Intrafamilial transmission of human cytomegalovirus (HCMV): Long-term dynamics of epitope-specific antibody response in context of avidity maturation

Abstract Background The role of a special early family formation (PEKiP® ), which is popular in Germany, as a potential origin of HCMV-transmission to seronegative mothers is not documented. Objectives To describe the clinical courses, to identify the virological origin and to evaluate a new tool for diagnosis of a cascade of intrafamilial HCMV primary infections. Study design This prospectively analyzed long-term course of HCMV primary infection leading to hospitalization of two family members, included the evaluation of different IgG/IgM/IgG avidity-assays with an epitope-specific recombinant immunoblot-assay. Additionally, neutralization (NT) assays using fibroblast-and epithelial-target cells were performed to correlate NT50 values to avidity maturation. HCMV gN/gO/gB-RFLP-genotyping and phylogenetic analyses were performed using urine viral isolates. Results The clinical courses of the sequentially occurring intrafamilial HCMV primary infections were unusual, leading to hospitalization. Long-term-serology of the mother revealed concordant results for an unimodal IgG-course and a rapid decrease of IgM-indices from week 7 to week 21 p.i. Interestingly, the cut-off definitions for low and high avidity ranged discordantly from 15 to 25 weeks, and from 18 to 42 weeks p.i., respectively. A good correlation was found between the increase of fibroblast-adapted NT50 values and the appearance of high avidity using the epitope-specific immunoblot (>18 weeks p.i.). RFLP-genotyping and sequencing could identify the index patient as member of PEKiP® -meetings. Conclusions PEKiP® -meetings with naked babies may be an important source of horizontal HCMV-transmission to seronegative pregnant mothers in Germany. Using epitope-specific immunoblots, persisting HCMVp150-IgM-reactivities and good concordance between high IgG-avidity and increase of fibroblast adapted neutralization capacity were found.