Human cytomegalovirus infection: recent developments in diagnosis and epidemiology

Cytomegalic inclusion disease (CID) is caused by a horizontally or vertically transmitted human herpes virus infection and may persist for life without obvious clinical symptoms. A serious course of horizontal primary and recurrent infections, however, is often observed in immunocompromised persons such as recipients of organ transplants and patients receiving fresh blood transfusions. Vertical infection may cause fetopathies. The human cytomegalovirus (HCMV) is thought to inherit an oncogenic potential as lately discussed for AIDS and M. Kaposi. Laboratory diagnosis of HCMV infection is performed by light microscopy (inclusion bodies), electron microscopy, virus isolation in cell culture, demonstration of viral DNA and antigen in clinical specimens, by histochemical methods (e.g. immunoperoxidase technique) and by DNA and peptide analysis for identification of different isolates and viral finger prints. Evaluation of cell-mediated immunity in HCMV infection is performed quantitatively (assessment of Thelper/Tsuppressor ratios) or qualitatively (specific lymphocyte stimulation by the antigen). In most cases laboratory diagnosis is achieved by serological methods, i.e. demonstration and quantitation of HCMV-specific antibodies. In this context, a number of liquid- and solid-phase immunoassays have been developed, of which immunofluorescence and ELISA are most commonly used, besides complement fixation and passive haemagglutination. These procedures on the one hand allow the use of different antigen preparations as early and late viral proteins, and on the other hand permit a specific determination of different Ig classes and subclasses. A variety of assays has been established especially for determination of virus-specific IgM antibodies, which are predominantly found in active infection. These, however, at least in part may show non-specific results caused by interference of rheumatoid factor or IgG competition. Such problems have now been dealt with and are avoided by IgG precipitation or IgM immunosorption ("mu-capture" technique). These recent methods allow an exact epidemiological identification of risk groups for CMV infection. Results from our laboratory revealed 13% HCMV-IgM positive patients among pregnant women, 16% IgM positive patients among renal transplant recipients, 4% IgM positive cases in patients after cardiosurgery and 1.7% IgM positives among prostitutes. The prevalence of HCMV infection as indicated by specific IgG antibodies was 56%, 90%, 83%, and 90%, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)