Human Herpes virus-6, PCR-quantitative
Why this test?
For differential diagnosis of children's infections with high temperature and rash.
When diagnosing infectious mononucleosis with a negative Epstein-Barr virus test.
In the complex of examinations of patients with lymphoproliferative diseases and hemoblastoses.
When examining recipients of organs and tissues before and after transplantation.
In the diagnosis of virus-associated diseases in HIV-infected patients and in other immunodeficiency conditions (for example, chronic fatigue syndrome).
When monitoring the effectiveness of antiviral treatment.
In what cases is it prescribed?
To confirm the presence / absence of infection.
In order to determine the course of the infection - active / inactive.
For differential diagnosis of herpes infections.
Human herpes virus type 6 (HCV-6) was first identified relatively recently, in 1986, in the blood of HIV-infected patients. To date, it has been established that HCV-6 infection is widespread and has 2 genetically distinct subtypes - A and B. In general, subtype B is more common, but subtype A is more often detected in patients with immunodeficiencies.
Full replication of the virus occurs only in T-lymphocytes, but HCV-6 can also be detected in other cells - monocytes, B-lymphocytes, as well as in brain tissue, liver, salivary glands, and endothelium.
The most likely way of infection is airborne, with saliva, the transmission of infection from mother to child during pregnancy is not excluded.
There is also a possibility of infection during organ transplantation, hemotransfusions, through medical instruments. Drug addicts and medical workers can become infected by accidental injection with a syringe needle containing the blood of a sick or infected person.
The first time of infection almost always occurs between the ages of 4 and 24 months. In most cases, HCV-6 is asymptomatic, and if it is detected, it is most often a sudden exanthema and a rapidly developing high fever that lasts 3-4 days. A few hours after normalization of the temperature, erythematous spots or a spotted-papular rash appear. The similarity of a sudden exanthema with the symptoms of measles or rubella most often leads to a false diagnosis.
In some cases, there are complications from the central nervous system (convulsions against the background of high temperature, rarely encephalitis, meningoencephalitis, serous meningitis).
Adults are rarely infected with HCV-6, and their infection may be accompanied by symptoms of infectious mononucleosis (Epstein-Barr virus is absent in this case) or fulminant hepatitis.
HCV-6 is capable of causing transplant rejection in recipients. Complications due to HCV-6 activation have been noted in patients after bone marrow, kidney, liver, and lung transplantation. In particular, patients after bone marrow transplantation often suffer from diseases caused by HHV-6 (interstitial pneumonia, bone marrow suppression, meningoencephalitis). Activation of HCV-6 is the cause of 80% of cases of idiopathic leukopenia after liver transplantation. Fortunately, with timely diagnosis, HCV-6 can be treated with drugs.
HIV-infected people are another category of persons with immunodeficiency, in whom the activation of HCV-6 can lead to serious complications (to lesions of the central nervous system, to pneumonia, etc.) and to the progression of the underlying disease. In addition, active HCV-6 can contribute to the transition of HIV from latent to active form, so regular control of HCV-6 activity in HIV-positive patients is important for timely initiation of antiviral therapy.
Today, the possible role of HCV-6 in the development of multiple sclerosis, chronic fatigue syndrome, and lymphoproliferative diseases is being actively investigated.
Since HVCH-6 in its latent form is spread almost everywhere, it is very important to establish the nature of its course in time - active / inactive. The activation of any viral infection begins with the multiplication (replication) of the virus in the host cell. Then, in most cases, the host cells die, and new viruses enter the intercellular space (intracellular fluid) to infect new cells. From there, viral particles enter various biological fluids (blood, urine, cerebrospinal fluid) and iron secretions, where they can be easily detected using PCR. The detection of viral DNA / RNA in cell-free samples of biological fluids or glandular secretions is an unequivocal indication of an active viral infection.
However, the diagnosis of infection is complicated by the fact that HCV-6, after replication in the host cell, infects other cells directly, penetrating through intercellular partitions and avoiding intercellular spaces. Thus, confirmation of HCV-6 activity using PCR in cell-free samples of biological fluids and secretions is not possible in all cases. In this regard, there is a need to confirm the activity / inactivity of HCV-6 using serological methods. Polymerase chain reaction (PCR) is a method of molecular diagnostics that allows detecting the genetic material of the pathogen in the early stages of the disease. It is characterized by high indicators of diagnostic sensitivity and specificity, speed of obtaining the final result and availability. A feature of the method is the ability to detect viral DNA even with a small amount of it in the biological material under study. The method is based on a multiple increase in the number of copies of the DNA region specific for this pathogen. A variety of biological material taken from children, adults, people with immune system pathology, and pregnant women can be used for diagnosis. The method makes it possible to determine the number of DNA molecules of the studied virus, which is important in the diagnosis of an acute form of infection, reactivation of a persistent infection, the carrier of the virus, as well as in monitoring the effectiveness of antiviral therapy.