engleski

Molecular diagnostics of CMV infection

Cytomegalovirus (CMV) is ubiquitous pathogen which occurs in a large number of hosts. It is phylogenetically one of the oldest viruses that is outstandingly adapted to the natural host. Active viral replication in an immunosupressed host can lead to serious organ damage with significant lethality if unrecognized. Therefore it is of enormous importance to diagnose the activation of the virus on time, since effective therapy exists in the form of ganciclovir. Several methods of CMV detection are available: 1) detection of infectious virus 2) detection of viral antigens 3) detection of specific antibodies 4) detection of viral nucleic acids (NAT- nuclear acid technologies). The prognostic significance of positive virus isolation for the development of a symptomatic infection depends on the specimen studied, Whereas children or immunosupressed patients often excrete virus in saliva or urine without ever developing symptoms, the virus isolation from biopsy material or BAL correlates well with an organ infection requiring treatment. Viral antigens detection is principally based on the identification of the virus specific protein pp65 in granulocytes. It is abundant viral structure protein, the site of its synthesis is still unclear. The pp65 antigenemia test is quick (4-5 hours) and the sensitivity is higher than in virus isolation, it is a quantitative test and it has a better prognostic meaning for an CMV-associated disorder, however the test has not been standardized. Serology can be helpful in detection of acute infection in an immunocompetent host, but ia a immunocompromised individuals can only predict the susceptibility to infection/ or possibility of virus reactivation. It is generally accepted that the CMV disease is preceded by active replication of the virus, which can be most carefully monitored by quantitative nucleic acid assays. Those are the only tests that have been standardized, include negative as well as positive controls with known numbers of viral copies in a given volume of blood. Two basic molecular methods are commercially available: CMV-DNA soluble hybrid capture assay (Digene Corp) which is a signal amplification test and allows the quantification of CMV-DNA in the leukocytes of peripheral blood, and CMV-DNA PCR test (Roche Diagnostics), which quantitificates the free viral DNA in plasma. Both tests are sensitive enough and have a very high prognostic significance. However it is very important that in a given immunosupressed patient CMV-DNA level is measured by the same test. In a clinical settings dealing with immunocmpromised patients diagnostic algorithms for molecular CMV-DNA detection should be included: detection of baseline level, followed by weekly detection while patient is at a significant risk of developing CMV-disease (post transplantation period) and while receiving the antiviral therapy. Authors present their experience with CMV-DNA hybrid capture assay in immunocompetent as well immunocompromised patients.

cytomegalovirus infection

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