Evaluation of risk factors for congenital HCMV-infection

Congenital HCMV infection is the most common transplacental transmitted viral infection. The incidence reported varies between 0.2 % and 2.6 % of all newborn. There are many clinical variants in congenital HCMV infection, ranging from silent infections to the more severe classic cytomegalovirus inclusion disease (CID). In contrast to other infections, the presence of specific immunoglobulins in the serum of the mother does not prevent the transmission. The mechanisms of intrauterine transmission of HCMV as well as factors that lead to a symptomatic congenital HCMV infection are not known, but it can be speculated, that this depents on more than one factor. Factors which are most suspicious in this context are 1. the strain specific humoral immunitiy of the mother, 2. the virus load of the mother and 3. the cell tropism of the virus. These three parameters will be evaluated for their predictive value for viral transmission and the appearance of symptomatic congenital HCMV infection, considering interactions between these parameters. Beside this incidence rates of congenital and perinatal infections as well as the rates of symptomatic disease in case of an infection will be estimated. Beside this a score system for the use in clinical practice will be achieved by this work. This studies will be based on a screening programm for congenital HCMV infection, existing in Graz since 1993 and done in a collaborative study between the Department of Gynecology, the Department of Pediatrics and the Department of Laboratory Medicine/Blocklabor II.

The results of the project can be divided into three parts: 1.) Setting up and evaluating methods for the diagnosis of congenital CMV infection 2.) Investigating samples of congenitally infected as well as not infected children and their mothers for the determination of in-vivo differences. 3.) In-vitro investigation for the investigation of CMV-trophoblast interactions Ad 1. Since commercially available CM\/-IgM ELISAs differ widely in sensitivity and specificity, there was the necessity to evaluate those systems which could be used for the screening of newborns. An important result in this context was the implementation of a statistical method forte comparison of different assays in the absence of a golden standard, which did not exist until now. For CMV-DNA determination there was the problem of insufficient sensitivity at low levels of CMV-DNA for commercially available assay systems, which fulfill international recommended standards. The assay system, which was developed within this project, is the most sensitive system until now. Ad 2. Pathophysiological phenomenmum of congenitally CMV infected children could be investigated until now only in tissues of deceased children. No data based on investigations of blood, urine and cerebrospinal fluid existed until now, which allowed conclusions on organ involvement and changes within organs during therapy. Cell- association of the virus and organ involvements were seen too by our investigations in children which were not that severe ill. Furthermore, predictive parameters for the prognosis of the children were found out, and the effectivity of therapy could be seen concerning the reduction of virus replication. Another point was the investigation of the CMV specific humoral immunesystem in mothers transmitting the virus to the child versos mothers not transmitting the virus to the child. This investigations too showed interesting and maybe predictive differences within these groups. Ad 3. The investigation of pathophysiological interactions between CMV and trophoblasts showed as major result the release of the proinflammatory cytokine interleukin 6 prior to the start of virus replication. This release starts after me entry of the virus and exists also in the absence of virus replication. This findings would explain histological findings in the placenta, showing CMV inclusions, in the absence of an infection of the child. In this cases the local activation of the immune system could have hampered the transmission. In conclusion it can be said, that within this project methodological, clinical and pathophysiological questions could be answered.