TORCH Profile:- Part 2 – Cytomegalovirus (CMV)
The sample for the TORCH profile
- Venous blood is collected to prepare the serum.
- The other sample used is blood, urine, and spinal fluid for evidence of the infections for TORCH.
- Diagnosis can be confirmed by the culture of one of the specific pathogens or by increased levels of IgM against the specific pathogen.
Purpose of the test (Indications)
- TORCH profile is done to find the cause of premature birth or abortion.
- TORCH is used to screen infants for infections such as toxoplasmosis, cytomegalovirus, herpes simplex, rubella, and syphilis.
TORCH profile facts
- TORCH profile includes the following tests:
- Toxoplasmosis antibody.
- Rubella antibody.
- Herpes Simplex.
- some people include syphilis as well.
- These infections may lead to birth defects, growth delay, and brain and nervous system problems in the baby.
- If TORCH screening on infants is positive, more testing will be needed to confirm the diagnosis. The mother will also need to be checked.
- The test is ordered when a pregnant woman is suspected of having any of the TORCH infections.
- These infections can be serious during pregnancy because they can cross the placenta from the mother to the developing fetus and cause congenital defects in the newborn.
- The TORCH infections cause a syndrome characterized by:
- Sensorineural deafness.
- TORCH infection signs/symptoms are:
- Fever and poor feeding.
- The newborn is often small for gestational age.
- A petechial rash on the skin may be present, with small reddish or purplish spots due to bleeding from capillaries under the skin.
- An enlarged liver and spleen (hepatosplenomegaly) are common, such as jaundice.
- Hearing impairment, eye problems, mental retardation, autism, and death can be caused by TORCH infections.
- The mother often has a mild infection with few or no symptoms.
- The examiner may test blood, urine, and spinal fluid for evidence of the infections for TORCH.
- Diagnosis can be confirmed by the culture of one of the specific pathogens or by increased levels of IgM against the pathogen.
Sample for Cytomegalovirus (CMV)
- Culture is the choice of method.
- Blood of the patient to get the serum.
- Biopsy material.
- White blood cells.
History of Cytomegalovirus (CMV)
- 1904 first histologic changes characteristic of CMV were published.
- In 1966 the actual isolation of the virus following blood transfusion and raised antibody titer was noted.
Definition of Cytomegalovirus (CMV)
- CMV is one of the herpesvirus groups.
- The Herpesvirus group consists of the following:
- Herpes simplex I.
- Herpes simplex II.
- Epstein-Barr virus.
Cytomegalovirus (CMV) structure:
- CMV can survive for variable times in the urine, saliva, blood, breast milk, cervical secretions, and semen.
- All these viruses are relatively large, enveloped DNA viruses.
- These DNA viruses undergo a replicative cycle involving DNA expression and nucleocapsid assembly within the nucleus.
- The viral structure gains an envelope when the virus buds through the nuclear membrane that is altered to contain specific viral proteins.
- All these viruses spread from cell to cell, most likely via intercellular bridges and antibodies in the extracellular phase.
- These viruses produce subclinical infections that can be reactivated under appropriate stimuli.
Epidemiology of Cytomegalovirus (CMV):
- CMV infection is endemic worldwide.
- CMV infection is widespread because serologic evidence is found from 30% to >90% is found in different geographic areas.
- There is a lower incidence in some parts of Western Europe and some parts of the USA.
- CMV is considered the most important cause of congenital infection in the united states of America.
- Acquired CMV infection is usually asymptomatic and can persist in the host as a chronic or latent disease.
- Dissemination of the virus may be:
- By organ transplantation.
- By fresh Blood transfusion.
- CMV needs intimate contact with secretions or excretion of:
- Respiratory system.
- Genital secretion.
- Feces of an infected person.
- The most common is the venereal route through contact with infectious viruses in body secretion.
- The seropositive population is 60% to 80% positive in the western world, while it is much more in developing countries.
- Seropositive cases increase with age and in the lower socioeconomic group.
- The percentage is high for the people employed in the childcare facility.
- After the neonatal period, infection is through contact with saliva or urine.
CMV signs and symptoms:
- The incubation period is 6 to 8 weeks (4 to 12 weeks).
- In this stage can find CMV antigens.
- You can confirm viremia by the culture of the blood.
- Now the virus is shed in secretion for months or years.
- CMV infection is seen in two different age groups:
- Fetal life.
- Early childhood or late adolescence (or young adults).
- There is increased risk in the following groups:
- Transplant patients.
- The majority of the patients with acute CMV infection are asymptomatic.
- The patients who develop symptoms are sick for 2 to 3 weeks.
- (CMV) may have flu-like symptoms that are not easily differentiated from other illnesses.
- This is seen in infants and is contracted in utero.
- CMV causes serious and life-threatening infections in neonates and immunocompromised patients.
- Congenital infection is acquired in utero during passage through the infected birth canal.
- CMV may be isolated from the throat.
- Immunocompromised patients have more severe illnesses.
Cytomegalovirus (CMV) inclusion in the cells:
- The affected cells typically show nuclear and cytoplasmic inclusion.
- In newborns and young children, these inclusions are seen on urine sediments. These are basically renal epithelial cells with inclusions.
- These inclusion are an intermittent phenomenon, so several samples must be needed.
- Staining the fresh urine sample instead of 24 hours urine is advised, where the cells may integrate.
- Biopsies are better than a urine sample.
Immunology of Cytomegalovirus (CMV):
- CMV produces an increase in the absolute number of suppressor cells (CD8+) lymphocytes and a decrease in helper cell (CD4+) lymphocytes.
- This lymphocyte picture persists for months.
- There are atypical lymphocytes in the peripheral blood smear.
- Is there any role of CMV as an oncogenic virus?
- Viral antigens or nucleic acid have been found in human malignancies like adenocarcinoma of the colon, carcinoma of the cervix, Kaposi’s sarcoma, and cancer of the prostate.
- There is substantial direct evidence of CMV for Kaposi’s sarcoma. But a direct cause-and-effect relationship has not been established.
Disease pattern of Cytomegalovirus (CMV):
- The pattern of the CMV disease is as follows:
- Acquired infection. This is usually asymptomatic and can persist as a chronic or latent infection in the host.
- Latent infection. This persistent infection characterized by the period of reactivation is called latent infection.
- Congenital infection.
- CMV infections are asymptomatic. After the infection, the virus may remain latent in the body.
- Subclinical disease may be seen in early infants.
- Disseminated or fulminant disease is seen in infants, and infection is contracted in utero.
- Late acute disseminated disease is seen in patients with leukemia and malignant diseases.
- Liver disease is a chronic slow CMV infection that occurs in children from 6 months to 8 years of age.
- Post-natal infection may lead to hepatitis.
- In short, there are three groups:
- Perinatal disease (Congenital infection).
- In an immunocompetent person with mononucleosis syndrome.
- In immune-compromised patients are at risk of solid organs and bone marrow transplantation.
- Antibody testing on the mother will help the physician diagnose an infection that may harm the unborn baby.
Congenitally infected infants:
- The test may be ordered on the newborn when the infant shows any signs suggestive of Congenital disease infections.
- The congenitally infected babies show:
- The exceptionally small size was relative to the gestational age (low birth weight).
- Mental retardation.
- Heart defects.
- Enlarged liver or spleen (Hepatomegaly and splenomegaly).
- Low platelet level Leads to hemorrhagic pneumonitis and petechiae.
- Jaundice due to hemolytic anemia.
- Cerebral calcification.
Diagnosis of Cytomegalovirus (CMV):
- A complete blood count shows leucocytosis.
- There is relative lymphocytosis.
- There are atypical lymphocytes in the peripheral blood smear.
- In infants, there is thrombocytopenia. It is seen in 10% to 15% of the cases.
- Splenomegaly was seen in 35% of the cases.
- Lymphadenopathy was seen in 15 % of the cases.
- Liver function tests are abnormal.
- The biopsy is useful in diagnosing pneumonitis and gastrointestinal disease due to CMV.
- Biopsy shows typical intranuclear (owl eye) and intracytoplasmic inclusions.
- The virus is isolated from:
- Biopsy material.
- Urine, sputum, or mouth swab are preferred, and fresh samples are taken.
- Freezing of the sample must be avoided, as it will inactivate the virus.
- If you keep the sample in the fridge, the sample may be used for up to one week.
- The urine sample is diluted with an equal volume of alcohol (70% to 90%).
- Urine positive for CMV indicates:
- Acute infection.
- Asymptomatic patient.
- Active disease.
- The urine sample is the best sample for the recovery of CMV.
- There are inclusion bodies in leucocytes of urine sediments.
- Washings, swabs, and biopsies are kept in sorbitol diluent or keep the sample at -70 °C. (another reference says that freezing the sample is not good in the case of CMV. It prefers to refrigerate the sample).
- CMV culture can not differentiate between acute infection, reinfection, or reactivation of the latent virus.
- CMV culture has three exceptions, and it will indicate a congenital infection:
- Positive culture of the blood indicates transient viremia.
- Positive culture of fetal amniotic fluid.
- Positive culture of the newborn or neonates.
- A fourfold increase in the titer indicates acute infection when the samples are taken 1 to 2 weeks apart.
- The antibody to early antigen undergoes a relatively rapid decline after the recovery but can persist for up to 250 days.
- This antibody can detect recent and active infections.
- Antibodies to the early antigen are strongly associated with viral shedding.
- The prevalence of CMV antibodies varies with age and geographical location but ranges from 40% to 100%.
- Detect antibody IgM for acute infection indicate primary infection.
- The positive serological test in infants’ first three weeks indicates congenital infection.
- Positive after the 4th week indicates an infection of postpartum or intrapartum infection.
- IgG indicate convalescent stage.
- The increasing titer of IgG antibody indicates acute infection.
- The most common methods used are:
- Enzyme immunoassay (EIA).
- Indirect immunofluorescence (IIF).
- Complement fixation test.
- Anticomplement immunofluorescence.
- Indirect hemagglutination.
- Serological tests are positive in a population after the age of 30 years, between 40% to 100%.
- Policy for pregnant mothers:
- Test the pregnant mother in the first trimester.
- If positive, then test for viremia every three months.
- Congenital infection can be confirmed by the fetal blood or amniotic fluid for the IgM antibody.
- Amniocentesis is not helpful before 21 weeks of gestation because of inadequate urine released by the fetus.
- PCR may be advised on the newborn blood sample.
- False-positive serological tests are seen in patients with Rh-factor, heterophil antibodies, and varicella.
Treatment of Cytomegalovirus (CMV)
- There is no cure for CMV infection, but antivirals may be tried.
- For congenital CMV, treat with Ganciclovir or Valganciclovir for six months.
- Treatment of other CMV conditions is treated with Ganciclovir with Foscarnet.
- Cidofovir is reserved for resistant cases.
Questions and answers:
Question 1: What is the best sample for the diagnosis of CMV?
Best fresh samples are urine, sputum, and mouth swabs are preferred.
Question 2: What is the significance of the serology for the diagnosis of acute CMV?
Fourfold increase in the titer is indicative of acute CMV infection over a period of 1 to 2 weeks apart.