than in children. It is mainly characterized by fever and fatigue. After 1-2 weeks of fever, the absolute value of lymphocytes in the blood increases, and there are abnormal changes in the spleen. Swollen and lymphadenitis, cytomegalovirus mononucleosis caused by blood transfusion, occurs more than 3-4 weeks after transfusion, the symptoms are the same as the general giant cell mononucleosis, occasionally interstitial pneumonia , hepatitis, meningitis, myocarditis, hemolytic anemia and thrombocytopenia, etc., renal transplant patients almost always have cytomegalovirus infection within 2 months after surgery, 50%-60% Symptoms, 40% -50% of patients showed self-limiting non-specific syndrome, AIDS patients almost every cytomegalovirus viral infection, there is extensive damage to internal organs.
Examine
Inspection of cytomegalovirus infection
Laboratory tests for cytomegalovirus infection:
First, the virus is separated
It is best to use saliva, urine, genital secretions, milk and white blood cells to inoculate and separate into human fibroblasts. Cytopathic effect (CPE) appears after 1 or weeks, after fixation and HE staining. Giant cells can be observed, inner inclusion bodies in the nucleus, perinuclear halo and eosinophilic intracytoplasmic inclusions, much like the owl's eye can also be fluorescently stained with monoclonal or polyclonal antibodies. Method check.
Second, serum antibody testing
The most commonly used are complement binding assay (CF), indirect immunofluorescence assay (IIF), immunoenzyme assay (EIA), indirect hemagglutination assay (IHA) and radioimmunoassay (RIA) to detect CMV-IgG and IgM antibodies. A single serum sample has been determined to have a serum specimen immediately when there is a CMV infection, and serum samples can be left at intervals of 2 weeks, 4 weeks, and 8 weeks. Combined with virus isolation, the primary infection can be diagnosed.
Third, DNA probe
It has been widely used to detect CMV, with 32P-labeled probes being the most sensitive, and for some specimens, hybridization methods may be more sensitive than virus isolation.
Fourth, polymerase chain reaction (PCR)
Diagnosis
Diagnosis and identification of cytomegalovirus infection
It can be diagnosed by laboratory examination and does not need to be differentiated from other diseases.
